Wind Sun Waves driven sailing machine
The Wind-Sun-Waves driven sailing machine is a yacht concept, meant to be environmentally correct, where energies from Wind, Sun and Waves are utilized for ballasting, propulsion and on board energy maintenance.
In general it is easy to claim such a thing, however here is presented concept
which makes Wind-Sun-Waves driven sailing machine possible.
The ultimate goals are:
- to make easy to use, environmentally correct sailboat
- to make the boat more energy self-sufficient
- to make the boat faster by using: solar energy, waves energy and wing-sail
for propulsion - sometimes all energy types at the same time
It seems to be possible to achieve these objectives by two innovations:
- one is by using described here, automatic controlled multimember
active lateral ballast system
- second is by using described here, automatically controlled from inside an variable wing-sail
Above: An image of 3D printed, bi-plane, LBVW boat model LOA=645mm
Above: the essentials of the WSW sailing machine is the ballast system
(the green ring) and the from inside controlled variable wing.
Above: the by computer created an image of the boat conceptual model - from outside the boat is pretty clean?
Except for safety equipment, the all standard sailboat equipment necessary for sails control is gone!
Note that the wing-sail control system is expected to cooperate with the control system of the active ballast system in order to drive the boat fast and safe.
As the wing-sail is also 360 degrees free (on mast axis) and the boat gets two rudders in line - one astern and one midship as rotating centerboard - then the maneuverability of this boat will be exceptional.
This boat is meant to be used in a special mode named "e-motor-generator for propeller assisted sailing" in order to increase the apparent wind speed which means that the wing-sail area is not necessarily big or with other words the wing-sail high.
At the end of the development these boats will represent almost a new "sea animal" as they will be able to feel the waves pattern, "understand" the hull motion in sea, wind strength and direction at any wing-sail height and the load on wing-sail in the same moment as it appears in order to correct the attack angle, or/and wing-sail thickness or/and ballast position.
The era of pulling ropes is going to THE END....?
The Wind-Sun-Waves driven sailing machine is very complex but not for the user.
The complexity is not necessary related to its mechanical construction as it will be built of standardized functional units.
- 2 exactly same rudder units with build in small propellers.
- 6 - 12 exactly the same ballasting units
- 4 - 6 exactly the same controlled ribs units inside the wing-sail or bi-plane wings
However, the complexity is in the behavior of the ballasting system interacting with the wing-sail and in the interaction of the boat with the wind and sea.
The proposed LATERAL BALLAST SYSTEM:
The goal is to design a sailboat with a ballasting technique using ballast members moved in the lateral plane (“horizontally”).
The need for such a boat was triggered by my wife claiming that the engineers fail to develop a sailboat after I explained to her that the boat must heel otherwise no driving power can be developed.
The “floor” should not be angled – I am not comfortable – she replied disappointedly.
Big ships do have a stabilizing system for rolling – they are using underwater wings (passenger ships) or special tanks filled with water to a calculated level in order to damp resonant rolling (Flume system i.e. on container ships).
Moving ballast in the lateral plane (sideways) is a tradition on sailing boats. The following was or/and is still used:
- Body of the crew (natural)
- Sand bags inside the boat (not nice – old technique)
- Water ballast tanks (requires big volume and take time to make change)
In addition, we do have a canting keels – most effective way to ballast a boat however this idea introduces several new problems:
-- the mass is located far outside the hull producing high dynamic forces on the hull and keel control system
-- the arm to control the ballast is short therefore a hydraulic system is necessary
-- the time for moving from side to side might affect tacking speed
-- the draft of the boat is to be high in order to take advantage of the canting keel
-- additional 2 dagger boards are necessary in order to compensate for lost keel function
-- necessary continuous power (a combustion motor + hydraulics) to operate the canting keel
-- the under-water body with protruding parts via openings is not a perfect solution
-- not suitable for small boats?
The idea to solve my wife “problem” is to install a "virtual crew" as 4-12 ballast units moving on a circular path.
The similarity with the living crew is in that one can put the amount of the ballast at a place he wants/needs.
The most important characteristics are however the redundancy of the proposed ballast system.
All ballast units are autonomous and exactly the same.
The difference of presented idea is that the traditional boat above 30 foot is not designed to have the crew as ballast only (as it is not practical - a lot of food). The boat would not be operating if the crew is not present).
Therefore, the weight of the boat keel/ballast cannot be lowered by design yet?
Why any lateral ballast boat as proposed here is not yet developed?
Probably the answer is: it is not that easy as we think - people as ballast are very agile and smart.
The electro-mechanical system must reassemble those skills.
The area occupied by ballasting units can be located in a way that they are not intruding much in the cockpit area and the entrance to the cabin. The first boat can be aimed for a lake (not open see) and the hull of the boat can be designed for max 20 degrees of heeling.
However, I do believe that once the technology is mastered it can be beneficial to use it at open see as well.
This technique can be used with big benefit also on big ships, especially on fishing ships.
Below: simple sketch depict one of the possible ballast areas. Note that the ballast area location is not final as it will depend on boat balance solution.
It is clear that the ballast ring can be of higher diameter than depicted below – it might protrude outside the hull thus increasing the possible righting arm or several ballast rings can be placed along the center of the boat. (On paper it is easy to have variants - I know)
Above: This is not a boat design - just a sketch to visualize the idea.
In general, the solution how to locate and move the ballast is very important in order to get a maximum of useful weight at the wanted spot. There are several reasons to move the ballast units circularly as will be discussed later.
A good idea will be to use purpose build e-motors/generators as an integral part of the ballast weight.
When the motor can be designed with heavy materials it will be beneficial when included in the ballast weight and make the whole system more efficient– see below:
Above: Only 2 motor-weight units are depicted for clarity of the sketch. It is to be understood that when they can on demand move simultaneously with the same speed then the gravity center (LCG) remains at the same x while the center of gravity moves transversally (TCG). Using several ballast members it will be possible to influence pitch and heeling of the boat, damp excessive hull movement and produce electricity – sometimes all at the same time. As the hull is going to be close to horizontal position there is possible to move the ballast units to wanted position just by gravity.
This is telling us that the idea has a big potential for development and is kind of universal.
Universal ideas/solutions are most powerful.
The proposed VARIABLE WING:
Before digging deeper into the lateral ballast system I would like to explain little more about the Variable Wing idea.
The triangular sail of today is close to the end of its development road.
With that, I do not mean that it will be not used anymore - it is just not possible to do many new improvements.
The wings of today have still a long way to go. I do believe however that the wings are the future.
Presented here Variable Wing (VW) is one idea which solves many problems of triangular sails.
In addition improves the wing solution for sailing boats on the fly.
The Variable Wing is based on fact that if a foil shape is rotated and projected on surface
then the camber and thickness of this foil are changed however the general foil shape is intact.
This is explained by following sketches:
Above:Clark-Y wing foil shape thickness = 11.7% and 17.25%
Above: the Clark-Y of 17.25% gets rotated by 60 degrees and projected
on the surface. Now both shapes are of thickness = 11.7%
In general, the spar (mast) is inside the wing, is freestanding and non-rotating.
Probably it needs to be built of sections.
On this spare are mounted rotating ribs. The ribs have a fixed shape of chosen foil type.
The ribs can rotate 180 degrees or more exact +/-90 degrees from their 0-degree position.
In addition, the ribs can be rotated endlessly on the spar/mast axis.
It is obvious that the first attempts are going to be done on model
therefore, the RC servos are used in order to move the ribs.
This is explained by the series of sketches made for the wing model and depicted below:
Above: A sketch of Variable Wing having 4 rotating rib units.
Note that the thickness and twist of the wing are changing from bottom to the top
Above: wing tip solution is one of the possibilities how to end the wing with low drag?
The very top part is rotating together with the last rotating rib.
(the top part looks strange - we use to call such look : exotic!)
Above: the wing skin edge is ending close to the surface. There is necessary to have a little gap as the skin is moving vertically and horizontally.
This gap is, however, tightening by foam rubber - the same apply to the deck edge.
Above: Top view of Variable Wing having 5 rotating rib units - the skin is removed.
The twist is 5 degrees per rib and the ribs are angled
in order to change the section thickness.
Above: Side view of rotating rib unit in its neutral position
This design is not any final however the parts are now ready 3D printed
In general, the rotating rib unit depicted above is for the wing model only in order to
test the kinematics and to develop the wing skin characteristics.
Based on that the wing for boat model will be designed.
Above: Depicted the nose part of the rib inclusive the carbon fiber bars in order to stiff it up
and 3 RC servo (1 servo 22 gram)
The upper servo can rotate the rib endlessly 360 degrees thus set any attack angle
of the wing.
The nose servo and the tail servo has electrical axis and can rotate +/- 90 degrees
from their neutral position.
The black CF pipe is a part of the spar (mast) structure and is not rotating.
Above: 3D printed at Shapeways.com rotating hub of the rotating rib unit.
The servos are Hitec HS-5087MH and are just for the wing model.
Above: the wing skin is very different from the skins of today's wing sails.
The wing is very stiff at the tail part - with very stiff I do mean
that it is not possible to put it in the bag.
It is so stiff that there is no deformation of the surface between
the successive rotating ribs.
