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 Prototype Development

    Thanks to my brother I may be able to build this boat. It replaces the Dream Flyer here: http://www.boatdesign.net/forums/multihulls/dream-flyer-fl-18-daysailing-trimaran-42340.html It's been a hellish year so far so all bets are off that this boat will actually get built anytime soon though a lot of money has been spent toward that end.
    ----
    I "dared" to choose the name "Crossbow fl" because, from above, this boat looks more like a crossbow than the original 60' speed racing proa did! The "fl"
    is to honor my brother. My reason for doing this boat is that it will be far easier for me to handle than anything I've come up with so far. And the concept of the boat using the Trapwing movable ballast system and Hugh Wellbourn's DSS has a great deal of potential to open up new avenues of performance sailing in a planing hull singlehanded dinghy for disabled and physically restricted people. Proving this concept means everything to me at this stage of my life and it could make a real difference in the lives of a lot of sailors who might otherwise have to be content with the peformance of boats like the 2.4 meter and Martin 16-excellent boats but relatively low performance.
    Also, I've had a lot of support from the guys in the original Dream Flyer team in going in this direction.
    The Team:
    - 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've retained 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.
    - 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.
    =================
    Specifications: (changes are to be expected)
    LOA-14.6'
    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- 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' 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(crew weight range is exceptionally wide on this type of boat since the crew contributes very little to righting moment)
    All up sailing weight including crew-473lb
    DSS Foils: each 1.63 sq.ft.( 6" X 39") 6.5/1 aspect ratio, Welbourn section.
    -------
    Ratios-
    DLR=67
    SA/D=
    --upwind-31.6/1
    --downwind- 63.3/1
    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 the 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.....
    ===========
    Pictures 1 &2-Rough working plans: (the actual plans won't be complete until the boat is built and tested),
    Picture 3-scale model of an 18 foot singlehander using the same sliding ballast wing.
     

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    Last edited: Jun 24, 2012
  2. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Crossbow fl-the model

    Here is a series of pictures illustrating the construction of the model-which is not complete. The "spray rails" are actually a lot more than that. They substitute for having flare to the sides which is impossible with this method of building. But I think they'll work well for keeping somewhat dry and for having buoyancy fairly high up the sides.

    click on images:
     

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  3. Doug Lord
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    Doug Lord Flight Ready

    A couple pictures mocking up a version of the deck:
    actual front deck will be curved with the front end forming the spinnaker tube entry.
    click on image:
     

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  4. Doug Lord
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    Doug Lord Flight Ready

    Pictures show the crew seat which will slide fore and aft as well as tilt each side 10 degrees, the Spanish Cedar DSS foil cores about ready for carbonation, and miscel "toys" to help document testing, and the Crossbow logo, versions 1 & 2:

    click on image:
     

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  5. Gary Baigent
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    Gary Baigent Senior Member

    Doug, why don't you have a sliding seat, a la rowing skiff type? With a semi- swiveling seat. Then you could use your legs to slide right out to the windward gunwhale for better positioning for steering, looking at the rig, weight in a better place and so on - that is, compared to a fixed leaning seat arrangement. Cheers.
     
  6. Doug Lord
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    Doug Lord Flight Ready

    Thats worth considering, Gary. The only problem is taking buoyancy out of the side tanks at a position where they need all they can get. I've tried the 10 degree seat-its easy and moves the crew to weather a small bit while letting the crew sit vertically at the designed sailing angle of 10 degrees. Also allows F&A movement....
    PS-One of the important concepts here is that crew weight presents little or no advantage-so it shouldn't move too far outboard.
     
