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  #1  
Old 01-04-2019, 06:53 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 4,936
Default Fretting/Rubbing of Intersection Fairing

Well it is time for my condition inspection, and it is interesting to see how the years of build actually work.

The photos below show some rubbing on the fuse of my RV7 at 69 hrs TT. There are no screws in this area and the fairing was bedded with a thin layer of micro to ensure even contact.

I find it odd that it moves and there the contact points (black spots) are, 1- on the LE of the VS and then on the fuse like the whole empennage was wiggling side to side. There are no other marks on the entire contact perimeter, but this is the only section without any screws.

Question:
Is this part designed to be structural?
Have others found this condition and what did you do?

Options:
1) Don't worry and put HDMW tape under it to accommodate the movement.
2) Add a screw to the fuse at the forward tip of the fairing? ( it won't fix the VS rub)
3) Replace the aft deck increased thickness material to .050"

Let me know what you have found, Thanks

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  #2  
Old 01-04-2019, 10:06 AM
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JonJay JonJay is offline
 
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Location: Battleground
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Very common.
I simply used the thinnest HDMW I had and put a few patches of it here and there where the contact marks where worst. It worked to stop the fretting, or stop the mild damage the fretting was doing.

I also did not finish my glass to a mirror surface. Out of sight out of mind right? It helps if you finish the underside of the fairing as nicely as the top side.
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Last edited by JonJay : 01-04-2019 at 10:09 AM.
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  #3  
Old 01-04-2019, 11:00 AM
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az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
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Smile

I used this stuff at 0.005 thick, but my main fretting was on the top and bottom gear leg intersection fairings. A lot of movement against the glass leg fairings.

https://www.amazon.com/dp/B00823JBVG/

The stickum seems to hold up well in the AZ heat.
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  #4  
Old 01-04-2019, 12:03 PM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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I don't think there is much movement on the emp fairing, though it probably doesn't take much to lightly fret the AL. My skin is painted back there and I have seen 0 damage to the paint under the fairing at 600 hours. Therefore, the amount of movement must be pretty slight.

Larry
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  #5  
Old 01-04-2019, 07:01 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
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Jon, Gil, Larry, thanks for the comments direct to the problem. I was thinking it had to be common, but had never read about it. Jon, I did use some .0025" thick packing tape to mud the fairing to perfectly match the skin. It is mirror smooth, maybe too well matched, though. Gil, I have UHWM but it is .010" thick, so I think the .005" will be perfect, so I ordered a roll.

I have tended to make parts fit precisely, and this one obviously needs to breathe.

Thanks for the suggestions!!

Update: I was reading the instructions for Fairings-Etc and they mention leaving attachment holes large and using Tinnermans to allow the glass to expand contract. I did not do this and it was all snug. I'll give that a go, add the UHMW and update this post with final results in 2020. If I am still here.
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RV-7
1st Flight 1-27-18
Phase II 8-3-18
Repairman 11-15-18
Instrument Currency 12-17-18
Shrunken Exit = ??
No Photo? => PM me.

Last edited by BillL : 01-05-2019 at 08:51 AM.
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  #6  
Old 01-12-2019, 06:46 AM
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Steve Melton Steve Melton is offline
 
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 1,963
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I saw some of this also before paint. I smoothed the intersection fairing with scotchbrite and that seemed to help. No issues after paint.
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