Basic metal patch forming question

[Greg28]

Hi there, getting there with my mig welding so almost time to start fitting some patches, most of the areas needing work are fairly simple but this part has a bend on a bend (is there a word for that?) which leads to the metal folding into itself

Is the best way to deal with this to stick in a relief cut and weld it up once its tacked in place on the car?

I was thinking about the metal shrinkers i have seen used on wheel arch lips but I have a feeling two tight bends like these would not be suitable.. advice please!

Attached images are pictures of the rusty piece and then pics of my initial attempt at a patch

 

[PSweeney]

make the releif cut, tig or gas weld the joint. Grind it back, and finish the compound corner over the ball end of a ball pein hammer held in the vice

 

[Greg28]

Thanks for that, I just did a single cut with my grinder there but was left with a lot of overlap, should a relief cut be more of a triangular shape to eliminate the overlap? If so I presume the size of the triangle is something that comes with experience rather than a set method of calculating its size?

The tip about the ball pein in the vice is great, ill be using that

 

[Spot the welders dog]

Thanks for that, I just did a single cut with my grinder there but was left with a lot of overlap, should a relief cut be more of a triangular shape to eliminate the overlap? If so I presume the size of the triangle is something that comes with experience rather than a set method of calculating its size?

The tip about the ball pein in the vice is great, ill be using that

One method I've used to minimise the overlap on such bits was to cover the piece in masking tape, then overlay some duct tape for strength - contour lines are optional.
When removed you can snip the corners so the template lays flat on the repair section on which you scribe > Now when you fold it up the corner pieces can be welded to form the shape without having an excess of metal to tuck away.
You may find a few templates working to various cut lines and depths brings a solution that you'll be happy with.

OR;

If that section is buried in the body of the car: never to be seen again; I would be tempted to negate the curves and make it as a simple 'wedge box' with only two welds, or beat it out from a single piece for no welding.

 

[marlinspike]

The tip with masking tape is what I have used on occasion and it works really well. There is a great thread on Retro Rides called Panel Making, posted by bmwtony, that has great advice on how to form various shapes.