Thoughts on plywood repair/fix on undercarriage

[Drizzt321]

So I've had my little 14.5' vintage canned ham for a while now, things are mostly good, but it's old. I recently notice some exposed plywood near the front that is delaminating, unofrtunately.

2025-03-09_16-01-07 smaller.jpg (884.18 KiB) Viewed 656 times

My thought is to do a 2 step process. First, use some spray (Super77?) or construction adhesive and some deep throat clamps (using other pieces of wood to protect surfaces) to mostly get it back holding together. Something that's outdoor/water exposure rated. Let it sit for a couple of hours.

Second, doing some light sanding to clean up the surface slightly, then using some construction adhesive and new 1/4" - 1/2" thick wood custom cut to fit, and the clamps again, to add some fresh wood to provide fresh support. After a couple of hours, removing the clamps and using pilot holes and counter sinking to put a number of screws in to help keep things together. Next I'll clean off the area around some with a bit of sanding and then some SEM Solve https://semproducts.com/product/sem-solve/38373 to clean off any gunk, and then use SEM 40463 https://semproducts.com/product/low-voc-undercoating asphalt based undercoating, probably 2 or 3 coats, to build up a protective coating.

Reason I'm looking at the SEM products is they come in spray cans. I don't have a air compressor nor know anyone I can borrow, don't have any place to store one, and I really don't need to do _that_ much of a surface area where it'd make sense.

For the 2nd part I'll be doing a bunch of taping and plastic bags and such to prevent overspraying or dripping on the ground. Also going to be using full face shield & VOC respirator, I'm sure even in the first step there will be nasty stuff coming off the sanding. Even more so the 2nd step.

Thoughts? Better product(s) to use? Am I going about this completely wrong?

[tony.latham]

Thoughts? Better product(s) to use?

There are a lot of ways to deal with this. Me? I'd coat it with epoxy. It soaks into the wood and plasticizes the surfaces. I can recommend Raka's epoxy.

Beware of products that water may get under and sit.

Tony

[Drizzt321]

Thoughts? Better product(s) to use?

There are a lot of ways to deal with this. Me? I'd coat it with epoxy. It soaks into the wood and plasticizes the surfaces. I can recommend Raka's epoxy.

Beware of products that water may get under and sit.

Tony

Hm, interesting idea. But I do want to get the end back to flat(ish) for the one that's really curling away, so I'm going to need to do some kind of clamping as well. Also...how to get it to soak in? This is on the bottom, so it's going to run downwards towards the ground pretty badly.

Maybe something thicker that I can push/squeeze up the gap, and then clamp and hold it, but I don't think it'll soak in the amount that would make it worth while. If I could turn the entire trailer upside down to keep the epoxy where it should be. I think the coating it with the asphalt based coating will be sufficient.

[tony.latham]

Also...how to get it to soak in? This is on the bottom, so it's going to run downwards towards the ground pretty badly.

Paint it on like a thin coat of varnish. I recommend their thin set. Let it get tacky, and put a second coat on.

Tony

[Pmullen503]

Also...how to get it to soak in? This is on the bottom, so it's going to run downwards towards the ground pretty badly.

Paint it on like a thin coat of varnish. I recommend their thin set. Let it get tacky, and put a second coat on.

Tony

You can put some plastic and cauls over the uncured epoxy and clamp it while the epoxy cures to get it flat again.

[Drizzt321]

Also...how to get it to soak in? This is on the bottom, so it's going to run downwards towards the ground pretty badly.

Paint it on like a thin coat of varnish. I recommend their thin set. Let it get tacky, and put a second coat on.

Tony

You can put some plastic and cauls over the uncured epoxy and clamp it while the epoxy cures to get it flat again.

I was basically going to do that, although I don't have room to completely go across, because of the way you see it.

I actually decided to get some DAP Weldwood Landau Top & Trim spray. Seems to be extremely strong, and I can spray it up into the delaminated area to be sure to get it all the way up into the edges, and designed for laminating things together with high temp & moisture resistance.

https://www.dap.com/products-projects/p ... gh-streng/

Then I'll put some wood across the area, with the bottom section with painters tape in case it a bit squeeze out and gets on it or comes through the thinner/broken up bits of the wood. I'm thinking Baltic Birch as the sister/covering wood, 1/8-1/4" thick. Just enough to provide additional strength and support without significantly adding bulk or weight.

[Drizzt321]

Ok, an update. So far things are going well. Also chipped off some flaky or coming loose undercoating, so have a fair bit of area to also coat/re-coat with the undercoating besides the side.

Ended up going with 1/4" thick poplar, mostly going to be to help hold things together and provide an outer surface that's stiffer/thicker, should the undercoating start coming off entirely again.

Here's after I sprayed and clamped the delaminated plywood (original picture above).

2025-03-23_11-42-45.jpg (850.27 KiB) Viewed 383 times

And here's with the poplar clamped up with more of the spray glue. I'm waiting >24hr (can says 24 hrs for full cure), and then pilot hole and stainless steal pan head screw to provide additional hold through.

2025-03-23_15-27-23.jpg (994.24 KiB) Viewed 383 times

[OP827]

Also...how to get it to soak in? This is on the bottom, so it's going to run downwards towards the ground pretty badly.

