Modifying fiberglass ?

[roverman]

Perhaps some  experts could advise ? I need to section/reduce the length/width of a 1 piece tonneau cover. This isn't for an LBC- BUT,  maybe others could benefit from learning a good procedure ?  Subject is one piece chopper gun, with low flex resin. Brand is likely LEER, or similar.I need to narrow approx 1 foot and it has a 2.5"r, turned-down rolled edge.Seems to me, it would be best to narrow, near the start of the rolled edge area,(less flexure/span stress than in the middle) ? I'm considering making my cuts at 45 deg., through the thickness, again for more strength. Would I need to pop rivet a spanner plate, from underneath, across the seam ? Suggested resin ? Your skilled input is appreciated, roverman.

[Preform Resources]

Art, I'm assuming the part has  some sweep in both directions so use some 1/4" tempered hard board or a sheet of aluminum you can use some 2 sided tape and som long reach welding clamps to hold the two pieces together this backer matl should be 18" wide to get the  sweep of the part and support everything while working as far as the rounded section  just form up some thin aluminum  and tape in place to prevent resin from dripping through( put this lot on the exterior of the part ) .
lay up a strip of mat 10/12" wide first then lay up two more stagering the  8 /9 " for ther second 6" for the third let it sit overnight or longer particularly if you use poly resin.

after it has set up good and hard strip off the backup matl and grind a 3" wide valley at the mating edge of the  taper it from .090
deep at the center out to 0 , lay up strips of glass and resin in the vee'd out area and let set up for a day or so , try to sit the part
so as to mimick the shape while this lot is curing  then just sand down the center strip and usr bondo to achieve a surface prime
and paint.
I don't think you will need or want to attach anything else to maintain it's integrity the curved portion you mentioned should aid
in the part keeping its shape.   I hope this helps.
Dave

[roverman]

Dave thanks,I can narrow the part anywhere,(center or near edge). Is center simpler, and with 3 layers of mat, strong enough ? Is cutting through thickness at 45 deg., stronger ? Cut with what tool ?  Which poly resin ? Part is likey cheap/low-flex resin. Match the flex ?  Pop rivets not needed ?  Onward, roverman.

[Preform Resources]

Art, this is just a tonneau cover ?? right ? so theres no real load on it if you split in the center that would offer the least amount ot of change in the surface I think, its probably made with GP (general purpose ) poly resin, make sure you get any paint off the substrate inside the part and do the layup as I suggested you end up laying up on both sides of the part so the saw cut will not appear after you refinish the exterior. The part is probably  only .200  thick so 45 degree cuts won't do a damn thing a 3" (or more) wide bevel in the top surface should provide excellent adhesion, you can use poly resin or epoxy, epoxy is stiffer but doesn't work easily with mat and i recomend using mat because of it's randomness I ve seen cloth repairs that you could peel right back out of a job, If you have any other questions call me it will be easier. 313-720-9381

[roverman]

Dave, Thanks for the expert advice, Art.