emlang93
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- Mar 4, 2017
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I want to start a new thread on shock cords because I have not seen a thread that answers all the questions to the point. Particularly length seems to have a lot of variation in the answers I get. I have heard 2x all the way up to 5x the rocket length. For size I have seen people say rate to 75G. which for me means a 30lb 4'' rocket can safely use 1/8'' tubular kevlar (Which I have done successfully). Some have said that 1/8'' is okay then others say no less than 1/4'' kevlar on a rocket that size. I have built a lot of rockets and I always feel uneasy about the shock cord length and size, so let's start a discussion and agree on a standard.
So here are the questions.
I added 3 and 4 so if others come alone I hope it can answer some of these questions too. Feel free to elaborate on things.
If there is another thread with all of these questions answered, or a 1 and 2, please let me know.
Thanks for the help!
So here are the questions.
- How long should a shock cord be for a high power rocket? 3''? 4''? Component weight considerations? How to know if the parts slow enough in separation?
- Kevlar cord size and pull strength? Is, 75G x attached component mass, sufficient? Should there be a buffer of say 15%? (If the cord is the right length do you really need 75G strength?)
- Flame protection on Kevlar? Should you use flame protectors for kevlar? (I don't and haven't had any issues. I just change the harness when it looks rough)
- Where should you place the swivel for the chute?
I added 3 and 4 so if others come alone I hope it can answer some of these questions too. Feel free to elaborate on things.
If there is another thread with all of these questions answered, or a 1 and 2, please let me know.
Thanks for the help!