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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 26320
Location: Livermore CA USA
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 Posted: Sat Oct 30, 2010 5:14 pm Post subject: Canopy Skirt Buzz... |
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Hello Listers,
After the very first flight on the RV-8, I discovered that the fiberglass skirts around the canopy loved to buzz against the turtle deck skin at anything over about 100mph. To soften the intersection between the skirt and the skin I added a row of Velcro-brand "loops" tape all the way around the base of the canopy skirt on the inside including around the bottom of the windscreen so that when the canopy was closed any skin to skirt areas were cushioned with a thickness of the Velcro.
That worked great and totally eliminated the buzzing and also sealed up the cabin nicely. I was pleased.
But, after a Summer in California and 112 hours of flying, the Velcro just didn't hold up. In the Summer sun, the glue became gooey and the tape slipped out of position along the curve behind the passenger and looked like grandma's slip was showing. Along the extreme rear where the skirts come together and the fit is pretty tight, the glue squeezed out from the heat and kind of goo-ed all around on the metal.
So, I removed the skirts a couple of weekends ago and literally spend a whole weekend removing the Velcro and all of the glue. I was lucky and the in the process I didn't remove any of the textured paint on the skirts or windscreen frame - whew, that was a scary two days.
This weekend I finally got to take her out for a flight after the oil cooler replacement (all went fine, btw) and try out the new "tape-less" installation.
Holy COW!! It was SOOOOOO noisy! At 200mph I took the headphones off and couldn't believe the DB level. I really couldn't stand the noise level with the headphone ON, and without then it just plain hurt. I slowed down to about 150mph and the noise decreased slightly, but not that much. I slowed down to a stall and finally the buzzing stopped, but as soon as I pushed the nose over and speeded up a little it started again.
Obviously I'm going to have to put something like the Velco back on the inside of the canopy frame. But what? I'm guessing that all RV-8's must have this issue. I surprised there isn't something in the plans to deal with it. Is there some magic tape/insulator that people are using for this that will hold up in the heat of the Summer sun?
Thanks in advance!
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Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Blog
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 112+ Hours Total Time Since May 2 2010 Test Flight!
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Matt Dralle
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Speedy11(at)aol.com
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| Posted: Sun Oct 31, 2010 8:50 am Post subject: Canopy Skirt Buzz... |
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Matt,
I haven't had that problem.
Stan Sutterfield
| Quote: | | I'm guessing that all RV-8's must have this issue. |
[quote][b]
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 26320
Location: Livermore CA USA
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| Posted: Sun Oct 31, 2010 9:04 am Post subject: Canopy Skirt Buzz... |
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At 09:45 AM 10/31/2010 Sunday, you wrote:
| Quote: |
Matt,
I haven't had that problem.
Stan Sutterfield
I'm guessing that all RV-8's must have this issue.
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Stan,
Wow, really? Do you have anything between the fiberglass skirt and the top of the turtledeck? Foam, velcro, etc?
Do you have a perfectly tight fit all the way around? I've got a little pooch on both sides kind of at the center of the concave, roundy part.
One thing I forgot to mention in my original post was that I tried unlatching the canopy to see what impact it would have. The buzz got even louder.
Another thing I tried was adjusting the Prop RPM. There was definately a relationship between the buzz and the RPM, not related to speed of the aircraft. A harmonic of sorts.
Another odd behavior was that when I was climbing out, I didn't hear it at all. It wasn't until I pushed the nose over and started picking up speed that it started.
Matt
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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: 111+ Hours TTSN - The Fun Never Stops...
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vshimsl(at)live.com
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| Posted: Sun Oct 31, 2010 10:45 am Post subject: Canopy Skirt Buzz... |
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I use the more expensive p-channel door seal from Home Depot, meaning it is
not. Trick is, I heat the tape glue with a heat gun before applying it. Same
for Velco. Stuff doesn't budge.
You could use the 1/4 inch sound damping foam (sandwich of foil, foam, glue)
from ACS on the underside of the turtle deck to stiffen up it up. Come to
think of it, this may be just that, a turtle deck problem rather than a
canopy skirt problem.
My skirt doesn't buzz either. But then, I used super sound proofing and the
above mentioned foam wherever I suspected 'oil canning' might be a problem.
Regards,
Vince H.
Washington State
RV8 69.5 hours & still stalling on the wheel pants, fairings, and paint.
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av8er2fly(at)peoplepc.com
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| Posted: Sun Oct 31, 2010 1:23 pm Post subject: Canopy Skirt Buzz... |
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I used some 1/4 inch weatherstriping semmed to seal just fine. Mark
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Speedy11(at)aol.com
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| Posted: Tue Nov 02, 2010 7:55 am Post subject: Canopy Skirt Buzz... |
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Matt,
I have nothing between the skirt and the fuselage anywhere along the skirt. I do have a nice fit all around, but part of the difference may be in the way I modified my skirt. I didn't like the appearance of the standard skirt where it has an upward cutout area just aft of the rear seat. I suppose the idea was to have a better fit over the fuselage contour. But it is fiberglass, so I decided to fill in that area and continue the line from the bottom of the skirt smoothly up to join the curve at the rear of the skirt. It produced a better appearance to the skirt and MAY have inadvertently solved the problem you're describing.
You can see the glass work at http://www.rv-8a.net/2009Feb.htm and the finished skirt at http://www.rv-8a.net/2009Mar.htm.
The only problem I've encountered with the skirt so far is that the slipsteam bows it out on each side at the rear cockpit. Then when flying in rain, the water is drawn up through the bowed spot and into the cockpit. I think I can solve that problem by adding a "strake" or stiffener on the outside of the skirt to force it to retain its shape.
I also added a "hat shelf" to the aft end of my canopy with the intention of stopping the cold air that others had reported blowing on the passengers neck. I had planned to use a "V" shaped seal on the bottom of the hat shelf to stop the draft. But, most of the draft has already been stopped by the hat shelf, so I still have not added the seal. My hat shelf is shown at http://www.rv-8a.net/2009Jan.htm.
Regards,
Stan Sutterfield
| Quote: |
At 09:45 AM 10/31/2010 Sunday, you wrote:
| Quote: |
Matt,
I haven't had that problem.
Stan Sutterfield
I'm guessing that all RV-8's must have this issue.
|
Stan,
Wow, really? Do you have anything between the fiberglass skirt and the top of
the turtledeck? Foam, velcro, etc?
Do you have a perfectly tight fit all the way around? I've got a little pooch
on both sides kind of at the center of the concave, roundy part.
One thing I forgot to mention in my original post was that I tried unlatching the
canopy to see what impact it would have. The buzz got even louder.
Another thing I tried was adjusting the Prop RPM. There was definately a relationship
between the buzz and the RPM, not related to speed of the aircraft. A
harmonic of sorts.
Another odd behavior was that when I was climbing out, I didn't hear it at all.
It wasn't until I pushed the nose over and started picking up speed that it
started.
Matt |
[quote][b]
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