How to build up edge of opening?

[PaulProe]

Any fiberglass guru's here? I need to build up the edges of my exhaust cutout openings. They are cut in the wrong location.

What is the best way to make sure the buildup adheres to the edge. I know to use Tiger Hair which is glass reinforced, but I don't want the butt edge breaking a couple miles down the road.

Is a V-groove better or maybe a roughed-up generous cut-back on the inside so the bond area is about 1/2" or greater?

How do you keep the joint from cracking later?

Thanks

Paul

[mickmate]

Hey Paul, I'd thin down and roughen up an edge so you can lap it to the patch and keep the surface flush and strong.

[bkozlow]

Paul,

What I would suggest is to use a V groove. If you can use on the back side and the front side 1/2-1 oz. fiberglass cloth. This cloth is like silk and is thick as tissue paper but very strong because of the weave. Even if you use a 1/2 strip across the gap, it will stop cracks from coming to the surface and cracking your paint. You want a very shallow film of filler over the cloth so that it is very near the surface when sanded smooth.

Bill k

[vettestr]

Paul,
I would glass in the opening about an inch smaller than needed and then come back and trim the hole as needed. Blend and tapper your repair back into the body an inch or so from full thickness to nothing for a proper repair.

Use resin and mat or cloth for this and not kitty hair. It is tough to do a surface repair with kitty hair and not get air bubbles with this stuff and is more of a filler or bulk builder.