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Microwaves to dry boat hulls
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 |
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