Fin Can Help

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Well-Known Member
May 25, 2004
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Ok im building a 3" iris and I want to put fiber on the inside joint of the fins and BT and the Fin MM. Im trying to figure out the best way of attaching the aft CR so I can put the Motor tube assy into the BT and attach the fins but then take the aft CR out so I can put in the fiber.

What I've done is use blind nuts (also referred to as T-nuts) and bolts for motor retention. Set that up and just insert the bolts into the blind nuts to pull out the CR when you need to.

Or, if you don't plan on doing something like that, just drill a small hole or two (maybe 1/32") and thread some string through with knots on the inside. leave the string hanging out and just pull on it to remove the CR. When you're ready to permanently attach the CR, just glue some cardstock over the holes on the inside and fill them with epoxy.
Being that this is my first HP rocket and I dont have my motor tubes yet Im not sure where to put the hardware for my motor retention yet. So I guess the string trick is what im going to use for now. I dont want to wait on the build till I get the rest of the stuff.

The way PML says, and I have done this three times, is almost certainly what you want. Make the aft ring pretty loose on both mmt and BT. Glue on the forward ring to the mmt. Put 3 -4 tape tape on the rear ring. Put the glue in the forward section of the tube, and slide in the motor mount. Then just let the glue dry with the mmt straight. After the glue on the front ring it dry, pull off the rear ring.