In general, the skin is hanging from the top and is pulled toward the tail bar.
Pulling the skin toward the tail edge is the idea but different solutions
for how to do it can be used.
The skin is, however, semi-elastic at the nose part as it needs most reshaping.
One can imagine a zipper at the tail edge just for mounting and remove?
Above: this sketch is just for an explanation about what way the skin needs to be stiff.
In vertical direction is maximal stiff - little less at the nose
In horizontal direction needs to allow bending - much less at the tail part
Ok! what to do with such stiff wing in the harbor - was the question of many people!
The idea how to handle the wing when not in use come from nature:
the wings of insects and birds are put along the body after flight
– this feels like the very correct solution.
The mast lay-down mechanism was investigated and the result is looking promising.
The general idea is as follow:
The mast is the non-rotating type and during sailing the mechanism for laying down the wing/mast is not possible to use as the mechanism is in the tube under the deck.
Therefore, it can take full load – the mast is locked in the tube.
When after sailing the wing is de-powered and hoisted up so the rotating joint is exposed the wing can be lay-down to astern.
It can be also lay-down to bow for instance during repair or maintenance.
With this arrangement, the wing can also be placed at a proper height above the deck.
De-powered wing in a horizontal position can be utilized as a roof or when covered with solar panels as charging batteries device.
The mass center of the wing is in this way lowered substantially which can be used
in very bad weather.
This is explained by the sketches below:
Above: the left servo is rotating the spar (mast) and is moving together with the lower part of the spar while the right servo, fixed under the deck, is hoisting or lowering the spar/mast.
Above: the spar (mast) in sailing position. The rotating joint of the spar is not exposed (inside the tube). This way there is fewer requirements on the strength of spar rotating joint and safety.
Above: some details about the spar/mast hoisting mechanism.
It has to be stressed that the technique of laying down the wing, when not in use or when in an emergency, is very crucial for the wing technology of the future and needs to be mastered.
The idea to lay down the wing is the key to open for best design
of the wing itself and the wings “skin”.
Very important issue is also easy for the maintenance of the wing.
The following is expected:
- The skin is made as one piece - do not need sections
- The skin can be very stiff especially behind the spar (mast)
- The skin can be removed easily by opening it at the tail (kind of zipper)
- When the skin is removed from the spar there is an easy access
to the spar and rotating rib units from the deck level or shore
Above: It will take many attempts before we get it looking good but eventually it will!
How to move these parts....
Generally, the RC servo has lower max continuous holding torque compared to max short term useful torque.
In addition, the RC servo cannot provide max short term useful torque for longer time than few seconds.
Still the power consumption is very high when max continuous holding torque is applied.
Note that not all applications require such very high continuous holding torque, however, some applications are not possible without.
Depend on wind attack angle on the variable wing there will be in most cases a force to rotate it on the spar (mast) axis.
This is true especially when the wind attack angle is approx. 90 degrees.
It is, therefore, necessary to hold the attack servo position for a long time under load or…
the simple solution is to lock it mechanically as soon the servo arrives on target position.
In this way, no power is consumed while during longer periods of time the servo is keeping required attack angle.
The same applies for control of the rib angle servos, spar (mast) laying down mechanism and mentioned ballast units.
This is the detail where the devil is sitting, therefore, I will explain about it little more in depth.
Some work has been done by me about the “Hyper RC servo” necessary for our purposes as the requirements are different from the standard world.
Five additional requirements for each Hyper RC servo unit are defined below:
- Wireless control with multimode capability within boat area
- Fast acting mechanical lock to “keep position” without energy consumption
- Positioning for 360 degrees endless rotation with 0.1-degree accuracy
- 12-24V DC supply
- Water tight and low weight
The “Hyper RC servos” are necessary for a real boat, while standard RC servo can be used for the wing model testing and with some modifications for the 1.8m boat model.
Some sketches below will explain little bit about the servos "business" - how to add locking functionality to standard RC servo:
Above: Standard size RC servo housing and gears. In the middle at the bottom of the gears is the first gear which is the target for fast acting mechanical lock in order to keep servos position without energy consumption
Above: the first sketch - micro servo is about to engage the lock and on the second sketch, the micro servo is in the right locking position. Both servos can be de-energized (no supply) and still will keep its position at max load
Above: the first sketch locking servo side mounting - the second sketch locking servo front mounting solution
Such modification is an easy task as the locking parts can be 3D printed however the other requirements of "hyper servo" are still not fulfilled.
In order to get some feeling how big and heavy such "hyper servo" might be a little investigation was carried.
See the results on sketches below:
One of the issues when built compact electronic units is the electrical interconnections between parts. Connectors are often soldered and then pushed the male part into the female part. This is an expensive and not very reliable way and should be used only when the disconnection is a necessary feature.
In order to get the Hyper Servo very compact the electronics is divided in 6 tiny Printed Circuit Boards
1- wireless communication
2- FPGA or Microprocessor
3- Flash Memory
4- Voltage regulators
5- Motor driver/control and interconnection
6- Micro servo fixing and interconnection
The bottom PCB is carrying the motor control chip and is connecting one side of these 4 tiny PCBs.
The upper PCB is fixing the locking micro servo and connecting the other side of these 4 tiny PCBs.
Above: 6 PCBs connected by "direct soldering"
Above: the internal parts of Hyper Servo. Main motor (yellow) and micro servo as locking device (light green). The antenna is visible to the right and Flash memory PCB is removed in order to show the voltage regulators PCB.
It is to be noticed that there is maybe an unconventional way to make the interconnections without connectors. This is maybe a new method to fix all the parts together at the same time?
It is surprising that the interconnections between PCBs have only one soldering point per signal. It must benefit as well.
Below are depicted serie of sketches explaining how this is possible:
The conclusion is that it is possible to build “hyper servo” with full functionality to size bigger by approx. 10% compared to standard RC servo including functionality:
- FPGA control, 50MHz clock, flash memory, programmed via USB Blaster (ALTERA)
- 2.4 GHz wireless control nRF24L01+ NORDIC SEMI
- Mechanical break by means of nano servo HS-40 HITEC
- H-bridge with motor current measuring MC-34931
- Output shaft position resolution 0.1 degree INFINEON (parts from 01Mechatronics)
- Digital I/O for additional 2 RC servo control
- 7.4V nominal supply voltage (internal regulators: 5V, 3.3V, 2.5V. 1.2V)
The main idea is that Lateral Ballast has following advantages and promises when compared to other existing ballasting systems:
The benefits of the system to be discussed:
- The boat can be built lighter as the ballasting arm can be already at a maximum when the boat has 0 degrees of heeling.
As the boat is lighter higher speed can be obtained by same driving force
• The lateral ballast is using several ballast units thus providing redundancy of function.
• By using, several ballast members the ballast system can provide ballasting (opposing heeling) and trimming (opposing pitching) of the boat hull at the same time.
• The boat hull will not uphold upside down position, as the ballast control will let the weights to lowest position by gravity.
• As the ballast is divided into several members, it is easier (low weight) to rotate the motors by hand action in case of emergency.
• Advanced dynamic ballasting can be obtained by moving the weights round-round to damp the (resonant) boat movement.
• The force to move the ballast to wanted position mostly come from gravity force thus this system will require only little additional energy. (think dinghy tacking technique) The wanted slope in order to move the weight will be provided by the wing-sail control system
• If the movement of ballast caused by gravity needs to be slowed down thus the ballast driving motors can act as generators to produce electrical energy. (charging super caps or/and batteries)
• The ballast can be made of pure lead (12) thus using a small volume of the boat internal volume. Traditional keel often can not be of pure lead as it is too soft. No strength is required from the ballasting material itself within presented idea.
• The ballast weight will be the motor/generator/battery/electronics - each ballast unit can be autonomous inclusive control electronics. The electric motor is build as heavy as possible (i.e. Yorkalbro). In this way the “dead” weight is minimized – up to 90% of the ballast system is useful weight. With “dead” weight is meant all not movable material necessary for the ballast system.
• The underwater body and appendage can be very effective hydro-dynamically when minimal heeling is obtained and only one rudder and one centerboard are required. As the keel is more like centerboard (not heavy) it is then possible to rotate the centerboard like the rudder. This will change the the fact that the hull axis will be set in travel direction thus minimizing drag due to leeway ?. 2 rudders? Breaking speed by setting the rudders starboard-portside at the same time? Or move the boat sideways or resist turning effect by side wind during maneuvering.
Or driving the boat in an emergency by flapping rudders fins in opposite direction? (joke? -maybe not...)
• As the ballast weight is moving on circular track there is no hard end at any point of travel– just smooth motion.
This makes the most effective production of electrical energy as the operation can be continuous – endless 360 degrees rotation.
• The weight of the ballast moving is within the hull, therefore, the inertial moment is low compared to canting keel?
• Two weight members can utilize the same track (depend on size/solution …) therefore the weight resolution can be increased thus enabling advanced operation like damping resonance heeling or generating electricity while ballasting.
• The system can be made quiet when the motor/generator is of Lorenz motor type (no cogging and short term 10 x nom torque!), direct drive (no gears) and drive its self around the track by means of i.e. rubber wheels.
