Optimum daggerboard angle for a 33 foot trimaran?

Discussion in 'Multihulls' started by SpiritWolf15x, Oct 2, 2012.

  1. SpiritWolf15x
    Joined: Apr 2010
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    SpiritWolf15x Senior Member

    Hi guys, I was wondering if any of the racer builders out there had any ideas as to what, for performance and control on a 33 foot Buccaneer Trimaran, the optimum angle to have the daggerboard raked to, I believe my daggerboard's angle is currently 46° and it inserts in front of the mast.

    Thanks,

    Wolf
     
  2. Richard Woods
    Joined: Jun 2006
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    Richard Woods Woods Designs

    Trimaran daggerboards usually exit the deck in front of the mast so you can pull the daggerboard up if you run aground while sailing to windward.

    However you need the CLR to be behind the CofE, so most trimarans have a very raked board whereas most catamarans can have a vertical one

    Realistically there isn't much you can do to modify an existing boat

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  3. SpiritWolf15x
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    SpiritWolf15x Senior Member

    Hey Richard, would a more vertical board provide better performance or would I get more out of leaving the angle where it is and tweaking the blade shape?
     
  4. Richard Woods
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    Richard Woods Woods Designs

    Design is always a balance between the rig forces and the leeway resisting forces

    So there isn't a lot of point in tweaking just one factor. Usually better sails make a bigger difference to performance than changing board shapes. Remember also that what is best in theory is often not so good in the real world of daggerboards that are never removed from the boat, a fouled hull bottom etc. The AC boats are dry sailed and have polished foils, so can be fully optimised with no regard to the typical owner who keeps his boat in the water full time

    And also, for example, a high aspect ratio foil will work better on such a boat - but they are sailed in flat water by very skilled helmsmen. Sailing in waves means a less steady water flow and it is then better to have a more "tolerant" foil, as of course it is if you are someone who's attention wavers when sailing to windward (speaking generally of course, not just to you Robbie!)

    I'm writing this in a Seattle motel en route for Oklahoma and then the UK so will go "offline" soon

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  5. SpiritWolf15x
    Joined: Apr 2010
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    SpiritWolf15x Senior Member


    Ok, thanks Richard.
     
  6. bruceb
    Joined: Nov 2008
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    bruceb Senior Member

    board upgrade

    Wolf, I have a B-24, so consider the source:rolleyes When I purchased my 24, among the paperwork was an article about a 33 that had tried an end plate and also a longer dagger with good results. The longer board was about 10-11 feet overall while the end plate was on the "stock" size dagger. I am not at home, but I will review it later this week. I built a new long board for my Buc and as the 24 allows a more vertical board, I built it to allow some adjustment. It works best the more vertical I can get it. I will post the 33 details when I can, but it seems that longer is by far the easier way to go. B
     
  7. bruceb
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    bruceb Senior Member

    as promised

    Wolf, this info is very old- but so are our Bucs;) The 24 uses a board angled the same as the 33, just placed behind the mast. I built a new 7' board for my 24, (about 2' longer than designed), cut the top away so I could tilt it forward some at the bottom (more vertical), and I point with or out point the local melges fleet. It works!!! I can work up under them and force them to tack- they hate it:D (I hope you can read these copies- if not I will try to clean them up) B
     

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  8. SpiritWolf15x
    Joined: Apr 2010
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    SpiritWolf15x Senior Member


    Thanks Bruce, very informative.

    -Wolf
     

  9. bruceb
    Joined: Nov 2008
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    bruceb Senior Member

    shape matters

    Wolf, I built a "maxi" board to fit the existing trunk. I used a shorter cord and maxed the width available in the trunk- it worked out to be about an 8.5% board with a modern shape, tapered at the bottom also. Both the longer aspect ratio and the shape help. I don't seem to have any problem stalling the board out of tacks, but I suspect our slab sided floats and main hull help also. I can really tell a difference when I let the leeward float put its side to work. I also braced the top of the trunk (it was already rotten and needed help) to help with the extra load from the long board. The 33 has so much more depth than the 24 that it should be able to take the stress from the long board.
    B
     
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