Floor Surgery

[goodolarchie]

This weekend is all about dealing with the floor. All four pans have rust through, though driver side is the worst. Here is some recon (let me know if these images are too large, they should fit fine on anything larger than 1024):

(Yes that is speaker wire from some hack job done by PO

And now for the patching:

Tacked real snug by using a jack below.

(Was this fiberglass filler beneath the undercarriage coating? Lots of whispy fiberous crap came off..)

Then the tacks were stitched together with lap welds

First one done, passed the dye penetrant inspection.

There is about 1/2" overlapped underneath that needs to be seam sealed and POR coated.

Now on to the BAD metal!

 

[Peter Coomaraswamy]

really nice work

Thanks for sharing- Please keep the pics coming! I had to have afriend help with the welding because I knew I would make a mess of it.

 

[74EuroE9]

Metal repair

Nice work! I'm curious why you did not use repair panels or good used sheet metal harvested from a donor E9? I know the repair panels are $200 / each, but isn't the small extra outlay justified for a better end result better and the ultimate value of your car? I'm new to this and trying to learn and understand)):wink:

 

[Sven]

goodolarchie - I have a partial front left floor pan I fabricated for my car, but ended up not needing it. You can have it for the cost of shipping. It has been sitting in my garage for a couple of years (a bit of surface rust only). The depression is the same size as the existing floor rectangle depression. The turned up flange should fit against the inner rocker. You would need to add some material where the front curves up to the firewall.

At the driver's floor I would not use just a flat piece of sheet metal. I think it would be too flexible for that large of an area. I suppose in some ways even the floor pans add strength to the car's body.

 

[John Buchtenkirch]

This weekend is all about dealing with the floor. All four pans have rust through, though driver side is the worst. Here is some recon (let me know if these images are too large, they should fit fine on anything larger than 1024):

(Was this fiberglass filler beneath the undercarriage coating? Lots of whispy fiberous crap came off..)

First one done, passed the dye penetrant inspection.

There is about 1/2" overlapped underneath that needs to be seam sealed and POR coated.

Now on to the BAD metal!

It’s most important to blow paint into that overlap before you go near it with any seam sealer. A spray head with a plastic tube (from a penetrating oil or undercoating spray can) installed on whatever spray paint you chose will really blow that paint into that overlap. The blued metal from welding heat will start to rust almost immediately, that is why it’s so important to get paint in there.

Your weld bead is pretty high or what we in the auto body business call proud. You might consider trying one or even two heat ranges higher on some scrap pieces and see if you have better results. Don’t let me discourage you, what you have there will work fine, just trying to help you do even better :grin:. ~ John Buchtenkirch

 

[goodolarchie]

Delayed response here.. sorry it was a busy weekend and I appreciate all the comments :-o

Nice work! I'm curious why you did not use repair panels or good used sheet metal harvested from a donor E9? I know the repair panels are $200 / each, but isn't the small extra outlay justified for a better end result better and the ultimate value of your car? I'm new to this and trying to learn and understand)):wink:

This is the $1m question isn't it! For me this was a practical and financial decision boiling down to

• I am not doing a concourse restoration
• You and I will probably be the only ones who will ever see the floor and substructure of the car "naked"
• I will NEVER sell this car!
• I have loads of spare 16ga mild steel
• Fabricating your own panels is way more fun
• I can always buy Jaymic or factory panels later if I change my mind or happen upon a wrecked bank heist vehicle.

goodolarchie - I have a partial front left floor pan I fabricated for my car, but ended up not needing it. You can have it for the cost of shipping. It has been sitting in my garage for a couple of years (a bit of surface rust only). The depression is the same size as the existing floor rectangle depression. The turned up flange should fit against the inner rocker. You would need to add some material where the front curves up to the firewall.

At the driver's floor I would not use just a flat piece of sheet metal. I think it would be too flexible for that large of an area. I suppose in some ways even the floor pans add strength to the car's body.

D'oh! I would have jumped on this but as you were posting, I was cutting and welding so the front left pan is done. In fact, the entire floor is done :grin: I will post more pics soon.

It’s most important to blow paint into that overlap before you go near it with any seam sealer. A spray head with a plastic tube (from a penetrating oil or undercoating spray can) installed on whatever spray paint you chose will really blow that paint into that overlap. The blued metal from welding heat will start to rust almost immediately, that is why it’s so important to get paint in there.

