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


    I’ve swallowed plenty of lake water before I learned that as soon as it starts to lift off you have to sheet in hard, as the apparent wind shifts in a hurry. Otherwise it rolls to windward on top of you and then you get dragged down the lake by the one foot that invariably gets stuck under the hiking strap.

    On the other hand, they’ve successfully foiled an Optimist pram.
     
  2. J Smythe
    Joined: Jul 2019
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    Location: USA

    J Smythe Junior Member

    Sounds about right.
     
  3. tlouth7
    Joined: Jun 2013
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    Location: Cambridge, UK

    tlouth7 Junior Member

    That's awesome! Did you beef up the rudder pintles at all? Also it looks like there is no adjustability on the rudder, do you have any control other than shifting your weight around?
     
  4. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member


    No, I did not have to beef up the pintles at all. The lower pintle (closest to the water) doesn’t carry much of the load. The upper pintle rests against where the two halves of the boat meet, and that’s where most of the load is carried. My boat is up there in years and has the original pintles (I did get replacements before taking it out on the water but I figured I’d break the old ones first. Hasn’t happened yet and I’ve put some amazing stress on them at times.)

    One thing no one thinks about until it happens: T-foils make squeaking around anything with an anchor line impossible. Wide berth is necessary to avoid fouling the line.

    The rudder is adjustable. There’s a flap on the rudder just like on the daggerboard. The tiller extension is attached by a rubber universal joint to a 105 degree angle gear drive originally meant for portable drills. This in turn spins a SS tube that goes down the middle of the tiller. At the other end of the tube (at the back of the tiller, over the rudder) I welded a small piece of SS threaded rod, with course acme threads and a brass nut, that originally was meant as a repair kit for cheap 3D printers. The brass nut has a groove in it and I put a corresponding flat metal piece for it to slide on inside of the tiller, so the nut doesn’t spin when the threaded rod does, but instead moves forward and backward. So I attached a rod to the brass nut, which is attached to a rocker arm on the rudder, which in turn pushes and pulls on the rod directly attached to the flap at the bottom of the foil.

    I borrowed the concept from how I think the Moth class is doing it now, if I’ve read the description correctly, though I’ve never seen one but the one I made.

    In practice it needs a little modification, as it seems to have a preferred area it likes to rotate to one it’s own. I figure this might be the flap liking to fly at a certain spot, though I’m not sure.

    Plus, the direction you twist the extension to make the flap go up or down changes when you tack. Takes a little getting used to. (The actual spin of the threaded rod doesn’t change, but whether it’s clockwise or counter clockwise from the skipper point of view does. It kinda blows your mind at first.
     
  5. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    Sorry. I got some video, but it’s mp4 and for some reason that’s not allowed here.
     
  6. OzFred
    Joined: Nov 2015
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    OzFred Senior Member

    Your rudder system is more complex than it needs to be. I don't know if you can adopt the Moth system to a Laser as Moths don't have a pintle/gudgeon system, they sort of have dual gudgeons held by a pin. The rudder foil is fixed to the strut (either permanently or bolted) and the whole rudder adjusts, essentially pivoting on the lower gudgeon. The tiller extension connects directly to a shaft inside the tiller by a short piece of flexible high pressure hose which acts as a universal joint. The other end of the shaft has a worm gear that pushes and pulls the top of the rudder shaft depending on which way the shaft is rotated. The direction of rotation for bow up/down (or rudder shaft top forward/backward) is the same on both tacks.

    Consider visiting a Moth fleet to see how it's done, they might be able to get you some parts like the worm gear.
     
  7. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    Link to video:

     
    tlouth7 likes this.
  8. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Bravo!
     
  9. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    A lighter weight (by 40 lbs) friend of mine took her out on a day where I could only manage a couple of lift-offs, and managed to fly just fine, and reported better performance in and off the foils with the skippers weight forward, more like where one would be positioned on a beat.
     
  10. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Yah, weight's a bummer.
    Enemy of speed, that's for sure.
     
  11. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member

    Yep, a couple of times it seemed like as soon as was up on the foils, I could shift my weight forward fast enough to prevent the main foil from stalling, which precipitated a hard nose dive.

    I’ve also had a couple of times where I didn’t shift my weight fast enough to keep the main foil from breaking the surface, which lead to abruptly taking several inches of water over the nose as the boat tried to submarine.

    Needless to say weight kills speed, and weight distribution and redistribution is a critical skill to learn for successful foiling.
     
  12. OzFred
    Joined: Nov 2015
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    OzFred Senior Member

    Congratulations!

    You should try to get weight 100% on the main foil, the rudder is just for pitch trim. Your rudder foil looks way to big to me, drag also kills speed. ;-)

    The Moth technique for learners is to start close hauled, then slowly bear away, heel to windward and sheet in as you accelerate. Windward heel helps to increase RM and reduces wetted surface, which I think would be important in a Laser.

    Starting foiling downwind is harder because the boat needs to be kept flat (your video shows the problem with leeward heel), but maybe you can't get enough speed going to windward?

    Have you compared your foils with those from Glide Free?
     
    Last edited: Aug 16, 2019
  13. J Smythe
    Joined: Jul 2019
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    Location: USA

    J Smythe Junior Member

    Is anybody using any kind of trim tab set up yet? I know with aircraft you have to set your trim to account for speed, so figure you'd need to do the same with foils or you're going to have a bad day.....or a high learning curve.
     
  14. Kevin Charles Rissell
    Joined: Aug 2019
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    Location: Oakland, MD, USA

    Kevin Charles Rissell Junior Member


    Thank you.

    It’s been a steep learning curve indeed, and your suggestion of weight placement is spot on, which also means that the rudder foil is indeed too large.

    So far, using the Laser full size rig in conditions where only the puffs have enough oomph to get the Laser airborne, it’s been necessary to try to get as much speed on a reach as possible, and then angle off on a broad reach. Leeward heel accompanies this approach, and the only result from healing to windward under these conditions is the opportunity to swim, since it’ll roll right on top of you as soon as the foils begin to lift off.

    Again, you are correct in that breaking the large wetted surface of the Laser is difficult. Getting it 3/4’s flying is difficult, but after that it leaps out the rest of the way.

    I haven’t had any opportunity to compare them with the Glide-Free foils, as there aren’t any examples anywhere locally, and honestly I’d like to get to the point where I could foil with enough control and finesse to make a decent comparison.

    I intend to turn the lessons I’ve learned this summer into Version 2 over the winter season.
     

  15. J Smythe
    Joined: Jul 2019
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    Location: USA

    J Smythe Junior Member

    How is it sailing when not foiling? Are they acting like underside anchors with drag, or can you barely tell the difference?
     
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