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Re: Strip: Epoxy and fiberglass cloth
By:Paul G. Jacobson
Date: 3/28/2011, 12:20 pm
In Response To: Strip: Epoxy and fiberglass cloth (Carl Kessler)

: I am building a bootlegger canoe out of mahogany and about ready to
: glass. I have seen Nick put kevlar in bottom of kayaks is there
: any reason to do this with a two person canoe

No reason to use kevlar at all unless you are expecting some severe service issue. Generally you can get all the stength you need from using glass alone.

: (hopefully
: wouldn't be hitting any rocks) should I use a 6 oz glass cloth
: or heavier?

6-ounce glass works fine for canooes. So do lighter weights. I think of 6-ounce glass as the heavy end of the spectrum for most tandem canoes. As with kayaks, 4-ounce glass should do fine. If you have a very large canoe, you can put on additional layers.

I used 6-ounce glass on my 14'6" canoe and put one layer inside, and one layer outside, with a second layer outside on the "football" shaped area of the bottom, strictly to protect from scratches from the sharp rocks (construction debris) in the local river. I over built! I could easily have gotten by with 4-ounce glass for the overall sheathing, and an additional 4 ounce layer on the bottom. Currently that canoe is sitting with the bottom glass removed. It will be replaced with 4 ounce glass. After 15 years of use and unprotected outside storage it was time to go down to the bare wood and re do things. I'm leaving the inside alone.

On a canoe, the inside of the boat needs to be stronger than the outside. If you are going to use 6 ounce cloth, use it on the inside. the glass on the inside not only holds the strips together, but it serves structurally in place of the ribs (which are not present) in most cedar-strip canoes. The outside just needs to repel water and hold the strips together. Anything on the outside which is thicker than a coat of varnish will keep out the water, and even very thin glass cloth has great strength in holding the strips together. A thick bottom layer of built-up glass, or a layer of graphite-filled or aluminum-powder-filled epoxy does give added protection in the areas which get the most wear. Think of it as a shield which you can replace every so often in rough service, or never--if you treat the boat gently.

If I was building an 18' or longer canoe I'd consider using 6-ounce cloth again, but my next canoe will probably be a version of a 12' Wee Lassie, and use the Thayercraft 3.2 ounce cloth, with two layers on the very bottom. I do like grunge layers.

: Second I have used west system epoxy on my sailboats
: and find it very troublesome in high humidity. Does anyone know
: if the Mas or system three would be a better choice of resin to
: use as the humidity is often high here in north carolina.

I think you'll have problems with high humidity when applying most epoxies. Once they set up it should be fine. Sounds like you will wnt to get the boat 'glassed inside with good air conditioning, or in whatever week the weather report says the humidity will be low.

If you check the archives for posts on "Tenting" a kayak while glassing it, which is a technique used by Northern kayak builders who want to keep the kayak warm while they glass it in the winter, perhaps you can adapt the tent to your use. Depemding on the sirflow and the amount of humidity, would it be possible to create a warmer and drier pocket of air inside one of these plastic tents?

In an extreme case I'd consider getting a 5000 btu airconditioner (Wal mart had these for under $100 last year) and enouch 2x4s to frame a workspace around my boat, cover that with cheap polyethylene plastic, mounting the airconditioner to it, and working inside untile the job was done. Or maybe just air condition a garage for a week. Those small window units are designed to just cool one small room, but they do a great job of dehumidifying a larger area. I've seen people in damp warehouses use them inside the building with no exterior venting, to keep an office area cooler and drier. The exhausted heat and moisture just goes into another area of the warehouse.

good luck mastering your weather conditions.

PGJ

Messages In This Thread

Strip: Epoxy and fiberglass cloth
Carl Kessler -- 3/28/2011, 8:59 am
Re: Strip: Epoxy and fiberglass cloth
Paul G. Jacobson -- 3/28/2011, 12:20 pm
Kevlar use...
Robert N Pruden -- 3/29/2011, 10:54 am
Re: Kevlar use...
Bill Hamm -- 3/29/2011, 12:40 pm
Re: Strip: Epoxy and fiberglass cloth
Bill Hamm -- 3/28/2011, 12:37 pm
Re: Strip: Epoxy and fiberglass cloth
Robert N Pruden -- 3/29/2011, 11:29 am
Re: Strip: Epoxy and fiberglass cloth
Bill Hamm -- 3/29/2011, 11:43 am
Re: Strip: Epoxy and fiberglass cloth
Robert N Pruden -- 3/29/2011, 12:38 pm
Re: Strip: Epoxy and fiberglass cloth
Bill Hamm -- 3/29/2011, 1:08 pm
Re: Strip: Epoxy and fiberglass cloth
Robert N Pruden -- 3/29/2011, 1:29 pm
Re: Strip: Epoxy and fiberglass cloth
Bill Hamm -- 3/30/2011, 1:44 am
Re: Strip: Epoxy and fiberglass cloth
Malcolm Schweizer -- 3/28/2011, 1:20 pm
Re: Strip: Epoxy and fiberglass cloth
Charlie -- 3/28/2011, 5:12 pm
Re: Strip: Epoxy and fiberglass cloth
Carl Kessler -- 3/28/2011, 10:13 pm