On Sun, 4 Apr 1999, Michael Graham wrote:
> I want to repair the rusted metal under the battery in my TR6 with
> Fiberglass. Fiberglass instruction say to remove paint before applying
> fiberglass. Area was pretty badly rusted and I have wire-brushed and coated
> affected area with an rust inhibitor. I would prefer not to remove this
> coating before applying fiberglass and do not want to do too much
> grinding/sanding 'cause the surrounding area is a little "thin". Will the
> fiberglass stick to the painted surface and the rust "inhibited" area, or
> do these really need to be ground down to bare metal? I not so much
> interested in maximum strength, rather I hope to be able to stop further
> rusting and fill the holes that have been eaten through the metal.
I went through this battery box repair on my TR4, before I'd got all my
welding gear together.
-Fiberglass resin is like Bondo; it's sticky. Provided your surface is
free from grease and oil- and that the rust inhibitor (what did you use?)
sticks real well to the base metal, you won't have trouble.
-Wear an organic vapor mask to protect your lungs and maintain your
sanity. Polyester Resin vapors are bad for your head as well as your
lungs.
-Clean the base metal with acetone right before you put the resin on (wait
a few minutes for it to flash off).
-I ended up with about 4 layers (of just cloth- it's stronger than matt).
I put bits of metal, re-bar style, into the still-soft second layer.
-Fiberglass resin seems thick but it can seep through TINY holes. Make
SURE that you've got a drop sheet below your work area- doubly so if your
carpets are still in!
-Resin does NOT stick (well) to polyethylene. (Plastic garbage / shopping
bags). Use these for masking.
-Resin eats most glues and plastics. Be careful what you get it on.
Vinyl and some duct tapes won't hold up to it either. Neither will
styrene.
-Try to get any forming done (like the ridges under the battery) while the
resin is still liquid. Don't mess with it too much. If you want to abort
your attempt, remove it ALL, and don't put it back- it's wasted. Once the
resin starts to set ("go off"), it's finished. It will be in a gelatinous
state for a little while; depending on ambient temperature and amount of
MEKP you put in, etc.
-You can sand/machine the f/glass when it won't dent under fingernail
pressure. (sometimes better to wait-a-little-longer in this case). Put
your OV mask back on; I use dust pre-filters for sanding to keep the big
chunks out of the carbon filters.
-Malcolm
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