Fiberglass top repair filler

[anwat]

So, I'm installing a camper shell window in the fiberglass top on my K5. I've done it a couple of times before, but never ran into this issue. This window is shorter than the others, and I didn't realize how concave the top is right above the window. I'm left with about a .25" gap between the aluminum window frame and the fiberglass top. The frame extends about a half inch into the top, but doesn't go past the inside lip of the fiberglass window channel. Meaning any water will go right down the inside of the back window and soak everything inside.
I can only think of two options...if anyone has any other ideas, please let me know. I can fill the whole gap with clear silicone, or I can try to fill the gap with bondo or fiberglass repair or epoxy or some similar material and hope that there isn't enough flex to crack it and allow the water through. I am reluctant to try to shave away any more of the corners since I'm seeing fibers already and I don't want the top to be so thin it won't support the weight of the glass. And I will never be able to get enough off to make it lay flat.
Suggestions? If I go the filler route, what would be best to use? Fiberglass repair, bondo? I will be painting the top when it's done, so appearance is not an issue, plus it'll only be visible from the roof of the truck, so it doesn't have to be pretty.

 

[76zimmer]

Use flexpaste!
You can get fiberglass mat in thickness up to 1/4”... Lots of videos on how to do it out there too.

 

[ryoken]

either or.. you could either just pump it with a silicone, or urethane like a 5200.. or yeah, you could "pad" that whole lower flat out from the bodyline down.... i would prolly just do it in dynaglass.. 36 grit it all to put a good cut, dynaglass, shape, maybe some bodyfiller or glaze in any pinholes or minor defects, prime, paint.. obviously more work than pumping it... i wouldn't bother glassing it.. but i wouldn't run regular bondo either.... too thick and could crack.. the dynaglass should be fine for that.. it's not flexing a ton i would guess...

 

[anwat]

At the risk of being stupid, are you serious about the flexpaste? Sounds a little fishy, coming from the same company that does those goofy commercials....but if you're serious and have tried it, I'll give it a try. I read their claims, and they are certainly very ambiguous....like "it will last for years". Is that 2 or 12? If you are joking, then my bad, have a good laugh, you got me..
I feel honored to have a reply from ryoken, and because it was mentioned twice, I'm leaning towards the dynaglass. I don't know about the flex, that's what worries me, it goes across the middle seam of the top, which is where the flex will be if there is any. I figure if it cracks, it will be easier to silicone up a crack instead of the whole gap, right?

How about trying to fill the bottom portion with urethane and then doing dynaglass on top? I'm thinking the urethane would flow into the voids better not only keeping the water out but making the install a bit stronger by flowing around the frame, and maybe giving a little support to those bolts to keep them from wearing through the holes in the fiberglass. Just an idea...worthwhile or overkill?

 

[diesel4me]

Just remember pretty much nothing sticks to silicone,so if you use any,put it over whatever you use underneath it!..

I would use something like Mar-Glass,a bondo that is fiberglass based with short fibers ,and is waterproof...regular bondo is just talcum powder with resin and it will soak up water like a sponge..it is OK for final finish coats but not for filling gaps or holes ,or preventing future rusting ..

I haven't tried Flex Paste yet,but I know their other "Flex-Seal" stuff is not UV resistant,it'll fade and degrade over time with exposure to sunlight..it shows Flex Paste being "paintable" on the commercial,so you could top coat it to protect it..

 

[diesel4me]

Another idea ...

On my van,one of it's rear door windows is a rather ill fitting aftermarket screened slider,that had enough gaps to let rain flow inside..
If I used silicone caulk to seal it,some would get in the track,and not let the window slide properly..

I picked up one of these "drip caps" at an RV center nearby ,they sell them in various lengths,and I caulked under the mounting lip of it and that ended that problem..I bought a pair and put them over both rear door windows so it'd match and not look goofy..

 

[anwat]

That's a good idea for insurance...I'll have to grind a flat spot to mount it, though, and make sure it will clear the opened glass. If those windows weren't so expensive, I would just try to find a taller one that fits above the concave section like the other two I did...but this one fits so nice other than that..... I'm thinking Mar-glass is similar to dynaglass, which is what I'm leaning towards. Figured out there shouldn't be too much flex, there's a metal band that runs around the opening which would make it pretty rigid right at the opening...probably to protect the factory glass from breaking.

 

[diesel4me]

The ones I got were stamped aluminum and pretty thin gauge,they will flex some to conform to slightly curved surfaces..
They also had ABS plastic ones but they costed more and felt too brittle so I went with the aluminum ones..

