Rocket Fin Design Tips

[DylanJohn]

I'm in the middle of a project for my university to design a low altitude (10,000ft) rocket. My role is the 'fin aerodynamics' portion of the rocket. I'm struggling to evaluate which fin shape and cross section is actually the best for any specific rocket case (mine is subsonic, M~0.8) for my report. I've found very conflicting results, and most of the literature is on aircraft wings/fins, which are much higher aspect ratio than rocket fins.

From what I've gathered so far, a trapezoid or clipped delta seems to be the best for this case, but I can't really explain why. Swept wings bring back the aerodynamic centre so the rocket becomes more stable but less manoeuvrable? Rectangular wings have the highest induced drag and lowest lift coefficient? Elliptical wings have low induced drag but low lift coefficient? I'm not even sure how to calculate lift coefficients for rocket fins because of their low aspect ratio.

Any tips on textbooks, papers or reports giving a bit more detailed information on fin planform shapes would be fantastic. What's more, our rocket will have static rear fins but active canard fins, which makes things more complex (albeit more interesting). Any help would be greatly appreciated!

 

[Voyager1]

I assume you have been performing simulations in OpenRocket or RockSim. There is also fin simulation with AeroFinSim which might be more useful.

 

[dhbarr]

https://www.offwegorocketry.com/userfiles/file/Nose%20Cone%20&%20Fin%20Optimization.pdf

It's a good primer, jump down to the end for references.

 

[trialsguy]

https://www.offwegorocketry.com/userfiles/file/Nose%20Cone%20&%20Fin%20Optimization.pdf

It's a good primer, jump down to the end for references.

The link does not work.

 

[BMcD]

https://www.offwegorocketry.com/userfiles/file/Nose Cone & Fin Optimization.pdf

I had to google "fin optimization siteffwegorocketry.com" to get there, and the URL is above. I can't see any difference between mine and dhbarr's, but oh well.

So the site seems to automatically replace the colon followed by an o with and I don't know how to fix that.

 

[dhbarr]

The link does not work.

Works for me in Tapatalk, doesn't in Chrome on Android.

 

[ThreeJsDad]

Take a look at what folks are using for NAR competition rockets. I wonder how much the tip vortexes effect the drag. The answer to your clipped delta question may be found by exploring that. A stubby version of the Super Marine Spitfire or Hurricane wing was once considered a very clean design.

 

[dr wogz]

The Spit had the beautifully elliptical wings, the Hurricane's were linear. (The Hurricane was also made by Hawker, not Supermarine)

Sorry, being snarky, but I've done some extensive study on the Spit! (Later models had laminar flow, rectangular / trapezoidal shaped wings.) The P-47 was another which had elliptical wings.

The Fliskit Cougar also had elliptical fins, as well as an older Estes kit (don't remember the name) A lot of LPR high flyers / competition models used the elliptical shape. Taper then fin all around (except the root)

 

[BABAR]

The Fliskit Cougar also had elliptical fins, as well as an older Estes kit (don't remember the name) )

Sprint?

 

[ThreeJsDad]

The Spit had the beautifully elliptical wings, the Hurricane's were linear. (The Hurricane was also made by Hawker, not Supermarine)

Sorry, being snarky, but I've done some extensive study on the Spit! (Later models had laminar flow, rectangular / trapezoidal shaped wings.) The P-47 was another which had elliptical wings.

The Fliskit Cougar also had elliptical fins, as well as an older Estes kit (don't remember the name) A lot of LPR high flyers / competition models used the elliptical shape. Taper then fin all around (except the root)

No Apologies needed, it has been a while since I built any of those models. I did not mean to imply that Super marine made the Hurricane, I simply could not remember who made it. I should have looked at my files because it is listed as the "Hawker Hurricane". I will leave you and your Spit to enjoy.

 

[Ez2cDave]

https://webcache.googleusercontent.....php?page=Resources+&cd=9&hl=en&ct=clnk&gl=us