Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 26321
Location: Livermore CA USA
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 Posted: Sat Apr 02, 2011 9:07 am Post subject: Canopy Skirt Buzz... (Follow Up) |
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Since I wrote the message below, the ambient temps have gone up quite a bit and I started opening the air vents in the cabin again. Well, the combination of the warmer canopy parts and the extra pressure inside the cabin because of the vents, the buzz returned and was pretty loud. At cruse, the buzz was louder than the engine!
So yesterday I took a look at where the buzz might actually becoming from. Closer inspection showed that, about right in the middle of the fiberglass skirt "curve" behind the rear seat it wasn't quite lying flush against the top fuselage skin. I found that I could kind of hammer on the skirt with my finger at the high point and make a sound similar to what I was hearing in flight.
Last Summer, I had put a strip of Velcro "loops" all the way around the base of the canopy skirt which definitely deaden the noise. BUT, after sitting out in the 110 degree sun, the glue on the Velcro got all melty and the tape started to slide do to the side "stress" of applying the tape on the curve.
I noticed during a trip to Lowes last night that they have a "Heavy Duty" version of the Velcro tape that is suppose to hold up to outdoor conditions. I bought a roll and headed out to the airport.
I didn't really want to put tape all the way around the base of the skirt like before in case this new Heavy Duty stuff didn't hold up in the sun either. So, I found the aforementioned high spots on the left and right sides, and simply applied a 3" long strip at the "transition" area between where the skirt was touching the skin and the high-point of the skirt above the skin. I noted that tapping on the area didn't yield nearly the buzz as before.
I went out and flew and I'm extremely happy to report that the buzzing is completely gone!! I feel its kind of the perfect solution in that now I have a nice layer of UHMW all the way around the canopy skirt to minimize the top skin abrasion, and have stopped the buzzing with a simple and easily replaceable solution.
Matt's $.02.
Best regards,
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Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 160+ Hours TTSN - Paint job is all that's left...
At 12:15 PM 3/22/2011 Tuesday, Matt Dralle wrote:
| Quote: | At 10:25 AM 3/22/2011 Tuesday, you wrote:
>Matt,
>Did you settle on a material that you preferred for deadening the canopy buzz [on your RV-8]? We are experiencing the same thing but at a very narrow speed range. Before we reinvent the wheel I figured I would ask.
>
>Thanks,
>Robin
Hi Robin,
Yes, solved mostly. Here the stuff to get:
http://cshyde.thomasnet.com/viewitems/tapes-with-psa/uhmw-tape--black-anti-stat-rubber-adhesive?forward=1
This is black UHMW table with a rubber adhesive (good to 150F). I got the .020" stuff.
Its not very bendable sideways, so don't try to get the .5" kind and wrap it around the s-curve in the back. It definitely won't stick for very long.
Get the 6" wide stuff - Part number <http://cshyde.thomasnet.com/viewitems/tapes-with-psa//item/tapes-with-psa/uhmw-tape--black-anti-stat-rubber-adhesive/anti-stat-uhmw-19-20blk-6-5?>19-20BLK-6-5 (5 yards) or <http://cshyde.thomasnet.com/viewitems/tapes-with-psa//item/tapes-with-psa/uhmw-tape--black-anti-stat-rubber-adhesive/anti-stat-uhmw-19-20blk-6-18?>19-20BLK-6-18 (18 yards) - and lay it flat over the skirt on the inside and then trace the contour. Move it up by about .75" and then trace again. Then cut out the piece which should be a perfect fit around the inside edge of the canopy skirt. I forgot to take any pictures of the process! That's so not like me! 
I also used the .5" stuff (<http://cshyde.thomasnet.com/viewitems/tapes-with-psa//item/tapes-with-psa/uhmw-tape--black-anti-stat-rubber-adhesive/anti-stat-uhmw-19-20blk-5-5?>19-20BLK-.5-5) for along the straight left and right side of the skirt. Although, I wish I'd used the .75 stuff.
Seems to dampen the vibration and also doesn't mark the paint/metal due to its low co-efficient of friction. Its basically the same stuff that Van's sells for the flaps, but much thicker and black. I also like the high-temp rubber adhesive. We'll see how it holds up over the Summer.
My only complaint is that I wish they made a .040" thick version.
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Matt Dralle
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