PMF Questions....

[BulletProof]

Going to build a plywood bed-in-a-box (don't want to call it a teardrop cause that ain't the shape!)

Have some questions about the PMF method:

1. I have a full bolt of unbleached cotton muslin (25 yards - 4oz). Will that work? Or does it need to be heavier?

2. Is there any issue painting latex over TB2? I was thinking of using TB2 and fabric for all of the trim, edges etc, and then a latex primer and fabric for the larger areas.

3. Latex Primer: Read on here that "Gripper" seems to be the ticket - but I can't find that up here in the frozen north ( ) Will any good quality latex primer work? Or is there something special about Gripper?

I love this community! It is so cool finding people that build stuff and use it!

[John61CT]

Gripper is indeed special.

Personally I would use it alone rather than TB2. That way no transition layer, more long-term water resistant, and sticks well to just about anything.

Do you mean a foamie? If so might get better responses in that sub

[BulletProof]

Plywood - not a foamie!... and the product "Gripper" is not available in Canada (or I can't seem to find it here!)

BP.

[lacofdfireman]

I’m currently building a trailer and doing the PMF Method. It’s actually been kinda fun. It’s my first time doing this method and so far so good. I used full strength Titebond ll on the Wood then put the canvas directly on top of the glue and smithed out. Then once it’s all dry I will size the canvas with a 50/50 mixture of Titebond ll and water to dilute the glue down and help it absorb onto the canvas better. After this is dry I will use gripper primer over that layer. Once I have a full layer of gripper I will then probably do 3-4 coats of latex paint for the finish product.

Few pics of where I’m at right now with the project.






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[John61CT]

I'm curious, what is the practical function of the fabric?

I come to PMF via the foamie idea, so much so I thought the foam part was essential to the definition of PMF, that using sheet plywood meant it is no longer PMF.

With foamie, the fabric is there to give tensile strength, which foam on its own has very little.

But with ply already being strong that way, is the purpose of the fabric still functional?

Or just cosmetic?

[tony.latham]

I'm curious, what is the practical function of the fabric?

I come to PMF via the foamie idea, so much so I thought the foam part was essential to the definition of PMF, that using sheet plywood meant it is no longer PMF.

With foamie, the fabric is there to give tensile strength, which foam on its own has very little.

But with ply already being strong that way, is the purpose of the fabric still functional?

Or just cosmetic?

Here's what he's fixing:

http://www.tnttt.com/viewtopic.php?f=21&t=71357

[John61CT]

Yes. My question is a general one, regardless of any particular example.

[tony.latham]

Yes. My question is a general one, regardless of any particular example.

There are two things that need to be done with traditionally built teardrops: The wood needs to be sealed and protected from the sun.

Tony

[BulletProof]

Still trying to figure out what the fabric is doing!

Maybe I should just build the box and paint it! I was going to PL all the wood joints anyway.

I get that the PMF was an old technique for building kayaks and airplanes but that fabric was stretched over frames.
With a solid wood box, why add the fabric? Like a former poster mentioned - it makes sense with a foamie, but why on a solid wood box?

Glue it together, make sure all the joints are well sealed, prime it and paint it.

[lacofdfireman]

Still trying to figure out what the fabric is doing!

Maybe I should just build the box and paint it! I was going to PL all the wood joints anyway.

I get that the PMF was an old technique for building kayaks and airplanes but that fabric was stretched over frames.
With a solid wood box, why add the fabric? Like a former poster mentioned - it makes sense with a foamie, but why on a solid wood box?

Glue it together, make sure all the joints are well sealed, prime it and paint it.

For me it adds a barrier against moisture like fiberglass and I’m sure adds strength also which may or may not be needed.

As you lay the fabric on top of the glue it seeps into the fabric and makes a solid shell. After doing it now I’m pretty happy with it and it maybe added 20lbs to my total project which to me isn’t much.

I had to tear this trailer apart once. I’m pretty sure after doing this PMF I’ll never have to again.


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[tony.latham]

Glue it together, make sure all the joints are well sealed, prime it and paint it.

Take a close look at a ten-year-old house sided with T1-11 or another plywood sheathing. Even if it's been painted two or three times, I think you'll find some checking.



Tony

[BulletProof]

Don't get many plywood houses around here.... but I'll take your word for it!

Found this.... https://liquidrubber.ca

Will start new thread...

BP

[tony.latham]

Don't get many plywood houses around here.... but I'll take your word for it!

Found this.... https://liquidrubber.ca

Will start new thread...

BP

Don't forget what started this thread. Somebody gave him bad advice and he coated unsealed plywood with a urethane bedliner.

That liquid rubber would probably work if you sealed the plywood first. Now, what it would look like is another issue.

T

[lacofdfireman]

Don't get many plywood houses around here.... but I'll take your word for it!

Found this.... https://liquidrubber.ca

Will start new thread...

BP

Don't forget what started this thread. Somebody gave him bad advice and he coated unsealed plywood with a urethane bedliner.

That liquid rubber would probably work if you sealed the plywood first. Now, what it would look like is another issue.

T

It would probably work. But I’m done experimenting. Found out the hard expensive way. That’s why I’ve gone with PMF. It’s been tried and proven.

[John61CT]

The more experience the PMF expert has around here, the more they emphasize each project is its own experiment.