• When the boat runs on an underwater obstacle and damages the centerboard/center-rudder then the maneuverability of the boat can be still maintained. Some of the maneuverability can be maintained as well when the stern rudder gets damaged?
• When the boat is on the buoy or anchor then the hull motion on the waves can be used to produce electrical energy by letting the
e-motors/ballasts to “run downhill-uphill” damping the boat movement at the same time – now it is easier to understand while circular motion is beneficial ? – the movement of the ballast can be continuous thus more efficient.
Disadvantages of the system:
- The ballast system is complicated and has to be computer controlled for easy use and good efficiency.
• The stability is limited when the computer system is OFF or broken – the ballasts have to be moved by hand control to a neutral position?
• The stability is decreasing when heeling at large heeling angle, which is in contrast to traditional keel design !?.
There is, however, possibility to design the boat safe and maybe safer than the traditional boat which can be in worse case stable in upside down position.
The advantages/disadvantages mentioned above has no weighting – it means that maybe some of them are not necessary some of them are useless – take it as a list for discussion.
Generally, a system that is more complicated is more vulnerable, however; people still use cars, airplanes and computers in the hospital. Today’s electronics tend to be less faulty than people – self-driving cars might be an example on where we are heading.
Our perception is shifting …slowly….
The energy conversion technique from waves energy to electrical energy need to be done in an efficient way so the energy can be retrieved also by very low revolutions of the motor/generator.
Proposal of such a system is depicted below:
Above: The generator/motor of the Lateral Ballast Unit is to be connected/reconnected via Inverter to two DC-links: The Boat System DC-Link for motoring and reconnected to special Intermediate DC-link when generating. This Intermediate DC-link needs to be kept at a level adequate to the actual speed of the generator/motor in order to provide less inrush current and efficient load when S2 is closing.
The voltage of the Intermediate DC-link is to be regulated via U1 step-down converter and U2 step-up converter. The U1 step-down converter is charging up the C1 capacitor bank up to level corresponding to actual EMF of generator/motor while the U2 step-up converter is discharging the capacitor C1 to mentioned level if necessary.
Once the generator/motor of the Lateral Ballast Unit is in regenerating mode then switch S1 will open and switch S2 will close enabling the U2 step-up converter recharging battery B1 and supply the Boat System DC-Link as well.
Note: the Boat Propulsion System is very similar to the block diagram presented on the left side. The only difference is that the generator of the Lateral Ballast Unit is rotated by gravity while the Boat Propulsion Systems generator is rotated by the boat propeller while sailing.
The Lorenz motor/generator is the key component in this system, therefore, it must be specified in first place for the real boat.
Note also that the US firm Bodine Electric has similar motors in production (e-Torque).
Still it have to be mentioned that the final motor/actuator/generator design and the power conversion is not yet ready.
The ballast units on the tracks:
How the ballast units will run on the track is not yet solved finally as different ideas need to be tested.
For the model of the boat, the solution is different when compared with normal size boat due to little size of the model.
In order to simplify the installation, the weight is related mechanically to the center of the ballasting ring.
This is making easier to keep the weight units on tracks as it will be explained later.
The principle of the ballast units for model boat is depicted below:
Above: 8 ballast units (one above each other) used for simulation. The mass is 800g per unit.
The boat model is 1.8m long.
Still another sketch will explain this better.....soon.
Some work has been done on the section of the ballast area for full-size boat and how to mount the tracks and get 2:1 or 3:1 ratio for the motor/generator. As the driving wheel is mounted direct on the motor shaft then the ratio is depending on motor diameter and wheel diameter.
The motor/generator is an important part of positioning/holding the weight on the track.
Above: 3 tracks are necessary: one “L” profile on each side holding against gravity. Still they need to be C-profiles if up-side down operation is required.
And one C-profile on the floor: left surface for driving while right surface for holding the weight horizontally.
Above: One track cut out section - depicted conceptually how the bearing based wheels hold the weight and the motor/generator on the track.
The precision of position is guaranteed by C-profile as it will be not possible to make the track with very high accuracy for 3m diameter.
Note that the ballast weights of lead are skipped in this picture.
Above: One track cut out section view from the bottom- the motor is axial type direct-drive driving direct against the C-profile surface.
The bearing wheels provide positioning accuracy = tension. Note that the ballast weights of lead are skipped in this picture.
The ballast systems requirements for full-size boat are:
- Quiet operation when moving ballast weight unit
2. Very high torque motor/generator gear free of Lorenz type at low motor/generator speed
3. Weight speed/position adjusted by electrical driving/braking of the motor/generator
4. Functionality of battery charging by gravity and hull movements
5. Low friction (no gears) when moving the weight by gravity to make recharging more efficient
6. Locking of the weight unit at a stand still required in order to save energy?
7. Multiple weight units (6 – 8 or more) in order to provide redundancy and functionality
8. Continuous rotation of the weights possible (means endless 360 degrees around the track)
9. Motor/batteries/electronics used as weight – generally design must provide good weight distribution (minimum dead weight)
10. Damping of resonant hull movement shall be possible
Note that the requirements above are probably equally weighted – it means that all requirements must be fulfilled for the success of the prototype.
Next question is how the ballast system described until now will scale-up?
Presented simulation is for the 30-foot sailboat which is about 3m wide it means that 2.8m track can be used.
The result of such simulation is presented below:
The green and red traces show pitching and rolling of the deck then the blue trace show the power of the motor (pink)
which is negative. This means that the motor works as generator opposing downhill ride on 10 degrees slope.
So to describe it in a simple manner: the deck is heeling to starboard and then is pitching with nose down and then is rolling over to port-side and the nose is rising up and it continues 6 periods.
Above: the track is 2800mm diameter the weight of the ballast is 500kg. The power produced by this system is approx. 2kW.
As shown above, the scale-up is giving good results 2kW is much power however it is approx. max. during used circumstances and 30% less can be probably achieved in practice – still a good result.
The ability to produce electrical energy is most exciting characteristic of this horizontal ballast idea and opens for the possibility of a new device for wave energy to electric energy conversion on board.
Some verifying calculus:
For 300kg weight on 15 degrees slope and 2.45 m/s (15 km/h)
Force on weight acting parallel to motion is:
F = mass * 9.81 * sinα = 300 * 9.81 * 0.2588 = 762 N
P = (force * velocity) = [N * m / s] = 764 N * 2.45 m/s = 1871 Watt
When Lateral Ballast concept, which in general is using an electric generator in order to break speed of weight unit traveling on a slope, gets utilized for energy production from waves we can arrive at very efficient system:
- The specially built vessel (ship) containing Lateral Ballast is autonomous when sailing and automatic when charging batteries
- The vessel arrives at harbor’s terminal when all batteries are charged and gets empty batteries for new trip
- Wind energy can be used for vessel propulsion as well
- As part of this energy can be used for vessel propulsion then the waves can be meet more frequently (energy chasing)
- When the vessel is moving say 45 degrees to the waves front it will provide "continuous slope"
- As the weight units run on circular tracks the higher frequency = speed of the generator the more energy is produced
- The generator can easily adapt the system to different waves height and waves frequencies
- The infrastructure on the shore is minimized as the electric cars can use the charged batteries immediately
- The best waters with bad weather can be utilized as no crew is present on the vessel
Back to the wing and spar of the kinematic model which is meant to help in developing the wing skin:
This kinematic model is not to be used on boat model, therefore, the weight is not the issue, however, the whole idea is to be as close as possible to boat model and real boat design.
The sectional built of the spar is dictated by the need to be able to replace broken parts of the rotating rib and be able to perform maintenance.
Once the wing is laid down it will be possible to get access to all the wing parts from the boat deck.
One section of the rib rotating unit which includes also spar of carbon fiber is depicted below:
The parts connecting the carbon fiber pipes are 3D printed. The pipes are 30x28x500mm and 20x18x333 mm
Two different parts are used. One integrates the non-rotating part of the gear which is 1:1 the other enables passing the supply and control cables.
Above: the first test with Rotating Rib Unit programmed to tacking at close hauled...working as expected - not funny...
Above: CF pipe joining parts are manufactured as one piece. Small bridges on the top keep small pieces together.
They will be cut away. These parts have cavities for nuts on part placed inside the 20x18 pipe
The funny part is the tail bar holder. It requires some freedom in movement of the tail bars when the wing gets twisted. After several attempts with different solutions the choice is 3D printed part - see cross section below:
Note that the max diameter is only 15mm. the space between balls is 0.2mm (0.05mm is the process minimum)
Note that the arms kan move separately or simultaneous when a round bar is inserted to connect them.
Above: the screw retaining ring is made in one go with the other parts as well....
Some additional work has been done about the top end of the wing in order to get it simpler, lighter and better looking:
The "Latex" style is a flexible end part which follows the necessary shape by being elastic in a special way
The end of the wing tip is not very critical for the Variable Wing regarding the tip vortex.
As it is known the tip vortex is producing drag. However, this drag can be minimized as the variable wing has the ability to twist and change the foil thickness at the same time. This means that the tip can be set to zero attack angle thus equalizing the upper and lower skin pressure. As this feature is not always needed it is very convenient to be able to control it on demand.
