Door skin patch panel question

[red57]

Restoration in progress (only 2 years in) and I'm at the stage now to repair the doors. I got Kilmartin lower door skin patch panels from British Car Specialists. They run almost up to the swage line. In my case the rust is limited to the bottom 3-4" of the door. My questions is: is it better to use the entire replacement panel and cut the old skin up near the swage line, or is it better to just cut off the lower area where the rust is and trim the patch panel down to match. I'm thinking some of you have faced this decision and possibly have some advise/recommendations.
Thanks,
Dave

 

[Healey 100]

I have not made that specific repair, but I would definitely cut the patch down to the smallest size possible while still being able to connect it to solid, unrusted metal. I would keep it small because the larger the patch, the more problems you'll have with distortion of the door, oil canning, etc.

Just a comment: While all my repairs have been butt welded, they were made many years ago. Today I would look into epoxy bonded overlapping joints. Many body shops are using this technique and it really cuts down on the distortion you get with a welded repair. The strength of these joints is amazing and the epoxy seals the overlap against water infiltration.

 

[red57]

Thanks Bill, I agree to cut out as little as possible, and have been doing that throughout on the inner stuff. In the case of the doors, at least one of them will have to have the bottom 2-3" cut out the entire length of the door. And in that case the weld length will be the same whether I cut high up or just the bottom. I have been looking at the accessibility from the inside for dolly work after welding and, except for the brace with the wood insert, there is pretty good access. I am unsure if there will be a difference in the distortion. I'm Oxy/Acetylene butt welding so hammer & dolly is possible, but I am lazy and mostly novice at bodywork. I just can't decide if there is an advantage one way or the other. On the other door I may get by with a couple of shorter patches. No matter what I do, I'm sure some bondo will be involved....

Epoxy bonded lap joints seem appealing but also seems too hi-tech for me - I would worry about getting a bad joint and a failure soon.

Thanks,
Dave

 

[healeyblue]

If you have to weld the entire length of the door then the closer you get to the swage line the stronger the metal will be because the swage will act to strengthen the metal and prevent it from warping. I strongly advise against gas welding unless you are very proficient at it. Short bursts with a mig will induce less heat and have less chances of warping. And by all means do not braze the panels on. I curse every time I see old braze repairs.

 

[Barryp]

Hi Dave,

I'm five yrs into my two year project, but the body is ready for paint. I had several patches to do also and I struggled with what method too. The one I that I think worked the best was place the patch over existing panel about 1" larger than is needed so you have some good existing metal to weld to. Tack it every couple of inches then take a thin cut off wheel and cut at a 45 deg angle on the edge of the patch panel. Cut four or five inches push the two pieces together and retack. You can end up with a gapless patch if your careful. I'll try to attach some pics. I played with the oxy and had some good success but the mig seemed to work best on these types of patches and had less distortion on the larger flat panels ie: bottom of the door.

Barry

 

[Bob_Spidell]

Barry,

Looks like you used Kilmartin patch panels with the correct wire bead. How did you 'merge' the bead on the panel into the existing bead on the wheel well?

Thanks,
Bob

ps. Nicely done, BTW.

 

[Barryp]

Hi Bob,

Yes Kilmartin, I took the easy way out and used the original wire on this fender, as it was in good shape however you could onroll the lip on the original and cut the wire a few inches back, but weld the new wire to the existing and roll the lip back over.

Barry

 

[red57]

Thanks, for the responses.

Healeyblue - that is exactly why I asked the question. It seemed to me the swage line might help keep it straighter but wasn't sure. And I will never braze - a PO brazed up old holes in my boot lid from a luggage rack and something (maybe the flux residue?) has screwed up paint twice over the years. I also have an oil pan that someone brazed and it keeps cracking where the brass is - too rigid I think. Anyway, no brass going into this project.

Barryp - that sounds like a good method for having no gaps, I will have to try it. As to the oxy/vs mig debate, the main reason I have been using oxy with no filler is that the panel remains ductile & malleable for hammer & dolly work. The mig wire is so hard it can actually crack when trying to straighten after grinding down to parent metal thickness - trade off = more distortion with gas but workable metal, less distortion with mig but not very workable. I have found on some of the inner sheet metal that the oxy caused a fair amount of distortion but I could work it back to shape. In some cases I used the mig and sure found less distortion - but these were all fairly short welds compared to the door (plus most aren't going to be visible). I've done a lot of research and the oxy method was how they did a lot of custom coachwork in the 30s & 40s and I have seen some beautiful results (not necessarily mine though). Most recommend tacking every 1/2 inch or so and then one continuous weld without filler making a very uniform HAZ the entire length of the weld - on practice sheets it seemed to work well but I'm now ready to tackle the real thing and am a bit nervous about the outcome.

Again, I appreciate all comments.

Dave

 

[Barryp]

Dave,

Please let me/us know what method you use and what the results are. I really wanted to do old school style repair work on this car and have tried to use oxy/acetylene as much as possible, it's what I grew up with and really enjoy using, but even with a mini torch it can put a fair amount of heat into to the peice if one isn't very careful. And then hammer and dolly and some shrinking is called for. I hate to say it, maybe I just got lazy but the mig method does work pretty good. It does make for a more brittle area, but less plastic filler can be used, I guess that's the trade off. I have a real soft spot for the fabricators that could make, or repair anything with a torch and a coat hanger. I played with tig, oxy and mig on these patch panels and really felt like the mig was cheating, and it pains me to say but it works pretty good. The trick is not laying beads just hundreds of overlapping tacks, so there is no HAZ.

Barry

 

[Keoke]

I have made that specific repair and I would definitely cut the patch down to the smallest size possible while still being able to connect it to solid, unrusted metal. Keep it patch area small because the larger the patch, the more problems you'll have with warpage- distortion of the door metal, oil canning, etc.

-- With Bill Sullivan-Additionally if you can find a metal man that knows how to " Hammer Weld " you will get a proper fix.
It does not matter where you cut the panel just so all the rusted area is removed The modern techniques may be good I just have never used them. You know old folks old world techniques--:highly_amused:

 

[Bob_Spidell]

Technique I've seen used for butt welds on TV shows--haven't done any bodywork in a while myself--is to hammer-and-dolly the tack weld flat while still hot, then use compressed air to cool the weld. Make your tacks as far apart as possible, then interleave the welds, known as 'stitch welding.'

 

[Keoke]

BOB:
cumulatively this is how the " Hammer Weld " is done mostly only skilled metal men can accomplish this repair.