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Wheelpant Repair - Fiberglass

7

7DeltaLima

Well Known Member
Hello all:

The Powertug slipped a few months ago and left a couple of gashes in the wheelpant. With the cold and ice, I thought it about time to repair.

I've laid up a couple of strips behind the gashes but how should I fill the hole? I have some Fiberfil that I've used and it's easy to work with but not sure if it is appropriate for this big of a gap. I built up the edges of the cabin in a couple of places with some cotton fiber / resin. Since the move, I have no clue where any of the cotton fiber is or if it made it from Iowa to Georgia.

Once the surface is smooth again, I'll have to drill the 1 inch or so hole for the tow bar to pass through again and I think the cotton fiber may just grab.

IMG_0896-XL.jpg


IMG_0897-XL.jpg


Thanks in advance,
Doug
 
If you just use filler it will likely crack, especially if you have the tow bar in there. You need cloth in there. Feather out the step around the edges and lay in some cloth. I find an angle air tool with a 2" disk works well for this. You can't have a butt joint. There needs to be overlap. Once that has cured you will have to trim the edges flush with the surface and fill imperfections as required. Again the die grinder is great for this. You want to try and keep the filler to a minimum because it is prone to cracking.
 
Exactly as Scott says...you want a scarf joint, so grind the edges back and lay in a few plies of glass. Either layup below will work. I'm partial to the second one.

Scarfed%20Repair.jpg
 
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Thanks Guys:

I've seen the diagram from Dan before but always focused on the first picture and while I've understood the concept, quite honestly could not fathom how you could actually execute multiple layers of cloth, cut precisely to fit working with the thin material we're working with.

I never really paid enough attention to the differences in the first versus second. Looking at the second diagram, I can execute this one. I understand the concept is cutting smaller pieces and building up accordingly.

Please correct me if I'm stating this wrong, but reality is that if I lay these cloths up overlapping the edges a bit (i.e each piece a bit smaller than the last but each piece at least as high as the original surface), when I sand back smooth with the original surface I'll accomplish layers as described in the diagram.

Regards,
Doug
 
7DeltaLima said:
Please correct me if I'm stating this wrong, but reality is that if I lay these cloths up overlapping the edges a bit (i.e each piece a bit smaller than the last but each piece at least as high as the original surface), when I sand back smooth with the original surface I'll accomplish layers as described in the diagram.

Regards,
Doug
Click to expand...

Correct...
 
7DeltaLima said:
Please correct me if I'm stating this wrong, but reality is that if I lay these cloths up overlapping the edges a bit (i.e each piece a bit smaller than the last but each piece at least as high as the original surface), when I sand back smooth with the original surface I'll accomplish layers as described in the diagram.
Click to expand...

Correct. Actually, the sizes of the individual plies doesn't matter very much. This repair style is more than adequate for the composite loads placed on RV glasswork.

Scarf%20Joints.jpg


Key concepts are (1) the idea of using a sanding disk to cut the dished scarf in the original glasswork, and (2) NOT making repairs like D.
 
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Ouch!

Doug, easy fix. Don't loose heart. Good advise provided above.
Couple of points, maybe all is already clear... or moot.

1. Epoxy won't adhere very well to any surface that isn't recently sanded / roughened. Inside or outside.

2. Mark the center of the existing holes before grinding away the exterior in prep for exterior plies. This will make re-drilling (re-locating) the hole a bit easier. Glass is mostly clear, a Sharpie mark on the inside surface will be visible from the outside after cure.

3. The thought of repairing / repainting four-color wheel pants drove me to a monochrome wheel pant scheme... and probably cost me a trophy.

4. How can we prevent this type of damage from recurring?

- Roger
 
All excellent points, especially the need to rough up existing epoxy. I think you avoid this happening by pulling on the prop and using the tow bar only for steering and making sure the towbar soring is good and stiff
 
DanH said:
Correct. Actually, the sizes of the individual plies doesn't matter very much. Below, A and B are really the same thing; both sand out to become C.



Key concepts are (1) the idea of using a sanding disk to cut the dished scarf in the original glasswork, and (2) NOT making repairs like D.
Click to expand...

I hope this shows as well in the picture as it does in person. I did "B"and this is what "C" looks like after sanding. Thanks all for the direction and guidance.

I had a "chunk out" around the tire. I built up a solid backing and then laid up 4 layers of cloth which you can see feathered in after I sanded it back down.

IMG_0903-L.jpg


This one is the one where the Powertug slipped and gashed the wheelpant. Same scenario .... built up with 3 or 4 layers of cloth then sanded back down.

IMG_0904-L.jpg




Thanks again.
Doug
 
Finished product

Picked the wheelpant up from the paint shop and it turned out great. One note as was pointed out to me earlier is to consider the number of colors on the wheel pants. A bit more involved by having the four colors that the paint guys had to deal with.....

Regardless - turned out pretty good.

IMG_0908-L.jpg


Thanks again for the help and guidance.
Doug
 
7DeltaLima said:
Picked the wheelpant up from the paint shop and it turned out great.
Thanks again for the help and guidance. Doug
Click to expand...

It is a great pleasure when the student does such a fine job. Those are textbook, aerospace, steely-eyed missile man scarf joints! if you don't mind, I'm going to upload them, and then drag 'em out the next time somebody asks how to do it.
 
Question for Doug....

In post #1 you mentioned backing the hole with a couple of strips. Were those necessary for your repair or did you have to cut them out to make the scarf. I can visualize a situation where the backing strips could be helpful either in place or not. I'm just curious what you did.

If you left them in, did you fuss over the curved nature of the wheel pant?

And lastly...I'm glad you asked this question. I might have been tempted to mix up some epoxy and flox to do the repair rather than scarfing and laying on new layers.
 
Bevan said:
As discussed elsewhere, it is not advisable to push/pull on a CS prop.

Bevan
Click to expand...
Ok. I'll bite. Since when can I not push or pull a plane (single, normal human strength) with the root of any prop? Take out ring scratches and claw marks. Then relate to the movement of the plane under power.
 
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