Crossbow fl

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

  1. Doug Lord
    Joined: May 2009
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    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    Key facts that are ignored or overlooked about the technical aspects of the Crossbow fl Trapeze Power Ballast System:

    1) The wing is shaped to reduce aerodynamic drag.

    2) The ballast is sealed inside the watertight wing. It is accessible and can be reduced or increased thru a watertight access hatch.

    3) The wing and ballast move simultaneously allowing the ballast to wind up around 12' to windward of the CL of the boat.

    4) The wing will keep the boat upright even with the ballast max out to lee(or to windward). In the event of a knockdown the wing can be used to right the boat. The buoyancy of the wing is many times greater than that needed to float the ballast.

    5) The wing/ballast combo will move faster than any human crew from side to side,max out to max out.

    6) Battery capacity will be enough for at least two 12 hour days of racing with frequent system use.

    7) The sealed ballast wing pivots about a vertical axis and about a horizontal axis running fore and aft:

    a. the wing pivots about a vertical axis to move weight aft and for trailering.

    b. the wing pivots about the horizontal, fore and aft axis to allow the windward end of the wing to drop a bit(and the leeward end to rise) as the wing/ballast combo is moved to windward. This same movement is automatically reversed should the immersed wing be moved to leeward helping to right the boat.

    8) The wing-tips contain one cubic foot of buoyancy and are shaped to provide dynamic lift in the event of incidental contact with the water at speed.

    [​IMG]
     
  2. Doug Lord
    Joined: May 2009
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    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    Crossbow fl and Model Testing:

    Some people have a mental block when it comes to using RC models to test the characteristics of a fullsize design or to just explore a concept to be used on fullsize sailboats. Problem is that most likely they have no idea how accurate such testing can be-and may not know how many recognized designers have used RC models and static models to test various aspects of their designs. It is true that you have to know what you can test at model size and what you can't test. I was lucky enough to work with Dr. Sam Bradfield one summer when he used one of my large Flyer Cubed RC trimarans to test the foil configuration for his 40' Skat. We tested the rig postion relative to the foils, the CG relative to the foils, the boats balance and more. We could not (accurately) test the foil section, only the foil configuration and to a large extent foil planform and area.

    On Crossbow the testing of the Trapeze Power Ballast System on various RC models has led to development that will translate directly to the fullsize boat and has saved thousands of dollars and hundreds of hours of development time.

    -----------------------------

    Some of the well known designers that have used RC model testing to develop their boats and or a concept include:

    Greg Ketterman(Hobie Trifoiler), Paul Larsen(SailRocket), Alain Thebault(Hydroptere), Dr. Sam Bradfield(SKAT), Yves Parlier(60' cat),
    Hugh Welbourn(DSS), Bill Burns(CBTF), and many others.
    RC model testing works and is a valuable development tool that can save time and money.


    pix credits top to bottom: Bradfield(SKAT), Thebault(Hydroptere), Yves parlier(60'cat):

    [​IMG]

    [​IMG]

    [​IMG]
     
  3. Doug Lord
    Joined: May 2009
    Posts: 14,918
    Likes: 168, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    Attached Files:

    Last edited: Jan 15, 2018
  4. Doug Lord
    Joined: May 2009
    Posts: 14,918
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    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    Crossbow fl-S 2018: New version of Crossbow being designed-may be a big improvement on the original in many respects especially in that it will be a singlehander capable of comfortably taking someone else out for a sail-without degrading performance. Something not possible on the first version.
    The new hull will be radically different from the original-- 18.75' LOA, very narrow with an adjustable keel with a max draft of 4'. Beam of the hull at the waterline is 2.5'. Seats extend out each side at deck level along with a shorter TPBS-8' overall length. "New" type DSS foils extend out each side 4' but can be retracted above the waterline for light air.
    And a 5.5' RC model of the boat using a Trapeze Power Ballast System will be built to help with crowdfunding of the project. The full size version will have a radically different Trapeze Power Ballast System than the original(possibly manual instead of electric)---the model will use the new D2 type TPBS.
    This boat is very, very experimental which is why the model is being built.
    -----
    I'm going to try a system for building on the model that will eliminate most sanding: the hull will be made from thin balsa(1/8" okoume ply fullsize) then carbonated with 5.8oz carbon. Before the epoxy sets up very thin glossy carbon sheet will be bedded on the laminate so when it kicks the hull will be 95% finished with some detail work required at the chines, sheer line and cockpit.
    More to come in a new thread........
     
    Last edited: Mar 15, 2018

  5. Doug Lord
    Joined: May 2009
    Posts: 14,918
    Likes: 168, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    Crossbow fl-S 2018: Found a neat solution to "hiking seats" that may have value on the new version of Crossbow. The Swedish "D" Class Canoe seats seem to be spring loaded to pop up when the crew changes sides:

    D Class Canoe.jpg D Class canoe spring seats.jpg

    canoe- D class swedish.jpg
     
    Last edited: May 22, 2018
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