Been wanting to cut my sunroof out, and I originally wanted to just weld sheetmetal in, but a friend of mine got the idea of fiberglassing into me. It’s not structural either way, so it’s not like it would make a difference to the chassis, but I’m worried about sealing. I was thinking that when the car flexes under heavy cornering, the fiberglass portion might unglue itself from the rest of the roof and that could lead to it taking in water, causing rust, etc… Just wanted to know from the more experienced glassers how wise of an idea this is, because it seems a lot easier and appealing to do than welding in a piece of sheetmetal, since it would be easier to make it match the curvature of the rest of the roof.
just weld it, their will be alot less problems
spot weld it all the way around i would say.
be very careful with the heat levels, and dont make your welds right beside each other all the way around. make 2-3 spots, do it on the opposite side, then back to the other side etc to help prevent warpage.
i weld. i could do this job for you. i would also suggest bracing the sunroof opening like make a h-brace or X brace for rigidity antonio
Im sure TM or BAS will chime in here to say im wrong and give there “expert” opinions
The car is gonna be caged anyway, so I’m not worried about structural issues, mostly fitment, quality, durability, etc… Also pretty curious on how to make it look good after the piece is welded in. I don’t care if it’s visible from inside the car, but I want it to look like the car came without a sunroof from the factory when you look at it from the outside.
Funny you mention this… my story…
like most 240’s with sunroofs, my sunroof area totally rusted out on me to the point of huge holes etc. you get the picture…
I cut a new roof panel from Bings parts car, had it chemically dipped to strip all rust starting, and paint.
I trimmed it nicely and started chopping up my roof, chopping meaning measuring carefully so that the new panel just falls right in.
the good thing about the design is that the sunroof stays put, you dont take it out, it actually 4-5 studs that come with the roof, the rest stays put, so what that does is line everything up properly.
the fit was next to perfect.
next step was to tack weld it in like mentioned above… which i did all the way around, with the proper welder its really a JOKE and anyone can do it, no welding experience necessary.
After that came the bondo part, now this is where your question comes into play… cause what i should have done WAS use fiberglass first right on the metal, fiberglass cures and stiffens to shit, I think it would be more than strong enough to prevent cracks.
Of coarse by the time i figured this out I already laid bondo so too late, then what i found out is that body shops, put a thin layer of fiberglass on top of the bondo to strengthen it some more, which is what im going to do in the next few days.
… so this is the way I suggest you do it, cut, weld, fiberglass, bondo … Im not saying its easy, Ive NEVER done any body work, so it took me a while to get the roof just right.
Personally I think I did an awesome job so far I just hope it doesnt start cracking on me.
sorry for the story 
hope that helps
here is a pic of my progress, its since been primed ready for paint, but now like I mentioned im thinking of putting a thin layer of fiberglass on top.
Sounds good to me…
When welding a piece on, should I try to have the piece be larger and put it on top of the car, put it underneath from the inside, or attempt to exact match? With an exact match, I’m not sure how the piece could be held in place while being welded. Presently, I’m thinking going with a larger piece, and laying it over the roof, then welding the outside edges. After that, sand flat as much as possible, and start adding bondo to the edge to smooth it. And you’re saying fiberglass on top of that? That seems like a lot of crap on there, nearly eliminates the weight savings of chopping the sunroof out. Mine isn’t rusted at all, the reason I want to do it is for the weight savings, that and I don’t use the damn thing anyway, and it makes too much noise on the highway.
buy a car with no sunroof.
Err that seems like a wee bit of a pain in the ass? Was kinda hoping I wouldn’t have to invest in a whole new chassis for a simple problem.
I have done a little glass work, and i would think it would be alright to use if you put 2 layers under the hole and 3 above the hole so they touch…overlapping on the metal about 2-3" and i would also suggest curving the finished side into the car.(roll the panel into the hole) this will help you get a flat surface even with your 3 layers of glass.
i havent tried anything this physically large in one shot though, so you may need some sort of support to get the first layer on.
tip 1: hand grinder with a flapper disc works very well to remove humps ofglass/resin
tip 2:spend the money on the “weaved” type fiberglass. it is worth it after playing with the other crap.
-Matt
you dont want to overlap with this type of welding, you want a perfect matched cut and mate it edge to edge, then tack her all the way around.
Sol get your self a couple nice strong mangets to hold the panel in place while you weld it up.
If youre just gonna cover the hole you cut out with sheetmetal then yes this is a good idea, but if youre gonna do it the harder way, my way, no need cause it really holds itself
How would it hold itself if it’s exact match? That’s why I DO need the magnets, it’d have to be bigger to hold itself. I just realized that curvature wouldn’t be that big of a deal, since the sunroof itself is flat, and this wouldn’t be much larger.
If youre just gonna cover the hole you cut out with sheetmetal then yes this is a good idea, but if youre gonna do it the harder way, my way, no need cause it really holds itself[/quote]
If you want to do it really nice… then you need to make a lip about 1/2 wide and the same depth as the sheet metal is thick to set the new roof on then tack it in… You can get an air tool to make the lip with.
If youre just gonna cover the hole you cut out with sheetmetal then yes this is a good idea, but if youre gonna do it the harder way, my way, no need cause it really holds itself[/quote]
If you want to do it really nice… then you need to make a lip about 1/2 wide and the same depth as the sheet metal is thick to set the new roof on then tack it in… You can get an air tool to make the lip with.[/quote]
yes I forget what those rollers are called but this is the best way, the new metal will sit on the old metal, you can spot/tack weld it all around, then use the waterproof blue filler to fill the thin gap you left, you can use brushable seam sealer on the inside or even between the metal before you tack it
Could one of you draw this in like mspaint or something? I’m having a hard time picturing it.