Paint it on like a thin coat of varnish. I recommend their thin set. Let it get tacky, and put a second coat on.

Tony

You can put some plastic and cauls over the uncured epoxy and clamp it while the epoxy cures to get it flat again.

+1

[S. Heisley]

Take a look at:

http://www.rotdoctor.com

Here's why:

Wooden Boats
Repairing and maintaining wooden boats involves many variables and procedures. We cover the different types of construction and offer some advice on how to make repairs.

At least talk to them before you decide:

by phone 206-364-2155 or e-mail (send us your pictures) at [email protected] and we will gladly answer questions about our products or how to apply them. With 20+ years of experience and many more in the boating and construction industries, not much surprises us. We are here to help our customers solve their issues. Let us help you to not have any surprises in your repair project.

I used their products on my trailer and, 2 years ago, on the rotted facia of my home. (The painter had not heard of these products and was very impressed!)

Safety first!
Whatever you decide to use, keep your face away and wear eye protection. No matter what you use, spray or brush-on or whatever, it *will* drip down and/or splatter. Also, get the filler as smooth as you can while it's still moist so you don't have to sand a lot. The sanding also gets into eyes, skin, ears, clothing, you name it and it is a real bear when you're laying on your back, arms up in the air, sanding. I used a spray-on undercoating and you should have seen me after the first coat! Lay some cardboard on the surface underneath where you work. It will absorb a lot of the drips and splatters.

[nevadatear]

totally agree with the epoxy as a repair. Wood repair first, then epoxy. I've done a few old trailer repairs that way. You really need protection from road water.

[Drizzt321]

Take a look at:

http://www.rotdoctor.com

Here's why:

Wooden Boats
Repairing and maintaining wooden boats involves many variables and procedures. We cover the different types of construction and offer some advice on how to make repairs.

At least talk to them before you decide:

by phone 206-364-2155 or e-mail (send us your pictures) at [email protected] and we will gladly answer questions about our products or how to apply them. With 20+ years of experience and many more in the boating and construction industries, not much surprises us. We are here to help our customers solve their issues. Let us help you to not have any surprises in your repair project.

I used their products on my trailer and, 2 years ago, on the rotted facia of my home. (The painter had not heard of these products and was very impressed!)

Safety first!
Whatever you decide to use, keep your face away and wear eye protection. No matter what you use, spray or brush-on or whatever, it *will* drip down and/or splatter. Also, get the filler as smooth as you can while it's still moist so you don't have to sand a lot. The sanding also gets into eyes, skin, ears, clothing, you name it and it is a real bear when you're laying on your back, arms up in the air, sanding. I used a spray-on undercoating and you should have seen me after the first coat! Lay some cardboard on the surface underneath where you work. It will absorb a lot of the drips and splatters.

My plan is to use SEM asphalt undercoating https://semproducts.com/product/low-voc-undercoating to seal it all up. Fortunately no real rot at all, although in some of the places not on the plywood where the old undercoating had fallen off or had gotten pretty flaky there's some possible suspicious dots. So I'm getting some borate based stuff to 'paint' on, after I get some more of the crud off, to help either kill whatever might be there, or keep anything that might be there but not growing from getting trapped under the undercoating and starting to grow. https://www.cor-ten.com/product/penashi ... servative/

And yes, have 3M respirator with new organics filters, a full face mask, going to wear long sleeves I can throw away if needed for the undercoating spray, and will be masking with painters tape & plastic bags taped on to prevent overspray off the sides and anything that might drip down. Cardboard on top of that is a good idea, to help absorb it up so it won't slide around on the plastic.

I think I'm going to need to jack up the trailer further as well, try and get few inches or so of head height would be very nice! Time to get all my 2x4 bits out underneath the back stabilizer jacks & front jack.

A lot of my followup here is now to help others out who might face something similar, how I went about things, to inspire them to good fixes.

[tony.latham]

My plan is to use SEM asphalt undercoating...

I would be concerned that if moisture gets underneath that stuff, it'll stay put. I suggested above to use epoxy–– a product that soaks into the wood instead of encapsulating it. Another alternative is what's called The Mix. It's polyurethane varnish cut 50% with paint thinner. It too soaks in. Two coats would be the minimum.

Tony

[Drizzt321]

My plan is to use SEM asphalt undercoating...

I would be concerned that if moisture gets underneath that stuff, it'll stay put. I suggested above to use epoxy–– a product that soaks into the wood instead of encapsulating it. Another alternative is what's called The Mix. It's polyurethane varnish cut 50% with paint thinner. It too soaks in. Two coats would be the minimum.

Tony

Some points, but given that there was asphalt undercoating already, I'm not sure I can actually get it cleaned off enough without actually stripping off wood surface to be able to get epoxy to soak in properly, instead of staying on the surface. Even using some cleaners.

[tony.latham]

but given that there was asphalt undercoating already, I'm not sure I can actually get it cleaned off enough without actually stripping off wood surface to be able to get epoxy to soak in properly,

True story. I'm talking about the fresh wood.

T

[Drizzt321]

but given that there was asphalt undercoating already, I'm not sure I can actually get it cleaned off enough without actually stripping off wood surface to be able to get epoxy to soak in properly,

True story. I'm talking about the fresh wood.

T

Oh! Hm. Hadn't considered that, that's quite a thought.