One can imagine that if an airplane got the ability to modify the wing close to the tip in such a manner then during start the wing gets a high lift and when flying fast is changing the wing shape and attack angle close to the tip.
This is because at higher speed the airplane does not need "big wings" - hurray!
All this might apply to Ice boats, center boards, rudders, wind power, propellers and more?
The holding/forming part is rotating together with the last wing rib unit - the "Latex" skin is laying on it.
Some details of the part from above. It will be 3D printed for the model as well.
Back again to Lateral Ballast and particularly how to develop and test it.
In order to develop the algorithms for the Lateral Ballast behavior, we need to make a tests jig.
Otherwise, development will be difficult to perform on the water with the 1.8m model as some measuring equipment will be necessary which will add dead weight and not necessary will work from beginning.
In general, it is extremely difficult to simulate a boat in operation in water due to the complex shape of the hull interacting with the complex energy distribution of the waves. The buoyancy center is moving all the time as well when the boat is floating free on the waves.
And the boat has accelerations and inertia in all possible XYZ directions. All these facts make the simulation very difficult and time-consuming.
Boat movements can be divided into 2 categories:
1 - Rotational motions: Yaw, Pitch, and Roll
2 - Translations motions: Sway, Surge, and Heave
In addition, to that boats do have a hull conditions as Heeling, Trim, and Draught.
The best idea will be to suspend the “hull” of the model in a Cardan system where the hull can be affected by applying forces from the outside world.
Such a test rig can be even used to test the energy production by the Lateral Ballast system if the type of motors used for ballast units gets gear free.
However at the beginning a simple, “hard” driven test jig will be used. It is expected that this jig will enable the development of basic control algorithms and measure techniques necessary for control of Lateral Ballast Units.
It is to be stressed that this jig is not adequate for the development of the most advanced techniques for controlling the WSW boat model.
Above: A simplified test rig for simulation of the heeling and pitching behavior.
2 pcs ServoCity gears (5:1) are used for deck positioning. The deck area is represented by the circular surface build of Polycarbonate transparent plate 5 mm thick and 500 mm in diameter.
The hardware is already built and the electronics for controlling the jig is SSC-32U controlled from PC computer.
The sequencer which is free software for SSC-32U will be used to control the "deck" in different motion patterns.
This arrangement of the jig is hard driven which means that the heeling and pitching program have no feedback. This means that if 10 degrees heeling is set it will be held never mind the position of the ballast unit.
Therefore, the ballast unit in this arrangement will not be as heavy as designed for boat model as this is meaningless due to the fact that the jig is not reacting to the ballast units weight as hull on water will.
Many areas of the Lateral ballast design and control will be introduced and checked:
- Sensing the position of the ballast unit on track; finding the home position – hardware and firmware
2. 2.4GHz radio communication between the ballast unit with the boat control unit
3. Sensing of the deck slopes on the boat control unit
4. Moving the deck in different boat motion modes (however only combinations of heeling and pitching are used).
5. Testing the motors planned to use on boat model
The simplified testing jig is however not so simple in any way as the hardware requirements are the same as for boat model.
Above: The ballast units driving “servo” (gray) and sensing “servo” (yellow) mounted on the center arm by means of brackets from LYNX
The idea is as follow:
The driving servo is driving the ballast unit to the right or to the left. The servo motor is standard HS-645MG modified for continuous rotation.
The modification means that the servo is not servo anymore as its feedback potentiometer is disengaged and set to the neutral position.
The sensing "servo" is not a servo as the potentiometer is replaced be MagEnc V3.0 Low Rev., In addition, the gears to the motor are removed. It means that the wheel is driving directly the MagEnc V3.0 Low Rev
This makes the “servo” a rotary sensor with tracking wheel able to take the load.
The idea of two modified standard RC servos is dictated by the fact that the arm keeping the ballast unit on track is a week part.
Therefore, a weight mounted to one wheel will be unstable.
In addition, if the driving servo got the sensor for positioning one can expect that the wheel can slide when accelerating/de-accelerating thus the unit will loose it's the positioning.
The servo loop will be closed now via electronic boards FPGA controlling the ballast unit.
A fundamental problem is at start-up of the system as the control needs to find a HOME position.
For the test jig and boat model, the HOME position finding will be done by means of micro-switch with a roller.
It means that a little elevation on the track at the nose will be the indication of HOME position.
If the system is always left off side close to the elevation it will be easy to get the HOME position at the system start-up
by moving the ballast unit a little toward the expected elevation.
The sensor MagEnc V3.0 Low Rev is an absolute sensor for 360 degrees however for multi-rotation is of incremental type.
The MagEnc V3.0 Low Rev can, however, provide revolution counting signal.
In a situation when the supply is lost and back again, far from the HOME position, the ballast unit will drive along the track as long as necessary to find the HOME position.
This behavior is OK for the testing jig but on boat model, it will be necessary to increase the resolution of HOME position finding.
Still it can be done with one bit (micro switch with a roller) and several elevations placed in a coded manner.
Above: the elevations position increases by 2 degrees clockwise and anti-clockwise.
It is to be noted that the MagEnc V3.0 Low Rev can measure distance with very high precision which can be used in elevations recognition.
Let check how it works: As the program “knows” the direction of travel then the distance between elevations can be used for position confirmation during normal incremental/decremental operation and detection of a faulty switch.
In the case of lost position, due to supply decay, it is necessary to travel over 3 consecutive elevations which give us as best 10 degrees and worse case 52 degrees “seeking” angle before the system can write correct position into memory and begin normal incremental/decremental operation.
For real boat the method using a microswitch is not recommended due to reliability issue, however, is good enough for the boat model.
Above: The microswitch (green) with roller for HOME position finding.
Above: the Ballast Control Unit electronics (is moving with the servos) and the Boat Control Unit electronics mounted in the center (is moving on the deck but not rotating) Note the 3 pcs accelerometers (red break-boards)
Although the upper boards of the electronics units, the CoreEP4CE10 from WaveShare, are the same the lower boards need different functionality.
Above: a simple sketch of ballast control printed circuit boards.
The lower board of Ballast Control Unit electronics - needs following interface functionality:
- Connector to attach the radio board nRF24 L01p (8 poles)
- Connector to the rotary sensor MagEnc V3.0 Low Rev (6 poles)
- Connector to driving motor (3 poles + 3 poles for future use which is the brake control)
- Connector for Micro Switch for HOME position (2 poles)
- Battery supply (2 poles)
- Voltage regulators
Above: sketch of boat control printed circuit boards.
The lower board of Boat Control unit electronics - needs the following functionality:
- Connector to attach the radio board nRF24 L01p (8 poles)
- Connector to the ADXL345 (8 poles) - Heeling
- Connector to the ADXL345 (8 poles) - Pitching
- Connector to the ADXL345 (8 poles) - Heaving
- Battery supply (2 poles)
- Voltage regulators
As the work is proceeding some checks of what was said is evaluated again - sorry for inconvenience....
Below some checking and a new discussion about different ballasting systems and Lateral Ballast benefits, this time, more in comparison with canting keel idea.
A simple study of the center of gravity and buoyancy when different ballasting means are applied to the traditional boat.
The hull mass is 3800 kg while the keel mass (pink) is 2200 kg. The displacement of this boat is 6000 kg. Boat heeling is 20 degrees.
The pink dot is moved to different positions and the boat mass center is calculated.
The keel itself during this test is set to 0 kg.
Above: standard keel (no bulb) – righting arm = 588 mm
Above: keel with bulb – righting arm = 685 mm
Above: canting-keel at 60 degrees – righting arm = 1078 mm
( the fin is not angled - sorry for this simplification)
Above: poor man canting-keel – righting arm = 825 mm
Above: Lateral ballast - righting arm = 1140 mm
- Above: standard keel (no bulb) – righting arm = 588 mm
2. Above: keel with bulb – righting arm = 685 mm
3. Above: canting keel at 60 degrees – righting arm = 1078 mm
4. Above: poor man canting-keel – righting arm = 825 mm
5. Above: Lateral ballast - righting arm = 1140 mm
From this simple analyze is clear that moving the weight from the center of the keel to the tip is increasing the righting arm from 588 mm to 685 mm which is 16% change and it is not much... not much.
Poor Man Canting Keel gives us additional 20% change when referencing keel with a bulb or 40% when referencing standard keel.
The canting keel gives 57% change when referencing keel with bulb, which is a lot and 30% when referencing to poor man canting keel.
The Lateral_Ballast is giving a similar result to Canting Keel at 60 degrees however by much lower boat draft.
In addition, it should be taken into account that the Canting Keel needs dead mass inside the hull while the Lateral Ballast has almost none.
The advantages of WSW boat using Lateral_Ballast when compared with Canting Keel are following:
- Very high redundancy of the ballast system (6 - 8 or more autonomous ballast units)
- Moving the ballast weights on circular path -no hard end
- Possibility to adjust hull trim while ballasting
- Possibility of moving the weight easily by gravity as hull is crossing zero heeling often
- Higher speed of moving the ballast weight to certain position (high ballast agility)
- Possibility of production electrical energy – possibility to self-supply of the ballast driving system
- Possibility to have 2 rudders in line improves lee-way and maneuvering
- Allows less deep water as only 2 rudders protrude from the hull
- Excellent hydrodynamics as the hull is running on less lee-way and only 2 rudders and hull resists the motion
- Possibility to damp resonant or excessive boat movements
- No openings in the hull related to the ballast system ( 3 hull openings for canting keel)
- Lateral Ballast is changing completely the way the forces acts on the hull.
