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  #1  
Old 03-06-2012, 06:07 PM
HighSchoolBuilders HighSchoolBuilders is offline
 
Join Date: Jan 2009
Location: Hong Kong
Posts: 153
Default Cracked Dimple Repair.... 3/32" hole became 7/32"

Hi guys,

Today I tried to repair a cracked dimple in the F-811 Bulkhead, but end up enlarge the hole to a size 7/32 before all the cracks are gone.

Do you guys have a better way to fix these cracks? Luckily, I don't get these often, but when i do, it's almost certain an oops rivet or even 5/32" will be used.

For this particular boo boo, Can I use a AN4 bolt to fill in that hole? Or should I leave it open and fill it with some sealant or something?

Thanks!
Hank

Photo 1: Damaged/Cracked 3/32 hole on the bottom forward flange of F-811 Bulkhead. enlarged to 5/32 and still cracked


Photo 2: Same Hole on the F-828, not damaged, but enlarge as I tried to fit a larger rivet in.


Photo 3: Hole on F-811 after repair, now at 7/32


Photo 4: Hole in question
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RV8 Super Slow Build Kit
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First RV in Hong Kong
First Homebuilt aircraft registered in Hong Kong "B-KOO"
Completed RTW journey in 2016
Built with a group of High School Students
Aircraft donated to the Hong Kong Science Museum
In memory of Michael Tam
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  #2  
Old 03-06-2012, 08:08 PM
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GAHco GAHco is offline
 
Join Date: Dec 2006
Location: Paso Robles, CA
Posts: 1,177
Thumbs up Put a structural screw in it!

You could put an AN525-10R8 in the hole when you assemble it.
An aluminum washer under the nut would protect the structure.

It looks like you have plenty of edge distance.

The head should be to the outside.

If you wanted a little higher tech you could use a Hi-lok but I think that would be over-kill.

Best Wishes for your success!
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  #3  
Old 03-07-2012, 07:29 PM
chaskuss chaskuss is offline
 
Join Date: Mar 2005
Location: SE Florida
Posts: 1,511
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Hank,
Providing that the issue is "only" on the flange of the bulkhead, my suggestion is that you cut off the horizontal portion of the offending flange. Bend up an L shaped "scab" flange to replace the bad portion. A "scab" flange is commonly used to repair certified aircraft with a problem like this. One portion of the L is positioned against the rivet hole in the skin. The other portion lies flat against the web of the bulkhead and is riveted to the bulkhead. I had to use a number of "scab" flanges on my HS and wing main ribs, due to less than perfect manufacture of these items on my project. I have supplied a few photos, if the written description leaves you scratching your head.
For your situation, a simple L shape made from 2024-T3 of the same thickness as the bulkhead will suffice.
Charlie





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  #4  
Old 03-07-2012, 08:36 PM
TINBENDER TINBENDER is offline
 
Join Date: Mar 2012
Location: WATERLOO, IL
Posts: 9
Default

Quote:
Originally Posted by HighSchoolBuilders View Post
Hi guys,

Today I tried to repair a cracked dimple in the F-811 Bulkhead, but end up enlarge the hole to a size 7/32 before all the cracks are gone.

Do you guys have a better way to fix these cracks? Luckily, I don't get these often, but when i do, it's almost certain an oops rivet or even 5/32" will be used.

For this particular boo boo, Can I use a AN4 bolt to fill in that hole? Or should I leave it open and fill it with some sealant or something?

Thanks!
Hank

Photo 1: Damaged/Cracked 3/32 hole on the bottom forward flange of F-811 Bulkhead. enlarged to 5/32 and still cracked


Photo 2: Same Hole on the F-828, not damaged, but enlarge as I tried to fit a larger rivet in.


Photo 3: Hole on F-811 after repair, now at 7/32


Photo 4: Hole in question
Like Tom said, a Hi-Lok prob. would be overkill, but I would def use one over an AN525 panhead. I would recommend an HL18-8, prob. a 3 or 4 in length. You can go with an HL600 collar or an HL70 collar. Hope this helps!
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  #5  
Old 03-08-2012, 01:16 AM
HighSchoolBuilders HighSchoolBuilders is offline
 
Join Date: Jan 2009
Location: Hong Kong
Posts: 153
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Thanks for all the suggestions.

Charlie, I have a couple of those in my wing and HS as well, so I know exactly what you are talking about and did consider doing that...unfortunately, the backside of that bulkhead is the tailwheel spring mount, which I prefer not to drill thru it. Thanks for the photos and idea!

I never use a Hi-Lok, but I will look into it. The screw seems like an easy fix too....it's nice to have options.

Thanks again!
Hank
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Hank Cheng
RV8 Super Slow Build Kit
Titan IOX360, Catto 3 Blades RV prop, Full Dynon everything + Garmin GTN650

First RV in Hong Kong
First Homebuilt aircraft registered in Hong Kong "B-KOO"
Completed RTW journey in 2016
Built with a group of High School Students
Aircraft donated to the Hong Kong Science Museum
In memory of Michael Tam
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  #6  
Old 03-08-2012, 12:16 PM
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JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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This may not be popular, but I would have done nothing and moved on. The odds of that crack in an .025 skin propogating is minimal in my opinion.
In regard to the repair, I am sure it is fine, however, it appears to violate the edge distance requrements to the flange bend.
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