Some of you were asking how to repair rusted floorboards, and I mentioned using fiberglass. In an odd twist of fate, I ended up having to follow my own advice. My interior restoration project was derailed when I pulled out the carpets and looked at the floorboards. Apparently, some moisture made its way underneath the carpets, and slowly rotted away the metal. Here's the driver's side, near the firewall.
It was like that on both sides. I had to do alot of grinding and cutting to get all the rust out. A wet/dry vacuum really helps to get all the debris out of the floorpan. And in hindsight, I probably should've used a respirator mask. The dust tends to build up inside the Fiero cabin, even with both doors open. I had to stop every few minutes to let the dust air out. After I was done grinding away all the rust, and cutting out all the sheet metal that was too thin to be of any use, I was left with this:
It's hard to see in the photo, but part of the underseat frame rail is rusted away, as well. So in addition to filling the holes in the floor, I'll also have to rebuild those rails (more details below).
I then stretched some masking tape across the hole, from underneath. This creates a form that the fiberglass will sit on while it's curing. The tape ended up a little wavy, but that didn't really bother me. If you want your floorboard repair to be nice and flat, you could tape a piece of hard plastic sheet or sheet metal underneath the floor instead. Just make sure that you have all the edges sealed so no resin oozes out. Remember to clean the underside of the floorboard before trying to apply tape. 
I decided to use standard weave e-glass cloth and epoxy resin. I like the weave better than roving mat because it's stronger and doesn't soak up as much resin. I also decided to layup the fiberglass in 2 stages. The first stage will cover the flat portion of the floor, and extend into the bottom of the underseat reinforcing bars. The first stage is 3 layers thick, for the most part. I added a layer or two in spots that I thought needed a little more structural strength. Here's the first stage laid up:
I let the resin cure overnight, and the next day I continued with stage 2. Notice, in the photo above, that piece of wood wedged into the empty spot where part of the frame rail used to be. That piece of wood will act as a form for stage 2. The second stage will cover the top and side of the frame rail, to lend it some structural strength. I also made stage 2 four layers thick. Hopefully, this will return some of the structural strength that was lost to rust.
Now the fiberglass work is basically done. I let the resin cure overnight, then hit it with some 100 grit paper to smooth out of the rough spots and feather the edges a little. And I finished it off with a coat of black Rustoleum. Here's the finished product:
The total price for this project was under $50. It took 3 days, because I had to let resin cure overnight twice. But I only worked on it 2-3 hours per day. Here's the list of materials:
-- 1 quart resin (I only used half of it)
-- 1.5 square yards glass fiber cloth
-- 2 mixing bowls (get plastic ones with marks on the side for measurement)
-- 4 disposable brushes, 2" wide
-- 1 spray can of Extend rust killer
-- 1 spray can of black Rustoleum
-- 1 roll of masking tape
Keep in mind that you could need more or less material, depending on how large the repair is and how thick you make the fiberglass.
[This message has been edited by Blacktree (edited 04-28-2004).]
