Bob Krech:
Maybe you should have tried one of those pruning blades that can be extended on a pole and moved in a sawing motion either by pulling a rope or by moving the pole. You might have been able to cut the shock cord. That might or might not have freed the rocket though, depending on what was snagged.
Lance:
Thanks for the good advice on finishing epoxy and shock cord attachment. I've thought about the arm-thicker-than-the-tube problem and have no great answer. I
might use a longer MMT and a third CR to make a baffle, a la Bob Kaplow. That would give me a bulkhead I could attach a Kevlar line to, but it would probably still be too deep in the tube. I'll probably just use the LOC method.
Is the LOC-provided (nylon?) line good enough, or should I use Kevlar instead?
The LOC instructions would end up with some masking tape under the epoxy that holds the loop (anchor cord) to the inside of the tube. Is that a problem, or should I tack it in with a smidgen of CA in a couple of spots instead? Will the epoxy soak through the masking tape and into the tube? Do I need to make a few pinholes in it to help? Etc.
Should I add any reinforcement to the epoxy here? If so, what? I'm thinking that if I do I should add a straight epoxy layer first, to get good penetration into the tube.
DynaSoar:
Lots of good feedback. Thanks!
I might add fiberglass strips under the inside fillets. Seems like to do them outside would require either very narrow strips or very wide fillets in order to avoid having a bump at the edges of the strips. If I do inside and outside fillets, do I need the fiberglass strips for an LOC/Precision Graduator?
I thought about adding small wooden fin root braces, but may not, due to weight and COG considerations. I want this to be light enough to fly on a D if possible and an E in any case, yet strong enought to do a Level 1 cert on an H. I like the idea of having a wide range of motor choices.
I've never been able to get thick fillets with wood glue. I can put on a zillion layers, and it still comes out thin. They're strong enough, but they never come out to the shape and curve that I want. Putting on a thick glob all at once woudn't be as strong and would be prone to run, so I've never tried it.
Tell me more about JB Weld. I've seen it in the stores, and it has claims like welding tractor engines back together rather than relacing them, etc. How heavy is it? How strong? What applications should it be used for?
I'd considered using aliphatic wood glue, at least for the fin to MMT joints because I know that heat will weaken epoxy. I doubt I could justify the cost of the specialty high temp (500 degrees Farenheit) epoxy, so near burnout and on through ejection the fin to MMT joint is likely to be soft. Would JB Weld be good there? Would it throw the COG backward enough to require adding nose weight? Would wood glue for this joint and epoxy for the rest make sense?
Thanks all for the help and advice!
Steve