 

[JoshHefnerX]

I'd probably put a layer or 2 of glass in there to fill in the void and then filler over.

 

[anwat]

OK, Dynaglass it is. I'm headed out to get some. Post up with photos when I hit the next problem....

 

[anwat]

When you say 36 grit, you're talking sandpaper, right? The lowest I could find was 40, and it's pretty rough, but it still seems to leave the surface pretty smooth. I can see scratch marks in most of the existing glass, and it took the paint and gel coat off no problem. Am I looking for rough, or lightly scored on the existing glass before I put the dynaglass on? Here's what I've got:

 

[ryoken]

as rough as you can make it... 40 is ok.. just make sure you hit everything thoroughly... i would normally just zip that with 24 grits on a 2" roloc machine.. i would tape off up at the peak you want it to stop at, before filling... that way as you sand down your fill, it will get thin near the tape edge, pull off tape... final sand that edge with 180 before primer.. the fill i would do 40. than refill any pinholes, low spots, etcs... than 80 all that out.. quick 180, prime..

 

[anwat]

Thanks for being gentle, this is my first time.....So far so good, I think. I'll post some photos of my progress tomorrow when it's light. I'm using the glaze for pinholes, right?

 

[anwat]

Came out way better than I expected. My only issue is where the existing gelcoat (or whatever was on there) is left, I'm afraid there isn't enough of a blend area and you will see the different elevations. When I try to sand it and feather the edges more, it just makes a bigger area because the previous coating(s) are so thick. I don't really want to sand the whole top down, but I would like to get rid of the areas where the glass fibers are showing through on the top and several locations on the sides. The previous coating is also chipping/peeling off around the window frames. Should I just start sanding, or can that stuff be spot treated in some way? I'll be taking the whole thing in to the body shop to get the paint done, or maybe gelcoat or something thicker if it will be more effective in covering the hairy areas. Just trying to get the prep sort of done before to save time and money.

The Dynaglass is pretty cool stuff to work with, just hard to know how much hardener to put in if you don't use the 1/2 can at once. And you got to work quick once it's mixed. And it's a bitch to get out of the hair on your arm.

Pretty happy with the window fit, though, a bead of silicone around when I install it and I think it's easily more watertight than the roll-up window was. Any suggestions on the final coating to help cover the defects already there? I'm not opposed to going back to the orange peel of the original tops, it would probably help hide the branch scratches after every trip.

 

[anwat]

OK, so now I've decided to try to fix the spots where the gel coat has worn through and the fiberglass threads are showing. Most of this is the white areas on the roof. Why I feel the need to fix this, I can't say. Obviously I'll sand the areas first, then to I do dynaglass over them and try to sand them back flat, or just try to cover the hairs with the glazing stuff for pinholes? I figure I've got to pretty much sand the whole thing to get the paint off, anyway, so might as well try to fix the spots.....

 

[chulisohombre]

Cool repair. Looks like you got it pretty good set in there.

 

[ryoken]

OK, so now I've decided to try to fix the spots where the gel coat has worn through and the fiberglass threads are showing. Most of this is the white areas on the roof. Why I feel the need to fix this, I can't say. Obviously I'll sand the areas first, then to I do dynaglass over them and try to sand them back flat, or just try to cover the hairs with the glazing stuff for pinholes? I figure I've got to pretty much sand the whole thing to get the paint off, anyway, so might as well try to fix the spots.....

actually, the way to fix that is to resaturate the area with polyester resin... even thinned a tad with thinner sometimes, so it saturates all the hairs better... sand smooth, prime...

 

[anwat]

Update: never heard back on the thinner, so I used acetone, it seemed to work OK, hopefully I didn't screw it up. I figure it evaporates eventually, so it would work. Here's where we are now: I patched up the thin spots and cracks with dynaglass, then went back and used the thinned polyester resin to glue all the hairs back down. Sanded, more patching, sanded, and now I've primed the window openings. I'm going to use epoxy primer on the whole shell next, then raptorliner the outside. I also filled in the corners (the red circle) the tailgate won't cover to keep out the dust and water...I was thinking of using the rubber from the k5 tailgate, but figured this would look a lot cleaner and won't wear out.

 

[anwat]

While waiting for my bedliner supplies to come in, I decided to clean up the inside a little. Can anyone tell me what they used on the seams in these shells? It seems to be pretty hard, but still retains some flexibility. Especially where the two halves meet in the middle, the stuff has been pushed out, and at other spots it has gaps and holes. Would the stuff in a caulking tube that they call seam sealer work ?

 

[ryoken]

yup, seam sealer is fine for that...