Using epoxy rot treatment on subfloor

[Jacob D.]

I have a section of subfloor that has rotted, to the right of the door:



I think the cause is the installation of the lower awning bracket, which was just bolted through the shell around the end of the banana wrap, leaving some big gaps.

Anyway, the rot continues down the wall a little:



The crossmember or outrigger underneath the floor is also a little rusted.

So what's happened is that the shell has dropped down a bit, presumably just from bending the rotted floor, and that's caused the shell and interior skin to crack above the door. Couple of photos: interior crack, exterior crack.

However, as far as I can tell, that's all the damage that's done. The step and the floor above it seem solid. So I'm trying to decide if I should replace that section of floor, or whether I can use some kind of epoxy rot treatment (someone mentioned Rot Doctor) to stabilize the situation as it is. I can patch over the cracks in the shell and as long as nothing moves any further, it would be fine. Does this seem like a viable option?

I was still thinking I might cut into the belly skin underneath to to access the underside of the floor to treat it and to treat & repaint the rusted crossmember.

If I do need to replace that section of floor (which is pretty small), will I need to do something to support the shell while the floor is out, or will I just be able to wedge the new piece in under the C channel?

[LI Pets]

How soft is the wood, with a pick or screw driver, your hand?

Is it flake like or solid?

[Bob Thompson]

I tried Rot Doctor on a previous travel trailer with dismal results. The part I doctor'd still had to be replaced. Bottom line, you really need to eliminate the rot by replacing it with sound wood. I know it's not what you wanted to hear, but it is the right way to fix the problem.

[Wabbiteer]

The bananna wrap is almost too easily replaced after a crash - I had mangled outriggers floating above the wraps as witness to some oops somewhen that were cleverly hidden & forgotten by new sheet metal.

If the outriggers are not in allignment, welds popped and/or channel mount bolts sheared the plywood allows alot of vibrations to be transmitted - add in out of balance running gear and the twin shell cracks could've happened in a very short tow. Eyeball them before committing to any repairs...

[Jacob D.]

I'd rather hear in advance than waste time & money on chemical treatments that aren't going to work... I'm just glad that the floor damage is so limited. I've been over virtually every bit of the rest of the floor and it's all solid - when I read about people's frame-off floor replacements that gives a little perspective.

As for how bad, it's not falling apart, but it's somewhat soft - I could flake off bits of the surface at the doorway by hand, or probably push a screwdriver 1/8-1/4" into the surface along the wall.

I think the cracks happened gradually (from the attempts made by the previous owner to stop them by drilling holes), and I didn't notice them getting worse in the none-too-gentle 1,400 mile tow back to California. But it's true the trailer could probably use new axles and definitely new shocks.

[Kevbo10]

replace the floor section. epoxy WON'T help. kevbo

[LI Pets]

the correct chemical treatment is "Gitrot", but that area is too large.

you can cut the floor out to frame where the outriggers attach, about 15" from the wall, and slip in a new piece of ply. I would estimate 4-6 hours.

you can fiberglass it,
You would take 6 or 10 oz cloth cut it to fit over the area and paint in the epoxy, same underneath. it will work in part.

But you will not be able to glass under the C channel, it will continue to rot.

So it will fail in time.

So replace it.

[Jacob D.]

Replace it is then, I think. So will I need to do something to support the shell as I pull this piece of floor out, or will it stay in place? This seems particularly problematic since it's right by the door, and since the shell is already cracked at the top of the door. Perhaps I should reinforce the skin above the door before removing the floor?

[LI Pets]

How large a piece are you planning on cutting out say from the right side of the door in the pic how far foward?

You're only going in about 15" correct?

My first thought is no support is needed, I took out a 4' by 4' piece in the rear corner nothing moved frame wise.

[Over59]

Originally Posted by jacobwellcom

Replace it is then, I think. So will I need to do something to support the shell as I pull this piece of floor out, or will it stay in place? This seems particularly problematic since it's right by the door, and since the shell is already cracked at the top of the door. Perhaps I should reinforce the skin above the door before removing the floor?

Support never hurts. Looks like the shell will settle more at the door frame. Anyway you are going to want to get it back up where it belongs. To do the penetrating epoxy thing you must first kill the organisms that are rotting the wood. Research this online, especially at wood boat repair suppliers. It may be possible to treat, solidify, and top coat with fabric / epoxy. Do your own research so you are sure you are getting accurate information. I've never seen an exterior crack before. Has to be more to the story, like train tracks at 70mph.

