Fin Size vs. Fuselage Diameter?

Discussions about rockets, construction materials, adhesives, nozzles, nosecones and fin design.
skysaber89
WRA2 Member
WRA2 Member
Posts: 44
Joined: Fri Sep 13, 2013 11:14 am

Fin Size vs. Fuselage Diameter?

Post by skysaber89 »

Hello, I have a question I would like to pose to the more aerodynamically technical people here. Or if you just can answer the question, you don't have to be an aeronautical engineer I wouldn't think.

Does anyone know of some sort of ratio of fin size to fuselage diameter, or of any way to find the optimum size for fins based on a specific rocket?

I'm sure there are formulas for this out there, but I just don't know them.

Thanks everybody.

[edit] Grammar issues. Friggin autocorrect man
User avatar
bugwubber
WRA2 Member
WRA2 Member
Posts: 1087
Joined: Wed Dec 19, 2012 2:47 am

Re: Fin Size vs. Fuselage Diameter?

Post by bugwubber »

Fins should be as small as possible and still have a areodynamically stable rocket. Length and width of the rocket, nozzle size and expected acceleration all play into determining optimum size. Oh and fin shape.
Bugwubber

Team S.P.E.W.
skysaber89
WRA2 Member
WRA2 Member
Posts: 44
Joined: Fri Sep 13, 2013 11:14 am

Re: Fin Size vs. Fuselage Diameter?

Post by skysaber89 »

bugwubber wrote:Fins should be as small as possible and still have a areodynamically stable rocket. Length and width of the rocket, nozzle size and expected acceleration all play into determining optimum size. Oh and fin shape.
Do you have any formulas that can be used to determine the optimum fin size based on these factors?
Maru Ivan Rico
Advanced Member
Advanced Member
Posts: 15
Joined: Fri Oct 16, 2015 6:54 pm

Re: Fin Size vs. Fuselage Diameter?

Post by Maru Ivan Rico »

Fin to rocket ratios would be varied on different accelerations. You would normally use smaller fins if your rocket is expected to achieve high accelerations, since the rocket is fast enough that even small fins would take effect on stability. The higher the acceleration/top speed, the smaller fins you'd need.

I think you would have a 3:1 x-axis finspan to rocket width ratio and 5:1 y-axis finlength to rocket length ratio to be stable on accelerations lower than 5G, but higher ratios can be used on faster rockets.