Gelcoat Blisters - Diagnosis, Repair
Gougeon Brothers, Inc.
|This is the best and most complete book on blistering in fiberglass boats and proper
repair of those blisters. It is also a very inexpensive publication that anybody can
afford. Some will also want the Epoxy How-To video, which has information on blister repair
and is also produced by Gougeon
Brothers and stocked by us. At the very least you should have this book. I would not
recommend that anyone try blister repair without it.
From our own experience at our former boat yard operation I have the follow comments to make that I hope will be helpful when referred to while reading this book. Some of them appear critical of the book. But that is the nature of a good review. You tend to comment on the things you disgree with and not mention the vast majority of information which you may not only agree with but learn a lot from.
On page 2, paragraph three the Gougeon Brothers delicately mention that the trend has been toward thinner hulls which makes the structural integrity more and more critical. In my opinion, because of their association in the minds of many people with modern wood and epoxy construction there is a reluctance upon Gougeon Brothers' part to comment further here. However I, as a naval architect who designs in all materials, am quite willing to state that early heavier built fiberglass boats were in all probability engineered by true engineering firms and intended to be very long lived. Clearly most of the boats being built in recent years have not been in any sense adequately engineered. So please don't feel that protecting your boat against osmosis blisters in any sense guarantees you structural security if your boat was understructured originally.
On page 5, we are cautioned that it "may be impossible to define a laminate schedule, polyester matrix formulation, and manufacturing plan to create a laminate that is totally impervious to attack." Again it is important to point out that Gougeon Brothers is being very diplomatic here. Remember that they manufacture a line of laminating epoxies that may be used instead of polyester to create laminates much more resistant to blistering than a polyester based laminate is likely to be.
Starting on page 10 in section 2.3.1 there is a lot of discussion on removing gelcoat by "grinding". It appears that multiple people may have contributed to this section. In the introduction it is mentioned that the tool to be used is an "air or electric polisher, with an 8" foam sanding pad." This to me means a random orbit buffing machine used for sanding. Since this does not have a running edge like a grinder, disk sander or belt sander this is a good choice. We personally preferred a somewhat smaller 6" diameter random orbit sander with a dust extraction hose running to a shop type vacuum cleaner. Either the polisher or the random orbit sander will not gouge or damage the boat. However, further down page 11 a disk grinder is specifically mentioned as having been used. I must state in the very strongest terms that this is not the right tool for the job, has often resulted in severe damage to boats, and at the very least very much interferes with the fairness of the hull and increases the work of repair. In an extreme case in Florida I watched a yard hired to strip the gelcoat on a 37'er use a grinder. In one day they essentially destroyed the boat.
Section 2.3.2 discusses sandblasting. I'm pretty dubious about this. Fiberglass hulls are not very hard structures. It is one thing to sandblast paint off of steel and aluminum it is a pretty worrisome idea to use such a generally aggressive method on such a soft material. If you do it, use a small pressure blaster with no more than a 1/8" nozzle and with fine sand as the most aggressive media. Note that they recommend not going all the way through the gelcoat with the sand blaster. I concur. Don't sand blast more than the point that you start to see hints of the color of the laminate through the gelcoat. Sand the rest of the way.
On page 12 They describe sounding for voids with a small "mallet". I would suggest the kind that you buy at the hardware store with a yellow transparent plastic head. This is excellent for sounding fiberglass hulls for voids and delamination problems etc. It is also excellent in sounding for fastenings problems and rot in wooden hulls. A good tool to have.
Page 13 Section 2.4.1 suggests that small voids in the laminate up to a few square inches can be repaired by drilling holes, drying the laminate and injecting epoxy. While I assure you this is the best book on this subject, I have become convinced that this type of "repair" is mostly wishful thinking. You can't really see what you're doing, you can't be sure you've really dried it out, and you can't be sure you've filled the whole void when you inject the epoxy. Further you've just drilled a lot of holes into the structure of the boat. If delamination is big enough to detect I would always opt for grinding out the material above it and relaminating. On the other hand I am perfectly comfortable with their section 2.4.2 treatment of large voids. This type of repair has always worked for us.
Their information on moisture meters is happily free of the over enthusiastic hype with which these were introduced. They are a tool. It is also important to recognize that they will detect metal or water behind the laminate as well as moisture in the laminate.
The information on drying the hull is sensible. Some yards have been pressured into rushing repair jobs such that the hull isn't given enough drying time. Do whatever it takes to get the boat really dry.
On page 19 in section 4.1 there is a brief suggestion that you might steam clean a hull once it has been dried out to remove surface contaminents. This may work fine but I would add that the hull has to be really dried out as I have seen steam cleaning apparently, if I understand what I'm seeing, cause moisture or other chemicals to flash to vapor behind the gelcoat and create an enormous amount of additional blistering. If you're doing this professionally this will cause the customer to become exceedingly upset. Fortunately I saw this happen before it occurred to me to try steam cleaning myself so I've never had a problem.
I hope everybody reading this review will note that we are endorsing this book very strongly. The above picky little points from our own experience are meant to add perspective from the view point of long time yard workers like us. (tm)
52 pages, profusely illustrated with excellent line drawings, $7.50
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