The forces acts now between mast/spar and the ballast ring structure.
The hull is somewhat just attached to these structures consequently can be made less strong = less heavy.
- No parts of the ballast system are protruding underwater sideways of the hull. (dangerous feature of canting keel)
- The mass used for ballasting is well contained within the hull, therefore, the dynamic forces from water do not exist.
- Pure lead metal can be used to minimize used space as there are no strength requirements
- Losing the "ballast keel" is not likely to happen
- Lower dead mass of the ballasting system (all parts of the ballast are used as ballasting masses)
- Ability to provide storage volumes on sides of the Ballast Units for other less frequently used stuff as the Ballast Units can on demand drive to the inspection window for access. This is further lowering the “dead weight” on the boat.
When compared the different ballasting methods it shows that the Lateral Ballast is superior in many areas
even not in all as it not simple and expensive - the only similarity with Canting Keel solution.
As all Lateral Ballast Units can be standardized - the same part used on different size of boats - then the price/unit can be lowered and the quality increased. (more is different)
The Poor Man Canting Keel is not a part of this project, rather a spin off and probably will be never used; still it deserves some words of explanation:
Pure man canting keel shows nice performance. The winning is the depth or/and weight of the boat.
Note that an electric, folding propeller can be mounted directly to the upper-lower keel axis as electrical power is maybe already there.
Above: the canting angle is 30 degrees and fixed when the boat has negative heeling.
So the work is done by gravity. No power is necessary except for locking device. The locking device might be by hand or electromagnetically controlled.
Above: strait keel need to be much longer (= deeper) when compared to PMCK
Above: As only part of the keel is canting the lifting force of the whole keel remain closer to the performance of straight keel due to the fact that the boat is not heeling as much and the keel is forming better foil configuration like a wing tip on airplanes?
Back again to Rib Rotating Unit.....
During testing of the rotating rib unit, it shows that the rib can be 3D printed inclusive stiffeners.
Right now the stiffening-up was done by means of carbon fiber bars glued into the rib.
This results in a lot of work (many parts to be cut and glued) and the result is not very convincing.
The fixing of the rib to the servo needs improvements as well – used standard servos metal horn was not stiff in all directions.
Based on that experience some work has been done in order to re-design the rib to be one part (no glue) and improve the fixing to servo as well.
Above: the improved rib unit ready for 3D manufacturing - by blue are indicated the new parts holding and stiffening up ribs frames.
It is to be said that a several different design was evaluated via finite element simulation with the target light and stiff.
The result is that the first structure (counted from servo horn) is to have high torsional rigidity (“square” hollow part) while the parts holding the rib frame are I-section structures. The new design is also utilizing the possible thickness of the rib allowed by the spar (mast) diameter.
Above: the rib unit rotating hub is holding the servos and the ribs better than before.
This is due to the extra support for the servos housing and that the ribs are attached now via the big "standard" servo horn (red).
This red servo horn allows holding the ribs at so wide fixing base as possible due to a spar (mast) dimension which is max. 35 mm.
Note also that the spar (mast) pipe which is 30 mm in diameter is not present in the sketch above.
All this is giving us some hints for the design of boat model and the real boat.
Above: photo of 2 ribs - working and ready for skin development.
See very short animation on https://youtu.be/eXUIQzNxRkc
NOTE: It is necessary to set the video player to LOOP atherwise it is to fast/short
On the video the lower rib is changing the thickness while the upper is changing the thickness
little more and is twisting at the same time.
Issues related to electronics and control principles .....
In general, the control electronics need to be decided at an early stage as the sensors like to influence the way the model is designed/build.
Above: block diagram of the model boat electronic units
Above: block diagram of the boat electronic units and proposed sensors.
1. Boat Control Board includes: CoreEP4CE10 / ADXL345 x 3 / nRF24L01+
2. Variable Wing Control Board includes: CoreEP4CE10 / nRF24L01+
3. Ballast Unit Control Board for each ballast weight includes: CoreEP4CE10 / MagEnc V3.0 / nRF24L01+Motor/Generator control
4. Each Controlled Rib Unit includes: HyperServo x 3 / MagEnc V3.0 / nRF24L01 / Break nano RC servo / SPI interface x 2
5. MEMS Pressure sensors: not chosen yet – probably MSGSTR
6. Centerboard control includes: HyperServo x 3 / MagEnc V3.0
7. Rudder control includes: HyperServo x 3 / MagEnc V3.0
8. Wind sensing board includes: MagEnc V3.0
9. Standard RC receiver to receive commands from external RC transmitter in order to control rudders and give general commands.
Issues related to general conceptual ideas .....
As the new variable wing developed for WSW is opening a new window of opportunities I have done some work to check what happens with the system when two wings are installed instead of one.
Above: A sketch of twin wing WSW boat.
With twin wings it is expected following:
- Shorter wing (important when the wing is to be laid down as it protrudes less to astern)
2. Lower force center on the wing
3. Lower weight center of the wings
4. Possible more wing area for the same amount of ballast?
5. Possible improvement of aerodynamic due to biplane configuration
6. Wing redundancy
7. “Reefing” is possible by laying down one of the wings
8. Auto balance when Running
9. Improved visibility forward
Some additional minor advantages, not mentioned here can be observed as well.
Above: wing settings depend on apparent wind direction
As the wings can rotate 360 degrees on spar and camber, thickness and twist of the wings can be set as necessary and several new configurations how to set the "sails" are possible.
It can be observed that when RUNNING 3 different settings are possible (3, 4, and 7). It is not easy at this stage of the project to say which is to be preferred. One of the settings (7) is self-balancing.
During BROAD REACHING (2) the wings can be set very effectively from the aero-dynamical point of view – probably the fastest configuration.
It is possible to reduce the power (reefing) to half by laying down one of the wings (5).
De-powering is possible at any wind direction by making the wing thin and setting attack angle to 0 degrees (8).
Note also that it is easy to mount 2 wings as the deck on these boats is very wide for the Lateral Ballast purpose already.
As always there are some minor disadvantages however it feels that this is the right solution as the wing redundancy is one of the most wanted characteristics. Note that the Lateral Ballast system is already highly redundant.
The concept to have 2 wings and lateral ballast ring requires some new thinking about the hull appearance.
Above: One of the ideas how to include the lateral ballast ring into the hull shape for the 1.8m model boat.
Above: Support for wings when lay down is at the stern....
A conceptual idea is to add wing top connector as depicted below. This will stiff up the spars inside the wings by using just a little weight at the top.
Still this concept will allow laying down one or two wings – some simple solutions how to handle the top connector are found possible.
Above: simplified wing top connector depicted conceptually
Just for the record some information about the sensing of hull movement in the water.
As the floating boat is a system without reference it is very difficult task to decide its position on the “horizontal reference” or true gravity direction.
The gravity direction is a very good reference as long as the boat is not accelerating/de-accelerating.
As the MEMS sensors become relatively cheap and very small they are the first choice, however, there are difficulties.
The accelerometer is indicating deviation from free fall. This means that at free fall the accelerometer shows 0g however still is accelerating 9.8 m/s2
At a stand still the accelerometer indicates 1g while falling with (9.8 M/s2)/3 will indicate 0.33g.
A MEMS accelerometer can be used as tilting/inclination sensor:
If 2 axes (XY) of 3 axes (XYZ) accelerometer are used then the sensitivity is constant and this system is for small angles
only little sensitive to tilting in the 3rd axis (XZ or YZ).
Alternatively, 2 pcs ADXL345 and 1 pcs LSM9DS1 can be used as LSM9DS1 include also gyro functionality.
When using 2 axes of one 3 axis accelerometer for measuring of tilt measuring the sensitivity is the same from 0 to +/- 90 deg.
However, still it will be difficult to measure with accuracy sub 1 degrees pitching or heeling with filtering like Kalman filter.
The reason for that is the acceleration and retardation of the boat due to waves.
What is the boat acceleration of normal size sailboat due to waves?
Acceleration of 0.2g at 3Hz is already intolerable by humans, therefore, 0.3g - 0.4g is probably the maximum acceleration to be considered on real boat.
A scale model will be moved with a higher frequency of pitching and roll as the small waves get the higher frequency.
The wave height of small waves is, however, low. Still this might result in higher accelerations/retardations compared to normal size boat?
The other benefit is that there is a possibility to measure 360 degrees in both X and Y axis.
Still the biggest problem is that this system is sensitive to acceleration in any direction in XY plane.
One idea for solving the problem of deck movement measuring will be to use 3 accelerometers (each 3 axes).
These accelerometers need to be oriented i.e. as on the figure below:
Knowing the deck position in relation to gravity direction is crucial for the LBVS boat application.
When the deck is heeling and pitching we need to know the direction of deck slope (lowest point) and magnitude of decks slope.
