Crossbow fl

Discussion in 'Sailboats' started by Doug Lord, Jun 21, 2012.

  1. Doug Lord
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    Doug Lord Flight Ready

    Crossbow fl / XPRO

    Sal, I'm considering using the hull discussed above as a platform for the trapeze ballast system-if I do that it would be done sometime in 2014. Otherwise, to do the Crossbow fl would be a couple of years for financial reasons. Both the manual and electrical versions will be tested at some point.
    What's your opinion of the concept?
  2. Baltic Bandit

    Baltic Bandit Previous Member

    Doug - you know that since you have an existing hull to work with, you could spend about $500 on some linear actuatators and $200 on a PLC (or an andruino controller) and for under $1000 (leaves about $300 for parts and materials) prove this out on your dinghy hull.

    Shouldn't take more than 2-3 weekends to get built. After all the prototype doesn't need to be sealed, you can simply use open foam duct taped in place. So all you really have to build is the rail system. and even if that's overweight because you use cheap aluminum pipe (heck you might be able to use thick wall PVC pipe) you can still prove out the concept well enough that you could run a Kickstarter campaign to fund it.
  3. Baltic Bandit

    Baltic Bandit Previous Member

    Here's a LA for $54

    Here's software that will turn an Arduino into a PLC

    And the Arduino Uno is going to cost you bout $50

    So for $100 you can have the controller. And a USB controller will cost you about $20 - and you can stick a commercial gaming USB Joystick on it for $20 joystick&sprefix=usb joystick,aps,297

    So I was wrong, that's about $150 for the controllers and actutators.

    Another $100 gets you the Pipe for the rack

    So that costs you $250 to get you to something that can prove your TrapWing at full scale.
  4. Doug Lord
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    Doug Lord Flight Ready

    Crossbow fl / XPRO

    I'd be interested to know how a linear actuator with a 6" stroke would be capable of the movement highlighted below.
    Thanks for the effort.....

  5. Baltic Bandit

    Baltic Bandit Previous Member

    Block and tackle gearing ratio Doug. or you can just use a large bell crank for the model. The horsepower is the horsepower Now if you want a pure motor control you can do that too direct control servo motors are a bit more price $300 for thiss 400W one and since your proprietary spreadsheet has the power requirements at below 400w. It should do fine for you.

    So that adds about $150 to the cost so instead of $250 in parts its $400 in parts.

    and if you show that it works on video, you can easily put together a kickstarter for the $20k to build the hull tooling the $20k for the "trapwing" mold and the $30k or so for fitting out a production floor for the mechanical assembly part. (total $70k) - and since you are sure there's a market for this, selling them at say $10k/pop you can easily sell the first production run right?
  6. salglesser
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    salglesser Junior Member

    Hi Doug,

    A bit slow getting to you. Apologies. I think the concept is fascinating. I don't doubt that it can be done. Making it work is going to be, in my opinion, going to require some persistence. Looking forward to hearing about your progress.

  7. Doug Lord
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    Doug Lord Flight Ready

    Thanks Sal! It sure will require persistance-and lots of work. But I think it will be worth it-theres just so much potential for developing an exciting new way to sail. I hope I can pull it together.....
  8. Doug Lord
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    Doug Lord Flight Ready

    I've discovered a way that will probably do this with a system that rotates rather than having the crew slide. The idea is to be able to sit comfortably with the tiller in my aft hand and go side to side easily. This idea uses a round track/platform that rotates easily so that the crew can pull themselves around with minimum exertion OR the system can be electrically powered. The system can be rotated to move crew weight fore and aft as well. The Skud 18 uses an electro-hydraulic system to tilt the crew seat and since we are using an electrical system to move the wing/ballast thats probably the best solution. Problems include when the crew is stuck on the lee side but I believe that can be worked out. By rotating the whole assembly, room is much greater than it would be with symmetrical seating shown in picture 2 below and described above. And it is far more comfortable than the original inline, tilting seat, but it is higher vertically which is ok. Mock-up of seat is last picture-very comfortable....
    Click for better view-

    Attached Files:

  9. Doug Lord
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    Doug Lord Flight Ready

    This is a detailed summary of the boat and its systems-most of it posted once before. When I'm finished the MPX/SRT model this boat will again become priority #1. I may have to try one of the "crowd sourcing" fund raising groups but I'm going to go for it. I believe that this technology can open up a whole new world of singlehanded performance monohull sailing to people who might otherwise never get to experience a planing reach with an asy flying! There is nothing like it anywhere and it would pioneer a whole new way to sail a fast monohull dinghy.

