Fiberglass/Epoxy Roof ?

[GeoDrop]

I'm abandoning my current plans of using a wood veneer on my roof after a disaster with the hatch. (Operator error, not veneer error)

I'm strongly considering going with a fiberglass cloth over the entire roof/hatch and using a tinted epoxy to get the color I want. The initial wet out would be un-tinted but subsequent would be tinted a tan. I've found some epoxy pigment from US Compsites. Seal the epoxy with a varnish for UV protection. Raka has various weights of fiberglass cloth. I'm thinking this will be the best approach... but a few questions.

Questions:

1) Any flaws with this plan?
2) Any thoughts on the weight of the cloth? I'm thinking 6oz... my only other option is a 12oz given my width of 62+ inches.
3) Will fiberglass/epoxy mask minor imperfections in the surface?


Aluminum is out. I've considered vinyl but hard to find in wider widths and right color. EPDM sounds interesting but only white or black in the wider widths. Mildly concerned about imperfections telegraphing through.

http://www.uscomposites.com/pigments.html

Appreciate input...

[Rock]

6 oz is plenty and overkill if it doesn't have much of a structural requirement. I used 6 oz that I had left over from my kayak. And my glass is structural for lots of the camper.

I have not used a tint in a translucent type epoxy application. I did tint some epoxy jet black to fill some cracks in the veneer. All I can say is stick with something manufacturer recommended - in other words if it's Raka use only a tint sold or recommended by Raka. If in doubt call them and ask.

As far as surface imperfections - whether it's a cosmetic blemish (stain, etc) or an actual imperfection in the surface - dent, crack, surface mis-match - it will all show through.

I can attest that this approach is a huge amount of work to get right - but you've come this far (as I keep telling myself )

Eric

[Rock]

Sand plywood, epoxy, epoxy and fiberglass, epoxy fill coat, sand epoxy to 320 grit, 4 coats of clearcoat, wet sand 600, 800, 1000, 1200, 1500 grit, buffing compound, polishing compound, imperial hand glaze, wax. Whew!

Eric

[Larry C]

I'm abandoning my current plans of using a wood veneer on my roof after a disaster with the hatch. (Operator error, not veneer error)

I'm strongly considering going with a fiberglass cloth over the entire roof/hatch and using a tinted epoxy to get the color I want. The initial wet out would be un-tinted but subsequent would be tinted a tan. I've found some epoxy pigment from US Compsites. Seal the epoxy with a varnish for UV protection. Raka has various weights of fiberglass cloth. I'm thinking this will be the best approach... but a few questions.

Questions:

1) Any flaws with this plan?
2) Any thoughts on the weight of the cloth? I'm thinking 6oz... my only other option is a 12oz given my width of 62+ inches.
3) Will fiberglass/epoxy mask minor imperfections in the surface?


Aluminum is out. I've considered vinyl but hard to find in wider widths and right color. EPDM sounds interesting but only white or black in the wider widths. Mildly concerned about imperfections telegraphing through.

http://www.uscomposites.com/pigments.html

Appreciate input...

I think your on the right track glassing the whole top. Glass will help prevent
seams from opening, allowing water to seep in.

After building several strip built kayaks and canoes, I feel the best glass is tight weave 3.25oz rather than plain weave 4 or 6 oz.. It is a little slower to wet out, but requires much less epoxy, and you can get by with just one fill coat. An extra layer can be use for more structural strength if needed.

Don't be concerned about glass width, as long as you overlap seams 2-3" you can use narrow glass, and use as many pieces as you want. For your application you don't need a continuous piece of glass, just use seams and carry on. If you use the 3.25 oz. glass (Raka and others) the seams won't show at all, and won't require a lot of epoxy to hide.

I would advise against the pigment. from my experience, pigments are not opaque, just translucent. If you want color, consider one of the quality marine paints. They flow on and self level, just like it's sprayed on. Also, epoxy pigment weakens the epoxy.

The marine industry has had a lot of time perfecting these coatings (marine paints) to handle the most severe conditions. I was really impressed the first time I tried marine paint. Plus, marine paints offer great UV protection.

The smoother you make the surface before glassing will make the final finish that much better. I would only fill with epoxy/micro balloons mixture, epoxy won't adhere to most other wood fillers. Epoxy fill coats must be applied evenly, with drips and runs scraped off flush with the surface.

Final epoxy sanding should show just a dull surface with no shiny spots showing. Shiny spots mean low areas that the sanding didn't level. Another (thin) round of epoxy fill may be necessary.

Also, too much sanding will cause you to cut into the glass which will leave a sparkling surface in some light situations, but that's not as much an issue if your painting, and not finishing bright (natural wood)

Good luck, and let us know how it's going.