Your weld bead is pretty high or what we in the auto body business call proud. You might consider trying one or even two heat ranges higher on some scrap pieces and see if you have better results. Don’t let me discourage you, what you have there will work fine, just trying to help you do even better . ~ John Buchtenkirch

Hi John, glad to have a Pro around for sound advice! What are your thoughts on weld-through primer going on before the panel gets welded in? I have tried this and the penetration is quite good but I notice the paint still pools up, I worry about a proper seal. I will take ever precaution before applying the seam sealer, including stripping the rest of the undercarriage to bare metal then likely using a POR product. That was my plan anyway.. it may change if I can find a good media blasting / coating operation that can fit me in before the body paint..

 

[John Buchtenkirch]

Hi John, glad to have a Pro around for sound advice! What are your thoughts on weld-through primer going on before the panel gets welded in? I have tried this and the penetration is quite good but I notice the paint still pools up, I worry about a proper seal. I will take ever precaution before applying the seam sealer, including stripping the rest of the undercarriage to bare metal then likely using a POR product. That was my plan anyway.. it may change if I can find a good media blasting / coating operation that can fit me in before the body paint..

I don’t care for or use weld-thru primer at all, it just messes with my weld beads too much plus I just have to wonder how much protection it really gives you at the actual molten weld point. Also the fumes from it really bother my lungs. My first and upmost priority is the structural soundness of my welds, if they break professionally I’m a bum, hack, mutt or worse ---- welding with weld-thru primer is like welding contaminated metal so I just don’t do it.

My next priority is rust prevention so I flood all my layered or lapped seams with paint. Worth makes a good rust prevention spray paint but I have used other primes with decent results, the big thing with me is I’m always looking for cans I can retrofit with plastic spray wands to get inside panels. Why the big spray bomb companies don’t make different head kits (different spray patterns and plastic tubes & such) for their paint cans is beyond me --- probably don’t want you changing out the clogged spray heads on half used cans, they would rather sell you another can of paint.

Anyway you could also use a brush to push POR into that lap seam but it’s going to be drippy / messy, beware if POR gets on you it’s an absolute bit_h to get off :shock:. ~ John Buchtenkirch

 

[aalto]

Thanks for the photos. Love these restoration threads!

Your car looks perhaps just a bit worse off than mine when i got it. I went the route that you seem to be on, that of doing a reasonable repair but making rather than buying many patch panels in an effort to create a good non-rusty driver. I agree that there is something quite satisfying about making one's own panels and welding them in.

Just curious about the relatively thick gauge of material you are using (if i recalll correctly most of the metal in the car is perhaps 20 gauge but i could be forgetting?). Do you find the thicker material easier to work with (less blow through with the welder for example) or is that just what you happened to have around? It will certainly create a panel that can resist rust-through for a longer period of time. I also suspect that it may be nearly as rigid as the original thinner gauge floor pans with their stiffening ridges and grooves.

Also . . . appreciate the great advice from John!

 

[goodolarchie]

Just curious about the relatively thick gauge of material you are using (if i recalll correctly most of the metal in the car is perhaps 20 gauge but i could be forgetting?). Do you find the thicker material easier to work with (less blow through with the welder for example) or is that just what you happened to have around? It will certainly create a panel that can resist rust-through for a longer period of time. I also suspect that it may be nearly as rigid as the original thinner gauge floor pans with their stiffening ridges and grooves.

16 ga is what I have on hand, and I am presently dealing with the substructure of the car, I like the rigidity and longevity. I believe you are right about 20ga being used on many of the outer panels. Where the wheelarch meets the floor panel, I had to get out the old dial caliper just to check, it was .040" +- .003.

I don't plan on doing too many more custom panels, other than some flat pieces for the RH fender substructure. I'll be ordering the LH repair bulkhead from Jaymic... mine is toast and beyond patching:

http://www.jaymic.com/shop/parts_CS_products.asp?grp=CSBDR&page=3

The other panels will be from BMW mobile tradition. Namely both fenders, front outer rocker covers, possibly LH quarter panel. I cannot order until after taxes :???: But hopefully the car will be wearing a suit of polaris before summer closes its curtains on the NW.

Also worth mentioning, Jaymic sells the floor plugs at 4 quid... I may buy two of these just for a nice touch of originality to grace my homemade butchering