# Whistler's Mother

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#### jqavins

TRF Supporter
I wonder of anyone has ever done a wind tunnel and CFD analysis of aerodynamic whistling. It seems like that would make designing something deliberately whistle would be a lot easier with that data available.

That might make for a university masters thesis.

#### GlenP

##### Well-Known Member
I am not an expert on whistles, but most of them would probably be much less loud than the engine itself. I think they have a particular air speed at which they are effective, which means on an accelerating rocket, they might only whistle for a short period of time while the velocity hits that sweet spot. But, it might be possible to have different types of whistles that are effective at different speeds during the ascent.

also, with a jolly logic chute release, and one of those football type of whistles, you could get a portion of the descent coming in ballistic and whistling, but not sure how safe that is if the chute release fails.

so, a couple of things to consider for keeping the altitude low and the speed slow: a saucer type or monocopter, or a spinning saucer like the Quinstar. You could put some surface Nerf-type whistles on something like that and have a better chance at hearing it while lower to the ground during the powered phase.

#### BABAR

##### Builds Rockets for NASA
TRF Supporter
Okay, work with me here...

Bagpipes have a mouthpiece reed and three drones. The drone reeds have a constant airflow through them supplied by the bag. Maybe something similar? The airflow through a drone reed wouldn't be that high.
The sooond of bagpipes coming from a rocket would really birl ma kilt!

#### Cape Byron

##### The BAR formerly known as Skippy-2
TRF Supporter
The other idea that just came to me was from that line drawing I posted:

Using that idea of an adjustable tethered 'tongue', maybe you could mount a styrene reed to the rear face of a NACA duct? Just thinking out loud. It's the voices in my head...

#### PatD

##### Well-Known Member
TRF Supporter
The other idea that just came to me was from that line drawing I posted:

View attachment 447383

Using that idea of an adjustable tethered 'tongue', maybe you could mount a styrene reed to the rear face of a NACA duct? Just thinking out loud. It's the voices in my head...
I would think that it partially depends on the stagnation layer depth as to whether you would get enough flow thru the duct.

#### Sooner Boomer

##### Well-Known Member
I was thinking a long tube with a forward "head" something like what's on an organ pipe, recorder, or pennywhistle.

Air enters from the left, travels down passage B. At sharp edge C, air stream oscillates between the inside of the tube and the outside, producing pitch (sound waves).

#### jqavins

TRF Supporter
That has the advantages of well moderated pressure and flow rate from the air source, and mostly still air out side the the opening C. When it's mounted on the side of a rocket it won't have those things. Passage B is like a tube fin that's too long for its diameter, and if you've ever tried to play a recorder or pennywhistle outside on a windy day (I have) then you know how important the airspeed above C is.

A coach's whistle works similarly, and I have read of those being mounted to the side of a rocket and not working at all. (I haven't witnessed or tried it.)

#### hcmbanjo

##### Well-Known Member
Bagpipe drone reeds (the reeds in the long stocks laying on the player's shoulder)
require a very constant air pressure.
Too little airflow and they won't "strike in", too much airflow and they shut off.
They might only sound when the rocket is at a certain speed.
(I haven't touched my Bagpipes in two years and really don't miss them.)

#### GlenP

##### Well-Known Member
There’s the electronic option, use a keychain personal alarm, ie a screamer, but rip the cord off at launch instead of at ejection. Those might be loud enough, depending on the motor, but not exactly an acoustic, wind-driven whistle. But it will keep sounding after landing to help you find it in the tall grass!

#### Sooner Boomer

##### Well-Known Member
That has the advantages of well moderated pressure and flow rate from the air source, and mostly still air out side the the opening C. When it's mounted on the side of a rocket it won't have those things. Passage B is like a tube fin that's too long for its diameter, and if you've ever tried to play a recorder or pennywhistle outside on a windy day (I have) then you know how important the airspeed above C is.

A coach's whistle works similarly, and I have read of those being mounted to the side of a rocket and not working at all. (I haven't witnessed or tried it.)
You went straight to "it can't possibly work" without trying to do "how the heck do I make it work".
Both a coach's whistle, a recorder, or even a transverse flute depend on a "splitter" and a resonating cavity. You don't need the "beak" or mouthpiece. *In theory* the resonating cavity could even be inside the main body tube. "All you gotta do"* is direct flow across the splitter. You could use a NACA duct, a funnel, you could probably mount the resonating tube away from the body on a pylon or standoff. Of course there would need to be multiple resonate tubes around the main body tube to make equal drag.

*famous last words...

#### jqavins

TRF Supporter
I can see where it reads like "it can't possibly work." My bad. My meaning was that the conditions with a person playing the instrument are quite different from the conditions on the side of a rocket. And two immediately apparent differences both work in favor of functioning on the ground, against operating on a rocket.

My gut feel is that it won't work, or the the arrangement would have to be substantially changed. I have experience indicating that simply attaching a whsistle to the side all but certainly won't be sufficient. Try holding a whistle of some sort out the window of a car at 60 mph (with someone else driving ). I've tried this and could never make it work.

You mentioned a transverse flute. I've tried the same car window experiment with a bottle, and that does work. However, the angle at which you need hold the bottle varies quite a bit with the speed of the car.

(People say that sounding a flute is just like blowing over a bottle. I can get bottles from a mini coke to a five gallon water cooler bottle to sound, but could never get a toot out of a flute. .)