Above: the quadrilles and sectors of the boat deck used for to determine the deck position relative the gravity direction
The deck slope magnitude is calculated from heeling ADXL345 and pitching ADXL345:
deck_slope_magnitude = SQRT ((heeling * heeling)2 + (pitching * pitching)2)
The deck_slope_vector is pointing the direction of the deck_slope
0 – 360 deg is represented by 0 – 3600
The deck slope vector calculus is more complicated as it is necessary to know in which quadrille and sector the calculations are performed.
This vector is parallel to deck surface and is pointing the highest slope direction.
The polynomial technique to calculate the deck slope vector is based on percentage relation between pitching and heeling signal. If pitching is smaller than heeling or heeling is smaller than pitching then:
It is a 12-bit digit describing 360.0 degrees as 0 to 3600.
90 degrees is then 900 (starboard)
180 deg is 1800 (stern)
270 deg is 2700 (port)
360 deg or 0 deg is 3600 (nose)
Below is a photo of the development board including heeling and pitching accelerometers (the red small boards)
Note that the display indicates the value of the deck_slope_vector= 272.9 degrees as the board is now tilted to port and nose.
A 2.4ghz communication board is also attached in the front.
Above: development board for sensing the deck position
Another issue is the filtering or the signals. A special issue is verification of the signals after filtering.
A specially developed technique is used. The idea is depicted in next photo:
Above: An accelerometer is mounted on the scale and is driven (rotated) by a servo motor.
As the servomotor angular position is "known" inside the FPGA then the signal from the accelerometer can be easily compared and by this verified. We are looking at the lag (delay) between real position and the measured position signal after filtering.
The work with wing skin for the model boat is started. The solutions for the real boat wing might be different.
Still the issues will show up enabling the development progress.
We can divide, known up to now, wing skin issues in 3 categories:
- Wing skin mechanics
1 - how to mount/remove the skin on/off the mast-ribs.
2 - how to provide adequate tension horizontally toward wing tail.
3 - how to provide adequate tension horizontally.
4 - how to hang the skin in the vertical direction.
5 - how is the load distributed on the skin during wing operation.
6 - what are the forces acting on skin surface when tensioned by wings internal means.
7 - what is the target weight of the skin.
8 - what is the magnitude of expected forces on ribs.
9 – what is the horizontal movement of the skin against the rib surface.
- Wing skin itself
1 - how to provide necessary flexibility/rigidity
2 - material choice
- Wing skin top and bottom
1 - how to end the tip of the wing
2 - how to keep the wing tight to the deck
Sketch presented below will help to understand the range of deformation of the wing skin.
Above: Principal lines of the wing skin. The tail is moving about 25mm on wing chord of 800mm (to 825mm) depending on adjusted wings shape.
It can be observed that the part of the skin from mast center toward tail can be made stiff both horizontally and vertically as it not changing much its shape.
However, the part of the skin from mast center toward nose needs to be highly elastic horizontally while very stiff vertically (along the mast).
The GRAY line is depicting the proposed shape for skin manufacturing.
If the skin is manufactured already with shape placed in the middle of the deformation range it will minimize the stress in the material.
There are on the market a single face corrugated paper and plastics which exhibit wanted characteristics: very easy to roll while very stiff in other direction.
The structure of the skin needs to be an advanced design due to complex stiffness-flexibility requirements.
The weight of the skin is very important and one of the most difficult parameters to deal with.
The wing skin does not need to withstand same stretching forces as traditional sails do therefore it opens for other less strong materials.
One of the interesting materials is Polypropylene (PP):
(Data from Profol Gruppe)
2. Resistant to water, chemicals, and most oils
3. Good dimensional stability
4. Easily fabricated (it means that the wing skin can be fabricated in one go as extruded profile?)
5. Density approx. 0.9 (floating)
6. Closed cells if made as foam – most moisture resistant
7. Young modulus 1300-1800 N/mm2
8. Not very resistant to UV
9. Resistant to fatigue – best of all plastics.
EPP foams (expanded or extruded polypropylene) are also of interest when they are covered with self-adhesive fiberglass tape reinforcing the foam.
Forces acting on the wing will depend on wing angle to apparent wind direction and apparent wind speed.
The close hauled or running will load about the same however it is different load mode.
The wing surface deformation when running does not matter however at close hauled we do want very small deformation.
- Wing area SA =1m2 and CHORD = 0.75 m
- CL=1 at attack angle 10o
- CD=0.2 at attack angle 10o
- Apparent wind speed VA =10 m/s
- Re = (VA * L * 100000)/1.5= 10 m/s * 0.75 m *100000)/1.5 = 50 000
It can be noted that by such low Reynolds we can not predict well the behaviour of this little wing.
The resulting force TA on the wing can be very coarse estimated:
Lift = 0.0625 * (VA)2 * SA * CL = 0.0625 *100*1*1= 6.26 kG
Drag=0.0625 * (VA)2 * SA * CD = 0.0625 *100*1*0.2= 1.25 kG
TA = SQRT(Lift2 + Drag2) = 6.38 kG – this is total force of wings both sides at apparent wind speed 10m/s
Below: Possible wing skin design by extruding Polypropylene:
Above: a cross section of wing skin made of Polypropylene. Note the nose part having more flexibility as part of the internal surface is taken away.
Note that this is still a much too heavy solution if done with 0.5 mm thick material.
The advantage here will be that it is very cheap to manufacture compared with sailcloth.
If the wing surface of 1.8m long wing with chord 0.75m is approx 3m2 then by using a material like Polypropylene of 0.5 mm gives mass of 1.5kg
So it is necessary to get it down to 0.2 – 0.3 kg/m2 for ready to use the material.
Hollow Glass fiber might be checked as H-Glass is more elastic and it gives 40% lighter composite compared with standard GF.
Technical data 160g/ m2:
Tread count /cm warp: 24 + 1
Tread count /cm weft: 18 + 1
Thickness mm: 0.19 +/- 0.035
Finnish: Amino Silane
Price: 79 SKR / 1000 x 920 mm
Probably H-Glass and Carbon fiber and Mylar plastic sheets can be used for the real wing.
It needs to be as a single layer for 1.8m boat model using a vacuum during curing in order to not use too much matrix.
The curing has to be done on wing form from a sketch from 2016-02-09.
Another question is what to use as a matrix.
In general, the surface for variable wing structure needs vertical stiffeners traditionally named spars and stringers.
A standard wing structure needs spars and ribs connected together – in our case the difference is that these parts are disengaged.
We can see 2 different directions for making the variable wing skin:
- Using today’s advanced sail making technologies as it is necessary to proof their validity for our wing
- Designing a special 3D structure to fulfill the special requirements
It is obvious that both directions for making the variable wing skin need to be tested.
The advantage of the specially designed 3D structure will be that manufacturing via extrusion is much cheaper however the material limitation makes it difficult to be successful.
First, it will be tested what advanced sail making technologies can offers.
It will be necessary to lay-up a special laminate cloth with proper characteristics for the variable wing.
Above: wing surface 1800 x 1700 mm for the boat model.
The upper right spline is controlling vertical ribbons. The left side is mirror copy.
The horizontal ribbons are controlled by the right lower spline. Other sections are just mirrored copies.
Above: wing surface 1800 x 1700 mm for the boat model.
The upper right spline is controlling vertical ribbons. The left side is mirror copy.
The wearing areas due to contact with controlled ribs are sketched as well.
Werft ribbons density (vertical) are controlled by upper spline curve while Warp ribbons density (horizontal) are controlled by spline curve to the right.
It can be observed that the area where the ribs are controlling the shape needs less Warp ribbons than between the control ribs.
The vertical ribbons are less dense in the nose area while most dense close to the mast (spar) area.
Generally, we can say that more dense vertically less dense horizontally.
Above: the technique of drawing lines with controlled density for hand is time-consuming therefore here is used
very simple but effective technique:
- across depicted above section any line shape can be drawn as spline lets call this control spline
- on that control spline, a several W points are distributed by pattern command
- quantity and distance between W points are controlled by the command: example 21 points with 5 mm distance between them
- horizontal lines (warps) are attached to these W points
- when changing the control spline shape the warps line density distribution will change automatically
- Warps get denser if the control spline is more horizontal while more vertical control spline will give the lowest density mostly determinate by the set distance between W points.
This technique looks particularly useful for designing skin surface for Variable Wing as the patterns between the ribs is repetitive vertically and horizontally.
The first attempt to design the lateral ballast according to the ideas from 2015-11-16 results in following:
Above: Conceptual sketch for boat model – 1 driving RC servo (gray), 1 distance measuring sensor (yellow), 3 masses of lead (dark gray), micro switch and control board with attached 2.4 GHz transceiver for communication with boat control electronics.
Note that batteries packs are not mounted as they are not yet chosen. The wheels are 22 mm in diameter.
Above: Small tags are protruding from the side of each track and will be sensed by microswitches located on each ballast unit.
The 0 degrees tags are “lighted” up. It is meant that the ballast basket might be 3D printed (material ULTEM) at Digital Mechanics.
The ballast unit is measuring the distance between the tags with high accuracy (0.1 degrees) by means of a wheel attached to the (yellow box).
