Rear Cab Corner Replacement - Fill with Fiberglass

[ShoeSlinger]

Hey replacing my rear cab corners and overall have very little rust. Just wondering if I seal the metal on the interior cab corner, then any reason not to fill the void with fiberglass resin? Then it would be solid and not prone to future problems.

[dsraven]

any steel i have seen that is covered in fiberglass resin has been rusted so the resin falls off leaving a hole. check with a supplier but it makes me think resin alone is porous unless coated in gel coat possibly.
i would remove the outer corner part as far as you need to in order to eliminate any future rust issues
try to get the area remaining and other areas, accessible when the outer corner is off, cleaned down to steel
epoxy prime everything in that seen area to seal the area and allow to cure
clean the epoxy off the new weld area for the outer corner replacement part so the welded area is bare steel on the front and rear side
weld that outer cab corner part in and do the related metal work to get the area smooth and ready for a skim of filler or whatever after a coat of epoxy is applied. the epoxy will seal the steel and then the filler,which is porous and can attract moisture/rust, can be applied over the sealed steel
then, again, clean the backside of that welded area as well as you can to remove any weld slag or ash residue etc, smooth it out as you see fit. clean it up to allow another coat of epoxy to stick properly, ensure to rough up the previously epoxied area with some scotch brite. also clean the outer surface of the replaced part and surrounding area
apply epoxy to both sides of the outer cab corner to seal it all. paint the area as you see fit. then fab up a cover for the floor area if you want to seal off that void and have a flat floor there. I would not weld that cover to the outer wall of the cab. that would make an area that may distort when the cab is twisted, like going over a speed bump at an angle, and may cause the cab corner to look "bent" below the weld or may make the weld noticeable especially on a hot day as the metal may expand at different rates due to the heat sink effect of the new attached floor extension.

just my thoughts. I usually try to leave fiberglass out of the bodywork equation because I have seen too many of those style patches cause rust issues when applied over bare steel. you could easily fabricate a new fiberglass floor section to cover the cab corner "hole" and then screw or epoxy it to the existing floor area, not attached to the exterior cab corner. seal the edges against the cab corner with some weatherstrip or the like? just a suggestion,
your truck, do what you feel is right. post a few pics when you get to working on it, we all like pics and sometimes it is what it takes to get us off the couch and back to work on our own projects

[ShoeSlinger]

My plan was to replace/weld in the sheet metal and coat the inside with POR 15 and then pour in fiberglass resin to just fill the void. The fiberglass is not part of the repair, just to seal off the area so that it doesn't collect dirt/water & critters in the future.

All new to 55's as this is my father in-laws and now will be my youngest son's truck.

[b-mac]

Not directly answering your question, but fiberglass and metal expand and contract at two different rates. Eventually, the fiberglass will crack, and those cracks can expose the metal to moisture, which will further your rust. It's possible that if you epoxy coated everything, you might stop the rust, but this is a temporary fix.

That not to say that plenty of people haven't done this successfully with decent results. Just as many have filled rust holes with Bondo. It's just the correct way to fix it, and it won't last.

[b-mac]

After reading your last comment, I have a better understanding of what you're trying to do.
I think you are the right track with everything. And the POR should keep you protected.
I don't think any body shop guy (and maybe they will weigh-in) would add fiberglass resin to what you've already got going.

I see your point with the somtime strange voids/crap catchers on these old trucks. I'm not as familar with the TF, so I don't know how much space you'll be filling. Might never be an issue, but still think the fiberglass will eventually sperate from the metal. Maybe that doesn't matter if the metal is properly treated below the resin.

[dsraven]

yeah, kinda what I was thinking as well. don't do it unless you have to. what about a garden sprayer with some undercoating so you can pressure spray the entire void to get to any cracks. let the excess run out a drain hole in the bottom (placed there on purpose to let out any moisture or condensation that may show up in the void) then cap it with a removable floor cover piece on top. it could be sealed for noise with some seam sealer but remain removable and not attached to the outside skin.
on another topic, be careful how you support the cab on stands. the running boards are pretty strong but can distort the rear cab corner if you end up sitting on the cab while repairing and the cab corner is a little suspect anyway. best to have a door hung in place and latched so you get the cab corner to door gap correct. maybe best to support the cab under the actual cab support areas to be safe. when I did my cab work I cross braced the cab with the doors on so it couldn't move., it was also siting on the truck frame so the contact points would also remain the same and not distort later when the cab is bolted down tight.
your truck though, do it like you feel you wanna.

[mr48chev]

Reminds me of those hack jobs from the 60's to be truthful.

Personally on an heirloom truck that you intend to keep in the family you need to fit right rather than try to put a bandaid on it that someone will have to remove later to fix it right.

Even if you can't weld you can cut the bad part out, fit up the correct patch panels as well as you can and the get someone to weld them in and then do the finish work.

Sorry but in the past I have had to deal with those fiberglass bandaid patches when I had to help fix something right and it was a bigger mess to get the glass out than actually do the patch right.

[ShoeSlinger]

The fiberglass resin is not for the repair at all (welding I have too much experience)...

It is just to fill the void to eliminate the problem area (mystery hole that collects everything).

