That's quite the response, Paul.

Good info.

Jason

> This is the classic fiberglass resin that has been used in almost every
> ``fiberglass'' item you can buy. It has been around for a long time, and
> has a long history of use in boat building. In the 2nd version of his book
> on building strip canoes. Gil Gilpatrick mentions his personal experiences
> with changing from polyester to epoxy resins. I am guessing that in his
> first version he mentioned ONLY polyester resin. I believe the third
> incarnation of this work is now on the market. If so, I'd be interested in
> seeing if he even mentions polyester anymore. The trend is towards epoxy.

> David Hazen's book on strip building canoes is old enough to mention ONLY
> polyester resin. If you decide to use this stuff I'd suggest you get a
> copy of his book as it gives a very nice description of how to work with
> the materials -- and he had full size plans for a couple of strip-built
> kayaks that come with the book.

> On most wooden boats polyester has provided a solid, waterproof, sheathing
> that extended the life of old wooden boats by decades, and made wooden
> boats practical home-workshop items. Red cedar is not a particularly good
> base for it, though. My sources say that there is a problem with resins in
> the wood interfering with the bond of the polyester to the wood.
> Apparently, this was well known years ago, and older wood strip canoes
> (not many people building kayaks then) were made from White Cedar. Pine is
> another good wood to build from if you are using polyester resin.

> Since pine is so cheap and easily available, and the polyester resin so
> cheap, the combination was well known for making ``cheap'' boats.
> Unfortunately ``cheap'' may not be the best label to put on a well crafted
> boat. My take on this is that the boats were inexpensive to make, so
> people assumed they were inferior. When people went to using cedar, and
> they had problems with the resin, they may have assumed it was the resin,
> and not the wood/resin combination.

> By the way, the trick I have heard for using red cedar with polyester is
> to seal the cedar with a coat of sealing lacquer and sand lightly before
> putting on the first coat of polyester resin. The lacquer soaks in deeply,
> sealing the wood, and the polyester likes to bond to the lacquer. Or that
> is the theory at least.

> A friend of my has built over 15 canoes from pine and polyester. He
> refinished the first one he built, when it was about 20 years old. When he
> did, he used epoxy. He (jokingly) said he was tired of refinishing boats
> every 20 years, and wanted to use something more durable. If you ask me,
> I'd say 20 years of use from an inexpensive resin is one heck of a good
> deal. If epoxy will last longer, then you`re looking at a service life of
> 30 years or more.

> For many people, when dealing with such a span of time, they will tend to
> go with the more expensive materials. Their rationale is that the cost per
> expected year of use is very modest. For example: a boat built with $200
> worth of cloth and resin that lasts 20 years is only $10 a year. One that
> costs $300 and lasts 30 years is also $10 a year. Therefore they want the
> more durable material up front. Either way sounds good to me. If you are
> on a tight budget then build with polyester.

> Epoxy soaks into the wood and seals it from moisture penetration.
> Polyester sits on the surface and has microscopic holes (like Goretex)
> which permit water vapor to penetrate. This is a very slow process, and
> far more common on boats that are in the water all their life (big
> sailboats). For kayaks that are in the water for a day and pulled out at
> night this is a nonissue. The longest kayak trip I've heard of was under
> 65 days. (Even a trip this long should not be a problem, although
> personally If I was travelling that long I'd use epoxy and put in extra
> compartments for holding fresh water. Epoxy has the edge when constructing
> tanks for potable water.)

> If you want to get on the water quickly and cheaply, use polyester, lauan
> plywood, and/or 3/16 inch pine strips. If you want a boat that will last a
> bit longer and will weigh a pound less, use epoxy resin and okume or
> high-grade marine ply and cedar.

> Some glass cloth is specially treated to work well with epoxy. Others are
> treated to work well with polyester. Some are treated to work well with
> either resin. Ask your supplier for the right stuff.

> Epoxy resins use a substantial quantity of hardener. Depending on the
> brand you may use one part of hardener to 1, 2, 3, 4 or 5 parts of resin.
> Packaging can be confusing if you try to compare brands. Most people
> forget standard measuring systems (English, or metric) and go with
> metering pumps. (two pumps of each, etc) With polyester you use a
> catalyst. The catalyst is concentrated, and nasty stuff. You want to be a
> bit more careful when mixing small batches as you may be measuring drops
> (was that a big drop or a small one?) In either case you want to mix the
> stuff well.

> After polyester has set, it will stay tacky for a very long time if it is
> in contact with air. As a result, it is great for adding additional coats
> (no sanding needed between coats, and it sets up tacky, but hard enough to
> recoat in a couple of hours) The last coat however needs some special
> treatment to exclude the air, so that the resin can harden completely. The
> usual idea is to put on a coat of resin that has some styrene plastic and
> parafin wax dissolved in it. The wax floats to the surface, forming a
> thin, airtight barrier under which the resin can harden.

> Because this method is so common, stores will sell two types of polyester
> resin. One is called a laminating resin, and it contains no wax. I forget
> the exact name of the other type of resin. I call it a surfacing or
> finishing resin, but I'm sure that is not the proper term. If you have the
> second type of resin (the one with the wax in it) then working with
> polyester becomes a bit trickier. You can put on multiple coats if you put
> them on while the resin is still tacky. However, if it hardens you have to
> get rid of the surface wax layer before putting on a second coat. So,
> either you work fast, and do three coats of resin on your boat in one day,
> or you work slow, and wait a few days between coats, and do some sanding.

> There are alternate ways to exclude air from the final layer. One is to
> put the entire project in a bag and suck all the air our with a vaccuum
> pump. (effective, and used in industry, but not cheap). Or, you can wrap
> the project in Saran Wrap (similar effect, no pump needed. Vaccuum method
> is superior as it serves to force resin evenly over the cloth, eliminates
> airbubbles from outgassing, etc). Another way is to spray on a layer of
> material that will block the air. A commonly used material is the mold
> release goop that is used when creating fiberglass products from molds.
> Once the resin hardens you wash off the mold release goop with water and
> then sand the plastic smooth. Then you can put on a finish coat.
> Fibreglast says that polyester is resistant to UV, so multiple coats of
> varnish should not be needed. Check their website at www.fibreglast.com
> for a catalog, FAQ, etc. They have books and video tapes which will
> provide much more information, more accurately, and in greater detail than
> my comments. Trust them more than me ! ! !

> I hope this gives you a base of information that you can add to. Best of
> luck with your building.

> Paul Jacobson