Fiberglass cloth, what weight is enough?

[The R/C Man]

Hey Everyone!

Well, I have purchase some epoxy but I'm still up in the air on what weight cloth to use if any at all. I have seen people just use a few coats of epoxy to seal the wood, sand, then paint it and call it done. (I did that on an RC boat and it worked great) So do I need to go through the extra effort of adding the glass? If so, what weight glass? Would 2oz. suffice just to add a bit of strength and some abrasion resistance? It seems to me that more than that is overkill really.

[bobhav]

Greg,

The strength is in the cloth, as is the flexibility. If you have areas that are weak, add an extra layer or two of cloth. A lifetime ago, I worked in a small fiberglass factory that made horse trailers. We always roller the air bubbles out that were trapped under the cloth. The rolling raised the resin to the surface and less resin was needed to bond the layers of cloth.

BobH.

[tony.latham]

Hey Everyone!

Well, I have purchase some epoxy but I'm still up in the air on what weight cloth to use if any at all. I have seen people just use a few coats of epoxy to seal the wood, sand, then paint it and call it done. (I did that on an RC boat and it worked great) So do I need to go through the extra effort of adding the glass? If so, what weight glass? Would 2oz. suffice just to add a bit of strength and some abrasion resistance? It seems to me that more than that is overkill really.

I just looked at your photo gallery to make sure I understood what you're up to. You're great-looking build is plenty strong. Adding one layer of 2 oz. fiberglass cloth will not add much strength but it will appreciably add to sealing the wood.

I'd use a plastic squeege when applying the epoxy. I'm an old cedar strip canoe builder. Here's a Youtube of someone doing a canoe:


You'll find the roof will be much easier to do than the sides. I'd tackle the roof by myself. With the walls, I think I'd want some help. It's too bad you can't roll that cabin over on its side to do the walls.

Tony

[kayakdlk]

I used 7 oz as I got a great deal on a large roll cheaper that the 4-6 oz I had planned, but then it used more epoxy that a 4-6 oz cloth would so in the long run not sure I save any money. I didn't really choose the cloth to save money. I was looking for strength and longevity. My outer shell is 1/8 Baltic Birch sandwiched between 3/4 foam, so the extra cloth provide good protection. I would at least use 2-4oz cloth on all of the seams and then roll a couple coats epoxy on the wood to seal from the elements. Anything more is just extra insurance against cheap plywood checking and penetration strength. I went with 7 oz cloth all over, 3-4 coats epoxy and then bedliner paint. Maybe overkill but I wanted 20+ years from the finish.

Dan

[The R/C Man]

Tony,

Cool video... I like the plastic squeegee idea.


Since the top is only 1/8" over foam maybe I should use 4 or even 6oz for the added strength and 2oz for the 1/2" plywood sides.

[tony.latham]

Tony,

Cool video... I like the plastic squeegee idea.


Since the top is only 1/8" over foam maybe I should use 4 or even 6oz for the added strength and 2oz for the 1/2" plywood sides.

That makes sense to me. Just be sure to do the roof first (since that's the easisest and will add experience) and let it cure before you try tackling a wall.

T

[KCStudly]

If you are covering bent plywood, definitely go with the glass weave. The strained wood fibers need reinforcing to help keep them from splitting which would later compromise water resistance. The epoxy alone does not have the tensile strength to handle this, in fact it is rather brittle w/o the glass.

Also, you want to reinforce any seams and corner joints with glass, as that is where cracks would likely start.

I would go with the glass. A small RC boat does not have the scale to where these loads and constant motion would necessarily manifest themselves in split wood grains and panel joint fracture, but a camper does.

Someone might make the argument that they never bothered to glass their traditionally built TD's, but with flexible sealer and aluminum skin it is much less of an issue; and when have you seen a really old classic 40's or 50's TD that didn't have split seams and rot damage?

Just saying, if you are going to use epoxy get the most advantage from it and glass, too.

[tony.latham]

It might be a good idea to fiberglass the roof/edge corner first (using hand-cut bias tape). You can read Larry C's not on this here: viewtopic.php?t=34887&p=633840

If you do, you'll need to run a router along your edge first with a quarter-round bit.

T

[The R/C Man]

In that video it looks as though they laid the fiberglass over bare wood and applied the first coat of resin at the same time. It was my understanding that I should put down a coat resin to seal the wood and then put the cloth down with the second coat resin. Is that a wasted step?

[tony.latham]

In that video it looks as though they laid the fiberglass over bare wood and applied the first coat of resin at the same time. It was my understanding that I should put down a coat resin to seal the wood and then put the cloth down with the second coat resin. Is that a wasted step?

If you put the cloth on bare wood, the epoxy will saturate into the wood. That's the normal practice.

Tony