    Crossbow fl

    Part 1--The key to this boat is the wing. The wing is sealed and allows ballast to slide side to side as the wing slides. The cg of the ballast(80lb) moves nominally 13' (slightly less in practice-about 12.5' in 3 seconds/ 4.17 feet per second/2.84mph) from the center line of the boat. Same weight movement as if the wing was 24' long! Trapeze wires support the wing and a carbon "apparatus" holds the wing at the center of the boat. This apparatus allows the wing to pivot around a vertical axis, and a fore an aft axis parallel to the centerline. Weight is adjustable in 9lb increments. Everything is adjustable including the speed of wing+ballast movement. The system will be electric with battery capacity enough for rapid and frequent movement of the ballast + wing over two 8 hour days w/o recharging. Capacity can be increased in special cases. Movement is controlled precisely by the crew using a joystick.
    Part 2- Another key to the boat is the buoyancy of the sealed wing and its wing tips which far exceeds the buoyancy required to float the ballast. That means the wing can be used to create righting moment( due to its buoyancy and not the ballast) in a knock down, righting the boat.
    Part 3- The prototype will test DSS foils which have worked very well -especially in the Quant 28 Sportboat(unparalleled race record) and in the Infinity 36. The foils will be used in an entirely new way -they will plug in rather than operate from a trunk in the boat. The other applications of DSS work in a trunk that allows the board to retract or partially retract. The new Quant 30 uses unique curved DSS foils that can be independently retracted and/or deployed. The Crossbow system allows the foils to be inserted and locked in individual trunks. The boat is designed to facillitate this by sailing at a 10 degree angle of heel keeping the windward foil clear of the water and reducing hull wetted surface. These foils appear to offer modest RM upwind and nothing short of tremendous RM off the wind. In a boat like this, where the crew weight has little to no effect on RM*, the combination of DSS foils and the Trapeze Wing movable ballast system, offer lots of power to carry sail and planing performance with an extremely wide crew weight range. For DSS to be most effective, the hull must be designed specifically for it to allow the foils to be in the proper position when exiting the hull. The foils must be at least 1 chord below the surface at a 10 degree angle of heel.
    *Depending on the viability of the crew rotation system(see previous post).
    Part 4- One of the most important phases of the development of this concept and the refining of the Crossbow fl prototype design is complete-model testing. For over 10 years the concept of the Trapeze Power Ballast System has been extensively tested on numerous RC models as well as a few non-RC models. The results are conclusive: the system works and a prototype has an excellent chance of success.
    In different places in this forum an ongoing, uninformed minority lash out at model testing which is too bad. Julian Bethwaite, among many other's, has remarked that model testing saves time and money. Alain Thebault(Hydroptere), Dr. Sam Bradfield(Skat, Rave , Osprey and more), Greg Ketterman(Hobie Trifoiler and Longshot), Bill Burns(CBTFco), Hugh Welbourn(Dynamic Stability Systems), Yves Parlier(Mediatis Region Aquitaine ),Bernard Smith(40 knot sailboat), Paul Larsen(Sail Rocket) and many others have used RC model testing to test basic concepts and refine the design prior to building a full size prototype. It is one of the best ways to test-particularly so in regard to the Trapwing System.
    Testing the movable ballast system is one of the areas of RC model testing where the results can be 100% trusted and where the potential of the Trapeze Power Ballast System has been thoroughly tested. One difference in the model testing of the system is that the skipper has to have faster reactions than are required on the full size boat, since, as the system is scaled up reaction of the boat and the ballast take longer to happen. That means that the skipper of the RC boat has to have quicker reactions and more "anticipation" than the full size sailor on Crossbow-and also means that sailing a Trapeze Power Ballast System model is excellent preparation for sailing the full size boat.
    Part 5-The Development Team: (from post #1)

