Advice as to the best way to fix body tube damage

[Bill S]

I had an Estes Vapor have a mishap on its maiden launch. I had bought some new kevlar 110# braided thread to use for a shock cord, but it tangled up and prevented proper parachute deployment. The rocket landed tail first and crunched the body tube. Normally I understand, it would be relatively easy to just put in some tube couplers to reinforce the area, but that won't be so easy because the damage is at the front of the fin area and there is a coupler at the halfway point of the rocket that joins 2 body tubes together. The only thing I can think of is to cut the tube in half right in front of the fins, and try to get a coupler under the crunched area, and re-join the tubes, as I don't think it will be possible to remove all the damaged tube without removing the fins as well.

What would you all suggest? Here is a picture of the damaged area (most of it anyways - some of it isn't shown as its on another part of the tube away from the camera and under a fin):

 

[BEC]

Here's what I've done in similar situations: poke some really fine holes in the paint along the damaged areas - maybe every 1/4 inch or so - in both the crumpled area and along the damaged spiral. I use some really nice modeling pins I've had for many years for this.

Then, pull the tube as straight as possible. To try and straighten it under that crumpled area, I'd gently try to bend the tube in the opposite direction enough to pull it as straight and smooth as possible without crumpling it in the opposite direction. While holding it that way as best you can with one hand, flow some thin CA into the pinholes in the paint, encouraging it to wick into the paper underneath. Keep holding it that way until the CA kicks (a few seconds, normally. Wipe off any excess that's puddled up on the paint.

After this treatment it will still be ugly, but it will be much stronger than it is now in the direction that counts most for flightworthiness.

How far back from the fins' leading edges are the slots for the tabs that go to the motor mount? Would you be able to put the repair coupler in deep enough without hitting the tabs? If so, the fix you proposed will certainly work and at least has the potential of looking better and even lasting longer, depending on how neatly you can make the cut and what you choose to do about the paint after putting it back together.

My suggestion is more of a field repair or one that keeps the bird flyable for awhile. I do have a couple of models where I've done this procedure more than once.

 

[Bill S]

There aren't any fin tabs.

I'm going to try cutting the tube in front of the fins and getting a coupler in there and see how it goes. I don't see any other way to do it. Fortunately the motor mount seems to have survived the impact just fine, as I can't budge it even with moderate effort.

 

[MALBAR 70]

Here's what I've done in similar situations: poke some really fine holes in the paint along the damaged areas - maybe every 1/4 inch or so - in both the crumpled area and along the damaged spiral. I use some really nice modeling pins I've had for many years for this.

Then, pull the tube as straight as possible. To try and straighten it under that crumpled area, I'd gently try to bend the tube in the opposite direction enough to pull it as straight and smooth as possible without crumpling it in the opposite direction. While holding it that way as best you can with one hand, flow some thin CA into the pinholes in the paint, encouraging it to wick into the paper underneath. Keep holding it that way until the CA kicks (a few seconds, normally. Wipe off any excess that's puddled up on the paint.

After this treatment it will still be ugly, but it will be much stronger than it is now in the direction that counts most for flightworthiness.

How far back from the fins' leading edges are the slots for the tabs that go to the motor mount? Would you be able to put the repair coupler in deep enough without hitting the tabs? If so, the fix you proposed will certainly work and at least has the potential of looking better and even lasting longer, depending on how neatly you can make the cut and what you choose to do about the paint after putting it back together.

My suggestion is more of a field repair or one that keeps the bird flyable for awhile. I do have a couple of models where I've done this procedure more than once.

This is exactly how I fixed my crumpled Executioner. I have also done the "cut and stuff" method, most recently on my Fliskits Alien8.
These methods both work quite good to stiffen a crunched tube.

 

[BEC]

There aren't any fin tabs.

Oh.... I don’t know why I thought the Star Orbiter (and its 24mm mount-equipped sibling the Vapor) had TTW fins. You’d think I’d remember as I’ve built three Star Orbiters. Oh well. Good luck on the repair!

 

[Bill S]

Thanks. I ordered up some couplers and hopefully it'll work out okay.

 

[Bill S]

Repairs completed. The repairs aren't seamless, but I think it'll work okay.