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Sunroof... Fixed the rear roof support (see previous pics), used the front half of the donor and cut and butt it in. Still some tidying up to do on it but most of the nasty welding is on the inside. Dave

Great work !!!

To eliminate warpage after you tack it in, do spot welds one on top of each other and do 4 at the most, then cool with compressed air. Move to another area and repeat so you get minimal heat in one area at a time.

Regards Greg

Wow Dave, all I can say.


FB ute fixer upper, EK van on rotisserie

Nice neat cut Dave. Great work from you as always. Hope to see you over the break sometime soon.

EK283 wrote: Sun Dec 19, 2021 12:31 pm Great work !!!

To eliminate warpage after you tack it in, do spot welds one on top of each other and do 4 at the most, then cool with compressed air. Move to another area and repeat so you get minimal heat in one area at a time.

Regards Greg

Yeah I will certainly take it slow and steady to avoid heat build-up and warpage. I do have a question however for anyone who wants to weigh in, on a patch panel like my roof with long edges, is it best to do first tacks on each side in the middle or on a corner?

I'll certainly be using every clamp I can but want minimise movement from the weld shrinkage.

Thoughts?

Cheers

Dave

Hi Dave,

If you have access to butt weld clamps then use those to set up the donor piece. I usually try and get a 1mm gap all round.

There are some tricky ways to achieve this, one is to lay the panel on with a overlap then use a 1mm cut off wheel and cut your new weld line in on both panels. You can use the new panel as the guide or the old one, which ever is easier.
The second way is to scribe the new panel with the existing hole edge etc then cut and trim until it fits in, again the optimum is with a 1mm gap.
Once the panel is fitting snug and with all the clamps in place weld the edges and your reference edge points so that if there is any movement it can be massaged and in an area you can get at with a dolly etc if required.
Tack the whole lot in every 5cm to start off, grind back flush and check to make sure it is all still flat and and then begin to fill as i described in my other comments.
The secret is to weld and cool and not be tempted to go to fast.

Regards Greg

Dave, I have a collection of those clamps you are welcome to borrow

Thanks Greg, Brett

I've still got some trimming to do for a final fit and will aim for the 1mm gap. I've got 4 of those butt weld clamps but must admit that I haven't used them previously but they look fancy.

Cheers

Dave

Observations from tack welding a roof cut in.... Firstly thanks to Brett (Wilma and Project 2) who came over to discuss welding strategies and give me some reassurance. We concluded that there could be a number of ways to approach tacking the roof cut in but that getting the front join right was most important so probably start in the middle there. The front join was pretty close, not even 1mm and maybe touching in a few places - in hindsight too tight.

I felt that the rear corners were a good fit and my reference so I clamped up the rear: Feeling that I wanted to make sure the rear corners stayed put I decided to do tack #1 about 7 inches forward of the RH rear corner - I was just a convenient spot. I figured that the rear wouldn't move as it was clamped and had the flange in it which was right. I didn't think tack #1 would affect the front join but that if it did there was plenty of metal to play with to rectify it - or I was prepared to cut the tack and do something different.

Tack #1 was enough to close the front join and make a slight overlap both to the left and right of the centre of the front join. Tack #2 on the LH side forward of the rear corner only alleviated this slightly. Tacks 3, 4 and 5 fixed the overlap on the RH side of front join but I had to very carefully use a dremel and cutting disc to relieve the overlap on the LH side. I then worked on the LH side working tacking alternatively down the front join and forward from the rear tack to creep up on the front corner. That all went nicely but interestingly created an overlap on the RH front joint below tack #3 - go figure... Then contrary to what I thought would happen, tack #17, the next one forward from Tack #1 on the RH edge, fixed it...But it also succeeded in significantly closing the RH edge gap as did successive tacks along there. Luckily the roof patch was always sitting inboard enough for me to carefully grind the mating edge back to make it fit. As per the LH side I crept up on the front RH corner alternating tacks on the edge and front. Blew a few holes and moving the roof patch panel into place became increasingly harder. Needed a prybar to help get the final few done.

Anyway, 33 tacks later averaging about 6 tacks an hour (there was also lots of looking and head scratching going on) it looks like it fits pretty well. The profile looks good. There are a few spots along the front join that will come up with more tacks and I haven't started on the rear, but so far so good. Still not sure that I've worked out how metal moves in response to welding though...

Cheers

Dave

Woo hoo! Good on ya Dave for getting it started. In a few days it will be yesterdays problem. Car is looking so good now, pity you don't post a bit more of your good work.

Great Job,

Not for the feint hearted that's for sure !!!

When i learnt to weld it was with an oxy set, the gaps needed to be adjusted as you went. In essence when you tack a weld it heats up the area, expands then cools and shrinks normally further than the expansion.
With an oxy set you get heaps of warpage and the welds must be dollied as you go, an advantage the weld is soft like the parent metal so is malleable.
Although the mig is much cooler the same principle applies, heat cool shrink, that's why the gaps move around.
The only disadvantage with the mig is the welds are high tensile so using a dolly to fix warpage is a little more difficult.

You can cut the gaps with a cut off wheel as you go if the there is pulling together as you weld.

Its a fine art but you will get the hang of it.


Greg

Bloody brilliant Dave
Not for the faint hearted indeed


FB ute fixer upper, EK van on rotisserie

Roof patch fully welded in. Rear seam is a bit messy but the remaining metal wasn't great and it will all be hidden. Left and right joins came out ok and the centre join looks good from a distance... But close up there is a low along most of the join. Interestingly there are also a couple of high spots (just bumps really) where I maybe should have relieved the join a bit more? Anyhoo, looks like filler will be my friend - a bit moreso than I had expected but I'll get over it. The overall profile looks good.

Next is to remove the floor under the rear seat so I can get in to fix the parcel shelf with thanks to Brett (Wilma and Project 2) who has supplied a spare Cheers

Dave

Great work Dave. Looks very neat.

Hi Dave,

The joints in long panels are always prone to some warpage, a dolly and slap hammer and file finish will get it better.

Good job none the less.

Greg