##### Lonewolf.... No Club
Try holding a whistle of some sort out the window of a car at 60 mph (with someone else driving ). I've tried this and could never make it work.
Depending on the rocket of course, the rocket will be moving at 250 mph, not 60. One would think that at some point, the air speed will be sufficient to make the whistle work.

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#### jqavins

TRF Supporter
My expectation, not that I have proof, is that 60 mph is too fast, not too slow. Certainly one's breath going into a whistle is moving a lot slower. And it's about, if I'm right, the air moving along the outside, over the throat where oscillation is supposed to be happening.

#### GlenP

##### Well-Known Member
Vertical velocity will increase during boost to a peak value, then decrease during coast, to near zero at apogee, then hopefully before velocity increases downwards by too much while ballistic you have chute deployment.

So, you may hit one particular velocity for two very brief instants, once during boost while accelerating and once again during coast while decelerating.

The whistle would have to be louder than the engine during boost to be audible, and close enough or low enough altitude to be heard during coast.

Maybe, if you have different types of whistles that operate at different speeds you might have a better chance of hearing one or the other for more portions of the flight.

If you have a rotor recovery, you might get enough speed at the rotor tips for a surface nerf type whistle to make sound on the way down?

##### Lonewolf.... No Club
I have an old chrome whistle, like coaches use. My Dad always used it to call the horses and dogs when it was feeding time.

I just did a bit of R&D out in the shop using my air compressor.
• If the air moves over the upper slot, the whistle doesn't blow (like holding it out the window with mouthpiece into the air).
• If you tilt the back down so the upper slot isn't in the slip stream of air, the whistle will blow at a low amount of air into the mouthpiece, but not as loud as when you blow through it with your mouth.
• Too much wind speed and the internal ball sticks in the upper slot.
So I guess the pipe organ design, as originally discussed, or the nerf style are preferred going forward?

TRF Supporter

#### Sooner Boomer

I was wandering through the rocketry section of Hobby Lobby recently and found these. Didn't have an extra $10. Maybe next time. #### lakeroadster ##### Lonewolf.... No Club I was wandering through the rocketry section of Hobby Lobby recently and found these. Didn't have an extra$10. Maybe next time.
Thanks for posting that! Imagine one of those with a BP motor, biggest that will fit. Have the motor rear eject itself attached to a streamer, and let the Scream Rocket do it's thing.

I mean.... what's the worse that could happen?

Scream Rocket 1202167

#### jqavins

TRF Supporter
It doesn't whistle, but along similar lines I did discover once than a MicroMaxx engine fits perfectly into the aft end of a Nerf dart. I launched one. It flew nicely.

#### DrewW

##### Well-Known Member
My mind wanders to rocketry when doing mundane home improvement stuff...

Has anybody built a tube finned rocket, lets say 6 fin tubes, and made (3) of the fin tubes scratch built whistles?

The rocket would sing to you on it's way to apogee.

John
I was working on this very design! Whistler for the BT60 airframe and Whistler's Mother for a notionally 3" scale up to be used only with long burn motors.

#### DrewW

##### Well-Known Member
(No time to read the whole thread at the moment. I'll get back to it.)

If you do get a three whistle rocket to work, please tune their frequencies in a 4:5:6 ratio. That's a major chord.
I was planning on a D-flat minor tuning

#### BABAR

##### Builds Rockets for NASA
TRF Supporter
It doesn't whistle, but along similar lines I did discover once than a MicroMaxx engine fits perfectly into the aft end of a Nerf dart. I launched one. It flew nicely.
potential?

#### teepot

##### Well-Known Member
TRF Supporter
You could glue all 36 to the the tube like warts. That would make a lot of noise. I think?

#### teepot

##### Well-Known Member
TRF Supporter
Those 36 darts are $60 on Amazon plus shipping. But....you can get 20 for$10. Hmmmm.

#### Sooner Boomer

##### Well-Known Member
Got all my bills paid early, and had just a bit left over. Went back to Hobby Lobby and bought a set of whistling rockets. Found some interesting stuff...

The head and fins are foam. The body is wrapped with a vinyl sticker. Looks like the fins are glued onto the wrap with hot glue or epoxy. The body, finger pulls, and the "hooks" are plastic.

I grabbed the finger pull and twisted. Was able to pull it out fairly easily.

The body tube is hard translucent plastic.

This is how the whistling head is attached...

It's kind of a "good news/ bad news" sort of deal. The body tube ID is too small for 18mm engines. 14mm will fit fine with centering rings. It looks like it *might* be possible to transplant the head onto BT20 stock, if I can tease the head out of the plastic tube. I have no problem flying this on a 13mm engine. I don't know if I will just spit the engine (they're really light), or try to build a motor mount with streamer/whatever. I also have no problem letting the plastic body with the foam-covered head free fall back. Obviously, it's going to arc over and come in nose first. Before you take that deep breath to start yelling at me, that's exactly what these things are designed to do. Label on the package says "flys to 150 feet". I don't know if a 13mm motor will carry it any higher, but I doubt there would be any significant increase in terminal velocity over the rubber band powered flights.

It's snowing and really, really cold outside right now or I would try one of these out with the rubber band. Nope for tomorrow. In fact, pencil out all of next week...

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#### teepot

##### Well-Known Member
TRF Supporter
I bought 20 of the whistling nerf darts. Just waiting on them to arrive. I'm planning on either taking the head off and gluing it to the side of a rocket or leaving them intact and attaching the whole dart to a rocket.