Fiberglass top repairs...first van...

[Scout80]

A little over a year ago, I picked up an 80-something Fiesta on an E350 chassis (I just own so many things from the 80s that I tend to forget details on which one is which year without digging up titles, lol). Usual story - bought it knowing it had "some" water damage, and by the time I got all the rotted wood out...I ended up gutting the whole thing, lol. Life happened, now I'm back on the rebuild project.



I know one of the leaks came in via the roof mounted AC, which led to delamination of the plywood/foam core. I _THINK_ it was either due to the van not originally designed to have AC, or the factory not properly bracing the opening in the roof for the weight, leading to bowing of the wood, and then water entry.

After about a month of trying to figure out how to support the roof well enough to install new plywood and cross bracing for the AC, I finally decided the best way to go about this would be to just remove the top altogether, flip it over, and do it on the ground (I have a crane on one of my trucks that is plenty capable of handling this).

Now for my concerns/question...I was looking at the sides today, and noticing that they both have a bit of an inward "bow" to them, which is obvious when a straight piece of wood is on the inside, and only touches at the bottom. This is all factory installed wood, or at least what was in there after I tore down the ceiling/walls. There were several joists that spanned the roof that just barely touched the tops of these side posts, and a few that made zero contact. The joists weren't mitered at the ends either, which makes little sense to me. I "assume" that it was intentional, and these pieces weren't intended to fully contact the sides of the fiberglass roof, given that the fiberglass straps are only on the bottom of the wood? Basically the only support that the roof had was whatever the joists provided by way of being screwed in to the laminated plywood.

My plan was to fully replace all of this, with joints that are mitered and screwed in to the parts that would be like studs, to hopefully drive the roof support load more in to the steel van body, but now wondering if I'll just be making more future problems for myself by doing this?


I'm also wondering about this plywood lamination. It LOOKS like there is a long piece of ply on either side of this opening where the AC was, with only foam in between the two strips. Here you can see my prior (poor) attempt at bracing up the rotted plywood, thinking I might be able to just cut out the bad part...before coming to the decision that I'm just going to cut it all out and start with all fresh wood.

I was thinking of replacing it all with plywood instead, and cutting it in 3 strips to match the existing roof line. Or at least, having a few inches of ply forward of and back
of the AC opening to provided more support, then also having a square frame of 2x2 lumber underneath, all tied in to the joints. But again, having never done this before..I don't know if there might be a reason it wasn't done this way originally other than simply a cheap build?
upaop

 

[bullfrog !]

A little over a year ago, I picked up an 80-something Fiesta on an E350 chassis (I just own so many things from the 80s that I tend to forget details on which one is which year without digging up titles, lol). Usual story - bought it knowing it had "some" water damage, and by the time I got all the rotted wood out...I ended up gutting the whole thing, lol. Life happened, now I'm back on the rebuild project.

View attachment 37010

I know one of the leaks came in via the roof mounted AC, which led to delamination of the plywood/foam core. I _THINK_ it was either due to the van not originally designed to have AC, or the factory not properly bracing the opening in the roof for the weight, leading to bowing of the wood, and then water entry.

After about a month of trying to figure out how to support the roof well enough to install new plywood and cross bracing for the AC, I finally decided the best way to go about this would be to just remove the top altogether, flip it over, and do it on the ground (I have a crane on one of my trucks that is plenty capable of handling this).

Now for my concerns/question...I was looking at the sides today, and noticing that they both have a bit of an inward "bow" to them, which is obvious when a straight piece of wood is on the inside, and only touches at the bottom. This is all factory installed wood, or at least what was in there after I tore down the ceiling/walls. There were several joists that spanned the roof that just barely touched the tops of these side posts, and a few that made zero contact. The joists weren't mitered at the ends either, which makes little sense to me. I "assume" that it was intentional, and these pieces weren't intended to fully contact the sides of the fiberglass roof, given that the fiberglass straps are only on the bottom of the wood? Basically the only support that the roof had was whatever the joists provided by way of being screwed in to the laminated plywood.

My plan was to fully replace all of this, with joints that are mitered and screwed in to the parts that would be like studs, to hopefully drive the roof support load more in to the steel van body, but now wondering if I'll just be making more future problems for myself by doing this?
View attachment 37031

I'm also wondering about this plywood lamination. It LOOKS like there is a long piece of ply on either side of this opening where the AC was, with only foam in between the two strips. Here you can see my prior (poor) attempt at bracing up the rotted plywood, thinking I might be able to just cut out the bad part...before coming to the decision that I'm just going to cut it all out and start with all fresh wood.

