Welding panel help

[yoshie]

Hi all, I have to weld the rear wing on my old Hillman Imp I always have trouble welding large, flat panels without the warping no matter how slowly I do it and giving it lots of times between tacks.
What I'm thinking about trying is joddling about 2mm of the old panel and 2 mm of the replacement panel so the join sits slightly low from the surface of the panel. I've tested on an old bit 1mm steel and joddling an edge certainly makes it a bit more rigid, it would also mean I wouldn't have to grind the weld completely flat and it would just need a skim of filler.
What does the team think..... is it worth while or am I wasting my time or does anyone have any other suggestions.

Thanks in advance

Mike

 

[pedrobedro]

If you can joddle the edge of the old panel you don't need to do the new one as well, the new panel will sit in the ledge formed on the old panel and there will be minimal grinding and filling to do.

 

[keith19]

When I worked in the trade, years back, we did a lot of joddled panel repairs.
Everything from floors to wings and rear quarters, even known it done on doors when new skins were not available. (Wouldn't advise it on doors though, unless you use a really high quality flexible filler)

We didn't do 2mm though?
Just used the joddler tool, which gives a lip of around 10mm wide in the original panel, you then either plugged or stitch welded the ingoing panel in place, and ground down if required before buttering over with filler.

To be pc on a modern car you are supposed to seam weld all around, by joining the stitches or tacks together.

Remember to round off the corners of the panel a bit if you can. The inexperienced always used to blow the corners of the repair panel away.

Some like to butt weld, just for the crack, of course. But no fun on an old Imp, any more than the wafer-thin metal on a new car.

 

[steveo3002]

will you be able to seal the flange on the rear ? i wouldnt be happy leaving it as is

 

[yoshie]

Sorry I've not made myself clear, the main problem I have is the panel warping and I was hoping that creating two joddled edges would give some rigidity to the panel but using a butt weld, something like this (hopefully this works) the original and new panel would both have an edge joddled all the way round. The actual width of each joddled part would only be a couple of mm.

Hope this make it clearer, I tried joddling the edge of a 6" bit of old panel and it certainly more resistant to bending.

Thanks for the replies

Mike

 

[keith19]

Never tried doing one that way, you will find butt welding steel that thin quite an interesting experience.
Certainly any kind of joddling helps rigidity to some degree, but you will have to be careful how the other sides of your repair panel are anchored, as there will be a tendency for the rigid butt-welded area to 'pull' on the adjacent metal, something like in the pic below.

The green circle is where it will be most rigid, of course, and the two arrows indicate the tendency to pull the adjacent metal upwards or outwards a bit.
Obviously if you go around your patch panel carefully spacing the welds well apart this effect should be minimised to some degree, but you will have to watch the centre of the repair panel doesn't tend to bow outwards.

 

[yoshie]

Keith, thanks I never considered the metal pulling as you described, I have the panel tacked in and I'm going to take it very slowly tacking around the repair panel and letting it cool completely. I've attached a couple of pictures to show the start of the job, I'll update it when it's complete.

Comments welcome

Mike

 

[keith19]

That's quite a sizeable panel, Mike. Looks like you've put a bit of curve into it around the wheel arch, so that should help rigidity too.

In a position like that, a little bit of 'pull' from the edges of the panel should not harm it a great deal, so long as you go carefully and don't allow anywhere to get particularly hot. A slight 'pull' all round will hopefully be lost in the overall slight curvature of the panel.

It's generally when one side suddenly gets hotter than the others, that distortion takes place and is sometimes very difficult if not impossible to shrink out.

Keep us informed on progress, don't rush it, and make a nice job.

 

[PaulMcElhinney]

Yoshie, I would pulse weld an inch at a time then use an airline to cool it. Yes it will take an eternity but it will be worth it. I'd add a few more tacks too, they are widely spaced. I would make sure that your butting is perfect all the way round. In my experience if the two pieces are out just the thickness of the metal it will increase the likelihood of blowthrough. If you can get access to the rear of the panel via the inner panels I'd try to get a willing assistant to hold a copper welding spoon against the back of areas being welded. Good luck with it. Incidentally I quite like your double joddle idea.

 

[yoshie]

Paul, I'm not in a rush to get it finished getting the panel on without it warping is the main thing, good idea using the air line, give my lungs a bit of a rest from blowing on the weld

Someone has suggested using Heatstop paste made by Wurth or similar I have heard of this type of stuff but thought it may be just voodoo magic has anyone tried it and what did you think of its heat absorbing abilities. The thing is on a repair panel my size how would it be best to use it?

Thanks

Mike

 

[steveo3002]

spose you could mound the putty around a couple of inches of weld then move to another area and so on

never used it myself..some say it works , some says its all lies

 

[pedrobedro]

If you keep the heat in one place surely it will increase the chance of warping the panel. The heat stop I've seen is sold by Frost and is to protect delicate parts near your weld, like screen rubbers when working on a scuttle.