On 4 Oct 2004 10:46:17 -0700, (Reuben) wrote:

I have a 1983 VW Passat GL5 which is in reasonable condition barring
some serious rust on the training edges of the doors and the tailgate.
Professional repairers seem reluctant to take on repairs like this -
they want to replace the doors (possible) and the tailgate (not
possible to buy new tailgate now).
I'm considering doing the repairs myself and I'd like to hear from
anyone who has experience of this kind of job in relation to materials
and methods.
I'm realistic about what I can expect to achieve - I just want a
passable job to keep the car legal. If it turns out really well,
that's a bonus.

First, you should forget about using fibre glass, resin, filler, and
suchlike. It's okay for surface dents and blemishes, but not where
structural strength has been compromised by rust. The most fun you can
have with a welding torch is brazing! You can inset pieces of sheet
metal and braze them in, thereby restoring (and probably improving)
the original structure - although be aware of any designed-in crumple
zones. Brazing is easier to learn than welding, and it really is a
pleasure seeing the molten brazing rod pool out and flow into the
join. DON'T do any welding/brazing in situ (or in an enclosed space)
unless you have someone to watch out for fire hazards. Be careful
about petrol and oily rags. Treat oxy-acetylene bottles with the
utmost respect. They are like bombs.

Obviously you have to have some solid metal to braze on to! It depends
how far gone a panel is. When I was doing my apprenticeship (forty
years ago now) we didn't even use Isopon at all. The correct way was
to melt large bars of solder on to the panel, then smooth it down with
a rasp. Stopper on top, then primer surface etc.

MM