I was thinking of replacing it all with plywood instead, and cutting it in 3 strips to match the existing roof line. Or at least, having a few inches of ply forward of and back
of the AC opening to provided more support, then also having a square frame of 2x2 lumber underneath, all tied in to the joints. But again, having never done this before..I don't know if there might be a reason it wasn't done this way originally other than simply a cheap build?
View attachment 37033View attachment 37034upaop

My opinion is a cheap build. I had an 1983 Barth motorhome with aluminum framing. Everytime we removed the roof AC the technicians were amazed that everything was intact and square. They often commented most construction of that period had failed allowing the weight of the AC to cause the roof to slump and leak making a bad situation worse. Often wood was encased in fiberglass to provide structure and a place to mount heavy items. Water or condensation causes wood to weaken and eventually fiberglass to crack. You also need to consider the extra weight you are adding to the top if you use extra wood and fiberglass. My opinion maybe consider getting as much weight off the top by doing away with the roof AC and install a mini split on a vertical wall surface. Possibly build out cabinets or new support walls from the floor up to the roof with aluminum supports for the roof running between them. Getting the existing fiberglass top off there will be a good chance of damaging it and it not sealing if reinstalling. Gorilla Glue is basically concentrated spray foam and is good at filling gaps. Lots to consider! Good luck!

 

[maki2]

Not to worry there is a very excellent fiberglass repair booklet you can download for free as a .pdf file to print out for easy reading and reference. It is intended for boat repairs but it includes everything you need to know for how to create some ribs to strengthen the shape and prevent those weak areas from sagging. Think of your fiberglass topper as fiberglass boat shell. This is a most excellent way to learn a lot about the subject! Way more informative than having a conversation in the forum because there are illustrations. This booklet has been around for a lot of years now and the methods are how the pros do it. You can too! Look lower on the webpage for the download link. You do not have to use that brand of epoxy for the job. If you have everything setup and ready and work very quickly you can use the other type of fiberglass resin sold at Home Depot and auto parts stores. Epoxy gives you more time for working before it kicks off but it is more expensive.
https://www.westsystem.com/instruction/instruction-manuals/

As to the existing shell being weaker. If the foam was fully bonded to the fiberglass and there was thin plywood bonded to the interior underside that multilayered sandwich created an engineered type of structure known as a SIP short for structural insulated panel.
I know on the old Toyota Fiberglass Sunrader motorhomes that is what was done. Before the upper shell was pulled up out of the mold a full coat of adhesive was spread onto the interior ceiling side area. Then a layer of insulating foam was stuck into that adhesive cost. Next another full cost of adhesive was applied to that foam and layer of 1/8 plywood glued to it. Finally a sheet of vinyl wallpaper was applied to the plywood creating a washable ceiling material. Then the upper fiberglass shell was pulled out of the supporting mold and it was turned over and stuck to the bottom half of the fiberglass coach body.
So if you do remove the roof you can take a similar approach and do those continuous glue bonded layers. But building in some structural ribs to help support the extra weight of an AC and solar panels should be done as well.

Good luck, you can do this, patience is important and get a helper too so you can work quickly before the resins and adhesives kick off. If you can use sawhorses and support boards to get it up off the ground to save on backaches.

 

[Scout80]

You also need to consider the extra weight you are adding to the top if you use extra wood and fiberglass.

This was part of my concern, but also why I was thinking of rebuilding the trusses so that they fully contact the side studs, with the idea that at least some of the load will then be transferred in to the steel van body rather than simply "hanging" it all off the roof. In a way, I'd basically be building out a frame work similar to how a site built house is constructed in concept, which the roof would then simply be sitting on top of, without the roof itself supporting the load.

At least, that's how it's playing out in my head. But it wouldn't be the first time that something that made perfect sense in my head didn't work at all once I tried doing it, lol.

I did consider just ditching the AC altogether, as it's pretty rare that I've used it away from home in the other campers as I'm boon docking 99.9% of my time out there, and I don't want to run the generator 24/7 just for AC. But then there's gonna be that one day that I get stuck somewhere hot and humid, and I'm gonna be kicking myself for not following the "better to have it and not need it" mantra....