Attaching fiberglass panel to plywood, usin contact cement

[Flyin_Finn]

Hi,

I am replacing a 6x6 foot section of my outside wall on on my 5th wheel.
The plan is to first glue the thin fiberglass panel to the 1/8" plywood, and then attach the sandwiched panel to the aluminum frame.

I already purchased the glue, a red contact cement called Helmiprene 4570, made by Helmitin. I will spray the glue to the surfaces.
Once the glue dries, I will join the surfaces together.
This is where I am getting confused: I am supposed to apply pressure to the surface. Why? I thought it was an instant, strong bonding. Is the purpose of the pressure to strengthen the bonding? Is the pressure just momentary, for example using a j-roller?. Or is pressure supposed to be applied for a given curing time?
I do understand that I need to make sure there are no air bubbles trapped between the layers.

At the moment, I am experimenting with the gluing process on some scrap pieces, to make sure I do it right when I do glue the actual panel.

[Flyin_Finn]

DaHose wrote:
What you want to use is 3M Fastbond 30. Sets fairly quick, water based so it applies easy and doesn't dissolve Styrofoam insulation.

It rolls on like paint and holds like crazy. Once set, it is water resistant. Follow instructions and don't overdo it. Try some test panels first.

Jose

I paid a lot for what I got so that's what I will use for the glass to luan.
I do need something else for the luan to aluminum/wood/styrofoam. Would the Fastbond 30 be good for that?

[DaHose]

What you want to use is 3M Fastbond 30. Sets fairly quick, water based so it applies easy and doesn't dissolve Styrofoam insulation.

It rolls on like paint and holds like crazy. Once set, it is water resistant. Follow instructions and don't overdo it. Try some test panels first.

Jose

[westend]

This glue-up procedure would be close to gluing down HP laminate onto a countertop surface. I used to use small strips of laminate on top of the glued countertop, position the glued laminate sheet onto the strips, and slid the strips out as I rolled the laminate down onto the countertop. Starting from the middle and rolling outward was the best practice to insure against any air pockets. Air pockets were very rare, usually caused by trying to speed up the process and not allowing the contact adhesive to "tack" before installation.

Good luck with the repair!

[Flyin_Finn]

Joe417 wrote:
I tried to do it using the method you mentioned and was unable to make it work. I tried several different adhesive without positive results.

Putting the glass on the wood first made the panel too stiff, it wouldn't conform to the curve of the front. Stiffness being the whole idea in "plywood", that extra 1/16" of glass made the 1/8" plywood too rigid for my use.

I then tried putting curf cuts about 1/8" apart which didn't work either.

I had to put the 1/8" plywood on the camper and then put the glass on the plywood.


That being said, I was using polyurethane adhesive which could have been the problem. I didn't try contact cement which may have some give to allow it to bend. Polyurethane works well for bonding fiberglass to other surfaces because it doesn't need air to cure.

Once finished, everything turn out great. Hope yours does too.

Keep us updated with the result.

The area I am working on is flat, no curves, and I am gluing this together on the garage floor, so I don't believe there will be any bending issues.

For a moment I thought about putting the luan up first, but I think that would make it harder for me to get a consistent, bubble-free bond between the glass and the luan.

I didn't know what adhesive to use, and the one I bought, is what the RV parts retailer carried, and recommended.
The MSDS sheet names the glue Polychloroprene Solvent Adhesive. So far, on my test piece, it seems to work good.

[Flyin_Finn]

Driving on the freeway, I heard thump thump, looked in the rear view mirror, saw a couple white sheets flying off. Stopped at a upcoming rest area. The stuff in there was wet, so must have been a leak, separating the luan plywood. The strong wind got in there and tore of the separated fiberglass.

[Twomed]

Flyin Finn wrote:

Earl E wrote:
Also, find some clean, dry wood slats or boards. Once the glue is dry lay the strips across the plywood 6" to 12" apart. That way you can lay the fiberglass on top the strips get it perfect,then pull the strips out one at a time as you stick the fiberglass down.

I was thinking about doing that, with masking paper, but I think the boards might work better. I do have some extra 1/8 and 1/4 plywood I can use for that

Old cabinet laminators trick...use 1/4 dowel material, work your J=roller towards the dowels, they will roll right up. Practice first 🙂

[Joe417]

I tried to do it using the method you mentioned and was unable to make it work. I tried several different adhesive without positive results.

Putting the glass on the wood first made the panel too stiff, it wouldn't conform to the curve of the front. Stiffness being the whole idea in "plywood", that extra 1/16" of glass made the 1/8" plywood too rigid for my use.

I then tried putting curf cuts about 1/8" apart which didn't work either.

I had to put the 1/8" plywood on the camper and then put the glass on the plywood.


That being said, I was using polyurethane adhesive which could have been the problem. I didn't try contact cement which may have some give to allow it to bend. Polyurethane works well for bonding fiberglass to other surfaces because it doesn't need air to cure.

Once finished, everything turn out great. Hope yours does too.

Keep us updated with the result.

[Flyin_Finn]

Earl E wrote:
Also, find some clean, dry wood slats or boards. Once the glue is dry lay the strips across the plywood 6" to 12" apart. That way you can lay the fiberglass on top the strips get it perfect,then pull the strips out one at a time as you stick the fiberglass down.

I was thinking about doing that, with masking paper, but I think the boards might work better. I do have some extra 1/8 and 1/4 plywood I can use for that

[Flyin_Finn]

I do have some practice :)... at work I use various self-adhesive polishing media on round 8" polishing plates. When applying, I have to start from the edge, and can't have any airbubbles getting trapped in there

[Earl_E]

Also, find some clean, dry wood slats or boards. Once the glue is dry lay the strips across the plywood 6" to 12" apart. That way you can lay the fiberglass on top the strips get it perfect,then pull the strips out one at a time as you stick the fiberglass down.

[Flyin_Finn]

Trackrig wrote:
To achieve complete contact and avoid any air bubbles. Lay the top layer down from one side or edge, don't try to lay it down all at once - if that makes sense.

Bill

Yeah, that makes sense. I was thinking about starting from one of the corners. It will be tricky, but doable!

[Trackrig]

To achieve complete contact and avoid any air bubbles. Lay the top layer down from one side or edge, don't try to lay it down all at once - if that makes sense.

Bill

[Flyin_Finn]

DrewE wrote:
Typically the pressure is to ensure complete contact, as I understand it. A good rolling with a good J-roller should be sufficient. If the instructions don't specify some duration for the pressure, it seems to me it's pretty safe to assume momentary pressure is sufficient.

Thanks for the quick reply. The retailer sold it in a generic can, with no written material or instructions, except for a MSDS printout. He did give some verbal instructions, such as spray it on rather than roll/brush.
Just a moment ago, I found the mfg website, and sent them email, asking for the info.

[DrewE]

Typically the pressure is to ensure complete contact, as I understand it. A good rolling with a good J-roller should be sufficient. If the instructions don't specify some duration for the pressure, it seems to me it's pretty safe to assume momentary pressure is sufficient.