Crossbow fl

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

  1. Doug Lord
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    Doug Lord Flight Ready

    "motorbike", if you'd like to try again and post detailed questions or comments I'd be willing to answer them in detail to try to help you understand the concept and boat more clearly.
     
  2. motorbike
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    motorbike Senior Member

    Doug, what problem are you trying to solve? If its high performance sailing for the disabled, then a cat is more stable and faster than a mono with a very complicated and expensive movable ballast system. As noted by other posters, you need to prove the concept rather than get carried away with reverse curve bows, carbon and squaretops. You are also asking your system to be 100% reliable, which is not possible in my view. What happens when your boat is a mile offshore in building weather and the system fails? As far as I can see the crew are in serious danger.

    For an able bodied crew the system is not necessary or desirable and for the disabled its a deathtrap(wing) unless its sailed on a pond in waist high water which takes us back to the original concept and the repeated comments about scalability.
     
  3. Doug Lord
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    Doug Lord Flight Ready

    ----------------------
    The Crossbow fl will be a very fast, high performance self-righting dinghy. A cat can and will capsize which seems kinda of a stretch to say it is safe for disabled people to sail alone! The Crossbow fl is designed to be able to be sailed singlehanded by physically restricted and many disabled people.
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    Not sure you are aware of the state of the art in disabled sailing but electronics are frequently used for sheets and steering and Bethwaites Skud 18 uses an electro hydraulic system to tilt the crew's seat to weather, increasing RM. Modern electronics and/or electro hydraulics can be very reliable like the systems offered for the Martin 16, the Skud and other boats.
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    The basic concept has been 100% proven in model testing over a ten year period-now it's time for a full size prototype. You try to discount model testing with some vague reference to "scalability". The model systems work just like the full size(except for buoyancy) and are controlled in exactly the same way-so much so that sailing an RC model with a Trapeze Power Ballast System will be excellent training for sailing the full size boat. To get the most out of model testing you have to know what can be scaled up and what can't be-thats something I'm pretty aware of as are the people involved with this project.
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    The full size system is actually pretty simple and will have a very high degree of reliability for the electrical version of the system, but should it ever fail the boat still wouldn't be able to capsize and depending on physical restrictions the crew may be able to move the system manually since there is very little load involved with the boat within 20 degrees of being upright(which is the maximum angle of heel with the whole wing + ballast on one side). The likelyhood of a failure is extremely remote but can be dealt with with the proper training on the boat. This boat should be able to be sailed by people with many levels of disability, but not every disability will allow one to singlehand this boat. And who can/should be qualified to sail the boat single handed will be the subject of extensive testing.
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    For people that simply want to sail a fast planing monohull w/o the usual athleticism, this boat will be the answer to a prayer since there is nothing like it anywhere. And learning to sail the boat will be extremely easy as the boat is designed to be quite forgiving and can be sailed with the full rig, reefed and with or without the asy spin. The thrill of being on a planing reach with finger tip control of the stability as well as the power, is something only those that have sailed the rc versions can really imagine but it will become a reality with this boat.
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    Design for safety is the priority with this boat as is design for performance. Even with the ballast on the maximum extention of the wing the thing won't capsize. And in a knockdown starting with the wing+ ballast max to windward the boat would automatically right itself due to the movement of the wing caused by gravity acting on the ballast inside it. And the crew can and will help by just moving the joystick a small amount.
    ---
    The reason for doing the full size prototype is to test the boat and its design and prove beyond a shadow of a doubt what the boat can do. We are convinced that this boat has the potential to be one of the most exciting new ways to sail that has been developed in a long ,long time. And rather than being aimed at the young 20 somethings, the Crossbow fl is aimed at 45+ experienced sailors with some disabilities and/or physical restrictions that haven't lost the need for speed and ,particularly, the need to plane off the wind with an asy spin. Of course , the boat will be able to be sailed by people as light as 100lbs and they will have the same power to carry sail as a 250lb crew(explained in the thread). It can be done, and hopefully, will be done, using the
    most modern technology and engineering available. It's a brand new implementation of a very old concept(see Herreshoff on-deck movable ballast-post 117) and has a lot to offer almost everybody.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Here are the updated Crossbow fl specs:

    Specifications: (changes are to be expected)

    Hull length-15.6'
    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- 161 sq.ft.
    -- downwind- 290 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.
    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.
     

    Attached Files:

  5. sharpii2
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    sharpii2 Senior Member

    Have you considered putting ailerons on your wing deck.

    Sailing upwind may produce enough aerodynamic lift to offset the ballast, or at least a good portion of it.
     
  6. Doug Lord
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    Doug Lord Flight Ready

    ---------------
    Hi sharpii2, I don't get it-why would you want to offset the ballast upwind?
     
  7. sharpii2
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    sharpii2 Senior Member

    I'm not saying that. I should have used the word "mitigate" in place of "offset".

    The take off speed of my dad's "Avid Flyer" is supposed to be around 25 kts.

    The ailerons would be to create negative lift.
     