At first, the ballast unit runs around the track clockwise and anti-clockwise 360 degrees and record to memory exact position at micro switch switching event. The distance between tags increases by 2 degrees to starboard and to port counted from zero degrees.
This way the ballast units are guaranteed to know exact theirs position, find quickly its position at start up and supervise the micro switches at the some time.
A system with 2 ballast units on same track will help in case one of the units gets own switch broken. Such “broken” system can still work until gets repaired.
Above: Conceptual sketch for boat model:
The ballast basket is providing 3 tracks which incorporate also information for coarse home positioning.
Small tags are protruding from the side of each track and will be sensed by microswitches located on each ballast unit.
3 tracks and 6 ballast units (2 units/ track) each ballast unit weight is 1-2 kg it gives range 6 -12 kg.
The displacement of the boat model is 15-20kg.
NOTE: it is to be understood that the solution for boat model is referencing the ballast units to the center. This is due to the fact that the mechanics get very simple (and the owners are never on the boat). On real boat, however, the ballast units run inside covered ring tracks and will require several wheels to keep the weights in position.
Above depicted proposed ballast solution has following characteristics:
- If one ballast unit gets broken then the other can bring the broken one to inspection window.
Note that the inspection window is not provided on boat model as there is easy access to ballast units anyway.
- Two ballast units run on the same track which gives some redundancy in function.
Suppose one micro switch is out of order then the other unit can “inform” the broken unit about its position.
- Less material for the basket when two ballast units run on the same track.
The load is no problem as it is distributed along the track.
- The ballast units need to move in a pair in order to be able to move the “center” of gravity as needed.
This means that i.e. one is always located forward while the other astern thereforethey do not disturb much each other.
- Due to used high geared servo motors, it will be very difficult to use the gravity for the ballast unit propulsion.
A special type of motors for the direct drive would be required but not find for such small size.
- The high geared RC servo motors are not suitable for generation of electrical energy.
The gears can get destroyed when too much torque applies to output shaft.
A general observation is that at 90 degrees or 270 degrees the ballasts are most effective for affecting trim/pitching/slamming.
The same is that at 0 degrees and 180 degrees the ballasts are most affecting heeling/rolling.
This is one of the beauties of proposed circular lateral ballast system.
Above: the heeling and trimming sensitivity of the lateral ballast system.
By the sensitivity, I do mean that the ballast unit needs to be moved shorter distance in order to change boat center of gravity by the same amount.
As the ballast mass is divided into several ballast units it provides energy effective ballasting as the individual mass used to correct the heeling can be located at the boat center line, therefore, at highest sensitivity. This means that less movement is necessary in order to correct heeling when compared with a mass position at far starboard or port (indicated by red)
This is the additional advantage of having several ballast units instead of one big mass.
There are some differences of LBVW (Lateral Ballast Variable Wing) boat when compared to traditional keel sailboat.
Traditional boat hull needs to be designed in order to cope with the loads from keel and standing rig.
On LBVW boat, the forces act differently – the forces acts between the ring of the ballast system and mast mast-wings-rudders forces.
Above: This is a conceptual sketch – means not necessarily ready to go design. By the green color is depicted where the big forces interaction occurs. Note that the ribs and stringers of the hull are not depicted for clarity of the sketch.
Shortened pipes of the mast are depicted and axes of the center rudder and stern rudder. The ballast units are contained inside the ballast ring.
It is obvious that the hull does not need transfer much load concentrated to a specific region. The hull is rather attached to the ballast ring via ribs structure. Some reinforce traditionally added to cope with heavy keel and standing rig with a lot of tension can be now skipped.
This might save some weight of the hull?
Note also that the fancy angles of the boat on my sketches are chosen for giving the most information possible
and is not necessary sailing position.
One of the problems to be solve is the name of proposed boat type/configuration:
LBVS - Lateral Ballast Variable Sail
LBVW - Lateral Ballast Variable Wing
HBVS - Horizontal Ballast Variable Sail
HBVW - Horizontal Ballast Variable Wing
HCMBVW - Horizontally Circular Moving Ballast Variable Wing
VWBR - Variable Wing Ballast Ring
The problem is that used word Lateral is not very common and not easy to understand without wikipedia:
"Geometric terms of location - Lateral – spanning the width of a body" in our case the boat witdh.
In addition, Wing is maybe better description what it really is as it is not soft sail.
Traditionally Wings are for flying while sails are for sailing however recently yachts use wings as well.
I decide today to slightly modify the name to: Lateral Ballast Variable Wing boat.
A decision was made to build a smaller model LOA=645mm in order to reveal some secrets of proposed LBVW boat bi-plane configuration.
The insights from that might be helpful when building the 1.8m model as it will be more complex.
This smaller model will have a limited functionality and all parts will be built by a 3D printing technique.
Above: 645mm model of LBVW boat. Displacement is approx. 1.5kg.
The seal of the boat deck is missing…..the wings are honeycomb cut out and will be covered with transparent self-adhesive foil.
Above: ribs and stringers
Above: A stern rudder mounting and driving.
The gear ratio is 1:1 and the gear are necessary in order to rotate the rudder +/- 90 degrees.
Note: on a real boat or bigger model the rudder is rotating 360 degrees.
Above: cross-section of midship rudder installation
Above: midship rudder and mast servo motors HS-5087MH.
The gear ratio is 1:1 and the gear are necessary in order to rotate the rudder +/- 90 degrees.
The servo motors for rotation of the wings are visible as well.
Note: on a real boat or bigger model the rudder is rotating 360 degrees.
Above: sealing the mast to deck
Above: the lateral ballast units moved to port. The batteries are NiMH 2400mAh or 4200mAh (23 x 43 mm) (57g or 87g)
Each ballast unit provides 3.6V (3 x 1.2V) and they will be connected in series inside the hull providing 7.2V for the servo motors.
The arms of the ballast units can moves +/- 90 degrees. It is also possible to mount the ballast units for different areas of ballasting.
Note that on the real boat the centre of the boat will be not occupied and the ballast unit will be able to move 360 degrees
around the track.
Above: top view with ballast space covered by honeycomb cut out lock. The wings and top connector are also visible.
Above: sealing the deck with transparent self-adhesive foil is easy.
Above: some of the basic wing settings on LBVW boat – the green arrows indicate the wind direction.
The most interesting setting is broad reaching (6) and (7) as it is fast.
The running is also nice as it is self-correcting the boat to keep the course (8).
The into the wind (1) is self-correcting but there is question if the boat will be standing still on buoy or anchor (not driving)
It is possible to use settings (1) to break the speed of the boat.
It is possible to set the wings to provide turning torque in order to support manoeuvring.
It is possible to perform “pumping” synchronised with the boat rolling in order to increase driving force.
It is possible to roll the boat with the help from the wind and wing angle adjustment in order to move the ballast units for electricity production. (not on this little model)
It is possible to provide boat heeling by setting for higher or lower heeling force in order to provide wanted slope to move the ballast by gravity only to wanted the position.
Some of this can be tested on planned small model with limited functionality.
Above: close-hauled on starboard tack
Above: broad reaching on starboard tack is the fastest course. (except when on trailer)
Above: Running (8) – Note that installed wings are maybe maximum high but not maximum wide yet.
Wing weight: approx.100g
When running, boats often gets excessive rolling. This is when wind and waves have same period as the boat rolling resonans frequency. Note that LBVW boat can damp this excessive dangerous boat movement easily by means of lateral ballast or wing
It is important to find the balance between wing heights to chord ratio and distance between wings.
The idea is to keep the wing rectangular as it is convenient for foil shape control – however this model is not equipped with this functionality due to size.
The wing loading on the real boat will be then controlled by setting foils adequate twist and thickness at the upper part.
One funny thing happens while designing this functionally limited model - the rudders asked to be tested as propulsion means. After a while, I gave up as it is a too tempting idea.
Water based living creatures use plenty of different methods to provide propulsion.
For us, 2 methods are of interest:
The first method is when the hydrodynamical lift is causing propulsive force.
One can imagine that the boat hull is moving from side to side when rolling on waves.
If we add to that rolling an oscillative rotation of the midship rudder via servo motor, properly synchronized with the rolling movement then we can obtain driving force. The top speed will be not high as the transversal speed of the rudder need to be higher than the boat speed.
The second method is when the pure oscillatory movement provides propulsion.
This happens when the rudder is oscillating by driving it via servo motor i.e. +/- 30 degrees.
In addition, it is to understand that the 2 rudders configuration in line provides the nice possibility to keep the hull on course by prohibiting zigzag.
The idea is to design the rudder/centerboard fins partly rigid partly flexible - just to mimic fish fins or swim fins.
The ShapeWays company has introduced a flexible material for 3D printing.
It is very complex matter to do the design right but the first attempt might look like these depicted below:
Above: The mid-ship rudder/centerboard build of two different materials – the rigid part (grey) and the flexible part (transparent)
It is to observe that the rudders are not heavy and are able to rotate 360 degrees.
This makes the fish fin like propulsion very interesting as trust can be provided in any direction relative to the boat hull.
As the mid-ship rudder/centerboard has bigger surface than the stern rudder it might provide useful propulsion force.
The idea is that the flexible part have to be stiff enough to act as rudder/centerboard fin during sailing while when moving quickly to sides it will bend properly.