    - I retained the services of Eric Sponberg to help spot glaring errors and to help with engineering.
    - I retained Rick Loheed to build the DSS "plug-in" foils.
    - I'll use Falcon Marine, LLC to "carbonate" the hull and to provide a portion of an A Class Catamaran mast for the Crossbow(laid up for this boat out of his brand new mold). Matt McDonald does some of the finest work I've ever seen on the cats he builds.
    - I've retained Sharon Dixon of Rockledge Architectural to actually carve the hull of this boat from a couple of solid blocks of styrofoam. The "boxiness" of the shape reflects her capabilities-no compound curves-etc. Using this method and having Matt carbonate it saves above $1500 over having the boat built out of wood. UPDATE: Wood may play a greater role than originally intended but Sharons styro capabilities will still be vital for the large rub rail.
    - I've received a great deal of help from Hugh Welbourn in deciding on the foil section , placement of the foil , angle of incidence and other matters relevant to designing for a DSS system. This boat will use "plug-in" DSS foils that will be installed on the beach(or not) depending on conditions. Testing will be facillitated by simply leaving one foil off.
    - I'll use Rick Willoughby for design of the electrical system. Between Eric, myself and Rick we will choose a supplier in the states for the parts required for a first class, reliable Power Ballast System.


    Summary of features and specs
    1) Self-bailing cockpit
    2) Boat rightable from 90+ degree knockdown by crew w/o crew movement using the wing regardless of the position of the sliding ballast.
    a. ballast wing is sealed and has buoyancy much greater than that required to float the ballast sliding inside.
    b. ballast+ wing can be moved manually or electrically faster than a crew on a trapeze could move.
    3) Rig utilizes modified rotating, A Class wing mast, sealed with masthead buoyancy to prevent turtling,
    4) Ballast wing pivots:
    a. to allow trailering
    b. to move ballast aft when required with wing extension.
    c. also pivots athwartship to keep weight low to windward and to keep lee side of wing clear of water.
    5) Ballast is adjustable in 10lb increments,
    6) Boat can be sailed off a beach,
    7) Boat features an asymetrical spinnaker, an underdeck spinnaker chute and retractable bow pole,
    8) Skipper sits in a sliding seat that can also tilt 10 degrees each side so the the skipper sits upright at the designed angle of heel of 10 degrees. Seat can be fixed in center so it won't tilt while still retaining the capability of sliding fore and aft.( see illustration below)
    9) Large, buoyant "spray rails" act to help provide a dry ride and knockdown recovery,
    10) Self-tending jib with variation of Swift solo single sheet system.
    11) Boat uses removable, "plug-in" DSS foils for greatly increased power to carry sail with speed.
    12) Boat can be "turboed" to be capable of upwind planing with addition of a maximum of 62lb ballast and a 150 sq.ft. rig.
    13) Boat has extremely wide crew weight range: approx 100lb to 250lb for normal sailing. All ratios are based on 250lb crew and would drastically improve with lighter crew weight. For class racing, it would be my desire to see a class adopt the maximum crew weight as standard with lighter crew carrying weight under the seat-or perhaps two "weight classes"-whatever it takes to encourage the widest participation.
    Specifications: (changes are to be expected)
    Beam- 4.75'
    ---at waterline-3.75'
    Sail Area-(boat will use a carbon A Class wing mast from Matt McDonald/ Falcon Marine LLC, laid up specifically for this boat).
    --upwind- 120 sq.ft.
    -- downwind- 240 sq.ft.
    Weight-sailing weight w/o crew- 223lb which includes:
    --hull, rig, foils-124lb
    --Trapwing Ballast System:
    ---wing-21lb. @ 12'-16' length overall, pivots for transport, and moving weight aft.
    --- max ballast 78lb(8 pieces of lead-removable-.25" X 8" X 12"-about 9.72lb each)
    Max Crew weight: 250lb-boat is designed as a singlehander(crew weight range is exceptionally wide on this type of boat since the crew contributes very little to righting moment-depending on whether or not the crew rotation system mentioned in the previous post is used.)
    All up sailing weight including crew-473lb
    DSS Foils: each 1.63 sq.ft.( 6" X 39") 6.5/1 aspect ratio, Welbourn section.
    Electrical System for moving ballast: Engineered by Rick Willoughby, who did the original "ballast mover" spread sheet.
    see Eric Sponbergs Design Ratio's PDF below
    --downwind- 63.3
    SCP/Total weight= .2
    Note 1: a ratio of at least .3 is required for upwind planing and could be achieved on this boat by adding 62 lb. to the ballast tray in the wing. Nice "turbo" idea for sometime as long as the buoyancy of the wing is enough for righting.
    Note 2: an interesting side note to the application of Bethwaites ratio to this boat is that it is not clear to me that proper "credit" is given to the lift potential of the DSS foils. For the upwind RM calculation the lift from the foil was calculated based on a speed of slightly over 5 knots. If the upwind speed were, say, 8 knots the ratio would increase to .27+. A speed of 10 knots with the 250lb crew changes the ratio to .295 and with a 180lb crew that ratio changes to .35.
    That adds a very interesting twist to testing in that it appears that reaching off a bit to increase speed may pay much larger than normal benefits on this boat. Speed increases the lift on the DSS foil expoentially and therefore increases RM dramatically. Sounds like fun to me.....