[mongocanfly]

Don't pour resin in there...for one thing it would take a great amount to fill it...another is the rust thing...if anything go ahead and seal it up like your wanting...just make a sheetmetal piece to cover the hole if it bothers you...
And welcome....

[ShoeSlinger]

Thank you everyone. Will skip the fiberglass resin and make an access plate.

[68blackbird]

Not sure if it was best thing to do, but on the '59 I did last year, after replacing the corners, I sealed the hole with POR15, then filled it with expanding foam, trimmed, tacked welded metal piece, then used seal seam to finish it off. Now, I have a plasma cutter and was going to make one, but was fortunate to have access to a CNC plasma cutter, so gave them my cardboard template and they cut 4 pieces so I could do top & bottom.

[ShoeSlinger]

Originally Posted by 68blackbird

Not sure if it was best thing to do, but on the '59 I did last year, after replacing the corners, I sealed the hole with POR15, then filled it with expanding foam, trimmed, tacked welded metal piece, then used seal seam to finish it off. Now, I have a plasma cutter and was going to make one, but was fortunate to have access to a CNC plasma cutter, so gave them my cardboard template and they cut 4 pieces so I could do top & bottom.

Really nice!

[dsraven]

'68, that's a nice fitting patch cover you have there. not sure about the expanding foam as it could be a sponge for condensation etc, but was thinking of the patch. could you make it a little bigger and then bend the edges up so it matches the contour of the outside sheet metal? if that were done you could attach the patch to the floor and then use seam sealer around the outside edges to seal the patch from the void and water couldn't find it's way in there but the patch could also be removed easily for access should you need it. another idea I was thinking would be to have some sort of self sealing drain for the void area. much like the ones used on some automotive a/c drains and also off road heavy equipment and farm machinery air filter housings. it is like an extended grommet or rubber tube that fits into the drain hole. the other end of the fitting has been formed flat and has a set of lip like flaps that seal against each other like closed lips but allow internal pressure, like the weight of water, to escape out the lips but seals other things from getting in.
just a thought.

[dsraven]

here is a link to a site with one of those drain fittings so you can see what I mean about the sealing lips. not the correct fitting for this application but you get the drift of the concept.

https://www.ioffer.com/i/a-c-water-d...00td-108592837

[68blackbird]

Originally Posted by dsraven

'68, that's a nice fitting patch cover you have there. not sure about the expanding foam as it could be a sponge for condensation etc, but was thinking of the patch. could you make it a little bigger and then bend the edges up so it matches the contour of the outside sheet metal? if that were done you could attach the patch to the floor and then use seam sealer around the outside edges to seal the patch from the void and water couldn't find it's way in there but the patch could also be removed easily for access should you need it. another idea I was thinking would be to have some sort of self sealing drain for the void area. much like the ones used on some automotive a/c drains and also off road heavy equipment and farm machinery air filter housings. it is like an extended grommet or rubber tube that fits into the drain hole. the other end of the fitting has been formed flat and has a set of lip like flaps that seal against each other like closed lips but allow internal pressure, like the weight of water, to escape out the lips but seals other things from getting in.
just a thought.

Yeah, I thought about the foam being a sponge, but since it is sealed on both the inside & outside, I figured that would keep any moisture out. Not sure if you can tell by the pic, but the last one is the bottom of truck, I could see where you might think it was the inside. Your point is well taken, Kel

[b-mac]

Originally Posted by 68blackbird

Not sure if it was best thing to do, but on the '59 I did last year, after replacing the corners, I sealed the hole with POR15, then filled it with expanding foam, trimmed, tacked welded metal piece, then used seal seam to finish it off. Now, I have a plasma cutter and was going to make one, but was fortunate to have access to a CNC plasma cutter, so gave them my cardboard template and they cut 4 pieces so I could do top & bottom.

I have an AD, but I was thinking of doing something similar, except leave out the foam, and put a hidden hinge on the bottom side, like a cabinet hinge. Then you've got two little hidden cubby holes.

[Foot Stomper]

The only product that should be used is epoxy primer and urethane paint.

This solution will last longer than anything else you can dream up.

[_Ogre]

resin or foam are both bad ideas and will result in rust that will be hard to fix
most body shops have dealt with both situations and will tell you it is a baddd idea

my son bought a 68 elco that was rust proofed with body cavity wax spray
didn't help with rust at all, every weld we did on it caused a fire
welding required a water hose, fire extinguisher and my dd truk chained to the frame in case we had to pull it out quickly
(on jack stands with no wheels)

[vics stuff]

Expanding foam will kill sheet metal. I know , I tried that process 30 years ago to a truck and within 3 years the repairs were already rusted through.
Vic

[hogfarm]

After the repairs on my 58 I sealed the entire floor of the cab with Raptor,it's like Rino coat for the beds

[duramax55]

personlay would just make sure it has a good coat of primer paint and leave open or at least have it so it can be open. Once filled if any moisture gets in, and it will it will rust faster because it cant dry out. yes those trucks rusted in the corner as most other old trucks but they were driven in mud ,dust ,rai ,snow etc. remember they are 65 years old. Fixed right it will be a long time before you see rust there again