Larry C

[bohemian]

Geodrop

I did my trailer with 6oz cloth, Three layers of epoxy resin and four layers of Captains varnish.
I applied the epoxy with a 3" black foam roller.
I would roll the epoxy out about a two foot square patch and then I would back brush it with a 3" black foam brush. This helps knock down the air bubbles.
I applied the varnish the same way. I have to say the epoxy was a lot easier to apply then the varnish.
And yes there is lots of sanding!
Good luck on your project.
Wayne

[TBuilder]

Geodrop

I did my trailer with 6oz cloth, Three layers of epoxy resin and four layers of Captains varnish.
I applied the epoxy with a 3" black foam roller.
I would roll the epoxy out about a two foot square patch and then I would back brush it with a 3" black foam brush. This helps knock down the air bubbles.
I applied the varnish the same way. I have to say the epoxy was a lot easier to apply then the varnish.
And yes there is lots of sanding!
Good luck on your project. :thumbsup:
Wayne

Wayne, can you clarify your steps for me?
If I'm reading correctly, you:
1. laid down the fiberglass
2. rolled on the epoxy in a 2 square foot area with a black foam roller
3. brushed over that area with a black foam brush to get the air bubbles out
4. repeated steps 2 and 3 until you covered the teardrop
5. rolled and brushed 2 more layers of epoxy
6. rolled and brushed 3 layers of varnish

Does that sound right? I've obviously never put fiberglass on anything before.

[bohemian]

TBuilder

1. Lay out fiberglass.
It is a good idea to have the room your doing this in to be warm, This helps the epoxy level it's self.
From what I'm told you want to apply epoxy on a dropping temperature. This will help alleviate air bubbles that are produced by the wood off gassing from the heat. Plus it helps draw the epoxy into the wood.
2. Roll on the epoxy resin so the cloth is fully wet out then use a plastic squeegee to remove any excess epoxy. Let this dry to a tacky state.
3. Roll on another layer of epoxy in a two foot square sections and back brush the epoxy to smooth it out and to blend it. This also helps to knock down the air bubbles
You can do all layers consecutively if you have the time and wait for each layer to get tacky near dry.
But if you let each layer cure then you will have to sand the epoxy coating before adding another layer.
4. Repeat this until the weave is filled.
When the weave is filled let the epoxy resin cure. I waited a week.
Now you can sand out any high spots and give it some bite for the varnish.
Be careful not to sand into the fiberglass weave.
5. Apply the desired layers of varnish using the roll and back brush method.
You will need the varnish to dry before adding another coat.
And yes you will have to sand in between coats.
You should apply the varnish is 2 foot sections at a time wile back brushing. Because the varnish drys so fast.
I had to tape off the trailer in three sections to get the varnish to lay down correctly.
It's not hard to do this, It's just time consuming
If you need anymore help with this PM me.
Wayne

[TBuilder]

Thanks for all the information!

[angib]

In memory of the epoxy-wood boatbuilder I used to work for, I should pass on what would make him scream about this method - putting 'dry' fiberglass onto the wood.

When the epoxy is applied, it will have a very hard time to reach the area under the fiberglass where the warp and weft fibers cross over - it has to squeeze in diagonally from the nearby gap in the 'weave' (even if non-woven) and there isn't much incentive for it to go there. In all likelihood, there will be millions of tiny voids at each of these points.

He would have insisted that a coat of epoxy is applied to the wood first and then the dry glass laid over it and a squeegee used to 'bring' the epoxy up through the glass.

[StandUpGuy]

I was going to say the same thing. I know that when laying fiberglass in a mold that after the gelcoat one is to apply a layer of resin to start.

[Larry C]

In memory of the epoxy-wood boatbuilder I used to work for, I should pass on what would make him scream about this method - putting 'dry' fiberglass onto the wood.

When the epoxy is applied, it will have a very hard time to reach the area under the fiberglass where the warp and weft fibers cross over - it has to squeeze in diagonally from the nearby gap in the 'weave' (even if non-woven) and there isn't much incentive for it to go there. In all likelihood, there will be millions of tiny voids at each of these points.

He would have insisted that a coat of epoxy is applied to the wood first and then the dry glass laid over it and a squeegee used to 'bring' the epoxy up through the glass.

I can see that being an issue with heavy glass such as roving, but I don't think it's an issue with modern fiberglass cloth and the current crop of very thin epoxies.

The typical cloth used by home builders is between 2oz and 6oz plain weave E glass or maybe S glass which is open allowing the thin epoxy to penetrate easily.

I think it's more of an issue having too much epoxy under the glass which allows the glass to float off the wood surface if not properly squeegeed.

I now always do a fill coat of epoxy over wood and let it cure till its tack free (overnight). This controls the absorption rate into the wood so the glass is not starved of epoxy during wetout.



Here's an excellent tutorial by Rob Macks on applying glass over wood. I have been migrating to his methods for over 25 years.



http://www.laughingloon.com/epoxy.html

My $.02