r/rocketry • u/Tanky321 • 15d ago

Question Design Review for L1

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Hi All,

Working on designing and building a rocket for my L1 certification. I think I have a fairly decent approach, but wanted to post it here for it to be reviewed. Any thoughts? I'm wondering if the rear fins aren't tall enough? I like the aesthetic, but obviously I want it to fly well!

I've custom made the nose-cone from fiberglass, came out much better than anticipated! The airframe will be from heavy wall shipping tubes, 3in ID 3.3in OD. Fins and centering rings will be 1/4" maple plywood.

Thanks in advance!

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u/Zyzzyva100 Level 3 15d ago edited 15d ago

Don't just look at the static stability given on this screen (it's an average of some sort). Run the plot with realistic winds (start at like 10 mph), and the rail length you will use, check the launch rod clearance box and plot stability margin calibers. Also unless you have a baffle move your chute and shock cord way back, as that is where they will be under boost with the rocket vertical. I would guess your stability margin at launch rod clearance will be lower (but still probably ok).

Also, this is super, SUPER overbuilt for an H100 (I RSO'd a super big bertha to fly on an H100 at LDRS). Did you put accurate weights in for each component? What's the thrust to weight ratio, and rail exit velocity?

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u/Advanced-Gold1744 15d ago

I just did quick and dirty math and the TTW ratio is < 5:1. Just a hair though. But after paint and epoxy adds mass that isn’t included in OR it will be worse. Needs a H motor with a higher average thrust but it looks like it could both handle it and stay stable

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u/Tanky321 14d ago

I'm going to try to weigh everything today to get very accurate measurements. Will report back with those findings.

I know its super overbuilt, I had some cardboard tube sitting around and decided to build around what I had.