1. I'm trying to select the shock cord i'm going to use for my first fiberglass rocket (scarab 54), and after reading through some of the threads on this forum i'm confused. The rocket will be somewhere in the 3lb range. It seems like a lot of people (at least in the threads I was browsing) are using 1/4" kevlar for rockets of similar size, but that seems like overkill to me. 1/8" kevlar has around 1200lb tensile strength. But then they use a 1/8" quick links, eye bolts and swivels, all of which are rated for 200lbs or so . Why get cord that is so much higher rated than the rest of the recovery hardware? Am I missing something? I think I read that a knot reduces the tensile strength by half (why?), but even then 1/4" seems like overkill at least for my rocket. Also i'm still not clear on how such large forces happen during ejection. I think i've read in another thread or two the worst case scenario would be where a motor with let's say 20g's of acceleration burns out instantly and you have rapid deceleration from +19g to -1g. But i'm not extrapolating the rest. The motor burns out, and all parts of the rocket undergo the same amount of rapid deceleration as gravity takes over. Then what?
2. Is there any point in having a drogue chute for something this small? Would lower ejection at apogee with no drogue and then free fall with deploying the main chute at 700 feet be a bad idea?
3. A question about openrocket: According to OR my CP and CG are pretty close, and so it seems I must put some weight in the nosecone to move CG forward. I tried putting a "mass component" object in the nosecone in OR (trying different mass types had no effect), but no matter how much mass I gave it the CG didn't change. What step am I missing?
4. I was thinking about simply putting on a coat of colorshift for the finish. Does it show well over black fiberglass, or would I need a coat of solid black paint first?
5. Is rocketpoxy pretty much just good just for fin fillets? Am I right that jb weld should be used for centering rings and motor retainer because it handle heat better?
This is going to be my L1 cert rocket and while I want to make sure it gets built properly, I don't want to blindly add unnecessary weight. And for those who have one, can this thing seriously handle any 38mm motor without falling apart? Even the full size J's? OR has it breaking mach on those.
2. Is there any point in having a drogue chute for something this small? Would lower ejection at apogee with no drogue and then free fall with deploying the main chute at 700 feet be a bad idea?
3. A question about openrocket: According to OR my CP and CG are pretty close, and so it seems I must put some weight in the nosecone to move CG forward. I tried putting a "mass component" object in the nosecone in OR (trying different mass types had no effect), but no matter how much mass I gave it the CG didn't change. What step am I missing?
4. I was thinking about simply putting on a coat of colorshift for the finish. Does it show well over black fiberglass, or would I need a coat of solid black paint first?
5. Is rocketpoxy pretty much just good just for fin fillets? Am I right that jb weld should be used for centering rings and motor retainer because it handle heat better?
This is going to be my L1 cert rocket and while I want to make sure it gets built properly, I don't want to blindly add unnecessary weight. And for those who have one, can this thing seriously handle any 38mm motor without falling apart? Even the full size J's? OR has it breaking mach on those.