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Thread: Getting Ready for SHTP 2021

  1. #331
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    Quote Originally Posted by tiger beetle View Post
    Which NACA shape did you choose? A NACA 12% profile is fairly forgiving as regards stalling as it has a relatively blunt nose. It's not difficult to create a shape from by plotting a template onto some paper, spray-glue that to some masonite, cut out female profile with band saw or sabre saw, and keep shaping until the trim tab matches your template across the length of the tab.

    http://airfoiltools.com/airfoil/deta...rfoil=n0012-il

    This assumes you have a fair bit of time available...

    - rob
    I used NACA 0015 for the rudder itself but the trim tab? I had a half inch s.s. rod for the backbone of it. I had a buddy weld a 1.5 inch s.s tang, edgewise to the rod to provide the resistance to torque, and glu'ed a 1/4 inch fiberglass rod opposite that, to form a rounded leading edge and give it at least a bit of balance. I glued some lastafoam to the tange on both sides and then when everything settled, went after it with 80 grit sandpaper and a wood rasp. Not very scientific! As foils go, it's pretty fat! It's a tich over half an inch thick and about 2 inches, maybe 2 1/4 inches in chord. It's got two layers of 6-inch glass tape in epoxy over it all. It's some sort of reasonably smooth, at least.
    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  2. #332
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    Well, I got a nice surprise today. I was out front in the yard / workshop and my neighbor walks up to the end of the driveway. I see him walking by with his wife and little girl, pretty often. He says to me...

    "Do you want some carbon fiber?"

    HUH? So I drop the piece of starboard PTFE that I'm shaping and he puts a box of stuff down on the end of my driveway. OH MY GOD.

    yards and yards of heavy 3-inch woven tape. A huge spool of linear roving. 30 feet of carbon tubing weave...and a bottle of epoxy and a bottle of catalyst!

    I thanked him profusely...about 5 x and offered to give him something for it but he just brushed it off. Said that he used to make bamboo bicycle frames, but was out of it, now for years. This was the last of his stock that he'd bought off of ebay. So I just repaired the slit in the end of the carbon fiber assy pole, and made a reinforcing sleeve at the midpoint. I laid some 6-inch strips of the tape lengthwise, forward of the midpoint of the pole and then got two wraps of heavy carbon tape around the pole that overlapped those. Everything was wrapped with plastic wrap, and then blue painters tape went around all that for nice even pressure all 'round. That pole was already crazy strong, now it's insane.

    Today, I also got a piece of shaped UHMWP under the shoulders of the eye bolt, at the end of the pole, which should limit the bending back-and-forth. I shaped a couple of pieces of starboard and PL-Premium'ed them to the side of the pole opposite the eye bolt that will hold the tack block for the assy. I'll put a small eye strap through it all, with a couple of machine screws and that will work for the bobstay. The difference between the load distribution of the eye bolt and the bobstay padeye is rather large, but I think it's all plenty strong enough. The eye bolt has a rated break strength of 1500 pounds, so a 600-700 pound load should be just fine. i can't see this kite pulling more than that in any wind I care to have it up in, so I think I'm good to go.

    While I was at it, I also worked on the bottom of the rudder, fixing the lowermost trim tab bracket in place. It's now bolted down, now that I've let the wood in the rudder dry for over a week. Everything is sealed with epoxy, and there's some structural "fairing" ...if you can call it that, done with sawdust and epoxy. I'll be reinforcing the bracket with carbon fiber, since I now have oodles of it!
    Last edited by AlanH; 12-05-2020 at 08:00 PM.
    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  3. #333
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    I'm adding some structure to the bottom of the rudder, to the bracket that supports the weight of the trim tab. This is not doing the surface flow that exits the back of the rudder, any favors, but I'm paranoid about it breaking.

    The assy spin pole is nearing completion! Today I'll probably wrap a few winds of 3-inch carbon tape around it for the bow bracket tube.
    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  4. #334
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    Quote Originally Posted by AlanH View Post
    I'm adding some structure to the bottom of the rudder, to the bracket that supports the weight of the trim tab. This is not doing the surface flow that exits the back of the rudder, any favors, but I'm paranoid about it breaking.

    The assy spin pole is nearing completion! Today I'll probably wrap a few winds of 3-inch carbon tape around it for the bow bracket tube.
    The bow bracket loop around the assy pole came off this morning. I could've done a better job, it took a lot of sanding on the inside to get it to fit, so I wrapped it 3x more. Once that sets up it'll be about 6 wraps thick of pretty heavy 3-inch tape. Should be bombproof.
    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  5. #335
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    Progress continues.

    the bracket at the bottom of the rudder that supports the trim tab is almost done.

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    and the essentially completed assy pole got a couple coats of paint, today. Note the reinforcement in the middle.

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    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  6. #336
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    Look what arrived in the mail, from The Sail Warehouse in Monterey. ...."find the Wildcat", taken from the ramp.

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    and....

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    Last edited by AlanH; 12-18-2020 at 06:34 PM.
    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  7. #337
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    I am getting tantalizing close to "done" with the trim tab! The whole thing is MUCH less friction that the last system. I have a good feeling about this!
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    Some details... Here's the trimtab shaft bearing at the bottom. It's made out of two 1/4 inch pieces of starboard (the plastic product..)

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    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  8. #338
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    More detail shots... Here's the "middle" bearing. I was going to use the aluminum and sintered bronze pillow bearing I got from McMaster-Carr, but in fact the wood bracket is not quite level, not quite perpendicular to the trim tab shaft. The pillow bearings are self adjusting, but I've been leery about having three dissimilar metals so close to the waterline, so I just used a spare piece of UHMWPE that I had not used, earlier. The shaft is still very low friction.

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    Top detail, showing the nifty pillow bearing. Sitting on the rudder is a stainless steel shaft coupling. A Stainless tiller for the system is currently out of the picture, setting up with JB Weld - steel dust reinforced epoxy. I had some inspiration about how to make a tiller system from wood, and since I had the time and the scrap wood, I made what you see here. The set screws, which jam down on the s.s. trimtab shaft are just stainless machine screws that I put on the grinder wheel, and flattened the tips, somewhat. They look a little funky, but the system works!

    Name:  trimtab-rudder-top-detail.JPG
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    I just took this one to show the s.s. shaft collar, which prevents the whole system from bouncing up and the lower shaft "jumping" out of the lower bearing. $5.25 at the hardware store, totally worth it.

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    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  9. #339
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    The s.s. "tiller' is made, now. It's JB-Welded together. It should, at most see 25-30 pounds of load. I can't see it getting more than that, the windvane simply can't generate that much force, so JB Weld should be plenty strong enough. And if it's not, I can just put on the wood one! It's a backup!
    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

  10. #340
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    DONE!.... time to put it on the boat and test it. It's heavy, but the One Design class rudder is even heavier. Some of the stuff at the top is a little on the crude side, but whatever!

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    1968 Selmer Series 9 B-flat and A clarinets
    1962 Buesher "Aristocrat" tenor saxophone
    Piper One Design 24, Hull #35; "Alpha"

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