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Fiberglass repair---wheelpant

Mike S

Senior Curmudgeon
I did a bit of a carrier landing a while back, and cracked one of the wheelpants when the tire bulged a bit too much and caught the edge of the pant.

Knowing that many of the folks here at VAF are a bit put off by the thought of working fiberglass, I thought I would document the repair process, and maybe help someone out in the future.

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As can be seen here, the damage went aft of the internal bulkhead. (and luckily the bulkhead was loosened up pretty good, so I removed it for the repair)

Wheelpant%2520repair%2520002.JPG


I used some CA glue from the local hobby store to put the pieces back in place as best as I could-----not perfect by any means, but all I am trying to accomplish is making the part steady enough to do the needed fiberglass work inside the pant.

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Next I used a cordless drill and a sanding drum to smooth up the area of the repair, and to break the surface of the fiberglass to give it some "tooth" for the repair to stick.

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I used an air gun to blow out the sanding dust, and wipped things down with MEK, then I mixed up a bit of epoxy resin. I also made up a small amount of resin and flox to use for leveling out any remaining roughness, and to fill any holes or cracks.

Here you can see the flox in place, it doesnt have to be smoothed out perfectly, as the next step will take care of that.

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First layer of cloth laid directly over the flox---you can see there is enough resin there to start wetting out the glass already.

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Here I have added a bit of resin, and gotten the cloth wetted out well in the repair area. The excess cloth is just left alone for now, will take care of it later. Note the paint brush with half of the bristle length cut off, this is to stiffen up the brush when "stippling"-----jabbing the brush straight on to the cloth to drive out any air bubbles, and get a good adheasion to the layer below.

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Second layer of cloth. Again, dont be concerned about looks, extra will be trimmed later.

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And finally the third ply of cloth is down, and wetted out. I will let it set over night to harden.

Wheelpant%2520repair%2520011.JPG
 
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Repair part 2

Next morning I used a utility knife to trim the excess cloth off the area repaired yesterday. I also used a sanding block with some 80 grit to remove the paint, and CA glue, and epoxy that had gotten on the exterior of the pant.

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In this shot you can see the original cracks and see that there are some areas where I could not get the primer out all the way. I will scrape them down to bare glass, and fill the grooves, holes, and other divits with flox.

Wheelpant%2520repair%2520013.JPG


Here is the pant after appling a single layer of cloth to the exterior-----this is just to make the surface smooth for the final painting, all the strength of the repair is in the three plys I did in the inside yesterday.

Wheelpant%2520repair%2520016.JPG


Tomorrow I will sand the exterior repair, and put the bulkhead back in place. This will make the pant usable again, and it should be pretty easy for the painter to deal with when I get the plane painted.
 
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Repair part 3

Here is the repair after knife trimming the edge of the opening and trimming off the excess cloth. I have also sanded the edged of the repair to blend into the wheel pant. You can see the blue line where I am going to trim a bit more off the opening, so the next time I bonk a landing, the tire bulge should have a place to go without grabbing the pant.

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And finally after trimming the excess back to the blue line.

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This is now ready to re-install on the plane, the paint will come later.

Thanks for looking :D
 
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Good Job!

That's the way I would have done it Mike. I also added about 4 layers of 6 oz. around the entire bottom perimeter for future incidents. I have experience with this (several times)

Steve
 
Follow up info

Some of you may have noticed that the only thing I used to repair the actual crack was the CA glue. The rest of the repair is glass cloth scabbed on the surface of the original part.

In this case, the CA is fine, but if this was a structural part, or much thicker part, I would have ground a wide "V" into the crack after doing the interior layup. The interior layup will hold the part in the proper shape while doing the balance of the repair.

I would then have used either flox, or layers of fiberglass to fill the "V". The reason for doing this is to regain the strength of the original part. I would still put a single (at least) layer of cloth on the exterior, but the real strength would be in the repair, not the added skin layer. This layer protects the edges of the repair, and help to blend the overall area for a better looking finished part, it is not a big factor in the actual strength of the repair.

When doing this type of repair, it is important to make a very flat "V"----at least a 7 to 1 slope on the sides. 10 or 12 to 1 is even better.

There is a lot of information out there on the internet, try Google. Look for "fiberglass scarf repair"

Here is a link to a rather well done site.

http://www.ericgreeneassociates.com/images/Repair_of_Composite_Boat_Damage.pdf
 
In this case, the CA is fine, but if this was a structural part, or much thicker part, I would have ground a wide "V" into the crack after doing the interior layup......I would then have used either flox, or layers of fiberglass to fill the "V".

Here you go Mike, from the archives....

Joint types:



Scarf layup schedules:



As noted, the wheelpant repair isn't structural so scab plies will do just fine. However, if strength/durability equal to the original is required you want either (a) balanced layups with a filled core, or (b) fully scarfed layups.
 
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Thanks Dan, good illustrations of what I was describing------or at least trying to describe.;)
 
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