This is really a very experimental and it is not expected to have a lot of driving force from rolling action of the boat.
The reason for that is that the traversal speed of the fin needs to be higher than boat speed in order to provide lift.
On the other hand, the oscillative method is not very effective.
Still, some propulsive action is expected especially during manoeuvring in the harbour.
Another idea will be to provide side motion of the rudders in order to provide more effective servo motor drive propulsion.
The side motion in combination with rudder rotational oscillations can mimic fish propulsion.
This technique might provide a higher speed of the boat when compared to rolling utilisation.
This is, however, may be a not robust solution and will probably remain unused in reality but tested here. KISS is to be applied.
Some work in progression: (2016-07-24)
Above: The midship rudder/centreboard is build of flexible material – carbon pipe as an insert in order to stiff up the driving part.
This technique of propulsion is used by sharks and they are using waving in order to provide proper attack angle on the foil when moving.
It is looking strange when attached to the hull but might be very effective. Note that the mid part between fin and pipe is flexing and mimic the tail part of the shark body. It looks difficult to design it successfully mechanically.
There might be different solutions to utilise this more advanced movement of the rudder foil when compared to pure oscillatory movement.
Above:The rudder/centreboard is build of flexible material – carbon pipe as an insert in order to stiff up the driving part.
It is looking better when attached to boat hull when compared to shark fin style and is mechanically more stable. As it is not planned for high speed it seems to be not necessary too much optimise it for drag. Still, the high efficiency is good to have when thinking about the batteries.
Above: Both rudders are flapping type but that is not a rule.
Note that there is not yet designed how long the midsections are and what flexibility is needed in order to provide efficient driving.
As the rudders are 360 degrees it will be possible to use them for advanced manoeuvring.
When the boat is rolling on the waves then it will be possible to use that motion for propulsion by adjusting the foils effectively.
The advantage of such configuration and design is that it is not very vulnerable to dirt.
Still, the difference to the standard rudder is that flapping rudder needed to be properly flexible.
A design choosen for manufacturing and testing is depicted below:
Above: By the blue colour is mark the flexible part of the flapping rudders
Note that the flapping rudders are (on the picture above) not mounted correct as the rudder holes are placed for standard rudders. (the hull is already manufactured)
However, this can be enough good for testing of the propulsive function.
It is obvious that the drag of such arrangement is higher that rudder fin only so the question is if the benefit of simple propulsive function make it valuable anyway. Still it is lot to be find out about the "flapping"......
When the foil is bending it provides a camber which is increasing the lift force of the foil....?
The first part is now just an elipse but may be designed to improve the flow around the main foil...?
A general observation:
A future sailboat needs to be fast, easy to use and safe.
In general, the safety is defined by redundancy and low probability for catastrophic failure.
Solved with LBVW boat design:
- “Sails” adjustment with high precision and very fast
- Fast sails reefing (50% off under 1 minute)
- Fast de-powering ( 0% camber and 0 degrees attack angle within seconds)
- Redundant mast (2 masts)
- Redundant ballast ( 4 – 12 autonomous, internal ballast units)
- Redundant steering ( 1 rudder + 1 centreboard/rudder)
- Redundant motoring (flapping with rudders + propeller)
- Using the wind, sun and waves energies for driving the boat and onboard energy maintenance
The catastrophic failures are in most cases when the boat lose the keel, rudder, mast or buoyancy.
Therefore making these parts redundant improves the safety of a sailboat a lot.
In addition less heeling of the boat implay that the deck is more safe for sailors.
Other catastrophic disasters are when the sailors get hurt by the gears.
The lines are a big problem and on some badly organised boats it looks terrible – sometimes less is more.
The winches are the second issue as fingers and hands get jammed already.
The main boom and spinnaker boom are dangerous devices as well.
This is what I like to point out – all mentioned above issues are addressed on LBVW boat.
Above: Conceptual sketch of full-size rotating rib unit (chord 2m) Spherical Roller Bearings are maybe of DELRIN.
Hyper servo is as described before. (the fixing of servos is missing but all are attached to rib rotating hub).
On the model the axis of the servos are used directely as it makes it simple and weight efficient.
Here, for higher loads the rib servos are additionally geared 2:1 while the mast servo is 3:1.
The "Sea Hawk" is taking my time now - will be back to design work after sailing season.....2016
As the weather gets bad.... som work has been done on the actuator/motor/generator.
As the generator, efficiency is main concern this specialized machine is designed carefully with minimum
losses in mind.
The revised block (black?) diagram of the Ballast Unit power electronics is proposed.
Above: Block diagram of power conversion technique. Note that it is based on a known PFC technology.
PFC stands for Power Factor Correction and is usually a step-up converter.
In our case, there is Buck-Boost (step-down/step-up) converter as I want to wire the generator for higher
voltage than the system voltage. This will make the generator be active already by low rev/s and results in lower resistive losses due to lower current for same power as well. (resistive losses Pr= current * current * resistance)
Possibly this machine and its electronics will be also excellent as a propeller-driven generator on WSW boat.
Note that this technique is promising for wind or water power generation as well.
Note also that not only the power conversion is important as following characteristics are required from the machine:
- direct drive (no gears except for driving wheel)
- very high torque (10x nominal torque for a short time)
- high dB/dt of magnetic field intensity
- active windings wire length to necessary windings wire length ratio
- low torque pulsation
- flat motor design
The very prototype machine will have 140mm diameter.
It will be 2-phase machine. The phases get seperate power electronics as depicted above.
The windings are based on SEMA windings concept. Two main ideas how to wind the machine will be investigate:
Above: to left separate colis - to right continuous coils (no interconnections, however some questions arised)
As expected, the machine will be integreated with the Ballast Unit car (for the model as it is small) and 3D printed.
Above: the motor stator is build of 4 3D printed parts and is an integral part of the Ballast Unit car
Note that the car depicted here is not including other functionality for clarity only.
One difficulty is the manufacturing of the SEMA style windings and for that, a winding tool is on the way to be manufactured.
Above: 3D printed windings tool for single coils. There is no wire crossing in the coil.
The bars are necessary to push the wire down while winding in order to keep it on the spot.
The knitting technique is also visible.....
Note: the 3D printed hull of 645mm LOA model got delivered from Shapeways 2016-07-14.
There is a Spin-Offs of the variable wing proposed for sailing boats and it relates also to aircraft.
The wing itself is described in separate documents or some information is mensioned somwere above .
A simple investigation was conducted in order to reveal what impact it can have on aeroplanes
As the proposed wing can adjust attack angle, camber and thickness in seconds it opens for some
improvements of aeroplane ability.
Following was observed:
1. Very short runway is possible at take-off due to safe flight at the ground proximity
The aeroplane body is horizontal to the ground during take-off so the tail is not scratching.
As the wings can adjust the lift (both up and down force) it is safe to be close to the ground.
Above: Note the thick foil and high attack angle while the plane is horizontal
2. This plane will cope with turbulent weather in an excellent manner both in air when cruising and during landing or take-off due to its ability to correct the lift (both up and down force) without changing body position.
Above: Note the different attack angle and camber on the left and right wing.
Note also that attack angle and camber can be changed simultaneously in sub-second time
3. The stall is going to be recovered very easily and much faster that with traditional wings.
Still, some altitude is necessary….
Above: The question is if this is a real scenario….maybe stall or spin with this type
of wings is not an issue at all.
It is also possible when we need to deal with very limited space to approach landing
so the aeroplane can kind of fall down as depicted above and shorten the way it need
to approach landing?
4. Fuel economy is expected to be high as the wing is homogenous and by that, I do mean
the drag is very low – no separate flaps and not necessary to have wing tips as the wing ends can be set to a minimum thickness and zero attack angle or little reverse in order to get rid on drag vertex.
Note that during flight at high speed, not whole wing area is necessary.
Above: As example - the wing at its root is 6% tip 3% thick
while the attack is at root 6 degrees while at the tip is 0 degrees
The camber is inverted at tip (?)
5. Visibility from cockpit during touch-down is improved as the aeroplane body is horizontal
Above: Good visibility provided. Note the wing lift force is directed down after hitting the ground…
6. After touch-down, the wings are used to break down the speed therefore very short runway is possible.
Above: Note that it will be possible to break down the speed by turning the wings.
7. Breaking down the speed dramatically will be possible also in the air
Above: Note that the wings are rotated with positive camber instead with negative camber
as depicted during landing.
8. Turning fast – hope the wings are still there…..
Above: This functionality is maybe good for UAV?
9. Rolling is always fun…and can be done in two ways: twisting the wings in opposite direction or inverting the camber
Above: Rolling when inverting the camber. The attack angle needs to be correct.
Wow… is it wind power station? This is functionality is maybe good for UAV?
Above: Rolling when twisting the ends of the wings.
This technique is used to correct the aeroplane position during cruising. Like the birds
10. One of the benefits of having kind of flexible wings is that de-icing can be done just by
changing the shape of the wing. The ice skin will break into pieces and fall down…?
11. As the aeroplane body is in most cases in horizontal position (in respect to gravity?)
so the coffee is not at risk….
However, the UAV might lift up instantly by just changing the attack angle.
To be continued......