DSS 49er

Discussion in 'Sailboats' started by revintage, Jan 12, 2019.

  1. revintage
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    revintage Senior Member

    Looked at the old 49er that we(two grumpy old men) are frankenboating this winter to a Sportboat, with 50kg bulb, carbon fibre fore deck and hiking wings. Like a smaller version of VX-One.

    Today we got the idea to do a Stage 2 mod with DSS style foils like Monofoil Gonet. Except for adding the foils the T-foil rudder probably needs to be moved a bit more to the rear.

    Below is some guesswork of how it could be done.

    IMG_3435.JPG 49dssfront4.png 49dssfront5.png Gonet monofoiler 30 knots.jpg franken9er.png
     
    Last edited: Jan 12, 2019
  2. TANSL
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    TANSL Senior Member

    The first thing I thought is, and apologize if the question is not very intelligent, would it be possible, or good, to eliminate the bulb keel?
     
  3. revintage
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    revintage Senior Member

    If you check a 49er as is, it is sailed by two athletes in trapeze on 60cm wings.

    It will now be sailed by two retired guys that have passed their best-before-date since long, with their behinds hiking out from 80cm wings.

    So a bulb will for sure be needed, to compensate for the lost righting arm. Actually a heavier bulb will be needed to make the two equal.

    Another reason for adding a bulb is that we then are allowed to participate in our clubs handicap races, no dinghies allowed.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    You might consider a "real" Welbourn foil that would be simpler and lighter . I imagine you have-or will- do the calculations to make sure the foil area you choose will work. The Quant 23 system designed by Hugh Welbourn also has the advantage of really light air takeoff. His Quant 23 was the first foiling keelboat ever....
    Good Luck-sounds like fun.

    Quant 23 foil illustration.jpg
     
  5. Doug Lord
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    Doug Lord Flight Ready

    revintage quote:
    "A foil like that is out of the question due to the costs involved. My solution will do the same job. How do you think I found out the take off speeds without doing the math?
    The lifting foil will be parallell to water surface at 16% heel.
    Will use my straight foil section described in my Trifoiler thread. "
    ----------------------------

    You think one "Gonet" type foil(foil+2 "legs") will cost less than one Welbourn foil? I seriously doubt it. Hope it works out.
    What is your projected takeoff windspeed?
     
    Last edited: Jan 12, 2019
  6. revintage
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    revintage Senior Member

    TANSL, it might be worth a try to use the original daggerboard(if it is long enough) in foiling mode, as the leeward foil ads righting moment by the lengthened righting arm. Have to do the math on that option.

    Will still keep the bulb for club races without hydrofoils.
     
    Last edited: Jan 13, 2019
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  7. revintage
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    revintage Senior Member

    Began by building the hiking wings, actually lighter than the original and elevated to give a better hiking position. 3mm Dyneema from the trapeze fittings on the mast lifts the wings in each corner. As tested on our Frankencat the leeward wing is arranged to lift when you sit on the windward wing. The rear line will then slack and be out of the way for the mainsail.

    About the DSS-style leeward lifting foil, it will probably be better to build as a bolt-on. Working on a no-hole-in-the-hull version where the foil lifts forward, revolving around tubing fixed to the gunwale and to the center, just behind or beside the mast step.

    Have calculated weight for both sides including foils including struts and fittings to max 20kg. This would result in 0.2 knots higher take off speed, when compared to 10 kg foils. The foils will be straight section N12FLAT as the ones on Windknife Windknife trifoiler build https://www.boatdesign.net/threads/windknife-trifoiler-build.61518/ , but with longer chord. On each side, two straight sections will be joined together as a shallow tilted dihedral on each side.
     

    Attached Files:

    Last edited: Jan 30, 2019
  8. OzFred
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    OzFred Senior Member

    Presumably that isn't your intended foil and you're sticking to the triangular configuration?

    I'm struggling to see how you can rotate the foil to deploy and retract it while still having enough strength to support the boat when foiling (and crashing). :)

    The hinge itself isn't an issue, but how do you lock it down securely?
     
  9. Doug Lord
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    Doug Lord Flight Ready

    Seems to me that it might be twice as heavy--and possibly not as strong--as the Quant 23 foil? Good Luck!
     
  10. revintage
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    revintage Senior Member

    Hi Ozfred,

    Noted you seems to have a great interest in single hull foils, I appreciate your points of view. Important to know is that this is a low budget, (almost)no carbon build. Take this as a brainstorming session (nothing decided yet) where this is a byproduct of my Windknife trifoiler build.

    The problem with locking should be no problem, with 10kg a side there should be enough to make a sturdy arrangement. Talked with Doug Halsey and he told me that you have to lock it both rear- and forward. The solution is not far from the Icarus arrangement in the 70´s. I can even live with 15 kg a side.

    Also remember this is a two person skiff, the crew has to work ;-) . The idea is to lift it forwards with something like 8:1. Did a RM calculation of the concept and it should not be as nervous as a "real" 49er. My calculations show designwind for 49er to just above 6 m/s and this one at almost 9 m/s with windward foil lifted. In case of not enough RM, a bulb of ca 50kg might be a solution? Can PM you my spreadsheet if you want to.
     
    Last edited: Jan 29, 2019
  11. Doug Lord
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    Doug Lord Flight Ready

    =======
    Wow! I apologize for anything I said that -apparently-offended you.
     
  12. TANSL
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    TANSL Senior Member

    If you have data or have done some study that confirms your statement "Seems to me that it might be twice as heavy - and possibly not as strong - as the Quant 23 foil?", there is nothing offensive, on the contrary, it could be a very useful advice. If this is not the case .....
     
  13. Doug Lord
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    Doug Lord Flight Ready

    =============================
    I used the words "might" and "possibly" to indicate that I was not positive about my assessment. I also wished him good luck!!!
    However, when looking at the foil sketch done on top of a Quant 23 foil the lengths of the struts combined with the foil length tends to raise a question about the weight compared with a structure similar to the Quant 23 foil- which is a simple design and relatively easy to build.
    revintage 4th sketch from the left:

    Quant-revintage sketch.png
     
  14. TANSL
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    TANSL Senior Member

    You also said "twice as heavy".;). That "might", "possibly", be too much, dont you think so?
    Sorry, I almost forget it, goog Luck!!!
     

  15. Doug Lord
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    Doug Lord Flight Ready

    =======================
    No, with the qualifier "might". Based on the sketch done by revintage, a rough estimate of "twice as heavy" is not out of line.
     
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