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Jan 17, 2021 19:10:56 GMT
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Hi guys,
Trying to make a patch panel for the sunroof on my Jag and coming across a few problems. Formed it to a close enough shape that it looked good, but now it's welded in it's panting (popping back and forth if you press on it).
The question I can't seem to find the answer to is if this means it's too curved or not curved enough. It sits most comfortably curved downwards and pants when you press it up.
Hoping someone might be able to help!
Oh, and before anyone mentions yes I have considered finding a donor panel, using the original sunroof panel to fill it, and all sorts of other options.
Ideally making sunroof filler panels is a skill I'd like to learn! Seems to be a lot of information around on the techniques to make panels, but not so much on what the causes of issues are so you can improve the next time.
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jgtr
Part of things
Posts: 270 
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Jan 17, 2021 19:42:45 GMT
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If I think back to panel beating school, it sounds like the panel is stretched and will need shrinking back to give it some rigidity. If I remember correctly this is done by heating the panel up with a gas torch until you get a red spot then use a shrinking hammer and dolly, the quench it. Shrinking hammer has lots of little squares on it which compresses the metal. I’ve also used a flipper (like a metal file) that you swipe across the panel to move the metal around and tighten the panel.
I only really did it when I’d f****d a panel up and just need to get some strength in to so I could put some filler in it lol, the good guys would beat it back to a metal finish.
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Jan 17, 2021 21:18:02 GMT
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Welding usually shrinks the surrounding metal, so I would expect it would need stretching.
Slapping some CROWN back in from underneath with a slapping spoon might do the trick of stretching it slightly and restoring its shape.
I've welded one sunroof skin into a roof a long time ago and it was not a pretty sight. That one was beyond saving with panel beating hammers.
I do believe there is an episode of Wheeler Dealers where Ant welds a filler panel into a sunroof skin (I believe it was a TA2x Celica?) that showed a bit of what goes into keeping the roof straight.
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Jan 17, 2021 23:51:48 GMT
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I managed to shrink an area of the bonnet on our minor that was doing the same by heating and quenching, it was by no means perfect but gave me a stable base to skim over.
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The issue is caused by the weld bead shrinking as it cools and contracts. The proper way to do this job is to tack the panel in place and immediately grind most of the tack off and check for warp. If you find any, place a dolly under the tack and smash with a hammer on dolly to squsih out the bead until the warp goes away. Repeat about a bazzilion times. I had about a dozen oil cans in my last project and used this guys method to find them and lock them in position. Mine were caused by sandblasting not welding. REd shows some of the many oilcans I had  Not without some filler, but the method worked. I used a shrinking disc to shrink the spots where the panel would lock in.  |
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Last Edit: Jan 18, 2021 1:16:57 GMT by bjornagn
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Jan 18, 2021 10:40:21 GMT
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Thanks guys  I've managed to get it much, much better by selectively cutting tacks and rewelding them with less tension put on the panel. I think I'd pressed up too hard while initially fitting it which had bowed the panel out as it was fixed in place. However, I've found a fun and interesting new effect to play with... So, as you say when you weld metal it shrinks. So, as you tack your way around the outside of the filler panel it puts more tension into it, drawign it flatter. What started as quite a nice, not too tense panel is now pulled quite taught. Wish I'd read about grinding each tack flat and sorting the tension as you go before doing that! Oh, and because it's my second time welding a skin in I don't have the sunroof mounting frame acting as a support so it's warped quite a bit more than the first time (which was quite warp-free, but not the right shape). I reckon I'm going to have a fair amount of work ahead of me to get it anywhere near flat. So, my current plan of attack is: - Cut a few more tacks on the opposite side to get that in a better initial position
- Try and find some method of clamping to help with distortion
- Use a dolly and hammer to stretch out the welds to take some of the tension out of the panel
- Use heat shrinking/a shrinking disc to smooth out some of the distortion I've created
- Crack out some filler to smooth off the remaining surface
Any hints or tips for fixing the distortion? Anyone tried both heat shrinking and a shrinking disc and prefer one or the other? |
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Last Edit: Jan 18, 2021 10:40:59 GMT by biturbo228
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Jan 18, 2021 18:23:59 GMT
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I've used a shrinking disc on my sandblasted warped roof to sort out oil cans.. works a treat, but it wasn't enough to get the roof back in shape, I had to smack the bejesus out of the panel with a slapper to get a somewhat correct CROWN back in it.
Just make sure you identify the problem correctly before attempting a fix. You don't want to exacerbate the problem.
