PMF, TB2, and Waterproofing

Canvas covered foamies (Thrifty Alternatives...)

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PMF, TB2, and Waterproofing

Postby Postal_Dave » Wed Oct 09, 2019 2:09 am

There has been some discussion about Poor Man's Fiberglass and whether or not it's waterproof. So I did a small experiment. :twisted: I love doing experiments. Here is what I found.

In a recent experiment, I showed that canvas, when glued to foam the right way with TB2, holds almost as well as Glidden Gripper, and better than almost anything that is still on the market.

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However, there was a persistent question about how waterproof canvas, soaked in TB2 mix, could be. So I took a small piece of canvas and soaked it in a 75/25 mix of TB2 and water. When I say soaked, I mean that I poured the mix on the canvas and rubbed it in with my hand until I made sure it was in every fiber. It absorbed a lot of mix. I then placed it over the end of a pipe to dry.

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It dried into something that reminded me of the ash tray I made for my parents when I was in elementary school. :oops:
After the first coat dried, I put water in it and it leaked right away. I then applied a second coat of the mix and I made sure to rub it into the fabric like I did with the first coat. It also took a good amount of the mix, but not quite as much as the first coat. After it dried, it still leaked but slower. A third coat was applied and the canvas did not absorb much of the mix. After it dried, it didn't leak, but under the canvas felt moist. So I put on a fourth coat and the canvas barely absorbed any mix. When it dried I filled it with water. No leaks!
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After a week

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Still full of water and no leaking. No primer, no paint, just TB2 and water was used in this experiment.
Conclusion, if you're going to use TB2 mix to waterproof your canvas, keep applying it until it refuses to absorb any more mix. I'd say a minimum of 4 coats of the mix, preferably more, and that you work it into the fibers of the canvas. Primmer and 2 coats of good exterior paint on top of that should seal the deal.
As always, don't trust me, do your own experiments and find out for yourself how this works before you build. :thinking:
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Re: PMF, TB2, and Waterproofing

Postby GPW » Wed Oct 09, 2019 5:18 am

Thanks for the testing Dave !!! :thumbsup: 8)
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Re: PMF, TB2, and Waterproofing

Postby swoody126 » Wed Oct 09, 2019 6:42 am

your efforts are much appreciated

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Re: PMF, TB2, and Waterproofing

Postby RJ Howell » Wed Oct 09, 2019 7:26 am

I did a small test myself, yet didn't go near as far as you did.. Nice job and report! :thumbsup:
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Re: PMF, TB2, and Waterproofing

Postby John61CT » Wed Oct 09, 2019 9:22 am

I would not consider using TB2 for waterproofing, only adhesion of the canvas to the foam.

The results after years of real-life usage will not be the same as a short term test.

All data points are useful though, thanks very much for this contribution.
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Re: PMF, TB2, and Waterproofing

Postby Postal_Dave » Wed Oct 09, 2019 11:31 am

I would not consider using TB2 for waterproofing, only adhesion of the canvas to the foam.

The results after years of real-life usage will not be the same as a short term test.


John,
You've been on this site for years. You've made over a thousand posts but you haven't built anything. You haven't done the first experiment or posted the first picture.

I, on the other hand, have made a camper, completed dozens of experiments and submitted picture evidence with each one.
BTW: I did say, "Primmer and 2 coats of good exterior paint on top of that should seal the deal."

However, I shall yield to your great, undocumented knowledge.
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Re: PMF, TB2, and Waterproofing

Postby GPW » Thu Oct 10, 2019 4:39 am

Hey Guys , just an idea ( yet unsubstantiated ) … How about the Mix for waterproofing canvas ??? Works on wood and wood products eh … canvas is basically same as wood ( plant based -cellulose ) :thinking:

Our long term problem with TB2 was over years of repetitive daily wetting on the underside of the trailer as the canvas folded over onto the floor bottom , the Morning Dew …. finally caused the glue to fail …and wash out … But then a simple “drip edge” solved that problem …

I’m just thinking whatever you use for waterproofing it must be THOROUGH , as water can seep in the tiniest of holes … I found out the hard way … :frightened:
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Re: PMF, TB2, and Waterproofing

Postby John61CT » Thu Oct 10, 2019 8:28 am

Postal_Dave wrote:I did say, "Primmer and 2 coats of good exterior paint on top of that should seal the deal."
That's fine then

I was not disagreeing, we're in complete agreement not to rely on just TB2 for waterproofing.

Just stating my preference for using the primer as canvas adhesive so it's waterproof all the way through.
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Re: PMF, TB2, and Waterproofing

Postby Postal_Dave » Thu Oct 10, 2019 10:01 am

Code: Select all
GPW wrote:
... the canvas folded over onto the floor bottom , the Morning Dew …. finally caused the glue to fail


:thinking: Hmm. That reminds me of the time I used regular wood, instead of pressure treated wood, on a foundation of a small shed. I painted those foundation pieces but after 10 years of sitting on concrete, they still needed to be replaced. I can see that happening to any wood or canvas in a camper where it is in contact with the frame.

