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Plan C...

asport22

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I need some blisters to go on the aluminum sheet covers over the Jodel landing gear attach. The bolt heads stick up above the surface of the wing about 1/2 inch. I wanted to form them into the covers, but realized that they are too close together to be able to do that with the tooling I built. So I tried forming just a single blister that I could rivet onto the covers. Didn't go so well...

failed wing blister.jpeg


I could try forming it half way then annealing, but I'm not sure I'm in the mood for that much education. Does anyone know of a source for stock blisters about 1 3/4 x 3 x 5/8 inch high?

Warren
 

Dave Baxter

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Warren Are you using tempered aluminum, like 2024-T3 or 6061 T 6 if so it is very difficult to do so with this type of aluminum, what you need is 6061-0 or 5052- 0 condition aluminum, as it forms much easier. Chris AKA Smizo might have some made from carbon fiber. Dave
 
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ndlakesdreamer

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Aileron cable covers for a high wing piper? I know they have slots in the back... tell everyone those are speed slots.
 

cwilliamrose

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Did you manage to draw some material into the blister from around the edges? The blank may be too large to allow that to happen but you should encourage that to happen in your next attempt.
 

TFF1

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The fancier the part, the more times you have to anneal to keep it soft. You might try starting with the piece with a curve in it, like starting to fold the sheet. Start hammering the curve into the mold.
 

PittsDriver68

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When I installed the factory option cross-over exhaust on my S-2A I discovered that the front left pipe contacted the cowling. This was after John Morrissey counseled me that it was a valuable upgrade. When I mentioned my clearance problem to John he then said, "oh yeah, it doesn't fit."

I made a bump from 0.050 3003H14 aluminum, hammered into a wood hollow that I made with a plunge router. Once the rough bump was formed into the wood female form, I used a 1" dowel with a rounded end held in a vise as a "spud" to work out the dented part until it was smooth enough to transition to sandpaper for a final finish. You start with 0.050 as it is easy to make a bump thinner but hard to add material.

As noted by previous posters, use soft material as you will be work-hardening it as you go.

Best of luck,

Wes
 

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asport22

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Yeah, I'm using 3003 H14, 0.025 thick. I've got a sort of crude "die" - two pieces of MDF with the outline cut through them, and a matching punch with the form carved on the end. Seemed easier than trying to carve a female die. The first try, I pounded the punch in with a two-pound hammer, and sheared the blank out of the sheet because I didn't radius the top edge of the bottom "die". Fixed that, and on the second try, I found that I didn't have a big enough hammer to get the punch down all the way. I switched over to the hydraulic press, and split the part.

I wasn't really too optimistic that there was a ready source of stuff like this in just the size I need, but you never know. I'll poke around at Oshkosh, and then take another run at it after that. I'm pretty sure that if I stop about half-way and anneal, it will work. I might try a smaller flange, too, but I have to end up with enough to be able to rivet it to the cover. And fiberglass is plan D. :)

I'm just at a point where I am more interested in getting this thing in the air than learning new skills or developing a production process. 200 MPH green tape is looking good for the first flight.

Warren
 

cwilliamrose

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If you made a female cavity you could control how and where the metal is stretched because you're not doing it all at once. Thicker material and several 'anneals' should get you there without resorting to the dreaded FG option. FG is best used to make the tools to create metal parts. :p
 

cvairwerks

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Couple of thoughts...Maybe too much material being locked up by the holder. Make the amount held smaller.. and probably not enough lubrication on the sheet to allow it to slip as needed.
 

Larry Lyons

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Blisters are available for the Ercoupe but don't remember who has them. I think they are larger than what your wanting though. I mounted a set last year on a T-Craft project, they are dead soft and can be tweaked to fit your cowl lines perfectly.
 

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