Two Layers of Fiberglass Cloth

[Doug Canada]

What is the best way to apply two layers of (4 oz.) fiberglass cloth?

At the same time?
After a period of (curing) time?
Days after the first layer?
Any other details would be appreciated.

I what to apply two layers of cloth to the bottom of a cedarstrip canoe.

Thank you & all the best,
Doug

[RodB]

Definitely do not let one layer cure and then add another...apply both layers AT THE SAME TIME so that the epoxy is all one homogenous mixture that cures chemically as a unit. It is quite easy to apply both layers at the same time and is the only way I would consider. You could apply one layer of cloth and wet it out...laying down the second layer of cloth while the first is still green...then thoroughly wet out the 2nd layer being sure squeege properly to apply enough resin to both layers of cloth.

Personally I would apply them both at the same time, laying on dry, and then saturating both layers at the same with with a squeege. This is the simplest method and works fine if you push the epoxy into both layers well (using a squeege) and saturate all...this will also use the least amount of resin.

If you are not comfortable with applying dry you can apply a first coat of epoxy and then lay down the first layer of cloth. THis is a thoroughly described method in the epoxy books like West and System III... For me personally, I just think there is no reason not to apply both layers of cloth at the same time dry and wet out as the next step...just so much easier. Just treat the two layers as one and you should not have no problems.

Also give yourself enough working time in choosing hardener and apply the 2nd coat of epoxy evenly... squeeged on and as you want to push enough epoxy into the double layers to fill the weave ... One final note on this... I would want to perform this glassing in the warmer end of the temp spectrum (70-85 degrees) as the warmer temps allow for less viscous epoxy which soaks into and wets out cloth quicker and thoroughly...and in laying double layers of cloth this would be optimal. Probably two layers of 4 oz cloth will be very little different than one layer of 6 oz cloth which many here have layed thousands of yards.

Naturally the final two coats are applied with a 3 1/2" foam roller ( the normal 7" cut in half) and tipped with a 2" foam brush. Make a 12" by 12" platten (working platform) to dump 3-4 oz of mixed epoxy onto and use the foam roller to pick up the epoxy and cover about 10 sq in at a time...then tip with foam brush. Just keep moving and the epoxy levels great ....until you fill the weave enough so that when sanding you never touch the fabric.

RB

[ 02-21-2005, 04:41 PM: Message edited by: RodB ]

[ssor]

I would lay it all at the same time, it isn't thick enough to creat problems of over heating. It will entail less sanding if you are careful to stagger your joints and will probably use a bit less resin. But listen to the others. smile.gif

[Todd Bradshaw]

I've always put the partial fiberglass layer on the hull first (dry) then spread the full layer over it and wet-out both at once. I do it almost entirely using a 7" foam roller and a typical polyethylene roller pan. I'll occasionally use a "squeegee" about 1/4" thick, cut from a block of ethafoam, for messing with any trouble spots, but don't go over the entire hull with it. Once it stiffens up enough, I roll on thin filler coats, one after another a.s.a.p. until the cloth texture is completely gone and then add one more for a sanding cushion. In my opinion it's just plain crazy to pre-determine how many filler coats it will take to fill the cloth since different application techniques and conditions as well as different brands and types of resin fill differently. It makes more sense to fill until the job is properly completed than to fill until you have some random number of coats on.

I've been using this same basic method for about 30 years on cloth up to 10 oz. on some of the big strippers and it hasn't failed me yet, so I guess it must work. It's probably worth doing a little test chunk on scrap wood to see how long your fabric takes to wet-out as some of the tightly-woven 4 oz. fabrics tend to be a bit stubborn, but I doubt you'll have any problems if you work carefully using any of the common methods.
http://www.imagestation.com/picture/sraid28/pe4cb7cbb9eee924b7ff9f4d9005fbded/fd680369.jpg

[RodB]

It doesn't matter whether you apply 3 or 4 coats to glass a panel, what matters is that you achieve the mil thickness necessary to allow for sanding while still covering the cloth. This process just takes a bit of common sense and no you don't have to set a predetermined amount of coats...unless you have worked out a consistent technique that always seems to produce the required epoxy thickness...which I have.

Now and then I have applied three heavier than normal coats and achieved the required results but over all I have glassed many many panels with fiberglass cloth and a standardized technique of 4 coats has never failed me.

