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Patching Rusty and Thin Sheetmetal - JB Weld? Fiberglass?

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bulletpruf

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The '72 Javelin project for the 24 Hours of Lemons race is a bit rusty. As a result, it's difficult to weld some of the sheetmetal without blowing through. Now that all four floor patches are welded in, there are several small holes that will need to be filled in.

There are a few that we may be able to weld a small sheetmetal patch on top of, but that's asking for more holes, and some areas really aren't conducive to patches.

I can use some fiberglass mat, I guess, but that doesn't seem like the best option to fill small holes. I'm inclined to use some JB Weld and call it good.

Thoughts?

Also need to make a patch for the roof where it rusted through; maybe about 4" x 6" and it's convex, too. Welding is going to result in blowing through, so I'm thinking of maybe drilling some small holes so we can plug weld and then JB Weld around the edges? It will be a lap weld, not a **** weld.

Almost forgot - I'm using a Mig. I've never gas welded, but I do have a torch and tanks, so that's an option if that would work better.

IMG_3282.jpg

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iagsxr

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If the holes are small and not structural I'd call them weight savings and ventilation.

If you plan to apply any sort of thermal barrier to the floor like Lizard Skin I'd tape the backside and spray the holes full. Check the consistency of your spray barrier to make sure it's thick enough for that to work.

LizardSkin - Spray-on Sound Deadening & Heat Insulation for Cars https://share.google/nWhtqkV1oqq1czEUb

Show us a picture of the hole in the roof. That may be a prime place for 200mph tape. It is a Lemons car after all.
 
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four.cycle

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@bulletpruf -

I've patched up many a lawnmower deck. The AYP (American Yard Products) decks made for Craftsman were the worst: they rusted out on the drivers side because the clippings would get stuck up under there and cause the deck to rot out.

Angle grinder with wire end brush (most aggressive wire you can find) - clean surface up as best you can - not necessary to go down to bare metal (but it helps).
Fiberglass cloth.
Epoxy OR JB Weld (I've used both, but the "metal" epoxy compounds are easier to work with.)
Cut fiberglass cloth large enough to more than cover the hole.
Spread the glue all over the metal surface.
Lay the fiberglass cloth down into the glue and smooth it out. (cut pieces out of old cottage cheese containers to make "spreaders")
Lay some more epoxy (or JB Weld) on top of the fiberglass cloth - smooth out a bit with the spreaders.
Walk away for a couple days.
I've patched up a mess of mower decks using this method.

YMMV
 
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bulletpruf

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iagsxr said:
If the holes are small and not structural I'd call them weight savings and ventilation.

If you plan to apply any sort of thermal barrier to the floor like Lizard Skin I'd tape the backside and spray the holes full. Check the consistency of your spray barrier to make sure it's thick enough for that to work.

LizardSkin - Spray-on Sound Deadening & Heat Insulation for Cars https://share.google/nWhtqkV1oqq1czEUb

Show us a picture of the hole in the roof. That may be a prime place for 200mph tape. It is a Lemons car after all.
Click to expand...
 

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gorilla

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Their is a type of filler commonly called kitty hair that's a fiberglass reinforced bondo that might be a good for filling the small holes it's probably cheaper than JBWeld. The roof patch says pop rivets and a hunk of sheet metal beat to fit.
 
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NightSky

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While looking over the Por15 site, I saw that they recommend using the brush-on Por15 version applied over fiberglass mat to bridge holes. See pics on this page: https://por15.com/products/power-mesh. I imagine that you would have to do plenty of additional work to achieve a smooth finish suitable for an exterior surface. Especially one so visible as the roof right at the door opening.
 
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WoodsTruck

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Take a couple copper couplers, one maybe 1/2" the other 3/4". Smash them almost flat, then slide the smaller inside the bigger and then proceed to make them as flat as you can. Now, you may need to put a slight curve in it, and then it can be held with a small pair of vice grips as a welding backer. This helps hold the heat in the bead until it cools instead of getting liquid and finding the top of your boot. Short burst of welding instead of attempting to run a longer bead seemed to work for me to get enough meat into a thin seam to start getting it built up.
 
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bulletpruf

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WoodsTruck said:
Take a couple copper couplers, one maybe 1/2" the other 3/4". Smash them almost flat, then slide the smaller inside the bigger and then proceed to make them as flat as you can. Now, you may need to put a slight curve in it, and then it can be held with a small pair of vice grips as a welding backer. This helps hold the heat in the bead until it cools instead of getting liquid and finding the top of your boot. Short burst of welding instead of attempting to run a longer bead seemed to work for me to get enough meat into a thin seam to start getting it built up.
Click to expand...