  7. Doug Lord
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    Doug Lord Flight Ready

    Crossbow fl--Trapwing movable ballast

    This boat will use the Trapwing system for additional RM in conjunction with a "plug-in" DSS foil system.
    The Trapwing system uses a sealed wing that slides athwartship with ballast sliding simultaneously inside the wing. The ends of the wing are supported by trapeze wires and shock cord allowing the whole unit to pivot athwartship so that when the boat is heeled 10-12 degrees the wing is level. The amount of pivot is adjustable. The buoyancy of the wing exceeds(by several times) that required just to float the ballast. The wing can be moved manually or electrically* and will be faster than a crew on a trapeze from full out to full out. The amount of ballast in the wing can be varied in approx. 10lb increments. The wing can be used to right the boat even with the lead ballast at the bottom of a vertical(90 degrees) wing. Masthead buoyancy and a sealed wing mast contribute to preventing turtling.
    In many years of testing variations of this system one thing was abundently clear: it is a blast to sail with this kind of system. The Trapwing system, in conjunction with the DSS foils, gives this boat the capability of planing offwind and, to the best of my knowledge, is the only design of its type featuring a crew that sits "in" a planing hull singlehander with the capability of righting the boat without moving. This can, potentially, open up planing hull sailing to disabled people and people with physical restrictions-a whole new world not available in any current singlehander that I am aware of.
    * Boats like the Martin 16 and International 2.4 meter are routinely and successfully equipped with electrical systems for steering and sheeting. The electrical system for moving the Trapwing would be operated using a "joystick" similar to the one used to operate a similar system on numerous radio control test models. The design of the system would ensure that:
    a) the weight from max out to max out is faster than any similarly moving crew on a trapeze( 3.5-4seconds max out to max out) and,
    b) the movement is possible very frequently for 8-12 hours a day or more. By "very frequently" I mean the design criteria for battery capacity would reflect tacking(max out to max out) every 6 seconds for 8-12 hours depending on owner requirements.

    Pictures of a model of an 18 footer designed to use the Trapwing system:
    click on image-
     

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  8. Doug Lord
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    Doug Lord Flight Ready

    Crossbow fl- DSS system

    The boat will use DSS foils for added stability both upwind and downwind. The system is being used with permission of Hugh Welbourn and all results will be forwarded to him in detail. These foils will plug-in to trunks on the side of the boat, port and starboard just forward of the CB(center of buoyancy). Most full size DSS systems use a trunk that allows the foil to slide athwartship or use a trunk that allows the foils to pivot on each side like a centerboard. The "plug-in" concept was chosen for simplicity. The foils are designed to add 158ft.lb. of RM(righting moment) upwind at "hull speed"( that is, at 1.34 X sq.rt. of the waterline length or about 5.12 knots) and 690ft.lb. downwind @ 10 knots boatspeed.
    The foils use a section from Hugh Welbourn, inventor of DSS.
    The boat is designed to sail at a 10 degree angle of heel so that the leeward foil is a little more than one chord below the surface and so that the windward foil is clear of the water. There will be an inclinometer in the boat to help the skipper sail at 10 degrees and another inclinometer will measure pitch attitude. The angle of incidence of these test foils will be adjustable.
    I just want to thank Hugh Welbourn for his generous advice and guidance with this project.
    ==================
    See Note 2 in post one: the effect that lift from the DSS foil has on Bethwaites ratio, SCP/Total Weight is very interesting in that upwind RM from the foil was calculated at a speed of slightly over 5 knots-any faster and the ratio changes significantly. One could draw the conclusion that, on this boat, it may pay to sail a bit lower than "normal" upwind in moderate to strong breeze to pick up rather dramatic increases in RM from the foil with increased speed.
    ==================

    Picture below shows the actual Spanish cedar foil cores just made by Rick Loheed . They should be carbonated soon and sent to Falcon Marine.
    click on image:
     

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    Last edited: Jun 23, 2012
  9. Doug Lord
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    Doug Lord Flight Ready

    Crossbow fl--"Rocker" seat

    The boat will use a light weight glass seat( from Aircraft Spruce-shown above) that will be installed to allow a 10 degree tilt to each side as well as fore and aft sliding. This is to allow the skipper to sit upright when sailing the boat to a 10 degree angle of heel.
    Rough sketch below:

    click on image-
     

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  10. CutOnce

    CutOnce Previous Member

    Good luck Doug.

    How about this?

    Keep your basic design simple, and keep your options open to add features as needed. The basic hull with DSS may be enough to accomplish your goals - keeping the ilting/moveable seat and trapeze balance system on the back burner till actual need arises. Having a deck where you could slide yourself around from side to side and back and forth may prove to be enough. With a clean footwell, you may not need the seat.

    I'm sure you've got the mobility to move around without the complicated seat, so why bother unless it is really needed?

