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[F-FT] Fixing a G10 fin

In launching my Black Brant VB yesterday, it corkscrewed off the pad quite badly. After recovery, I determined that one of the G10 fins had 'warped' slightly. I don't believe the warpage occurred naturally, I'm afraid the fins were probably bent out of true while traveling in the car when something fell against the fin tip, and it stayed that way for many hours.

Having said all that, are there any methods of un-warping a G10 fin?

I'm seriously considering making some kind of aluminum plate tool (much like an Estes fin alignment guide) to try and align fins in the future, and then use it to 'press' the fin back straight over a period of several days.

Any clues would be appreciated...

David Erbas-White

Reply to
David Erbas-White
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David,

My first thought would be to soften the resin by applying heat from a hot air gun or strong hair dryer and tightly press the fin between two flat plates.

Good luck,

Andrew

Reply to
Andrew Grippo

I've had this happen on one fin on every PML kit with G10 fins that I've ever made. Mine have all gotten slightly cracked at the bottom end of the fillet after a hard landing. Once the fiberglass fibers get separated, it is almost impossible to get them back together so that the fin will be straight again. The fin will rmain warped as long as the crack or crease is putting stress on the G10. The only way to really fix it is to dremel out (or otherwise remove) the cracked area, and fill in with epoxy and fiberglass fibers or some other strong filler.

You can try the press method, but my experience has been that putting the fin in a vice or press to "hold" it straight makes absolutely no difference even after a week. It just springs back as long as that stress from the crack is there. On the other hand, right before I launch, I can manually bend the fin really far the other way, and cause it to be nearly straight for a couple of minutes - long enough to launch. I do this right before I put it on the launch rod. Then it slowly goes back to the original warp over the next few minutes (Hopefully I don't have to wait for a hybrid launch after I've loaded up the rocket!).

Reply to
David

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