Foilers For A Catapult Inflatable Catamaran

Discussion in 'Sailboats' started by Miamiproas, Apr 10, 2014.

  1. Miamiproas
    Joined: Mar 2009
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    Location: MIAMI

    Miamiproas Junior Member

    Greetings from Miami:
    I have read many post about peoples foilers, etc. All are very interesting.

    I have an old inflatable Catapult catamaran that should be light enough to be able tomfit it with T foilers and elevation wands.

    I want to build my own set of foilers and adjustable tiller, and would like to know if anybody in the site is willing to help in the design. I do not want to break any speed nor do I want to break my wallet.

    The idea I have is to use the foils offered by Windknife
    https://sites.google.com/site/windknifecom/home
    And bouild my own home made foilers with a simple push/pull rod mechanism attached to water surface wand of some sort. If you take a look at the extrusions, you can see channels already where such rod can travel and push/pull the front of the foil.

    I am looking for ideas on how to put this together, I am sure they will be more clever than mine, and i will give 100% credit to the person.

    I need to dust off the calculations for the foil size for a take off speed of 5 knots if possible. The catapult is quite light. I did my own tubes out ofmhypalon so they are heavier than the originals made of PVC.

    Any comments are Ppreciated
     
  2. R.Finn
    Joined: Dec 2013
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    Location: Slidell, Louisiana

    R.Finn Junior Member

    With helium I think you can get the take off speed down to 2 knots.
     
  3. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    You might benefit from the book "Design Build Fly" from Ray Velinga probably still available at Amazon. It is a short course in foiler design for the amature and is well worth the price. You should study the specifications of currently existing catamaran foilers as well as the Moth foiler to understand what parameters you have to work with. You need to research foil areas, weight, foil configurations, altitude control etc. This is a fairly complex topic and requires some study and research to wind up in the ball park.
    Examples:
    1-Flying Phantom Catamaran-680lb all up, including two 175lb. crew.
    a. upwind SA=247sq.ft.= 2.75lb per sq.ft of sail area
    b. downwind SA=505 sq.ft.= 1.34lb. per sq.ft. of sail area
    ---
    2- Moth-241 all up, including a 175lb crew.
    a. upwind and downwind SA=86 sq.ft=2.8 lb.per sq.ft. sail area
    edit-add info on crew weight.
     
  4. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    The catapult is 210lbs with 107sq foot of sail area giving

    2.05lbs/sq foot

    The flying phantom as I remember isn't foiling much upwind, but they are getting it up sometimes, so you are probably ok. However more sail area would really be ideal for regular planning.

    Not that the moth weight is including the weight of the skipper, which I didn't.
     
  5. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ---------------------
    I included a 175lb skipper for the Moth and two 175 pounders for the Phantom crew. So if you didn't include the crew weight for the catapult it would be 385lb all up and 3.6lb per sq.ft. of SA including one 175lb. crew. The maximum is about 3.3lb/sq.ft. for foiling-and that is dependent on other factors as well(more so than lower sail loadings).
     
  6. Miamiproas
    Joined: Mar 2009
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    Location: MIAMI

    Miamiproas Junior Member

    Thanks for most of the answers

    I will buy the book, was hoping somebody would have share with me how they build their mechanism. OK I will report back.

    By the way, I realized back in 2009 I asked the group how to build pontoons for the catapult, i figured it out on ky own and they came out good

    Take care
     

  7. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Heres an experimental F16 with a single main foil and will have one or two rudder t-foils: http://www.catsailingnews.com/2014/01/foiling-for-all-budgets.html#more
    --
    Heres a website/blog dedicated to foiling-you'll have to translate it or just look at the pictures-I use the automatic translator with my computer-microsoft.
    http://foils.wordpress.com/
    --
    Also, look under "Multihulls" for the 2013 Little America's Cup-lots about foils there. Also, look thru the 2013 America's Cup thread in "Multihulls"( 34th America's Cup). This stuff will help you grasp the state of the art in catamaran foilers and that should help you to decide on the type of foils you want to use on your foiler.
    --
    Look in the "Aerodynamic /Hydrodynamic" section: http://www.boatdesign.net/forums/hy...ler-design-foil-assist-full-flying-40894.html It's only 5 pages and has some good stuff.
     
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