    In regards to the trapeze balance system, it seems like you've adopted the "belt AND suspenders" approach with two major systems solving the same problem. I'd try the DSS approach first and then only consider the trapeze balance complication if it is needed.

    By considering these two simplifications, you would remove a lot of weight, a lot of complication. Better yet, you would reduce a huge amount of work from standing in the way of getting the boat on the water - and more importantly a lot of money & fabrication time.

    You can always add these things later - as long as you build the basic hull with backing plates installed for the future options.

    I'm behind your current rationalisation of the big and complicated Dream Flyer to a more easy to handle size. I think you've got a far better chance of reaching actual use on the water with the Crossbow FL.

    I think this design would be eminently sailable and perform extremely well with just the DSS and your bum out to windward on a side deck - give it a chance! Kind of a superturbo Windmill with a modern rig and asym for giggles downwind.

    --
    CutOnce
     
  11. Doug Lord
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    Doug Lord Flight Ready

    Thanks for the suggestions-appreciate the comments. If I was to move from one side to the other for RM-I probably wouldn't be moving much longer. But it's really not about me-of course I like the Crossbow concept, but I think it has a lot to offer people worse off than I am by providing a planing hull singlehander the likes of which doesn't currently exist.
    DSS by itself would not provide enough RM at this size to allow a planing boat
    to function well:
    1) upwind-DSS provides about 14% of total RM,
    2) downwind- DSS provides 40-50% of total max RM.
    Like the Quant 28 & 30 and BBB, this boat needs movable ballast and on Crossbow that can't be the crew-but it will be the Trapwing system which not only offers extra RM but a method the crew can use to right the boat after a knockdown.
    Also, remember that DSS does more than just add RM-it reduces wetted surface and acts to dampen heave and pitch, positively affecting the quality of the ride-which is a speed producing result experienced by existing DSS boats.
    I can't sail like I used to-I have to restrict my movement as much as possible but I still love performance sailing. I've worked on this concept for a long time-starting way before I could conceive that this might be the ONLY way I can do performance sailing. So, maybe I'll get it done before I'm done..... Going to try like hell, anyway.
     
  12. Doug Lord
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    Doug Lord Flight Ready

    Crossbow fl-daggerboard and rudder

    Crossbow will use a daggerboard originally made as a backup for my 16' foiler by John Ilett of Fastacraft. The board may be modified with a leading edge taper so that when pulled up the board can be canted back at the top to clear the wing.
    The Dotan rudder was also backup for the same boat and is a pretty neat rudder with a postive lock down and good kick up action. It was specially made by Dotan and has a molded in tube for use for a push rod to control the rudder t-foil that it was designed to accomodate. The kick up system design allows the rudder to kick up while simultaneously neutralizing the lifting foil. For Crossbow, at least initially, the rudder will be used w/o the lifting foil. If the rudder foil is eventually used it will be placed at the point where the tip has been cut in picture #3 below.

    click on image:
     

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  13. Silver Raven
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    Silver Raven Senior Member

    Gooday mate. Great foils - had you ever thought of tapering them in both section & foil position & thickness - so as to reduce the 'tipping moment' -(of the bottom over powering & leading the top) reduce area (by 30%) & reduce drag - thus allowing for more even for & aft sailing attitude ??? Ciao, james
     
  14. Doug Lord
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    Doug Lord Flight Ready

    ===============
    Hi, James-the rudder foil was designed by Dotan and is tapered -at least on the leading edge and in thickness. The daggerboard was made untapered because it was back-up for the foilset in the picture below. My intention is to taper-at least- the leading edge of the daggerboard. Not for hydrodynamic reasons but because if the board is left untapered it will not clear the wing as it is pulled up. Tapering either at this stage is a big deal since I have to pay somebody to do it so I have to look at it very, very carefully. Improvements in these foils could definitely be made but it may not be worth it before testing the boat.
     

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  15. rapscallion
    Joined: Oct 2006
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    rapscallion Senior Member

    Doug.
    I really like the idea of trying to make a performance boat for disabled folks. The skud 18 is probably the fastest disabled boat out there, and like you i believe the performance can be improved. I wish you luck Doug! I would love to see the boat get built.
     
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