Low Power guying asking for High Power Advice-- Fin Whistling?

[BABAR]

https://www.rocketryforum.com/threads/whistler-fails-again-but-nice-flight.155173/

I have seen and heard about High Power rockets which whistle on Ascent, seems to have something to do with split fins. Above post is my try, using different splits, from 1/8" to 1/2". No joy on a B engine, may try a D.

Any advice on any fin configurations or velocity requirements are fin tapering or whatever would be appreciated.


Thanks!

 

[MikeyDSlagle]

My 4" Cowabunga whistles the most of all my rockets. Just a simple 3 fin short stubby rocket. All square edges on fins, 1/4" fins. My Tyrannosaur doesn't whistle, that I can remember, it is split fin, leading edge of forward fins are beveled and the tip chord edge of aft fins are beveled, 1/4" fins. Both rockets are polished pretty good.
Cowabunga hasn't flown fast and hard at all. I think only H motors. So it is still low at burn out.
Tyrannosaur has flown on a J315 and K600. If it whistled on the K600 it was too high to hear by the time the motor burned out.

 

[Binder Design]

Split fins won't always whistle especially if the fins are beveled. Fins with holes like our Galaxy or Terrordactyl will whistle like crazy.

 

[boatgeek]

The whistling is from turbulence coming off the fins. Square fin trailing edges (especially with thick fins), holes in the fins, and relatively closely spaced split fins generate a lot of turbulence and are more likely to whistle. Beveling/airfoiling fins makes for less turbulence off the trailing edge.

 

[kuririn]

My 4" Cowabunga whistles the most of all my rockets.

Fins with holes like our Galaxy or Terrordactyl will whistle like crazy.

Guess I'll have something "extra" to look forward to then.

 

[BABAR]

Okay thanks guys. My squared fins won't get any any squarer than they they already are so I've already tried that route. Time to punch some holes!

 

[DAllen]

I think for maximum whistle you want a shorter and higher thrust motor to get the bird up to speed faster and with a quicker burn-out. So I would think an AT H550 is much better suited for a whistle than say an AT H170.

 

[mpitfield]

I have seen quite a few Wildman Darkstars whistle, although mine doesn't. It could be that the ones I have seen use squared fins, whereas mine are airfoiled.

I am currently working on a whistling or screaming rocket design. However, I won't be launching it until next spring. Who knows if it is a waste of effort or will make any noise, but I will be surprised if it works as intended. Regardless I will post results either way.

If you get some consistent results, please post them and good luck.

 

[Nytrunner]

Maybe get a 24/40 case and try some fast burn reloads (or single use fast burns)

 

[kuririn]

Sub the head of a Nerf whistling dart for the plastic "supersonic whistle" in the Estes Screamin' Mimi.
https://www.oldrocketplans.com/estes/est2185/est2185.htm
The whistling sound when shot out of a Nerf gun is most apparent with the dart travelling towards you.
So you would have to launch it...……...
Never mind.
I have a clone in the build pile.

 

[Binder Design]

You could always tape some whistles to the rocket......

 

[BABAR]

You could always tape some whistles to the rocket......

Tried that. Even put a funnel in to duct the flow to the whistle. No joy.