On Fri, 26 Mar 2010 10:51:31 +0100, "Steve Lusardi"
wrote:

I do not think Microwave heating to eliminate moisture in fiberglass is practical. The oven in a microwave unit is a reflective
cavity. You would have to have a reflective chamber the size of the boat and a several megawatts of RF to be effective. There
would be dead spots and spots of excessive heating, just like in a microwave oven. Even if you would do this, you would still have
to provide a means of absorbing the moisture generated in the chamber's air. (Basic gas laws and equilibrium apply) There are more
practical ways of achieving this. It is important to understand the problem in order to find a solution. No construction material
lasts forever. They each have their disadvantages and advantages and a finite life. The failure mode of all fiber based plastics
are UV driven disintegration and osmosis. Osmosis is the wicking effect all fibers have when exposed to a liquid, which causes
hydraulic delamination at the weakest bond. Although FG is not waterproof, it is not readily permeable either and there is your
dilemma. Once moisture has invaded the material, it is next to impossible to get it all out.Even though fiberglass boat
construction has been around since the 50's, there are not many boats still around that old. The cost of FG hull maintenance is
only exceeded by wood. All other materials have a better TCO (total cost of ownership). I'm sure that statement will generate some
flames, but it is observable and self evident,
Steve.



I'm sure that you are correct regarding the micro-wave method of
drying a hull as in the article, I read, the writer sounded as though
he had discovered sex and was going to start a company to bring his
innovative methods to the multitudes. Certainly he stated that he had
dried his own deck, or parts of his deck, but I never read another
word about his company of anyone else using salvaged micro-wave ovens
to dry boats.

There also was an article, in Practical Boat Owner, about one of the
their staff who had purchased what was apparently one of the first
fiberglass yachts ever built commercial in the U.K.

For whatever reason the owner, or perhaps the surveyor, cut cores out
of the hull and had them tested. The cores tested at 90-something
percent of the calculated original strength of the hull material.

There was no mention of the boat's history or how much time it had
spent in the water, and in England many boats are hauled out for part
of each year, so the testing was hardly a comprehensive study but, as
the magazine wrote, it did show that fiberglass did not deteriorate
greatly with age.

Regarding the cost of wooden boats, there was another article in the
same magazine written by a bloke who was something of a pundit
regarding wooden boats. He had a "Channel Cutter" that had been built
in 1800-something, and after years and years had sold it. Apparently
there was a great hue and cry, he was a traitor to the traditional
boat world, and on and on.. His article was in justification of his
decision. He simply described, in detail, the trials, tribulations,
and costs of owning a wooden boat of great age. It was an eye opener
as the boat had required substantial repairs nearly every year since
he had owned it. Port garboard replaced, four ribs replaced, portions
of the deck relayed, recaulked hull, etc.

What most people don't realize when they see a wooden boat that when
they were built their life was usually expected to be about 10 years
and many of them were only afloat for a few years - read the history
of the tea clippers.

I once knew Chester Carter who's family had built boats on Miscongus
Bay, in Maine for generations. He told me that the conventional Maine
built work boat, oak timbers, cedar planking, fastened with galvanize
boat nails, would last about ten years and then needed refastening and
might last another five or six years after that. He was well aware of
fiberglass construction and didn't think much of it - not because it
was fiberglass but because it was lighter then wood and bounced around
a lot. He used to say things like "well, you should try pulling pots
in one of those things, jumping around like a rabbit".

Cheers,

Bruce