baha
+1y
I think the tech article is on RPS
There are a couple methods I know of, it will be alot easier if you unbolt that bed panel from your bed.
One method is to cut a metal panel out of sheet metal to the size of the opening. Next use adhesive to secure it to the backside. Once the metal panel is secure, lay your fiberglass until you fill the opening and fill it to the face of the panel. Give each layer of glass a little cure time, atleast until it's somewhat tacky before laying another layer.
The metal panel is used so you have something solid to work on.
After your fiberglass is fully laid and cured. Next it's time to sand it. To make sanding go faster if you are doing this by hand start out with 40 grit, then 80, then 120. Once it's sanded with 120 blow off the piece. You may have some pits, or crevices but that's ok, next lay the body filler over the entire area you have just sanded. Repeat the same process of sanding and increasing the grit of paper. 40 and 80 grit is mainly just to shape the piece. You still may have some small pits but it's ok just go back over it with body filler. Once this is all done block the area with 220 grit, blow off the area and spray the area with sandable primer. Do not use liquid cleaner on the area you used body filler, body filler absorbs moisture.
The other method is instead of using a metal panel on the backside is to first glass the backside then do the front as mentioned above.
Make sure you roughen up the panel before you lay the fiberglass, 120 grit should work fine.
Laying fiberglass can be a pain, you could probably get by with Fiberglass Reinforced body filler, but not body filler alone it's to brittle.
Hope this helps man
Rob