    Attached Files:

  10. Baltic Bandit

    Baltic Bandit Previous Member

    From an engineering perspective this is a nightmare. DSS+TrapWing+a brand new hull. Its as if Boeing went from the 737 to the 787 with the change to Carbon, fly By Wire and large Body long haul - all without first having had experience with the 747 wide body, the 757 fly by wire and the 767 use of composites.

    Just horrific engineering practice. DSS has been proven on hulls, it doesn't need reproving but it does complicate the dynamics calcs and tuning - shouldn't be on any first draft - and frankly Crowdsourcing largely attracts engineers and they will see this mélange as highly problematid

    There also is no need for a new hull. Its perfectly easy and cheap to find an old Laser II or similar high performance dinghy hull (Taser, etc) and simply put a Trapwing on that and see if the concept works. the advantage of that is that you have a known platform. Besides the engineering complexity advantages - this has the added benefit of being dirt cheap. Under $2,000 to prove out the prototype (or have it fail)

    Nor is this anything all that unique. The old sandbaggers in LIS from the 1890s had a skipper driving the boat, and "remote control" weight shifting. true not via joystick and a bit slower but it nevertheless was the same basic idea: lazy skipper rides in the middle and something/one else moves the ballast.

    Now as to the electrics. this is where I think Doug basically does not understand how fast reacting servo-mechanisms work - particularly ones that are sized to be optimal for the work load. See the weight doesn't just "stay put" once the motor moves it to the correct position. The weight has to be held there by something

    That something can be mechanical -but that adds a lot of complexity and also slows the responsiveness - or it has to be the motor itself holding the thing there. And that means that the motor is in essence constantly running. and worse yet - because in "holding position" the motor is largely salled, it is actually drawing a fair amount of current. So from a safety perspective, the power draw has to be based on the trapwing running full tilt all the time. I suspect it isn't because that means a huge amount of electricity being used.

    Now additionally we have the issue of "worst case scenario". Worst case scenario is essentially a captsize of some sort that has the Trapwing on the wrong side and the stop being fast enough that the passenger is thrown and lands on the trapwing or worse, under the trapwing.

    If the driver then operates the trapwing to right the boat, the body of the passenger gets mashed by the high velocity movement (this thing needs to move "stop to stop" in roughly 3 seconds - which is 10 fps - non-trivial particularly if your hand is jammed in the mechanism.

    And Doug can nay say all these issues as much as he would like - but they need to be addressed. and just making fun of the folks who raise them is not addressing the issues.
  11. Doug Lord
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    Doug Lord Flight Ready

