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Help! Body Tube Crushed Edge

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Pippen

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My son is working on a model rocket (Estes Gemini DC) for a 4-H fair entry. The rocket dropped from the hook it was hanging from while drying and the top edge of the body tube was crushed. What would be the best way to take off about a half inch of this body tube with a good clean cut? The inside diameter of the tube is about 14/16 of an inch.

Needless to say we'll be looking for a different method to dry next time.
 

SwingWing

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If it's not too badly crushed, could you re-form it and soak the tube in thin CA (superglue)? The Gimini DC is not known to be a greatly overstable model, and I'd hesitate to reccomend shortening it.
If you do resort to cutting the BT, wrap a paper shroud around the BT, mark a complete ring, and score with light pressure several times. Don't try to go all the way through in one cut. Use a really sharp blade and don't cut yurself!
 

hokkyokusei

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Mark the cut with a wrap of paper and a pencil. Using a new blade in an x-acto type knife, score along the mark. Go slowely and go around a couple of times, you're not trying to cut though, just produce a guide for the next step. Next, reverse the knife so the edge of the blade is uppermost. Apply just enough pressure to get the point of the knife through the tube. Then ease of the pressure and work it further in. You should now be able to cut along the prescored line. Take it nice and slow. The last part is the hardest, but again, patience is the key here. I find this technique works OK for tubes from Estes size up to midpower.

For larger thickesses of body tube I use a razor saw, with similar intial technique, but don't progress to the knife stage, just continue lightly sawing to produce a score, until the blade naturally cuts right through. At that at point I usually cut strioght through about 80-90% of the tube circumference, and finish off the rest by returning to the surface scoring technique for teh last bit.
 

phaar

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I always use a pipe clamp for small BTs. You can get them at any local hardware store. Just tighten it around the tube so it is very secure. Then just cut around the edge o f the clamp and you have a VERY straight cut that takes no time at all.
 

DynaSoar

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Originally posted by Pippen
My son is working on a model rocket (Estes Gemini DC) for a 4-H fair entry. The rocket dropped from the hook it was hanging from while drying and the top edge of the body tube was crushed. What would be the best way to take off about a half inch of this body tube with a good clean cut? The inside diameter of the tube is about 14/16 of an inch.

Needless to say we'll be looking for a different method to dry next time.
I use a razor saw almost as much as I use an Xacto. You can get a disposable at most any hobby shop for maybe $3. They have better handles than Xacto handles, even though Xacto saw blades might be cheaper.

To mark it, I tear a piece off of an index card and wrap it around so the edges match, then draw around with a pencil. You probably have the fin marking guide for the model, so you could use that.

You could always try to salvage it. Pull it up and out as much as you can, stick a rod of some sort inside, and roll it on the table to flatten it. To strengthen it you could glue a piece of tubing over the crushed part, and then pinch from inside and outside to flatten the crushed tube against the good tube. Actually for this I use strips cut from very thin styrene. Doing this actually makes the rocket more survivable, since the shock cord can't cut through the tube and "zipper" it. And depending on the model, it can actually make it look really cool.
 

Pippen

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SwingWing, when I told my son that shortening the tube could make it an even more unstable flier, in typical 11-year-old boy fashion, he said "Cool!" He'd probably enjoy a blowout or blowup even better...after the fair, that is. :cool:

The fair judges look for how well they follow instructions, construction technique, and skill level and the kids don't launch until after the judging is over. Given his attitude and what they're looking for we decided to risk making the fix. We used a combination of the suggestions here. First we did as much straightening as possible so only a quarter inch needed to be sliced off. I had a hose clamp but it wasn't perfectly straight so we used a piece of cardstock taped down with removable paint tape. He practiced doing the scoring but was just too unsteady so I did the actual cut. We put in a piece of 7/8 inch dowel rod and even though it didn't fill the tube completely it did help prevent crushing plus made it easy to spin while doing the scoring/cutting.

It looks great--you can't even tell it's been cut--so thanks a million!!! He had the runner up rocket for Best of Class last year and wasn't too excited about entering a damaged rocket. He likes doing well but I am thinking he would have a lot more fun slapping a few together and flying them, rather than this fuss. ;)

Thanks again! My daughter had a peek at that Barbie rocket so we might not be done yet.
 
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