GDJ
Semi-retired Rocketry guy
This one is for my 7 year old daughter (pending approval from her):
View attachment Genevieve's rocket (pending aproval from Genevieve).pdf
View attachment Genevieve's rocket (pending aproval from Genevieve).pdf
Freeform fin set (3) BalsaLooks good to me! I like upswept fins. What will you make the fins out of?
I think its cool looking with those type fins,but,I guess we wait for theThis one is for my 7 year old daughter (pending approval from her):
Looks good! I think it will be approved by the boss.
My daughter was looking over my shoulder one day while I was using Rocksim, and asked what it was. I told her I use it for designing rockets, and she said "COOL! Can I try it?" She went right to work and designed a rocket, and with a little help from me built it, and we flew it this spring. Flies like a champ. She beat me....I have yet to build or fly my own designs.
Freeform fin set (3) Balsa
With balsa fins shaped like that, I would definitely paper them. Because of the grain in balsa, I'd be afraid they'd snap off.
With balsa fins shaped like that, I would definitely paper them. Because of the grain in balsa, I'd be afraid they'd snap off.
[POW]Eagle159;226742 said:Or do a 2-part fins...if your worried.
Definitely worth considering. I've been considering Lexan as well.
If I go Balsa, I will probably coat them with wood glue, bondo scrape them smooth while wet, let them dry, then sand them.
I may do the Paper/glue coating. Worth considering.
Or use 1/8" plywood. It's not all that heavy.
How about 3/32" Birch?
I'm sure I can find it.
Just for S**ts and giggles, I ran a simulation with birch fins:
It's a bit faster with Balsa, but the stability co-efficient goes up to 3.99. It's a good trade off.
According to OpenRocket, Balsa is 0.17 Grams per cc, Birch is 0.67 per cc.
Wow, I didn't realize plywood was so much heavier.
Yep, but a trade-off is a thinner wing with Birch and one can gain back some altitude by lowering the drag.
Lexan is a bit over 1 gram per cc, but it's pretty strong stuff. Fins with a thickness of 1mm are possible, theoretically.
This would give an effective transfer of airloads from the main fin into the doublers and spread the attachment loads all along the new, longer root edge (still the purple line).
It would also make the fin root thicker and give you more bonding area for the fin root joint.
And if you tweaked the leading edge angle of that front end just a bit, and made it wider, you could make the reinforcement area a lot bigger on the inboard end of the main fin. The doublers would even help beef up the fin trailing edges to reduce the amount of damage there from landing and hitting those edges of the fin.
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