Fixing a 40 roof is a bit different from the rest of the car since it is glass fiber. But it is also much the same; sanding, applying filler and painting. And some glass fiber maybe.
The old roof was in bad shape. I also had a spare, and that was also in bad shape. They had a lot of cracks going deep into the glass fibers in all 4 corners. Quite possible to rescue, but it had been a lot of work with filler and sanding in the double-curved corners.
I picked the best one and removed the old steel rain gutter that was very rusty. The other roof had a good rain gutter so I removed it to use instead. This was a homemade rain gutter, and not looking quite original as it is missing the outer upward bend.
In addition to a few deep cracks the roof was also partly delaminated inside. The black stuff is paint some PO has applied.
When working with glass fiber you must choose your materials. The roof is made of glass fiber mats and polyester. It is laminated with a 6 mm foam mat in the flat middle part to get it stronger and also a bit heat insulation.
When repairing this you can use polyester, but strangely enough, fresh polyester do not stick very well to old polyester. It can be used, but epoxy resin is much better. And more expensive, but you don’t need much. If you start using epoxy you must continue that way because polyester do not stick at all to epoxy.
I started to sand the roof a bit where it had some minor scratched, but stopped fast when I saw the glass fiber had lots of mini-cracks underneath the outer gel-coat. As these did not go through the gel-coat it is better to sand very easy not to remove the gel-coat. That will also save you for a lot of difficult filler/sanding work because of the curved surfaces.
The deep cracks had to be done properly. I sanded from the outside pretty deep so I could get a glass fiber mat inside the groove. I cut the mat, applied epoxy, laid the mat in the wet epoxy, and applied new epoxy on top of that. To get the air of of the mat and press it into the groove a small aluminum roller came handy. Be careful not to allow the epoxy to run down the good parts of the roof. It really sticks! And must be sanded away.
Notice the long crack all along over the front. That is due to the rivets sitting there, and being a perfect starting point for a crack because of the stress around the rivet. So I decided not to use new rivets here, but instead gluing the steel member underneath with Tec7. That way you will distribute the stress all over.
When the epoxy had cured I sanded it and laid epoxy filler over it to build it up. Epoxy filler is more difficult to work with than polyester, and very hard to sand, so I did not get it perfect. Instead I used polyester filler for the last finish.
But, before the polyester I sprayed a thick layer of epoxy primer, as the polyester filler sticks to that. On top of that, another layer of epoxy primer before top coat, PPG Cyrus White. I used one liter epoxy primer. That is rather much, but it is important to have a strong surface to prevent small cracks. If it works only time will show.
On the inside I had to lay a new layer with glass fiber in the front. Where the old foam mat had disintegrated I used a 6 mm floor insulation mat to build it up. The green stuff is polyester filler used to even it out a bit. On top of that, epoxy – fiber mat – epoxy, as on outside.
I bought rivets from Cool Cruisers. Proper rivets is the original, and nicer than pop rivets, but the holes from the old rivets are 3.2 millimetre and the Cool Cruisers rivets are 4 mm. So I decided to use 3.2 pop instead. Also a lot faster to work with.
And since the steel rain gutter is not original, the rivets would not be a problem in that respect. As I could work faster with pop rivets I also decided to glue the roof to the rain gutter, using Tec7 / Sicaflex. That should solve the never ending problem with leaks here.
I laid the roof with the inside up on a table and applied Tec7 all the way around. Then with a little help I laid the rain gutter on top of the roof, adjusting it in place by popping a few rivets around. Then using clamps around the point where the rivet was inserted I popped all the way around. You have to work fast, preferably be two persons working, to get around all before the glue settles.
