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Natalie Y.

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I only have low and high power rockets, so I decided to build a mid power since I don't have one and have been wanting to do a scratch build for a few weeks. I have everything I need for the motor mount and the rocket itself, but I don't know how to make the fins. In the design I have now, I have the wingspan of the rocket at a little over 5 inches, and I don't know if that's a good size or if its too big.

What material should I use for the fins? Is a 5" wingspan an ok size for a mid power rocket?
 
Well, it depends. Do you have a way to post your design? Did you use Open Rocket or Rocksim?
 
Well, it depends. Do you have a way to post your design? Did you use Open Rocket or Rocksim?

I might be able to post my design, i'll just have to get the file downloaded. I didn't sim the rocket, since I believe you need a weight to get the proper results, and I cant use Open Rocket because my Chromebook doesn't run on java. I am getting a computer in 2 weeks for the purpose of using Open Rocket. I haven't used Rocksim before, but i'll look in to that.
 
I run Open Rocket on a Chromebook, but it's a bit onerous. I had to run a Linux shell to use it.
Can you give us an idea of the size, shape, and motor you want to fly? When you say wingspan, is that just one fin or all the way across 2 fins?
 
As long as your rocket is "standard-shaped," it will probably work well enough:
  • overall 10-20 diameters long
  • 3 or 4 fins
  • fins 1-2 diameters in width
  • fins 2-4 diameters in root length
  • fins at the aft of the rocket
I myself enjoy making scale models of rockets, so that might be a good source of inspiration to you. Here's a video on getting started in sport-scale scratchbuilding.
 
I run Open Rocket on a Chromebook, but it's a bit onerous. I had to run a Linux shell to use it.
Can you give us an idea of the size, shape, and motor you want to fly? When you say wingspan, is that just one fin or all the way across 2 fins?
I am using a body tube 24 inches long, and have an ogive shaped nose cone that expands the height of the rocket to 28.5 inches. With the fins I designed, the rocket is 30.5 inches tall.
When I said wingspan, I meant from one edge of a fin to across the body tube and to the adjacent fins edge. I intend to fly on an F motor.
 
As long as your rocket is "standard-shaped," it will probably work well enough:
  • overall 10-20 diameters long
  • 3 or 4 fins
  • fins 1-2 diameters in width
  • fins 2-4 diameters in root length
  • fins at the aft of the rocket
I myself enjoy making scale models of rockets, so that might be a good source of inspiration to you. Here's a video on getting started in sport-scale scratchbuilding.

Thank you so much!! This information really helped.
 
I am using a body tube 24 inches long, and have an ogive shaped nose cone that expands the height of the rocket to 28.5 inches. With the fins I designed, the rocket is 30.5 inches tall.
When I said wingspan, I meant from one edge of a fin to across the body tube and to the adjacent fins edge. I intend to fly on an F motor.

That sounds fine. What diameter body tube?

As to what to use for the fins, you could use plywood, basswood, or even balsa. I use 1/8" balsa on most medium power rockets, though I do paper the fins and use fin tabs and through-the-wall fins. It's fine on Es and Fs. Here's a build of mine from a few years ago: https://www.rocketryforum.com/threads/bnc80bb-design.130898/

It was designed to fly low and slow on Estes E9-4s, but they don't make them anymore...:(
 
The diameter is about 2 1/4 inches. I do have access to a 3D printer and thought about doing 3D printed fins, but I’ll look into the balsa. Thank you so much for your help
 
I played around with a design in OR, using BT70 tube from BMS. I used balsa for the fins and nosecone. Wingspan is closer to 6".
I have a BT70 tube at home and 1/8" balsa. Maybe I'll build this...
 

Attachments

  • MID POWER.pdf
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  • MID POWER BUILD.ork
    2.6 KB · Views: 21
If you just want to fly on blackpowder E's and F's (E12 in 24mm replaced the E9), balsa or 3d printing will be fine. Just make sure the layer lines or balsa grain are parallel to the leading edge of the fin
I prefer to use basswood skins over balsa, or 1/8 plywood since I tend to stick punchy composite motors in things

It was designed to fly low and slow on Estes E9-4s, but they don't make them anymore...

There's a reason E9's aren't produced anymore.

derek-waterman-e9-cato-003-jpg.381123
 
There's a reason E9's aren't produced anymore.

derek-waterman-e9-cato-003-jpg.381123

Never had a problem with E9s. Liked the long burn. Bought E12s, had two CATOs out of 4 tried. Admittedly a small sample size.
 
Funnily enough, I had a perfect run with them also.

But there was a statistically significant issue for the manufacturer
 
I run Open Rocket on a Chromebook, but it's a bit onerous. I had to run a Linux shell to use it.
Can you give us an idea of the size, shape, and motor you want to fly? When you say wingspan, is that just one fin or all the way across 2 fins?
I have google chrome book operating system. When attempting to add Java it does not offer support on the download page.
I would love to have open rocket but I cant seem to find a way. Any advice?
 
I have google chrome book operating system. When attempting to add Java it does not offer support on the download page.
I would love to have open rocket but I cant seem to find a way. Any advice?

Ha, I've never seen that page before!

Sadly OR is not too useful for those running Chromebooks.

It can be done. We are drifting off-topic, but, in short, it requires installing Crouton, then running Linux as a shell, eg, https://www.howtogeek.com/162120/how-to-install-ubuntu-linux-on-your-chromebook-with-crouton/
OR will work in Linux just fine. I have LXDE on an old Chromebook that I use for OR.
 
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