Boatbuilding like many other activities offers many ways to "skin a cat" and to further qualify my previous statements... I was talking specifically about System III epoxy and Okoume plywood in temp ranges of say 70-95 degrees... I was also talking about using a squeege for the first two coats which to my way of thinking is the best way to get really uniform thickness/wet out in the cloth and also allows for nice level initial coats which when added to with the final coats results in very a very uniform thickness application of epoxy.

Of course on vertical surfaces et al...the roller is used in lieu of the squeege.

The following decks, glassed with 6 oz cloth, sanded to a nice satin finish and are quite uniform and even.

http://www.imagestation.com/picture/sraid147/p0ad6cd30bf8b24a993dc8e0c1fbf302b/f6351210.jpg

http://www.imagestation.com/picture/sraid147/p25c62b82e46f6bd187063a58b3c4a9e6/f6351219.jpg

Rb

[ 02-23-2005, 06:28 AM: Message edited by: RodB ]

[Todd Bradshaw]

On six-ounce cloth using WEST 105/205 for painted stuff or 105/207 for clear finishes I more often than not end up rolling on about six thin filler coats. Since they're fast and easy enough to apply that even a brain-dead man could do it, I don't mind. It makes for a long day when you do all the glassing in one shot, but most of it's spent waiting for resin to harden. Once the hull has been sanded, I know I've done a good job when it's my fair-to-midling varnishing skills that mess-up my baby-butt-smooth hull - though learning to roll and tip varnish has improved that quite dramatically. This one got spray varnished as an experiment. About the third coat, it started to orange-peel a bit, but was so uniform that I kind of liked it and left it.
http://www.imagestation.com/picture/sraid47/p833aca0dbcd7ac25c646da0121ea28ba/fcc898c9.jpg

[Jim H]

Todd, if you're applying two layers of fabric at once, how do you deal with the fabric at the bow(and stern) around the stem?

[Todd Bradshaw]

I learned to build strippers using the methods of David Hazen, author of "The Stripper's Guide to Canoe Building" where most regular canoes had no stem pieces, inside or outside. The main fiberglass layers were cut to stop just short of the ends of the boat. After they were saturated and before the first filler coat, the stems were wrapped with bias-cut strips of fiberglass cloth which varied from two layers thick up top to as many as four or five layers down on the lower stems where they might encounter rocks. As soon as they stiffened up enough to work again, the filler coats began. The filler coats will go a long way toward fairing the bias strips into the rest of the hull, but any remaining level change is taken out when the hull is sanded.

Most of the abrasion that canoe stems get is concentrated in a rather small area and if you've built and used boats having similar stem profiles you can usually predict where that spot will be. In those cases, I like to add a sliver of Kevlar felt about 6" long, 3/8" wide covering that area. This can be done while glassing the stems or added later and faired into the stem shape (the stuff itself is impossible to sand, so fairing has to be done with filler or resin).

[Doug Canada]

Todd Bradshaw

I love the look of wood and glass, do you have any more picture, of the one above?

What is it?

Thanks,
Doug

[Todd Bradshaw]

I only have one other photo of it.
http://www.imagestation.com/picture/sraid28/pa87a6cad4a6b34da7cf71681258f5f23/fd6819a0.jpg

It's more or less a driftboat (14' L.O.A.) though I modified the seat styles to something more normal than the rowing seats and fisherman's knee brace/casting stations that most drift boats have. I built it about 1978 just becasue I wanted to try one and always liked the looks of them. Sold it a few years later when I was hard up for cash to build other stuff. Last I heard it was out in Oregon or Washington.

Stripping isn't the fastest or most practical way to build a drift boat, but it was a pretty boat. The side and bottom panels were made flat on a jig, sanded and glassed on their insides. Then they were flipped and the other sides were sanded. These were then cut to shape and the small vertical ribs stiffening the sides were glued in and then nailed from the outside (if you look carefully at the close-up side photo you can just make out a couple of the vertical rows of small copper nail heads under the glass). The three panels, the transom and the inner stem piece were glued together and the outside was glassed in one big piece. Then the chine seams on the inside were fiberglass taped and the trim-out process could begin. All in all a fairly tedious build and pretty experimental, but it only weighed about 125 lbs. and it was fun to row.