I do Not recommend pressure treated wood in a camper build. I'd be afraid of what it might "off gas" inside the camper, and there is a reason that's for exterior use only.

The drip edge idea is a good preventative idea, I'd like to see a picture of where you put that on the camper.

However, I'm thinking that we should come up with a way to protect bottom edges of canvas so that doesn't happen again. Anywhere that canvas makes contact with the frame, or floor, should be protected better.

Feel free to shoot this idea down and give alternate ideas. We should do some brainstorming here. My first thought is using epoxy to saturate the canvas fibers at the base. Then paint over that, just like the canvas. I've never worked with epoxy in this way so I'll leave that discussion to people that have.
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Re: PMF, TB2, and Waterproofing

Postby RJ Howell » Thu Oct 10, 2019 3:40 pm

Postal_Dave wrote:
Code: Select all
GPW wrote:
... the canvas folded over onto the floor bottom , the Morning Dew …. finally caused the glue to fail


:thinking: Hmm. That reminds me of the time I used regular wood, instead of pressure treated wood, on a foundation of a small shed. I painted those foundation pieces but after 10 years of sitting on concrete, they still needed to be replaced. I can see that happening to any wood or canvas in a camper where it is in contact with the frame.

I do Not recommend pressure treated wood in a camper build. I'd be afraid of what it might "off gas" inside the camper, and there is a reason that's for exterior use only.

The drip edge idea is a good preventative idea, I'd like to see a picture of where you put that on the camper.

However, I'm thinking that we should come up with a way to protect bottom edges of canvas so that doesn't happen again. Anywhere that canvas makes contact with the frame, or floor, should be protected better.

Feel free to shoot this idea down and give alternate ideas. We should do some brainstorming here. My first thought is using epoxy to saturate the canvas fibers at the base. Then paint over that, just like the canvas. I've never worked with epoxy in this way so I'll leave that discussion to people that have.


I personally love how you tested and showed TB2 to work. I didn't have the same experience yet probably due to the fairing I did. Another shows a fairing compound he finds works. I would never doubt those of real life experience and results. Give two thumbs up to both of you!
Would I not paint over.. As you state, only part of the procedure. Of course I would.

I love what you've done and appreciate the effort! :applause:
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Re: PMF, TB2, and Waterproofing

Postby Postal_Dave » Fri Oct 11, 2019 12:03 am

Thank you RJ, and everyone else. However, the truth is, that's the way many first generation foamies were covered. They glued the canvas to the foam with 50/50, then put a couple of more coats on before painting them. It's old school, but it still works. I like to think that we've improved the technique over the years and made several other advancements though. We just need to keep building and experimenting.
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Re: PMF, TB2, and Waterproofing

Postby GPW » Fri Oct 11, 2019 4:29 am

"The drip edge idea is a good preventative idea, I'd like to see a picture of where you put that on the camper. “


We used George’s idea and fastened some corner moulding to the outside edges of our floor boards ( see pic ), then covered over them… Easy, works great !!! ( solved all my water problems )
The pic is shown with the boards upside down ( naturally ) and secured with Stainless steel staples and the Gripper .
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Re: PMF, TB2, and Waterproofing

Postby swoody126 » Fri Oct 11, 2019 7:38 am

just a ponderment

¿ wonder how TB III would work given the same test ?

i built a small boat out of el cheapo plywood using the stuff for all joints and painted the ply w/ a 90% mixture b4 priming and painting w/ latex house painting products(an all big box store products build as an experiment)

that was only 3 years ago butt no failures the last time i looked her over

i built an exact copy using PL-Premium 3x at the same time and still no issues w/ her either

normally we build these little boats w/ miranti marine pywood(BS-1088) and epoxy and use latex semi-gloss for the finish w/o a primer coat

we/ve learned that if/when the finish coat suffers a ding/breach/trauma a timely sanding and touch up painting once the wood has dried out is about all they need to remain waterproof and protected

like i said Just a ponderment

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Re: PMF, TB2, and Waterproofing

Postby John61CT » Fri Oct 11, 2019 8:59 am

TB III does not adhere to itself once cured
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Re: PMF, TB2, and Waterproofing

Postby ghcoe » Wed Oct 16, 2019 7:41 pm

Yes, you don't want the canvas right on the trailer frame. With the TBII and paint it acts like sandpaper on the paint on the trailer. I would imagine with time the trailer would wear through the canvas and cause more issues. I added 1"x2"'s to lift the body up off the trailer and to add room for the drip edge.

Floor Spacers s.png
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