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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Jan 18, 2021 20:20:05 GMT
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Also don't sandblast your roof 🤣
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Jan 18, 2021 21:39:33 GMT
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Also don't sandblast your roof 🤣 ^ what he said. Don;t sandblast any outer panel for that matter. I ended up pretty much beating the bejeezus out of the roof panel in order to get it back into shape.Slapped from below to get CROWN back into the panel, then find the locking point for the inevitable oil cans and shrunk those and repeat until done. Be aware that sandblast damage is unique in how it works since it "pushes" metal around as if you were aiming an air hose at a clay surface. Contrary to popular myth, sandblast warping has noting to do with heat because the panel does not get hot when sandblasting If you think about it, you can relax the panel by inducing stretch anywhere in the panel. Think of a nice big lump in the middle of the panel. Then you just spread it around with a slapper until everything is smooth. Easier said than done, but in essence what you are up against. I am a big fan of the shrink disc but only after having used it successfully a few times do I feel that I have a feel for how to get a given outcome. |
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Jan 19, 2021 23:23:43 GMT
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Thanks guys Tentatively it seems to be going ok! I've got the fore and aft sections welded on, and left the sides for now so the warping has somewhere to go. I'll work to try and correct the bits I've welded already and then start on the sides so I don't lock it all in the wrong place. Interestingly, grinding down the welds seems to have relieved some of the stress caused by them. The whole skin was very taut by the time I'd finished welding, but less so after grinding. Nowhere near done, but moving in the right direction. I've gone up and down the rows of welds with the dolly and a flat hammer to try and stretch them a little where they've shrunk. It's tricky to tell how much to do really as there's not a great deal of movement at all from each pass (probably because the welds are quite hard, and also because the issue is caused by both shrunk and stretched metal in different areas). So I did the hammering with the dolly until the warped sections I'd left unwelded had stopped closing together, and then moved onto shrinking. I've got a blowtorch which seems to work slowly for shrinking, and I've also got one of those funny bumping files for shrinking. Seems to be moving in the right direction Not sure it'll help much but this is what we're working with!  Blue is the panel, with the dashed bits currently unwelded. Red are low spots and green are high spots. I'm currently working in the 3-8 section, but I have worked my way all around trying to stretch the welds a bit. Thatbit's fine as it's just wavy metal so you shrink high spots and bump up low ones until it's flat (seems to be working so far). The bit that I'm not sure how to sort is the long low sections for 11 and 9. It's these two that are really pulling the new panel taut and lower than it should be, but I'm not sure how to fix it. 11 is much worse than 9, so I was thinking of running up and down the line of welds there to see if it raises it up a bit. I suppose knowing where to hit it is one of those skills you can charge £60 an hour for!  |
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Last Edit: Jan 19, 2021 23:24:02 GMT by biturbo228
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Jan 19, 2021 23:48:15 GMT
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Thanks guys Tentatively it seems to be going ok! I've got the fore and aft sections welded on, and left the sides for now so the warping has somewhere to go. I'll work to try and correct the bits I've welded already and then start on the sides so I don't lock it all in the wrong place. Interestingly, grinding down the welds seems to have relieved some of the stress caused by them. The whole skin was very taut by the time I'd finished welding, but less so after grinding. Nowhere near done, but moving in the right direction. I've gone up and down the rows of welds with the dolly and a flat hammer to try and stretch them a little where they've shrunk. It's tricky to tell how much to do really as there's not a great deal of movement at all from each pass (probably because the welds are quite hard, and also because the issue is caused by both shrunk and stretched metal in different areas). So I did the hammering with the dolly until the warped sections I'd left unwelded had stopped closing together, and then moved onto shrinking. I've got a blowtorch which seems to work slowly for shrinking, and I've also got one of those funny bumping files for shrinking. Seems to be moving in the right direction Not sure it'll help much but this is what we're working with! Blue is the panel, with the dashed bits currently unwelded. Red are low spots and green are high spots. I'm currently working in the 3-8 section, but I have worked my way all around trying to stretch the welds a bit. Thatbit's fine as it's just wavy metal so you shrink high spots and bump up low ones until it's flat (seems to be working so far). The bit that I'm not sure how to sort is the long low sections for 11 and 9. It's these two that are really pulling the new panel taut and lower than it should be, but I'm not sure how to fix it. 11 is much worse than 9, so I was thinking of running up and down the line of welds there to see if it raises it up a bit. I suppose knowing where to hit it is one of those skills you can charge £60 an hour for! I feel your pain, I had similar problems repairing the roof on my MK2 Jag on my econojag thread. It took an age and I was chasing high and low spots around for a while. The trick for me was knowing when I had got it as good as I could with my skills and then crutially, leave it alone! If I kept trying to do just a bit more it ended up getting worse again. |
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Also, just ordered a shrinking disc hopefully that will help with that part! Then I gather that the technique is to bump up the low spots (stretching the whole thing) and then shrink it back down with the disc. Hopefully it works ok! |
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I feel your pain, I had similar problems repairing the roof on my MK2 Jag on my econojag thread. It took an age and I was chasing high and low spots around for a while. The trick for me was knowing when I had got it as good as I could with my skills and then crutially, leave it alone! If I kept trying to do just a bit more it ended up getting worse again. Yep! That's definitely a good lesson to learn. Find out where the limits of your current skill level is and stop before them! Unfortunately, for me that would have been 'don't chop out the sunroof', but now I get to learn I suppose |
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