    This is a response to the above comment posted in a different thread:
    Crossbow fl(the fl in honor of my brother) most certainly is the smallest DSS design that I know of.
    It is not, in any way shape or form a multihull.
    There are differences and similarities between my design and other DSS boats:
    1) Crossbow fl is the smallest DSS design that I am aware of,
    2) Crossbow fl ,like other DSS boats(Quant 28 &30, Brace Brace Brace(25'), Infinity 36) uses movable ballast. However, it is in the form of the Trapeze Power Ballast System(Trapwing),rather than a movable crew(even though crew may be able to move a small amount),
    3) Crossbow fl does not require keel ballast for self-righting as do other DSS boats: the Trapeze Power Ballast System allows the boat to be righted by the crew(with no crew body movement)-an advantage of it's size and the buoyant wing that is the key element of the Trapeze Power Ballast System.(Ballast is sealed inside the wing and both the wing and the ballast move. The buoyancy of the wing is substantially greater than that required to float the ballast and wing. The outboard ends of the wing are supported by Trapeze wires.)
    Skyak, these pictures illustrate how the Trapeze Power Ballast System works and that the system bears no resemblance to how a multihull functions--it is the same on Crossbow fl as on this boat-and would be the same on my version of the Skimmer(see post #7,Cox's Bay Skimmer thread). The wing is not designed to be immersed except incidently and momentarily as a result of wave action, heavy gusts etc. The RM derived from it's use in moving ballast quickly provides the power to enhance the function of DSS on such a small boat. The buoyancy pods work very similarly to the way the buoyancy pods work on the Moth(see picture 3 below) :

    Pictures,L to R- 1&2- shows the Trapeze Power Ballast System supported by trapeze wires from the mast at full extention to port, 3-A side note: the buoyancy pods on the end of the Crossbow fl wing (see wing pictures in my previous post 144)have exactly the same buoyancy as in the Moth buoyancy pods-1 cu'(64lbs in saltwater)-and are basically used for exactly the same purpose. Those "buoyancy pods" on the Moth do not cause the boat to be classified as a multihull by anybody.

    click for best view--

    Attached Files:

  12. Doug Lord
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    Doug Lord Flight Ready

    Here are some of the models used to test the Trapeze Power Ballast System over a 10 year period. The skill level to handle an RC boat with this system actually requires more coordination, faster reflexes and greater anticipation than operating the full size system because the model system is so fast-about 1.5 seconds side to side(about twice as fast as the full size version). That makes the model a great trainer for the fullsize system.

    Pictures,L to R=1-3--,36" Super Scow, 3-6-- Melges 24 RC, 7-8-- microMoth, 9-- D4Z F48 catamaran:

    Attached Files:

  13. Skyak
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    Skyak Senior Member

    Doug, the cross beam makes it look like a multihull. The fact that you are using it to support ballast weight in lulls rather than flotation in gusts is as they say 'too smart by half'. The beam also interferes with your identifying it as DSS. What you have is two righting concepts on a model and not enough time or money to develop them both. My advice based on where you are at now would be to put the cross beam aside, and get your boat built as a small DSS craft. The beam is nowhere near ready and it is unlikely that you will ever make it work on the model. The traps on the model change length in the tack and it also appears that the beam is changing angle relative to the hull. Which is it, linear or rotating? The DSS is ready and waiting. All you need is a little lead bulb and you have the design ready to build that is what you claim -the smallest DSS boat.
  14. Doug Lord
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    Doug Lord Flight Ready


    In the previous post to this one I posted pictures of a number of RC models that used the Trapeze Power Ballast System successfully over a long period of time.
    All DSS boats 36' and under need movable ballast-using DSS on this boat without it would be a recipe for failure.

  15. Baltic Bandit

    Baltic Bandit Previous Member

    Einstein once is supposed to have said "Make it as simple as possible, but no simpler. This is a good engineering principle to live by, particularly when doing groundbreaking work. A great example of this comes from the last America's Cup. Prada started with high dihedral foils and iteratively moved to more open ones as they learned to control flight better and better.

    Artemis, because of its crash, was forced to start with more open foils and gamble that they would learn faster... they didn't and were quickly eliminated by Prada.

    Doug - if you are seeking to design a high performance skiff with a robotic trapeze crew , you are best off sorting out that system and figuring out is dynamic resonances as well as stability points before adding another source of balance perturbation. DSS is a source of balance perturbation with yet a differ oscillatory resonance mode.

    Put it another way, your approach here is akin to trying to tune two strings of different pitch at once. It is bad design and bad engineering practice.

    I strongly recommend you reconsider that idea

    As for RC models "using the trapwing successfully" - you seem to keep ignoring that materials stiffnes coeff. and acceleration coeff of mass are not linearly scaleable. Acelleration is a Square function and stiffness is also a square function. Thus what works well at 1/4 scale, needs to work 16x as well so as to be able to have a chance at scaling to full size
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