question for sheetmetal guy?

I'm filling the roof of my model A sedan and was wandering if the insert should be flush and butt welded or if I can lap it on top the original sheetmetal?

 

Either would work, youre going to have to do some bodywork both ways. Lapped will be faster but won't look as nice in bare metal.

 

Depends on your welding and metal skills. Butt welded you need to have a handle on distortion and how to deal with it. This would be the method the pros use.

Lap will be more forgiving for a weekend warrior.

 

I'm definitly a weekend warrior, I kinda thought the butt weld would be prefered but I just wanted to make sure it will look right when its finished

 

If you butt it at the depression for the insert tacks you won't need as much fill/body repair. Yes, there's metal "under" the weld but not truly lapped over. Spray some weld-through primer in there and have at it.

 

I generally overlap the filler piece as long as it is sound. It's a bitch to butt weld such a large panel and not create more work in the long run. I used a 55 Pontiac top sheetmetal for the filler in my '31 Model A Coupe. I sand blasted the outside only, very lightly. It curled up a little but once roughed out and laid on the roof...Perfect! Once you have it fit into the joggle with a nice even gap( around an 1/8th" is good)all the way around, start from the back and space your initial tack welds generously. 6 to 8 inches is fine. You will want to work from both sides at once so get ready to walk! Work towards the front,one tack on left,one on right. Once you have it Mig tacked and it looks good,split the dif between tacks and go again,ect. You will have lots of hammer and dolly work,grinding,ect. to do as you go to do it right as this will shrink a lot. I get my fillers tacked to about an inch apart,then I tig weld the rest to control shrinkage and eliminate a shit load of grinding. Hope this helps. GJS

 

Another take on this age old argument about butt or lap weld quality and amount of plastic use, is this....
You should and can do =BOTH=......

By that I mean cut your new panel as close to the finished size as you can, then do about a 1/4" lap...Then lay it on the insert openening.

This can then be scooted easily into perfect alignment,and a tiny tack on all four corners.....scribe a mark 1/4" around perimeter.....

Then take a .045 cut off wheel on your tool and slice that 1/4" off by cutting thru the filler and roof both at same time.
go about a foot at a time on your "thru" cut"...

This then allows the roof to be bucked up flush with the new panel and then you tack it every two inches as you work around the hole/opening....'This is how I do most times and it allows very close fit and about the least time involved in doin this fairly tough job......
It also leaves you with the perfect fit....between the panel and hole in roof

=ITshould have about the same gap as the thickness of the steel, this will prevent heaving of the weld seams...


Once it is securely tacked all the way around you can then easily hammer and dolly any part to your specs....as a result your roof and fill panel are not ending up lapped....

 

I'm still a little worried that if I just lap the new top to the old one it will be hard to hide the bump

 

note: If ya RE READ THE ABOVE and you'll see it ends up flush....not lapped.

 

I'd but weld it if it was my car and I planned on keeping it. I worry about heat expansion and goast lines. If you lap weld it you have double thickness at the weld and you have a different expansion rate that may leave a line when the car it sitting in the sun. Dark colors soak up more heat so it would make it worst.

 

over lapped mine. very little filler if you use about a 1/4 " overlap. hammer weld and be sure to move around the roof to allow for proper cooling.

 

I can't quite visualize what you said before

 

Iv been doing metal work for awhile now, I would strongly suggest butt welding the top. When you lap weld it may warp more and you really can't do much with it. Also lapped panels can come thru body work. butt weld everything.

Ok here's how I would do it if I were you, whatever panel your using make it an inch and a half too big to fit the hole. A van roof works well. Lay the panel over the roof and clamp it in place. Use a air body saw to cut both panels at the same time. This will leave you with a perfect gap. You can tack it as you go. Once in place tack every inch or so and stretch the tacks work slow and take your time it'll come out better then you expect. Feel free to ask any questions.

Ryan

 

I was wandering what you used to fill the drip edge on the side of yours?

 

I think I'll Go ahead and cut it to fit. I think Ryguy442 kinda explained what choprods was saying

 

Yeah I just read his post pretty much the same thing. I just use an air body saw, just seem to get the tightest gap that way. I do alot of tig welding so I need almost zero gap. I always do my big panels like this I just did a few door skins like this. Let us know how it comes out!

Ryan

 

Try makin a removable insert. I think they look a it better imho

 

thats a nice idea

my weekly metal work blog www.themetalsurgeon.com

 

I did my coupe kinda like Kirk Hanning, except the trough is still there so I can glue down the top fabric and it looks original. No one will be able to tell its got a metal insert.

It is one heck of a lot easier

 

If you over lap the insert panel ,it could end up like this customers Model A

.http://www.jalopyjournal.com/forum/showthread.php?t=647440


Its now in my shop getting re worked and the over lap cut,and butt welded.



my weekly metal work blog www.themetalsurgeon.com

 

Nice work on the coupe!! What sucks is the original work could have been done by some famous shop for big $$$!!! Good advice here. Take your time and but weld it. You'll have more control working distortion out of a flat panel.

 

Here's how I did mine:

http://www.jalopyjournal.com/forum/showthread.php?t=465795

It's lapped and butted...

 

I have a technic i use for a large panel butt weld or smaller to. I trim the panel 1/4 in larger than the hole you want to fill as if you were doing a lap weld. Tack your panel in various spots to hold. Using a cut of wheel with the finest blade you can find, say 1/32, and cut the 2 layers at the same time for about 1 ft. Like you where cutting a carpet seam. Reach underneath and pull back the cut strip and let it hang, just bend it back for a handle later. Same on top, just bend the little strip back. This will leave you a tiny crack to weld if any. I prefer a gap for expansion. Now weld that area about 1 inch and grind. Grinding immmediatly gets rid of some hot weld material. Heat is the enemy. Take your time welding slow and cool. Do not cool rapidly with air or wet rag. I shrinks and hardens the metal. Go to a cold spot at the other end and do the same thing. This will keep you busy so your not rushing the welds.
So basicly what your doing here is holding the panel in the exact spot while you cut a bit, peel back the stips and weld some more.
The advantage of a butt weld is you can dolly out your hi and lo's with out that stiff layered metal.I did this welding NOS 1/4's on my 70 Torino convert. It was near a 7 ft butt weld and had total control of the panel. Did the same with the tubs.
Both ways work but the butt weld is just a hi end repair.

 

thanks for all of the advice glad I checked here first

 

This post scratches right where I itch. I am starting the same project and am bold enough to ask a stupid question... I'm doing a 30 ford coupe. the top wood is trashed. Do I replace the top wood or is the new metal enough? It would seem like it would need to have that structure to keep everything square and sturdy. Thanks for any ideas.

 

I am using the support rails from the top I cut to help tie everything together

 

marked for reference

 

Great shots, back when people DID, instead of talking about doing as we do today.