lost a fin

[bjphoenix]

This is a small and light rocket, BT-55 tube about the size of the Estes Goblin. I launched it with B6 motor and a large streamer, it fell on soft grass. The design has the motor tube hitting first. I put really big Titebond fillets on my models, and it still broke off a fin. You can see that the fillet spread out to almost 5/8" wide and has to pull that much tube off to fail, but apparently somehow it achieved the strength of paper. I'm going to clean off the fuzzies and glue it back on with some epoxy to give the glue a bit of a chance to soak in. At least it will fly again.

 

[neil_w]

Not sure what else you can do if the whole tube delaminates.

(I guess it’s just an argument for TTW.)

 

[lakeroadster]

This is a small and light rocket, BT-55 tube about the size of the Estes Goblin. I launched it with B6 motor and a large streamer, it fell on soft grass. The design has the motor tube hitting first. I put really big Titebond fillets on my models, and it still broke off a fin. You can see that the fillet spread out to almost 5/8" wide and has to pull that much tube off to fail, but apparently somehow it achieved the strength of paper. I'm going to clean off the fuzzies and glue it back on with some epoxy to give the glue a bit of a chance to soak in. At least it will fly again.
View attachment 632691

You might try poking holes (with thumbtacks) through the body tube under the fin and where the fillets are. That will "bond" some of the inner layers of the paper to the fin - fillet sub assy.​

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I frequently use pin holes with surface-mounted LPR/MPR. Through the body tube in a staggered line about 2 mm apart, and also into the root edge of the fins if balsa (difficult to poke pinholes in basswood or plywood). I use Tightbond II to attach wood to cardboard. After it dries, you'll be able to feel lines of hard tiny beads on the inside of the body tube that might need sanding down smooth to fit motormounts (or motors if it's friction fit to the BT).

With good filets, it seems to add another measure of durability and I've never noticed it to compromise the BT integrity/strength. Occasionally, I've taken a small paintbrush and painted a thin layer of CA over the bead line inside the tube just to toughen up the wall in the vicinity of the Tightbond-filled holes, but that's probably just unnecessary insurance. Trivial extra weight for the satisfaction of a little extra peace of mind...

 

[bjphoenix]

You might try poking holes (with thumbtacks) through the body tube under the fin and where the fillets are. That will "bond" some of the inner layers of the paper to the fin - fillet sub assy.​

That would be pretty easy to do.