Here's what we have to work...
Here's what we have to work with, a rusted, broken scrap of sheet metal, no better at keeping out the weather and engine fumes as a screen door. You may recognize this gem from our Super Beetle project as it is the very same rusted package tray.
There are plenty of things that can go wrong with a car, especially those as old as an aircooled Volkswagen. Of those things, rust is the most feared, and people spend countless dollars fighting it. Some would rather crunch a fender than have to do rust repair, but if you've set your mind on restoring/rebuilding your car, then there's nothing you can do but to work through it.
There are several places on this Beetle that have spots of rust, but none more evident as behind the back seat, otherwise known as the package tray or luggage compartment. Original window rubber gets old (as does the cheap aftermarket stuff, only more quickly), and when it does, it becomes cracked and porous. After that, there's not much keeping metal's mortal enemy, water, from coming through the holes. Proper care of your rubber parts is all it takes to avoid this whole situation, but once you can easily reach the starter from inside the car, it's way too late.
There are three ways you can fix this problem: One, pay a lot of money to have someone else do it; Two, tack a plate over the rusty holes and cover it with the rear carpet kit (nobody's going to see your dirty little secret...at least until the old rust comes through the new plate); Or three, cut out all the rust and weld in a replacement panel yourself. We chose the second option. Sure, it'll be a lot of work, but at the same time, it can be done by anyone right in their driveway with tools found in most home garages.
Our package tray replacement comes from JP Group A/S, an exhaust and sheet metal company based in Demark (www.jpgroup.dk). It is a full package tray piece (Part Number 951088-0 for all Super Beetles), complete with the horizontal firewall and rear engine seal housing.

Our replacement piece is a...

Our replacement piece is a complete tray, including the firewall and engine seal lip. Note the fire extinguisher nearby, as well as our MIG welder.

Start by measuring how much...

Start by measuring how much of the tray you'll need to cut away. You'll want to make the cuts large enough to include all the rusted parts, but even enough to make welding in its replacement easier.

Cutting away the old material...

Cutting away the old material is probably the easiest part of the job. Just follow your marks and take your time. We decided to do it in two pieces, the horizontal tray (including the carpet rail) and then the lower portion that connects to the tunnel and the body-to-pan cross member.
You'll need a reciprocating saw, a grinder, a hand drill and a wire wheel, along with a chisel, hammer and a wire brush. Most important, you'll need a welder, much like our Hobart Handler 135 model, specifically designed for 110 home and light shop use. We're using 35-guage wire good for this thickness of sheet metal. However, the most important thing you'll need to do a quality job is a good friend, because it is twice as fun to do a difficult job if you're not doing it alone. Since my wife finds welding as exciting as I find drapery swatches, my friend Chris Miller was nice enough to stop by and help with the project.
Start by laying down a tarp on your driveway. Small rusted particles that fall onto your driveway become small rusted stains. And if you spent as much time pressure washing your driveway as I have, you'll thank me. Since we're working with welding equipment, there are several safety measures you'll need to realize. First off, keep a fire extinguisher nearby. Second, protect your eyes. If you don't want to wake up in the middle of the night blinded as if your eyelids are 60-grit sandpaper, you'll shell out for a welder's hood. While you're there, get some gloves...and a welder's smock wouldn't hurt either.
Now that you're ready, drag your rusted car out to the driveway and follow along.

The lower portion (where the...

The lower portion (where the seatbelts bolt to the body) is spot welded approximately 40 times, every half inch all along the body. Instead of drilling out each of those welds, we decided to simply pry apart the two pieces. Since we aren't keeping it, it doesn't matter how pretty it doesn't looks.

You're right, it doesn't look...

You're right, it doesn't look pretty, but the spot welds are gone and both pieces are ready to be pulled out. Most of the damage is to the top piece.

A coarse circular grinder...

A coarse circular grinder works wonders here, shaving down burrs and removing any spot welds that still remain on the body parts we need to keep. Since particles are flying, it is best to wear a face shield protection.