Something like this?

image.jpg
 
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y'sguy

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3M Structural adhesive or similar for all the pinholes. It's a 2-part mix like jb weld but you can buy it in larger quantities, therefore cheaper. Also used to adhere any cheap thin sheet metal you can find to close up the bigger holes, All the body shops use it now or something similar, then you won't need to weld it. If it WAS a nice car it can be sanded filled and primed, and painted. hehe, no offense, it is a lemon entry. Come to think of it why are you even bothering to cover up the holes?
You are going to have some fun.
 
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y'sguy

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OK so I looked again at the pic of the hole in the roof.
I would definitely use the structural adhesive with a cheap roll of that galvanized roof flashing you can get at the Home Depot-type places used for roof flashing, etc. AND fixing holes in Lemons entries. You'll be able to make it as purty as you want or not. Just rough cut that crooked opening to get it sort of level and use the adhesive to glue down the thin metal. You should be able to get to easily follow the roofline. How nice you want it to look after that is up to you and bondo and sanding. Personally, I would then just paint over it and skip the detail work, Just brush some paint on it. It works fast.
 
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545_days

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Honestly now that you have cut the rust away, I would beat a piece of sheet steel to roughly fit, trim it and weld it in. use bondo to clean up any low spots and call it a day.

Or simply rivet it in. It is a lemons car after all.
 
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bulletpruf

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Ran out of time to finish, but tomorrow I'll finish forming the patch and then secure it with some rivets and JB Weld, unless I can find the 3M structural adhesive stuff locally.
 
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Hellpig

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driftpin said:
Was the joint compound expected to stick somewhere? I don't imagine it would last very-long.
Click to expand...

Just needed to get it thru MD inspection, and it did, lol.

A buddy gave $500 for it, ran great, new top, but body was holey. Guy wouldn't even come down a dollar, but we did get a couple beers out of him. And a cheap Styrofoam 7-11 cooler.

About 0200, one cold winter night, my brother was driving it home. Smelled smoke. Started getting thick. So what does he do?

Puts the top down so he could see and breathe.
That REALLY got the fire going.
Had just filled it up that day, so it burned into the road.

Gave it a hell of a wake the next night.
RIP AONEA
 
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four.cycle

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^ Next time, instead of joint compound, just stir up some "Fix-All" (now renamed "Fix-It-All") with some marine spar varnish until you have the right consistency and knife it into the hole. Can take up to a week to fully cure and dry, depending upon how many inches deep you're laying it. Be sure to level it off good with the knife, because it will dry hard as stone and load up 40-grit paper in the blink of an eye.
But water is not going to affect it once fully cured.
 
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PCustoms

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four.cycle said:
^ Next time, instead of joint compound, just stir up some "Fix-All" (now renamed "Fix-It-All") with some marine spar varnish until you have the right consistency and knife it into the hole. Can take up to a week to fully cure and dry, depending upon how many inches deep you're laying it. Be sure to level it off good with the knife, because it will dry hard as stone and load up 40-grit paper in the blink of an eye.
But water is not going to affect it once fully cured.
Click to expand...
Cough

Bondo

Cough
 
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four.cycle

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^ That's an old, old housepainter trick I learned long ago. I never did automotive body work.

The old "Spackle" - when you could still buy it in powdered form and mix it up - was great for patching small dings and dents and holes, but if it was a surface that took a lot of abuse - like the painted face of a kitchen cabinet door - the spackle patches would sometimes just "fall out". (Probably poor adhesion due to inadequate prep work.) The spar varnish acted as an adhesive agent, so the patching compound pretty much "bonded" to the surface.
I used it extensively in an old house I re-worked in which one entire kitchen wall was painted cabinets and drawers that had been beat to hell over the course of 40+ years.
Great techique, but you have to be mindful to knife it down smooth - it's not like laying mud on new drywall and then coming bag and sanding it. The "Fix-it-All" and spar varnish, once hardened, is like trying to sand rocks.

And yes, you could use "Bondo". I've stipped down pieces where it was clear somebody had used the stuff in the past. Just never used it myself. Sold a lot of it. Never tried it out.
 
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NYBODYMAN

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3M Panel Bond or equivalent would be a good move, especially if 100% aesthetics aren't an issue as there will be ghosting around the perimeter of the patch.
 
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Sumboodie

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gorilla said:
Their is a type of filler commonly called kitty hair that's a fiberglass reinforced bondo that might be a good for filling the small holes it's probably cheaper than JBWeld. The roof patch says pop rivets and a hunk of sheet metal beat to fit.
Click to expand...
My Dad used to call that $#@!& *****. It's color probably clues most on the word...

I fixed the cab corners and rocker in a C30 with the ***** and tape as a 1st layer backer.
 
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