what is that noise?

Hello, I fly a 1979 Nimbus 2 carbon, and since a few years I hear a cracking noise behind me. That noise occurs more often after a few hours of flight, maybe related to temperature change with altitude. You can hear the cracking noise in this video:

https://www.youtube.com/watch?v=pke-...ature=youtu.be

Did you already hear that noise? how do you think I can fix this ? do you think it is dangerous?

Thank you for help and advice

It may be as simple as your fiberglass seat back rubbing against some part of the fuselage interior. Can you duplicate the sound while sitting in the cockpit on the ground?

Le lundi 22 juillet 2019 13:22:57 UTC+2, a écritÂ*:
It may be as simple as your fiberglass seat back rubbing against some part of the fuselage interior. Can you duplicate the sound while sitting in the cockpit on the ground?

I don't think it is the seat back, no sound while sittin in the cockpit on the ground. Maybe I will try with somebody else moving /shaking the wingtip while sitting on the ground to check if I can hear that noise...

Another possible source of the noise might be the wing spars rubbing against each other. My Pegase made that sound, and then just to try to isolate it, I put a very light coat of cooking oil on any part of the spar that looked like it had been rubbed. Creaking noise was gone immediately, so I quit worrying about it.

Sounds like the wings are about to come off.

Kidding, I would be looking for signs of rubbing anywhere. Canopy is always a good place to start as they expand and contract the most.
Spars are a possibility.
Seat back.
After that the options become less. Good luck hunting

At 10:39 22 July 2019, gregv wrote:
Hello, I fly a 1979 Nimbus 2 carbon, and since a few years I hear a
cracking noise behind me. That noise occurs more often after a few
hours of
flight, maybe related to temperature change with altitude. You can
hear the
cracking noise in this video:

https://www.youtube.com/watch?v=pke-...ature=youtu.be

Did you already hear that noise? how do you think I can fix this ? do
you
think it is dangerous?

Thank you for help and advice

Possible rubbing of the canopy frame? The plastic canopy will
shrink when the temperature falls after flying for a while, especially
at higher altitudes in the mountains. You may only be able to
replicate the noise on the ground in cooler temperatures.

RO

Likely the canopy or spar. Clean the canopy rail and the area where it touches on the fuselage. A light coat of wax or a very thin open cell foam seal may help on the canopy. Check the spar for rubbing and wax any possibility areas.

Le lundi 22 juillet 2019 16:07:24 UTC+2, Tim Taylor a écritÂ*:
Likely the canopy or spar. Clean the canopy rail and the area where it touches on the fuselage. A light coat of wax or a very thin open cell foam seal may help on the canopy. Check the spar for rubbing and wax any possibility areas.

ok thanks, I think it is spar related, I will wax and check for rubbing

On Monday, July 22, 2019 at 4:01:58 PM UTC+1, gregv wrote:
Le lundi 22 juillet 2019 16:07:24 UTC+2, Tim Taylor a écritÂ*:
Likely the canopy or spar. Clean the canopy rail and the area where it touches on the fuselage. A light coat of wax or a very thin open cell foam seal may help on the canopy. Check the spar for rubbing and wax any possibility areas.

ok thanks, I think it is spar related, I will wax and check for rubbing

I used to have a Nimbus 2c. It was a long time ago but I still remember what I think is the same cracking sound you are describing. Quite loud and sharp. It never bothered me. Like you I thought it came from the spar stub area when there was a bit of turbulence.

On Monday, July 22, 2019 at 6:39:11 AM UTC-4, gregv wrote:
Hello, I fly a 1979 Nimbus 2 carbon, and since a few years I hear a cracking noise behind me.

Count your blessings. I have a howling banshee in my tail boom.