[CanoeStream]

Hello Jacob -- the front of your door isn't that far from the corner post. Even with the intervening window I would think the stiff monocoque shell would not have flexed just for this johnny-come-lately reason with the floor. Blowing up your exterior photo I see a second skin crack two rivets forward. The photo doesn't suggest any crack in the door main frame between the inner and outer skins -- is this correct? Do I see a slight buckle in the skin at the upper left corner of the window?

The step sides do function as outriggers and the forward one supporting this floor area sure looks good. These shells seem to stay pretty stiff even with two adjacent outriggers gone. My Argosy had a leak in the same area -- same reason with poorly installed awning mount. It had been going on longer than yours and actually lost thickness of about one veneer thickness.

So far, I'm throwing in my lot with Wabbiteer:

Originally Posted by Wabbiteer

The bananna wrap is almost too easily replaced after a crash - I had mangled outriggers floating above the wraps as witness to some oops somewhen that were cleverly hidden & forgotten by new sheet metal.

If the outriggers are not in alignment, welds popped and/or channel mount bolts sheared the plywood allows alot of vibrations to be transmitted - add in out of balance running gear and the twin shell cracks could've happened in a very short tow. Eyeball them before committing to any repairs...

I love the old trailer photo from the Oakland Museum!

[Wabbiteer]

I know similarities between a '64 and a '73 are not so close, but I thought of another angle to why I suspect spars and outriggers. I found the self-drilling floor screws were binding only by one thread across the sets of lower profile spars designed to accomodate the backer board for floor seams having an additional 5/8" of plywood to reach the metal, too short from factory to begin so had stripped either from re-tightening or just rough service...

Also found one spar behind axles without any floor fasteners at all. Also alot of the the fiberglass laid between frame and flooring turn into pink flour on mine - meaning loose floor; best I could do w/o a shell off was add correct length or tighten existing fasteners for now. Also the fiberglass wicked moisture 5 or more feet up from water leaks and held it next to plywood untill the veneer layer alongside it simply disapeared, a defect invisible from the top that surely adds to the jello shake.

Last weekend I replaced three broken bucked rivets above my door in the same spot as your exterior crack, and have three missing inside. My '73 has fewer rivets in the door frame, maybe they heavied up the extrusion thickness so I'm not fighting cracks too. The flex moment at the doorway is exagerated by motion elsewhere, think aft of axles on opposite side of trailer etc; its cracking at door because its moving elsewhere.. (?)

[LI Pets]

The floor must get bolted down tight, if you get under and take a screw driver between the frame and the ply floor and try prying them apart you should see where they need refastening.

I used 1/4" flat head self tapping screws in few places.

[Jacob D.]

Thanks for the advice. Interesting that the crack is unusual. There might well have been a railroad crossing at 70mph in the past, but don't blame me, I just got it! I'm pretty certain there hasn't been a significant collision though, just that awning bracket that let in the rain. The door frame itself is solid - no cracks or other damage apparent. I think though that the explanation of failed floor/shell and floor/frame connectors, a little movement downwards, and vibration is probably about right.

So I think the way I will go is - remove the inner skin above this section and see how the floor/channel/shell connection is there, then cut open the belly skin underneath and take look from under there. Then cut out about 15" wide by about 24" long section of floor, supporting the shell with a jack from underneath as needed, check out the outrigger & underfloor support and repair as necessary, then put in a new section of floor there and reattach the shell to it, at the original level height.

Then patch the cracks in the outer shell (I was thinking of using a crescent-shaped patch that would wrap around the top of the door - it would look like it was meant to be there more than a smaller patch would) and maybe replace the inside panel altogether.

[LI Pets]

Originally Posted by jacobwellcom

Then patch the cracks in the outer shell (I was thinking of using a crescent-shaped patch that would wrap around the top of the door - it would look like it was meant to be there more than a smaller patch would) and maybe replace the inside panel altogether.

What about having a pro weld it inside and out the polish it out.
You can weld a patch on the interior skin.

I guess 100-200$

[markdoane]

I like the crescent patch idea. I don't think you can weld 2024 AlClad.

If you want to know about age hardening, try working with the original skins on these old trailers. Some of the them are almost as hard as stainless steel. And brittle.