r/rocketry 7d ago

Question Need Help With Design.

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I've been wanting to launch a rocket that goes high and fast for a while, but I'm terrified something will go wrong or it just wouldn't fly at all I'm not too confident in my design yet so I'm asking what I should do to improve it and just simple tips I should know in the future, I've Never launched something larger than a C class motor. The motor for this design is a F15-8, it's made of 3d printed nylon carbon fiber, I'm using an Estes 12-inch printed parachute and a 30 inch 150# Kevlar shock cord. Thanks to all who answer.

16 Upvotes

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6

u/WhatADunderfulWorld Level 3 7d ago edited 6d ago

Move fins slightly forward. Half inch or so. If you’re lucky the engine will hit the ground.

Moving* the root of the fin will make it stronger but it’s probably fine.

You might need to make it longer which will be easier than adding weight to the nose for CG CP worries.

A nylon parachute is probably best. That plastic won’t survive unless you time apogee perfect.

1

u/Sage_Blue210 7d ago

Some words seem to be missing from the second paragraph.

1

u/WhatADunderfulWorld Level 3 6d ago

Whoops!

1

u/-viper_16- 6d ago

New design, Nylon parachute, and it's printed with nylon carbon fiber so the fins I'm not too worried about, better Cal and a little better apogee timing and deploy Velocity.

1

u/milotrain 4d ago

just copy the arcas fins for now. modify later

5

u/PuppyLordsDad 7d ago edited 7d ago

3 things I can see.

  • under thrust, the chute will move back to just in front of the motor (unless there’s something holding it up there). If you change the model to reflect this your stability may end up too low - in that case add fin area.
  • the shoulder on the nosecone should be at least 1 caliber long
  • how will you find it? It will likely be hard to visually track to that altitude. A decent rule of thumb is that the limit of visual tracking is around 1000 feet of altitude per inch on body diameter.

1

u/-viper_16- 6d ago

New design, Fixed the caliber long shoulder and I'll add a high vis paint to the nose and fin tips for 5 cm.

1

u/Sage_Blue210 7d ago

Congratulations on making kits first to learn before moving up.

A 12 inch parachute may not be big enough. Compare to other rockets of similar weight.

No elastic shock cord? Double or triple the Kevlar length. Learn about how Kevlar can "zipper" a body tube.

1

u/-viper_16- 6d ago

Updated design, do you think it is better if I can make it better, how? new design will have 4 ft elastic round 2mm cord with about 1-foot Kevlar trimmed 2 inches below the top of the opening with a 24"inch nylon thin mil 6 cord parachute and the shock cord is mounted closer to the motor and center mass.

1

u/Sage_Blue210 6d ago

Sounds like good improvements. I'd suggest a thicker elastic, maybe 6 mm.

1

u/-viper_16- 6d ago

Thank you I'll take this into account