  8. Doug Lord
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    Doug Lord Flight Ready

    =========================
    I know the guys with CBTF came up with a canting keel with a flap on it to add to the effect of the ballast in the bulb but I don't think the Crossbow fl would be fast enough upwind for a flap/aileron to create much downforce. I haven't actually looked into that though.
     
  9. Doug Lord
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    Doug Lord Flight Ready

    Well, I'm finally reaching the end of the building portion of the MPX model project and testing will begin relatively soon. As soon as it does I will begin to get this project going again. I don't have the money to do it by myself but I have some interested people that may fund the project partially or completely. At any rate, I will go for it any way I can. I believe in the Trapeze Power Ballast System technology and I think the application of DSS to a boat this size may produce tangible benefits. I want to sail one of these boats on a regular basis from now on showing how well these systems can work and letting as many people as possible see and try out the boat. It's going to be tough working this out but there is too much potential benefit for too many people for me not to give this my maximum effort.
    ---
    A lot of experimental work has already gone into developing the Trapeze Power Ballast System and learning how to sail with it on RC models. The models are more of a challenge to learn to sail with this system than learning the actual boat will be. And it will be a remarkable way to sail a fullsize boat-a whole lot of fun without a whole lot of hassle! It will open up sailing a performance planing monohull to many more people than have access now.
    ---
    While we're at this stage I encourage anyone with constructive ideas of how to make the boat or Trapeze Power Ballast System work better to come forward now with your ideas-please. And ideas on how to take this project to the point of having a fully functional fullsize prototype are most welcome.
     
  10. Navygate

    Navygate Previous Member

    Hmmmmm...
     
  11. Doug Lord
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    Doug Lord Flight Ready

    If anybody would like to put in more than Navygates' "Hmmmmm" I'd sure like to hear it. I can answer questions or talk more about the technology going into this project. Never can tell: you may have an idea I haven't considered or have and prematurely rejected. I hope I'm getting close to spending most of my time getting a proto built-if you have any suggestions or ideas let's hear them.....
     
  12. Doug Lord
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    Doug Lord Flight Ready

    This video illustrates better than anything I've yet seen the astounding level of machine control technology available now. The technology could be applied to the Crossbow fl system to make the movable ballast system 100% self-tending for some applications where the skipper wants that capability.
    Regardless of what you think of the Crossbow fl, I think you will recognize the incredible potential of this technology. Believe me: you should watch the whole video!
    https://www.youtube.com/watch?v=w2itwFJCgFQ
     
  13. sharpii2
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    sharpii2 Senior Member

    Cool video.

    This is how I think the trapwing can get into trouble.

    She's sailing on a nice reach across a 16 kt wind. She is making about 16 kts herself. The trapwing is extended about 3/4 the way out, so there is a little reserve in case of gusts.

    Sure enough one comes. It's almost 50% stronger than the original wind.

    Not only is it more wind, but because it is faster, it vectors aft, causing almost twice as much capsize moment, as it hits an over sheeted rig.

    The trap wing lifts.

    The motor extends the ballast further outward.

    But it's too late.

    The boat has rolled far enough, about 40 degrees, to negate the further extension.

    The skipper, being no fool, tries to steer out of the wind (like he would on a typical multihull)

    The asymmetrical shape of the hull resists. The rudder stalls and the boat veers into the wind instead.

    The roll suddenly worsens. The skippers world turns on edge.

    The masthead hits the water, but it doesn't fail. But it doesn't have much buoyancy either.

    The capsize continues until the sealed mast has enough buoyancy to arrest it.

    The boat now sits at about a 145 degree capsize.

    The skipper is still in his chair (he was strapped in) and the boat is still afloat. That's the good news.

    The bad news is he has no way to right the boat. If he lowers the trap wing (moves it to the low side), its immersed buoyancy only helps maintain his present capsized position.

    Cleverly, he lowers it about one third of the way. This takes some of the load off the rig and reduces the capsize a few degrees.

    The tide takes him out to sea.

    He pulls his cell phone out of his pocket. It is dry and functional.

    He hopes the rigging holds and the mast stays watertight long enough for help to arrive.

    It all happened so fast.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    Why didn't he let the main sheet go? Don't forget that the Trapwing pivots athwartship(around a fore and aft axis). You say the guy has no way to right the boat but simply moving the wing to the lower side would do it from 110 degrees and if it was moved during the event would have prevented the boat from going very far. With the wing centered or to the lee side it would be impossible to capsize. Of course, if the guy forgets to use the mainsheet to spill air he could forget to use the wing! We might have to have some sort of sensor that moves the wing automatically for such a person or just train them better? It reminds me of the Open 60's: when upside down they are stable unless the crew moves the canting keel.
    Thanks for thinking about it,thats a scenario we'll have to look at closely in testing the proto.

    PS- I'm not sure about strapping the crew in-especially if we go with the movable seat.
     

  15. Skyak
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    Skyak Senior Member

    His scenario can be reasoned away by an informed expert in their own mind. But what about a jury of our peers? If he just got off the stand in a liability case I am afraid you would be wiped out by the finding in an injury or loss of life case.

    Electronic control can do anything you need, but doing it flawlessly where safety is at stake is more expensive than you can comprehend. You can make it for yourself -fine. Doing it for others is too great a liability expense.
     
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