This is one of the jobs I had carefully shoved aside in the hope I would never have to get to do it. Eventually there was no way for me to keep ignoring the boot lid standing there all covered in dust… This is what I did:
Use thick paper to make models before you cut the pieces from metal (Cornflakes boxes are excellent for this job).
Copy the models on 1 mm sheet metal.
Cut the pieces of metal using a sheet metal cutter or a power jigsaw.
Fold the sheet metal in an L-shape on a workbench.
I used a spot welder to weld both L profiles together; alternatively you can drill holes in one profile and weld both profiles together by filling up the holes.
There is some special shrinking equipment available to bend the profiles to the same model as the window corners; most likely, you will find this tool in a garage that does car repair. Try cake or a six-pack of beer…
Carefully mark the places where you are going to fit the new window frame pieces, the better you make it fit, the less time you will have to spent on the finishing.
When the new pieces fit, use some spot welds to join the piece with the boot lid. Keep checking if it all fits well.a side to the other, cool using air to prevent the metal from deforming.
Use a multi-layer disk to grind away the excessive welds. A 2 or 3 mm grinding disk will do the trick in the corners.
Tip: When replacing a large piece of the window frame. Try not to replace it all at once, but leave pieces of the original framework in place. This way you will not loose the model of the framework, thus making sure the glass will fit when reassembling.
