Best way for inexperienced welder to weld in replacement floor pans

Wall-e wrote:

Streetwiseguy wrote: Hammer and dolly until its as close as you are capable of, then drill or punch the spot weld holes, then tack the other three sides, then use a hammer and broad flat chisel to beat the flange close as you go. That's a bit unpleasant because of the channel that's blocking your direct access, and there's no real way to clamp to the sill.

When you drill the holes to spot weld, drill a few of them through the panel and the sill. Then use self tapping sheet metal screws to pull the panels together and remove the screws as you weld.

I think this is the answer you are looking for.

Self taping sheet metal screws are your friend when doing this kind of work; screw the panels tight cause spot welds don't like gaps. Beat with the right size hammer if need be. The skill you are going to develop is filling the little hole in the middle of the spot-weld where the screw was when you get to that one.

This is all great advice, thank you all!

I have some options to pursue now.

Arise zombie thread, confuse and confound those who've forgotten you. It's 6am Sunday morning and I'm thinking about welding, maybe I do spend too much time here. 

Anyway, would these methods work with metal that isn't flat, but corrugated?

I'm going to have to do bed repairs on the truck, and the more I think about it and look at the contours of the bed, I have to wonder if I'm crazier than I thought I was. 

My thought is to come in about 10"from the front of the bed and cut straight across. That puts me 3-4 inches into good metal, and makers the only really difficult parts the two sides, mostly the driver's side because of the fuel bump. 

The way I see it, I have 2 options. Option A is to say berk the ridges and valleys, cut off all the rust and weld down a flat sheet of metal. I see big problems making a flat piece work well with the grooves, but I do have some big hammers and a growing anvil collection. Option 2 is to buy a couple bed floor patch panels, that are 16x48" but aligned long ways. This means welding in multiple 16"wide sections to span the width of the bed, which is something like 62 or 65 inches if I remember correctly. 

Option 2 is my preferred method, even though it allows much much greater room for me to really warp and berkeley things up, needing to stitch together 4 or 5 16"wide panels and connect them all to the existing bed floor. 

Would a flange tool be a bad idea in this circumstance? Or maybe it would be better to cut the patch panels a little large and screw them all in place before welding it all together? Would the flange tool make connecting the patches together easier even if it wouldn't help attach the patches to the bed?

Using the one count(no home) method, do I increase or decrease chance of warping covering long distances?

Just to make things more interesting, I'll be buying a tank of C25 specifically for this project, all my welding until now has been flux core. I plan on spending a good deal of time and wire getting the settings perfect before I take the plasma cutter to the truck bed, but it still adds up to some significant distance with this repair. 

Inside and outside will be covered in bed liner as soon as the welds are cool enough, but I should probably get a can of that POL #2 copper weld through primer for before welding as well, right?

It's a truck bed, as long as I can't see through it anymore like I can now, I'll be happy. Truthfully I'd just JB welds the E36 M3 together if I could find those big quart cans, but there's no reason to not at least try to do it the right way since I have the tools. 

Also, I already know I need to replace the front bed support and that front face piece as well. Thinking 2.5"(or whatever it measures out to) C channel for the support and a flat sheet of 1/8"steel for the side against the cab. 

When I replaced floors in my first 914, I welded an old 1/2" bolt to a clean spot so I always had a good grounding point.  Cut the bolt off when done.

Warp is not going to be your problem wwhen doing a repair like this. Get the panel tacked in place and do 1" welds before moving on to another spot or letting the panel cool down. It is a truck bed, not a concourse restoration; not losing your load of dirt out the bottom is as good as it needs to get. Bit of bedliner to finish off and it is all good.

Making the ripples is not really that hard if you have a cheap sheet metal brake, but it is a bit of a PITA. If you can buy a repair section, then do so. Aftermarket may or may not line up with the factory stuff. This was my first attempt at making a ribbed floor pan repair section

Pound the ripple out if it has to meet a flat mating flange or surface

And using the ability to count to one, it is in place. Zero berkeleys were given to warp while doing this. 

Pete

In reply to NOHOME :

I really need to get a passport so I can come buy you a beer sometime. 

In reply to RevRico :

If you make your proposed cut, you will be forced to go forward. You will end up with a working result..

If you do decide to do the repair with a piece of flat sheet, rahtern than a repair panel or a fabricated piece, bend a 90 degree flange on the rear end of the flat section where it is going to meed the cut line. This way you can weld up and around and down the ribs in the box as they meet the flat  bent up wall. This will be easier and better looking than beating the ribs down to meet the flat sheet.  You can put little scuppers into any low spots to drain water. 

Based on my limited experience, I think I would choose your option 2.  If you can swing the patch panels, that sounds like a good solution.  That way you have the basic shape in the metal already, and can do tweaks on it to make it fit what's already on the truck.

That being said, I would not hesitate to try NOHOME's approach.  But I enjoy doing that kind of stuff.

If you have any angle iron hanging around, you could make your own bending brake too.

RevRico,

I'd be more inclined to cut a strip widthwise from a junkyard bed than trying to cut a long aftermarket patch panel into short sections and putting them all side by side. It'll be better metal, fit better, cheaper, and less work.

Then bend a 90 for the front wall by flattening the ripples in a vice.

For a narrow section of sheet metal  like that truck bed I would also consider making some dies out of hard wood and then using a hydraulic  bearing press to shape the "ripples".