Body patch thoughts

[Blaszer]

On my FF, right where the cowl lights go.....there was a a rusty, rotted spot about 2 inches long by 1 inch tall....It included the 2 front holes for the cowl light.....In my mind, it was best to cut out the bad spot and cut a piece of sheet metal just a touch larger than the hole I cut out....Then I welded around the perimeter of the opening with the new piece on the back side of the panel...My plan is to use tiger hair bondo to fill the low spot created by welding the patch on the back side of the panel.....Does this sound like a good plan? I know it isnt as good as making a perfectly fit panel, but I dont have all the fancy shaping tools to make the perfect patch.....

[Bruce in BC]

Welder

What kind of welder do you have ?

[JStinson]

I use an air powered die grinder with a cutting wheel on it. If you don't have access to that, you can use a jig saw or a sawzall with a metal cutting blade. These tools will let you cut out the old patch and shape the new one pretty easily. Especially since your patch is small.

I would encourage you to make the new patch the size of the hole to avoid welding a randomly shaped patch behind the hole. It would work, but it would be crude. Plus, you'd have to use bondo to finish it, which can be avoided in this situation.

[Blaszer]

I've got a flux core wire welder....But I'm going to try my hand at oxy acetylene welding and brazing to see what I like best

[DavidGB]

You might consider using body solder (lead or equivalent) for any filling required. The Eastwood site might be helpful to you.
DavidGB

[Charles Talbert]

Not a good idea

Over lapping the area to be patched is not good, creates a place where rust damage can start between 2 panels. That is where 99.5% of rust through starts on M37's and power wagons.

You may be thinking if it's sealed up all around that no moisture will get to it. Forget that myth, it absolutely will, and the repair will destroy itself over time creating a worse situation to deal with later on.

It is best to cut out the damaged area far enough back to get into good solid metal, cut the patch panel slightly smaller, about a .040" gap all the way around will weld up great with a mig welder if you are a good welder. You will need panel clips to hold the patch in place to obtain an equal distance all around, and keep the 2 panels at the same height, or level with each other.

The reason for the gap all around is you can skip weld so as not to get the area overheated. This will prevent warpage, and you will have a much nicer end repair that will require much less in the way of filler or putty to finish off the repair. If the patch is a perfect fit with no gap, as the metal expands from the heat of welding, both areas being joined will expand pushing against each other causing warpage in every direction and then some. The gap allows for that and gives the metal space to expand with minimal or no warpage, also allows for welding all the way through creating a solid and much stronger weld.

Unless you are an experienced oxy/acetelyne welder and know the art of controlling the heat input with a torch, you will be better off not going that route. This will not be a good place for learning that art. Unless you are an experienced torchman, keeping from getting it too hot with a torch while getting it hot enough for proper bonding and penetration will be much harder to contol than skip welding with a mig.

Tiger hair is designed for repairing moderately severe damage in places that need the extra reinforcement a product like that provides, and not for finish type work on areas like you have described. You will only be creating more work for yourself in sanding and finishing if you use it in this situation.

Many have told me in the past; oh well I'm not experienced at this like you are, my answer to that is there is no need in getting experienced in going about a specific repair incorrectly. Attempting to learn a technique the wrong way from the get go has never been a help to anyone. It only teaches habits that must be broken later on in order to learn a better way.

Please don't take this the wrong way, I've said what I have with the best of intentions. I have no idea of your experience what ever, just trying to help you out in getting a good repair that will be permanent.

[Blaszer]

No offense or harm taken.....Places like this are great because of constructive criticism from people with more experience..Since I first posted the question, I welded in a patch that was just a touch overlapping and welded the seam around it...,,,filled with tiger hair,used my airboard to sand,,,then used bondo over the whole area...It actually came out decent...Now with the info I've been getting, I will be trying the "flush technique" Thanks.....Steve

[Bruce in BC]

Oxy acet welding in a patch

Triple 0 tip and a small but hot neutral flame . If you fit the patch tight enough you may get away with using no rod . If not go for the cleanest wire you can get your hands on and around .035 - .045 in thickness . Tack the patch in place then weld about 1/2 an inch and then hammer it with a dolly and hammer . You will be surprised how well his will work on a small patch in a curved area .
Some can do this in the middle of a flat panel but I am not one of them . The biggest part of this is not too build up a bead , you want the weld to be about the same thickness as the surrounding metal , full penetration

[Matthew Ziegler]

fancy tools

Blaszer you really don't need a lot of specialized tools, with a small sheetmetal break, some pieces of pipe and a vice you can form some fairly complex shapes a mallet and a few body hammers are also nice to have. make sure you cut out a square or rectangular patch, it's tough to fit and weld in something the shape of texas. one trick I use is to make a template of the hole using clear plastic, cut up 2 liter soda bottles work well, it's easy to cut and you can see through it , sort of like tracing paper, then transfer it to a piece of sheetmetal. Mig welding is clearly the way to go on this, gas welding can badly warp sheetmetal also if you braze it, I've run into problems getting bodyfiller to adhere to braze.

[Bruce in BC]

Machine rating for sheet

#1 Would be a tig machine , foot control , but you need practice and super clean metal for this .

#2 Mig certainly good enough for most of us , and if you can use and find .023 soft wire all the better . Less skilled machine and the metal should be clean but does not have to be spotless like TIG . I use MIG way more often than TIG for a ton of reasons but ease of use and time constraints rank high .

#3 oxy acet - it works but you need skill , skill , skill to avoid warping .

With TIG the metal structure stays the same but with MIG the weld ends up harder and resists shaping .

[BigSmoke]

Over lapping the area to be patched is not good, creates a place where rust damage can start between 2 panels. That is where 99.5% of rust through starts on M37's and power wagons.

You may be thinking if it's sealed up all around that no moisture will get to it. Forget that myth, it absolutely will, and the repair will destroy itself over time creating a worse situation to deal with later on.

It is best to cut out the damaged area far enough back to get into good solid metal, cut the patch panel slightly smaller, about a .040" gap all the way around will weld up great with a mig welder if you are a good welder. You will need panel clips to hold the patch in place to obtain an equal distance all around, and keep the 2 panels at the same height, or level with each other.

The reason for the gap all around is you can skip weld so as not to get the area overheated. This will prevent warpage, and you will have a much nicer end repair that will require much less in the way of filler or putty to finish off the repair. If the patch is a perfect fit with no gap, as the metal expands from the heat of welding, both areas being joined will expand pushing against each other causing warpage in every direction and then some. The gap allows for that and gives the metal space to expand with minimal or no warpage, also allows for welding all the way through creating a solid and much stronger weld.

Unless you are an experienced oxy/acetelyne welder and know the art of controlling the heat input with a torch, you will be better off not going that route. This will not be a good place for learning that art. Unless you are an experienced torchman, keeping from getting it too hot with a torch while getting it hot enough for proper bonding and penetration will be much harder to contol than skip welding with a mig.

Tiger hair is designed for repairing moderately severe damage in places that need the extra reinforcement a product like that provides, and not for finish type work on areas like you have described. You will only be creating more work for yourself in sanding and finishing if you use it in this situation.

Many have told me in the past; oh well I'm not experienced at this like you are, my answer to that is there is no need in getting experienced in going about a specific repair incorrectly. Attempting to learn a technique the wrong way from the get go has never been a help to anyone. It only teaches habits that must be broken later on in order to learn a better way.

Please don't take this the wrong way, I've said what I have with the best of intentions. I have no idea of your experience what ever, just trying to help you out in getting a good repair that will be permanent.

Ditto