Open source 12-15m high performance/semi-cruising catamaran design

Discussion in 'Multihulls' started by groper, May 10, 2017.

  1. jorgepease
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    jorgepease Senior Member

    I've seen the foils that are horizontal under the floor, it would be simpler to make a horizontal cassette and have a foil telescope out. Make it so retracts far enough so a plastic cap can be printed to seal off the trunk from marine growth. You aren't trying to foil, just trying to counter forward force, that should do it fine.

    You can add a scraper type ring so every time it's deployed it scrapes off any junk that makes it in there.
     
  2. groper
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    groper Senior Member

    i Cant get it to work on the inboard side either - well not unless you reduce the bend in the board to a point where your getting very little vertical lift and maintaining a full height doorway to walk through. You loose half the cross sectional area of usable space in the hull...
    This brings me back to C boards - at least you can fit these in, with much smaller trunks and alot less wasted space and acheive angles which give us as much lift as we could possibly want - i can get these to fit neatly and end up almost horizontal if want to go that far...
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Foil-rough sketches- I only had about 35 minutes to spend on these this morning but the foil works with the minimum size trunk as shown. You can have a water tight hatch inboard(and/or outboard) to access the inside of the trunk for cleaning. You can greatly increase the angle of the lower portion of the foil with a small increase in trunk size though this size trunk will allow a 147 degree angle(33 degrees) which is probably enough for foil assist considering two foils in the water. Also the trunk I show "leans" toward the inboard hull side -if it was straightened up you would have more board options particularly with cant. And there is no limit to the length of the angled portion due to trunk geometry, but you need to incorporate the radius more or less as shown:

    Groper Z foil  6-15-17 004.JPG

    Groper Z foil  6-15-17 001.JPG

    Groper Z foil  6-15-17 002.JPG

    Groper Z foil  6-15-17 003.JPG
     
  4. UpOnStands
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    UpOnStands Senior Member

    Believe that C boards got a bad rap from the full foiling crowd. But you don't want full foiling. You want dagger board function with 50-60% lift so the hull is never fully clear of the water, skimming along so resistance is very small but there are no total crash stops from 30k. Just 24k with little stress.
     
  5. UpOnStands
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    UpOnStands Senior Member

    not following telescoping out. You mean swing out?
    and the "counter fwd force"?
     
  6. jorgepease
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    jorgepease Senior Member

    No, they are completely horizontal and slide out.
     
  7. jorgepease
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    jorgepease Senior Member

  8. jorgepease
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    jorgepease Senior Member

  9. UpOnStands
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    UpOnStands Senior Member

    Nope. Works on monos with their deep hulls and heavy ballast. Groper wants daggerboard functionality which these horizontal foils do not provide.
    Also, in cats the foils would be far too close to the water surface and thus the lift provided would be minimal, IMHO.
    The foils slide to counter the heeling common to monos. Interesting idea but not cruiser-friendly.
     
  10. jorgepease
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    jorgepease Senior Member

  11. UpOnStands
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    UpOnStands Senior Member

    Doug, something is strange - look at relative lengths of yellow and red arrows Groper Z foil  6-15-17 003.JPG .
    As the board drops down it first hits the inner hull side and must be rotated CCW for clearance.
    but the board has to pivot around the bottom case exit, which would force the elbow through the vertical side of the case?
     
  12. Doug Lord
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    Doug Lord Flight Ready

    U, the board pivots as it goes up or down.
     
  13. groper
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    groper Senior Member

    Doug - the way youve drawn that board has very little angle or bend in it. How will this provide more lift or a better overall solution compared to C boards?
     
  14. UpOnStands
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    UpOnStands Senior Member

    Because it is long, very very long. And when the boat heels 20 degrees :eek: the lift will be enormous. Bet the experience will be anything but comfortable.
     

  15. Doug Lord
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    Doug Lord Flight Ready

    Geez, I already answered that question in post 198 though I was forced to eduguess because you did not answer the question I asked in post 188......
     
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