Home grown Laser Hydrofoils

Discussion in 'Sailboats' started by Kevin Charles Rissell, Aug 1, 2019.

  1. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    EBC73A5A-779C-4FDB-93BA-EE35904ACB29.jpeg A1F4781D-2D80-491D-9B47-952D4BF8B0E2.jpeg E6A261C0-0DC2-425F-8C5C-AA5C920E13CC.jpeg After 3 years of nights and weekends researching and designing hydrofoils, learning how to hot wire foam, make mold plugs, make molds from said plugs, learning how to do resin infusion, creating hinges and control mechanisms, and lots of sanding, my carbon fiber hydrofoils for my Laser lifted off for the first time!
     
  2. J Smythe
    Joined: Jul 2019
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    Location: USA

    J Smythe Junior Member

    Sweet!

    How much was the carbon fiber and resin total?
     
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  3. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    I spent approximately $1500 on the whole project, which included hot wire for a foam cutter, resin, hardener, carbon cloth, mold making gelcoat, vacuum bag sealing tape, polyethylene plastic sheeting (for vacuum bagging), solid carbon fiber spars for the structural centers, sandpaper (lots of sandpaper), and all the random miscellaneous hardware and accessories necessary for vacuum resin infusion.

    I did a lot of stuff using cheap alternatives. For example, my vacuum pump was an A/C compressor. After all, the output pipe is the compressed gas, but the input pipe has to suck the gas in, hence, a very good vacuum pump.

    I bought a spoil of wire for hot-wire foam cutters, made a frame out of scrap wood, and hooked a simple on-off switched rheostat mounted in a single gang box and plugged directly into the household ac outlet. Since it was and on-off switch, I could start from zero power, switch it on with the most resistance (least heat) immediately, and then turn the knob until the wire seemed hot enough.

    Doing the hot wire to make the plugs to pull molds from took practice, as did making the molds, as did learning to do resin infusion, etc.

    I read a lot of papers and tutorials written by people who developed foils for the Moth class of sailboats, and I borrowed heavily from their designs. I got the hydrofoil profiles from a free, online database site of airfoil sections.

    Almost all of the building skills and techniques I utilized came from reading tutorials on supplier web sites, forums such as this one, and watching numerous YouTube videos covering every topic applicable in any way to the foils construction.
     
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  4. J Smythe
    Joined: Jul 2019
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    Location: USA

    J Smythe Junior Member

    That's good stuff. I'd love to make a mini volvo 60 or something with one of the hanging bulb keels. Just attach it all to something about the size of lazer. Would be fun.

    Enjoy your work, dude.
     
  5. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Way to go!!
     
  6. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Nice work Kevin, well done.

    Curious why you didn't make the forward foil larger and aft foil proportionately smaller?
     
  7. Apple Hill Boater
    Joined: Mar 2019
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    Location: International Fall MN

    Apple Hill Boater Junior Member

    What wind speed/hull speed did it take you to lift off?
     
  8. wet feet
    Joined: Nov 2004
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    Location: East Anglia,England

    wet feet Senior Member

    Nice job and it looks like the boat flies with a nicely judged attitude.I hope it inspires others to do something creative.
     
  9. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    Actually, they are different, with the forward one being 6+ inches wider than the rudder and with an inch and a half more cord. It’s hard to tell with them being just clear coated carbon fiber.
     
  10. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    I don’t have an accurate hull speed, but the wind speed needs to be a minimum of 10-11 knots. 12 knots will guarantee that she flies with a larger guy like me (225 lbs).
     
  11. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    Thanks. I hope so too. Hopefully in the next couple of weekends I can get some decent video to post too.

    I sail/race on a mountain lake with plenty of puffs and shifts, so keeping it flying can be tricky.
     
  12. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Thanks for that.

    I mean 80/20, fore and aft.
    I know why: design, and load distribution.

    Yes, video please.
     
  13. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    To be perfectly honest, I read a rather technical report done on a study of several different foils for a Moth done in 2009 (if I remember correctly), utilizing a water tank, instrumented gantry, the works. This report listed the surface area for both the daggerboard and rudder foils. I also looked up the surface area for the hydrofoils available for Lasers from GlideFree in Australia, for both the daggerboard and rudder.

    I then just chose a ratio of daggerboard foil to rudder foil that was roughly an average of the two ratios I had been able to find that worked with a sailing dingy of roughly (or exactly) the same size. I weighted the already working Laser foils ratio a little heavier, but in reality, there wasn’t that much difference. I think they would have worked either way, although I think for the next iteration I will reduce the size of the rudder foil by 10-20%.

    I’ll post video as soon as I can get some. I personally don’t know how some of those on-the-water videos are taken, as any video I try to do tends to show the water close to the boat or the sky, and if I’m lucky there will be a boat in the frame or two that comprises the transition between the two.
     
  14. BlueBell
    Joined: May 2017
    Posts: 788
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I knew there was a reason, thank you.

    Have you a waterproof case or water camera?
    It can make a significant difference in how the pictures turn out.
    Using an aquarium suspended in the water and placing the camera down in it can make for interesting, transitional photos.
    GoPros work well too if you're able to do screen captures.

    Looking forward to the videos.
     

  15. J Smythe
    Joined: Jul 2019
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    Location: USA

    J Smythe Junior Member

    My guess would be years of practice attention whoring on "social media".

    We're really putting off the inevitable, and by "we're", I mean humanity, in that we might as well start trying to add trim tabs to these damn foils and be done with it already. We all know that's where it's going.

    Maybe I'll try slapping a C-17 planform under a dinghy and try to get it to work without drowning.....maybe.
     
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