Fin Design Question

[Ian A Dalton]

I am designing a 5.5in cluster to be built in the future. It will be all FG construction. Take a look at the fin design, will I have problems with the rear forward swept fins if this rocket goes trans-sonic and super sonic?

 

[K'Tesh]

Sorry, that's above my paygrade. Good Luck!!!

 

[Steve Shannon]

Very possibly. The swept forward fins are more vulnerable to angle of attack changes which puts greater stress on them.

 

[GlenP]

You could beef up the thickness at the root and taper it towards the tip, rather than using a uniformly thick fin. And maybe airfoil the fin like a diamond shape, with sharp leading edge, that might help.

 

[BABAR]

Maybe I am a Fuddy-duddy, but when you build this really cool looking rocket, why do you WANT it it go supersonic?

If you want speed and/or altitude, build a minimum diameter 3FNC, or something else aerodynamic with thru the wall fins. When you go for style, which this rocket has, pick a motor or motors that will give you a good flight without worrying about the fins coming off.


I see the same thing with two stage rockets, seems like everyone wants to put the biggest motor they can in the sustainer. That puts most of the sustainer flight beyond visual range and makes for more challenging recovery.

I know, to each his/her own

 

[Ian A Dalton]

Maybe I am a Fuddy-duddy, but when you build this really cool looking rocket, why do you WANT it it go supersonic?

I’m right here with you. Just wanted to know for my own curiosity in case I ever get the desire to burn $500+ in motors. I don’t by the way. If I did, it would be a performance rocket.

 

[jqavins]

Mmm, funkay.

I don't know about trans- and supersonic stresses. To me, even in subsonic the forward swept potions look kind of too finger-like. Just me, I'd make the leading edge valley a little shallower, making the pseudo-root of the finger wider, then use that to taper the finger down to it's tip.