brewster_rockit
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- Joined
- Nov 22, 2014
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Lately I've been launching lots of minimum-diameter (BT-5, BT-20) models and noticing that the shock cords are burning through (especially when using sewing elastic vs rubber shock cords.) My chutes and streamers are so tightly packed that they don't deploy well either. I've been thinking about switching to external shock cords to create a bit more room for the streamer inside the model, reduce the chance of burning through the shock cord, and lower the model in a horizontal fashion to minimize damage.
There's not a lot of advice online for external recovery cords, besides epoxying the kevlar portion to a fin root and letting it hang unglued starting at the burnout CG of the model. I'm thinking the kevlar portion should end before reaching the rocket's separation point, and tie onto a piece of thin tubular sewing elastic. The sewing elastic would slide through a hole in the nose cone shoulder, and be long enough to stuff into the body tube without having to stretch. Are there any rules of thumb for designing an external recovery cord besides what I've surmised?
There's not a lot of advice online for external recovery cords, besides epoxying the kevlar portion to a fin root and letting it hang unglued starting at the burnout CG of the model. I'm thinking the kevlar portion should end before reaching the rocket's separation point, and tie onto a piece of thin tubular sewing elastic. The sewing elastic would slide through a hole in the nose cone shoulder, and be long enough to stuff into the body tube without having to stretch. Are there any rules of thumb for designing an external recovery cord besides what I've surmised?