Simple Exercise On A DIY Foiler Trimaran

Discussion in 'Multihulls' started by yigitozturk, Nov 12, 2017.

  1. yigitozturk
    Joined: Nov 2017
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    Location: İstanbul

    yigitozturk New Member

    Hi,

    First of all I thank you all for this platform which is a great source for us amateur sailors. I am sailing for six years on different boats for recreational purposes and some little sweet racing. But I would to like to inform you that I have no claim on being a great sailor neither a boat builder. Just a humble architect and the grandson of a carpenter.

    I am planning to build an i550 and bought plans for it lately, and start researching on glue and stitch method. Meanwhile got overdosed with trimarans (They are everywhere when you are searching for s&g) and one day saw the Broomstick of Mr. Doug Halsey. It was an eye-opening moment for me. I read a lot especially here in this forum about hydrodynamics and current foiling tech and decided to give it a try. I never see a foiler here in Turkey and local sources are really limited.

    In the end I sketched a tri with my limited knowledge, learned from here and there, tried to design it as simple as possible. Simple form, no rocker, no detailed chin, easy and cheap to build are the key words. For sails, I am planning to use two second hand windsurf sails, rest of it is s&g and some aluminium here and there and used rigging from the workshop of our local marina. I don't claim any originality or rights on anything on the design. I have basic understanding of boat building and how foils works (NACA profiles, how lift generated, etc.) thanks to you people and some boat-designer friends will help me to calculate the draft, waterline and displacement if this makes any sense at all. Just looking forward to hear your valuable ideas and comments. They will be appreciated.

    Best regards,
    Yiğit.

    katamaran_640_1.jpg katamaran_640_2.jpg katamaran_640_3.jpg katamaran_640_4.jpg
     
  2. UpOnStands
    Joined: Nov 2015
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    UpOnStands Senior Member

    Sweet --Welcome to forum.
    reminds me of the Hobie Trifoiler in some ways. Like the foils, not the fastest but so practical -- except for launching. :p Your intention is to rotate the foils around the cross beams?
    Believe the masts will need stays. Trifoiler used a horizontal beam with wire diagonals.
     
  3. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Put some rocker and shape in your hulls.
    Hydrofoil boats have to be good boats before the speed at which they lift off, or they might never get going.
    You will also waste any speed you get when you try to tack.
     
  4. OzFred
    Joined: Nov 2015
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    OzFred Senior Member

    The centre of effort should be roughly over the centre of lateral resistance. In this boat, it's way forward to the extent it will likely be impossible to steer even before it starts foiling. Move the masts back (look at the trifoiler in profile).

    You're also giving up about half the righting moment by having the centre of lift only half way out on the cross beams. I think the floats are much, much bigger than they need to be (unless you're going ocean racing…).
     
  5. UpOnStands
    Joined: Nov 2015
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    UpOnStands Senior Member

    Better to move the fwd beam and foils to pick up on the mast bases?
    Would the aft foils suffer from the disturbed water flow off the front foils?
     
  6. yigitozturk
    Joined: Nov 2017
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    Location: İstanbul

    yigitozturk New Member

    Hi,

    Thank you for your critics, it is really nice to have some feedback from you people. Trifoiler is a great example, I learned a lot by reading about it. It is a shame that we don't have it in here. But it is way professional for me and my motives. I tried my best to apply the principles you mentioned in to my model. About the foils, distance between is extended further away but I don't know if it is enough for a clear run way for both of the foils. Here is wFoil 18, the close foils doesn't seem much of a problem. Maybe because it is a powerboat.



    I am planning to build the foils and the beam that binds them as a single structure. So both of those will be carrying all the load and in the end of the day it can be dismantled and stored away by taking away the body and floats. About the launch, I think it will be easy to use some temporary rollers or even some fixed ones under the foils and make this an amphibious-tri. I hope it makes sense.

    And here are the revised design, looking forward to hear more.

    katamaran_520_1.jpg katamaran_520_2.jpg katamaran_520_4.jpg katamaran_520_3.jpg
     
  7. Doug Lord
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    Doug Lord Flight Ready

  8. yigitozturk
    Joined: Nov 2017
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    Location: İstanbul

    yigitozturk New Member

  9. UpOnStands
    Joined: Nov 2015
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    UpOnStands Senior Member

    Believe your outboard stays are not effective as they are too vertical. Use the horizontal compression member between the masts as trifolier used.
    The motorized foiler appears to have the aft stays much outboard of the fwd foils so they do not encounter the disturbed wake of the fwd foils.
    oh, and lose the aft foils and replace with a single foil on the rudder. Should reduce your drag considerably and make tacking easier.
     
    Last edited: Nov 17, 2017 at 11:46 PM

  10. yigitozturk
    Joined: Nov 2017
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    Location: İstanbul

    yigitozturk New Member

    Hi again,

    Thanks again for your kind comment. I was reading and researching a lot lately about multi-hulls. As being an extra amateur boat builder and a good follower of 'less is more' I told myself, maybe I was making things harder than they need to be. This led me to consider a beach-cat like catamaran instead of a trimaran. Building time and cost will be roughly half of the later idea and by reducing the materials and using simple bolt and nut connections.I will be able to do more adjustments and follow a trial and error method ( I am not expecting the vehicle to be last forever, it is mostly for fun and science).

    In conclusion, I tried my best the keep the principles you people thought me here and simplify it further more. Also I am wondering about which foil profile will be suitable for this kind of project? A simple, straight back air-foil kind or a NACA 0012 like with some angle of attack? Here are the sketches, looking forward for your comments.

    Best,
    Yiğit.

    KATAMARAN_1.jpg KATAMARAN_2.jpg KATAMARAN_3.jpg
     
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