PMF TB2 thinning ? what precentage

[rustytoolss]

I've read so much stuff about PMF that I'm so confused , So how are most of you people thinning your TBII glue to do the canvas skin work ? I've read 50% glue & 50 % water...to 100% TBII ????? I bought my canvas at HF. I've also read that you need to wash the canvas...but then again others say that washing is not needed
Does anyone have a good video of doing the canvas/TBII install on a camper

[lthomas987]

5% water reduces viscosity by half for application without loss of strength.

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[GPW]

Rusty , if you don’t wash the canvas first it will tend to shrink a bit more during application ... always allow a little extra canvas for shrinkage, either washed or not ... Some feel that washing removes the factory sizing and cleans the fabric for better glue adherence... Your choice ...
We now use 100% TB2 rolled on liberally , then the dry canvas applied and smoothed out ... once dry and seams all glued, we “size" the canvas with 25% TB2 and 75% water , were strength is not needed , the object is the deep encapsulation (waterproofing) of the fabric fibers ( Note: too much glue and the primer doesn’t stick as well ( less “tooth” ) , we proved that to ourselves) ... then Primer and a good outdoor paint ... that works in our hostile climate ...

The reality of the glue is , you don’t need much strength in the glue as the Foam is the weakest element and always fails first in a glue joint .... That’s why the “tight sock” principle works for us , like a a shrink wrap , nothing needed to hold it together , the tight outer skin does all the work ...

[rustytoolss]

Rusty , if you don’t wash the canvas first it will tend to shrink a bit more during application ... always allow a little extra canvas for shrinkage, either washed or not ... Some feel that washing removes the factory sizing and cleans the fabric for better glue adherence... Your choice ...
We now use 100% TB2 rolled on liberally , then the dry canvas applied and smoothed out ... once dry and seams all glued, we “size" the canvas with 25% TB2 and 75% water , were strength is not needed , the object is the deep encapsulation (waterproofing) of the fabric fibers ( Note: too much glue and the primer doesn’t stick as well ( less “tooth” ) , we proved that to ourselves) ... then Primer and a good outdoor paint ... that works in our hostile climate ...

The reality of the glue is , you don’t need much strength in the glue as the Foam is the weakest element and always fails first in a glue joint .... That’s why the “tight sock” principle works for us , like a a shrink wrap , nothing needed to hold it together , the tight outer skin does all the work ...

How much coverage (on average) do you think you can get from a gallon of TBII at 100% applied liberally ? Is it best to iron the washed canvas ? Also how much canvas material overlay would you think is good ?

[rruff]

How much coverage (on average) do you think you can get from a gallon of TBII at 100% applied liberally ? Is it best to iron the washed canvas ?

In my experiments I used a little more than 2x TB2 by weight than the canvas on textured foam. Note that about half the TB2 evaporates. So if you use 10oz/sq yd canvas that comes to 1.11 oz/sq ft, so maybe ~2.5 oz/sq ft TB2. Or around 50 sq ft/gal.

YMMV. That was 2 coats of 100% TB2, one to stick it on, and another to fill the weave (not the best practice for paint according to GPW). I also used a fiberglass "bubble buster" roller. I highly recommend practicing whatever you do if possible. If you have one of those cheap little scales you can weigh it and see. IME wrinkles came out easily in the initial canvas application, and I washed (did not iron) the canvas first.

[rustytoolss]

So you put on 2 coats of 100% TB2, and it covered aprox 50 sf right ?

[ghcoe]

I do not have a video, but I did do a extensive write up on how I did mine.

My first wall started here: http://tnttt.com/viewtopic.php?f=55&t=54099&start=405
A improvement over my experiences with the first wall with the second wall: http://tnttt.com/viewtopic.php?f=55&t=54099&start=435
Roof coverage starts here: http://tnttt.com/viewtopic.php?f=55&t=54099&start=450
Hatch coverage here: http://tnttt.com/viewtopic.php?f=55&t=54099&start=510

I use a 50-50 mix and have no issues. Full strength is real hard to apply quickly. 50-50 applies quick and soaks into the canvas pretty good. In the above links I show how I work the glue into all the pores in the canvas, which is real difficult with full strength glue. Plus the glue seems to dry real quick when not diluted creating dry spots that you may not notice when you apply the canvas.

I did not wash my canvas. Used the canvas right out of the bag. I like the way it shrinks, it makes everything nice and tight. I did have a problem on the roof run though. The canvas shrinks more one direction than the other and I did not allow enough canvas for the long run on the roof.

I use HF canvas. I like working with it.

[rustytoolss]

Well after all this question asking. I did a PMF glue percentage test. I use a scrap piece of foam, and an old bed sheet for my test. I just did a small test. I was testing the 75% glue-water VS 50% glue-water. Both worked well. The 50/50 mix gave me more working time, and adsorbed into the cloth better. Drying time was a bit faster with the 75% mix. When dry both test pieces seemed to be equally strong
Early next week I plan to canvas my interior walls (fingers crossed). Time to get passed the fear of doing this part of the build.

[ghcoe]

Not sure if you read through my entire build thread of not.

I showed how I did my ceiling and interior walls starting about half way down this page http://tnttt.com/viewtopic.php?f=55&t=54099&start=600 . I did it by myself and it worked out better than I thought it would. The key is to get everything ready before you start. I used lots of stick pins....

Good luck.

[rustytoolss]

George , the information you've post about your build is a guide to many of us. Thanks for all your help. As for my walls. I'm going to have them laying flat on the floor. From what I've read, others have said it is much easier. When it comes time to do the interior ceiling. Your system looks like a great idea.
Question about doing PMF. My plan is to PMF directly over my pink foam. (which is how I did my testing). But looking at your pictures. It looks like you used gripper on the foam before you did your canvas work. Was this just a choice of doing it that way ? Or it there a reason to use a primmer/gripper under the PMF first ?
At this point , I do not need to make any mistakes, or miss any steps.

[ghcoe]

I used Gripper mainly for fairing (sanding) spackle and as a primer for the flashing. TBII will not bond to metal well, but it does bond to Gripper.