Vac bagging canvas to foam

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Vac bagging canvas to foam

Postby DavidAlex » Wed May 30, 2018 9:15 am

So, my understanding of PMF best practices is to lay up the fabric to the foam using glue, then go back and fill in the weave of the fabric with paint. Most people seem to use Titebond 2 for that, which I understand works best with good clamping, but I haven't seen much discussion of how to "clamp" the canvas to the foam. Has anyone tried vacuum bagging panels of foam and canvas prior to final assembly?
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Re: Vac bagging canvas to foam

Postby tony.latham » Wed May 30, 2018 10:26 am

DavidAlex wrote:So, my understanding of PMF best practices is to lay up the fabric to the foam using glue, then go back and fill in the weave of the fabric with paint. Most people seem to use Titebond 2 for that, which I understand works best with good clamping, but I haven't seen much discussion of how to "clamp" the canvas to the foam. Has anyone tried vacuum bagging panels of foam and canvas prior to final assembly?


I have not seen it done on this forum but I could have missed it. I'd be concerned the TB2 wouldn't dry.

:thinking:

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Re: Vac bagging canvas to foam

Postby DavidAlex » Wed May 30, 2018 11:28 am

tony.latham wrote:I have not seen it done on this forum but I could have missed it. I'd be concerned the TB2 wouldn't dry.

:thinking:

Tony

Yeah, you'd need a breather media on the canvas side, I suspect.
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Re: Vac bagging canvas to foam

Postby Tigris99 » Wed May 30, 2018 12:15 pm

Ya that won't work because the glue can't dry.

Much depends on if you are doing individual panels or the entire shell all at once.

Doing the entire camper shell all at once isn't as difficult as one would think. If you use large canvas, enough to wrap the entire shell, at least on wood the only location that needs to be secured is around the bottom. The trick being is for the canvas to be stretched during application which is why TBII is usually diluted with water, so it saturates the canvas allowing it to be stretched as it's installed and secured on the ends. Then as everything dries it will shrink literally compressing the entire shell together.

With wood paint is more than suffient. Foamies require something with better adhesive qualities. But unless there's a detail I'm missing the principal is the same.

I know when I finally get to build my foamy (I have a squaredrop I built already but I want less weight for the base camper) I'm thinking of doing a very thin wood skin. High humidity underlayment I can get here cheaply. Small weight penalty for something easier to finish and much less dent prone since it will be glued directly to the foam shell then PMF over it.

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Re: Vac bagging canvas to foam

Postby AzAv8r » Wed May 30, 2018 8:44 pm

I'd expect vacuum bagging to work well, simply because the vacuum pump lowers the pressure, and liquids in the TBII (water, primarily I'm assuming) would be vaporized (vapor pressure is constant) and drawn out by the vacuum pump. You'd probably actually accelerate the "drying", although perhaps not appreciably.

For any vacuum bagging, under the bag you need to place some porous media (a spacer) to allow a uniform vacuum under the bag. Now, preventing that porous media from bonding to the TBII might be an issue.

Worth an experiment if you already have the tools, supplies, and experience for vacuum bagging.
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Re: Vac bagging canvas to foam

Postby DavidAlex » Thu May 31, 2018 3:58 pm

AzAv8r wrote:Worth an experiment if you already have the tools, supplies, and experience for vacuum bagging.

I have none of those things!
:frightened:
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Re: Vac bagging canvas to foam

Postby theoldwizard1 » Fri Jun 08, 2018 7:47 am

DavidAlex wrote:So, my understanding of PMF best practices is to lay up the fabric to the foam using glue, then go back and fill in the weave of the fabric with paint.

I thought the "de facto standard" for gluing any thing to foam was Glidden Gripper primer. Lay down a tick coat on the foam, place your canvas and then roll on a second coat before the first completely dries.
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Re: Vac bagging canvas to foam

Postby DavidAlex » Fri Jun 08, 2018 10:11 am

theoldwizard1 wrote:
DavidAlex wrote:So, my understanding of PMF best practices is to lay up the fabric to the foam using glue, then go back and fill in the weave of the fabric with paint.

I thought the "de facto standard" for gluing any thing to foam was Glidden Gripper primer. Lay down a tick coat on the foam, place your canvas and then roll on a second coat before the first completely dries.

What about glueing foam to plywood? Gripper?
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Re: Vac bagging canvas to foam

Postby Pmullen503 » Fri Jun 08, 2018 1:55 pm

DavidAlex wrote:What about glueing foam to plywood? Gripper?


That wouldn't be my first choice. Gripper works (any paint does) on foam and canvas because it infuses the canvas and that moisture can evaporate so it dries.

Foam and plywood with Gripper would take a very long time to dry fully. I'd use something that didn't rely on evaporation: Polyurethane glues, P6000, epoxy etc.
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Re: Vac bagging canvas to foam

Postby Tigris99 » Sat Jun 09, 2018 7:03 pm

Pmullen503 wrote:
DavidAlex wrote:What about glueing foam to plywood? Gripper?


That wouldn't be my first choice. Gripper works (any paint does) on foam and canvas because it infuses the canvas and that moisture can evaporate so it dries.

Foam and plywood with Gripper would take a very long time to dry fully. I'd use something that didn't rely on evaporation: Polyurethane glues, P6000, epoxy etc.
TB 2 works fine for this. Dries plenty fast enough. Also I read using glue for foam, paint or gripper for wood.

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