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Whistling at 150 KIAS .. any ideas?

wjb

Well Known Member
I know my little RV wants to grow up to be a F4U Corsair, aka "Whistling Death" ...it's developed a pronounced whistle at 145-150 kts. It's a clean tone ~800 Hz, (~ A above middle C for musical types), significantly loud, and not a vibration; it's some cavity resonating in the airflow.

I initially thought is was something in the gear fairings, with the little cuts to allow the removal of the pants and root fairings. Played with duct tape thought I found the issue at the gear fuse fairing. Liquid shimmed the gap and made those nice and tight now, but it's still there. Yawing, etc, makes some difference, but nothing magical

Other threads have suggested the tail fairing and the cutouts around elevator attach points (rudder I suppose as well), which I'll check.

Anyone else have a baby Corsair on their hands as well? Any success finding your whistle? Any anecdotal info would help to prioritize where to look.

We have a lot YAKs on our field, and I don't want them to hear me coming up on their 6...
 
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My 8 does that sometimes. Its the canopy, I just push it shut and make sure the latch is tight and that helps. It seems to only do it when its cold.
 
Gun ports

Spitfires used to tape over the gun ports in the leading edge with red tape.

Back to the issue at hand, the only whistle or buzz I have had is when the rubber seal on the wing root fairing has had a loose end.

How tight does the lower flap skin fit up against your belly?
 
Canopy?

I have a 6 with a tip up, when I changed the struts to a bit stronger, I got a whistle. I had to put seal at the front of the canopy and that stopped the whistle. Unfortunately the seal does not stick very well, just some weather seal from Home Depot.
 
Whisle

We have a 182 on the field that does the same thing ... he claims it is coming from a drain hole ????
 
I prefer to think my airplane “sings” to me when it’s happy under certain G loads. :D

Me thinks it’s also the rubber gap seal on the wing fairing. RV-8.
 
Spitfires used to tape over the gun ports in the leading edge with red tape.

Back to the issue at hand, the only whistle or buzz I have had is when the rubber seal on the wing root fairing has had a loose end.

How tight does the lower flap skin fit up against your belly?

Hi Steve .. it's pretty snug, maybe a gap of 3/32 at the aft end. It's an easy thing to check, though .. just bump the flaps down a crack and see.

I did recently put a flap up limit switch to save the motor once the flaps are fully retracted ... I don't recall exactly when the whistle started vis a vis the limit switch install, but it was pretty close in time ... I need to check the logs.

If it is due to the flaps, it didn't show up earlier in the high speed flight testing; the up position may have been slightly different earlier on before the limit switch.
 
Canopy seal

A friend used this on his tipup -7 to stop the whistling. I had the same problem on my 7A tipup and used the same material. It fixed it. It compresses very thin and makes a good seal. Could quite possibly work on a slider or an -8.

https://www.amazon.com/Building-Pro...rds=Silicone+smoke+seal&qid=1613744925&sr=8-2

Sam, do you find this seal material sticks well, the stuff I bought from Home Depot hardly sticks at all around the sides. It is stuff others have mentioned using here on VAF but I’m having little luck.
 
Al,

Yes sir, it seems to be holding up well. It is stuck on the under side of the canopy where it meets the roll bar. It's been there going on six years.
Re-check the link that I had in my first post. I had linked a similar material and have changed it to stuff I used.
 
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I’ve been told my RV7A slider whistles on final and I don’t know why. It’s a great but conversation starter so maybe I wouldn’t fix it, even I knew how.
 
Hair line crack in the wind screen. They can be very fine and almost impossible to see, but can create a pretty good whistle. The higher the speed that they start whistling - the smaller and finer a crack they can be.
 
We have a 182 on the field that does the same thing ... he claims it is coming from a drain hole ????

It's a Cessna. Tell him if he throttles back to 75% power he'll be well below 150 KIAS - problem solved. :p
 
Seal

Al,

Yes sir, it seems to be holding up well. It is stuck on the under side of the canopy where it meets the roll bar. It's been there going on six years.
Re-check the link that I had in my first post. I had linked a similar material and have changed it to stuff I used.

Thanks Sam, my seal is required at the front of the canopy but in places it is near zero space, not sure this will flatten out enough.
 
Whistling Noise Resolved

During flight testing, around 130 to 140 kts, I would develop a high pitch whistling noises. Several builders suggested the canopy seal. After careful inspection, I found an area the seal wasn’t making good contact with the airframe. I replaced the forward seal and all whistling stopped. A small unsealed area will make a lot of noise.
 
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