Stress Cracks, Finishes and Surface Defects
Table of Contents
Claims to UV Resistance
Stress Cracks on Hull Bottoms
Gel Coat Voids
A Common Question
Should Stress Cracks be Repaired?
Gel Coat Crazing
Dark Colored Boats
Blotchy, Discolored Finishes
Longevity of Finish
Repairing Chips and Dings
Should Old Boats be Painted?
Maintaining the Finish
Rather than being painted, nearly all FRP boats have a finish called a gel coat. A gel coat is simply a highly pigmented plastic resin that is first sprayed into the mold, after which fiberglass fabric wetted with plastic resin is laid directly on top of the gel coat.
Thus the finish and the molded part become one. Many people ask why they don't paint boats instead of using gel coat which, as anyone with a little boating experience knows, is a rather poor finish.
The primary reason is that the gel coat ensures a proper mold release so a gel coat has to be used in any case. Without it, a hull or deck would probably end up permanently stuck to the mold. And for that reason, we are stuck with gel coat. Hatteras Yachts paints all their boats, but they don't make small boats anymore because no one can or wants to pay the price of that kind of quality.
Secondly, as we all know, paint finishes can chip. Gel coat can chip too, but not nearly as easily, and because it is bonded to the surface, it does not flake off like paint can. Gel coat is thick, and it will tolerate a lot of abuse, without scratches going through the surface to reveal the darker surface beneath. So while gel coat doesn't hold a shine well, it does have other advantages that painted surfaces do not have.
If you are familiar with boats at all, you are probably aware that gel coat does not hold that bright, shiny new finish for very long. The material is highly vulnerable to sunlight, despite the best efforts to create a gel coat that is durable. It will oxidize and become chalky.
If you're also wondering why boats are almost always white, it is for the same reason why the finish on dark color cars, particularly dark blue or black, fade more rapidly than other colors.
Basically, gel coats do what all plastics do in the sun: deteriorate, albeit at a much slower rate due to the high concentration of pigments. Thus, gel coat also serves to protect the structural substrate from U.V. damage.
When the gel coat does become chalky, that's because the plastic on the surface, after being bombarded by ultraviolet rays from the sun, has disappeared, leaving only the pigment.
Fortunately, this is only the surface layer, and if one polishes it away, at least some of the original shine can be restored. How much is a function of the quality of the gel coat.
Many folks want boats with colors other than white, but experience over the years shows that colored gel coats are a mistake.
They will fade and discolor very rapidly, and once it does, that finish cannot be restored. The boat will forever after have a faded, chalky finish that can only be remedied by painting with a costly urethane finish.
So, as much as you might detest a white boat that looks like every other white boat, there is a very high price to be paid for color. Only if you plan to keep the boat in inside storage should you consider any other color.
- A Guide to Discriminating Buyers
by David H. Pascoe
Publisher: D. H. Pascoe & Co., Inc.
David Pascoe - Biography
David Pascoe is a second generation marine surveyor in his family who began his surveying career at age 16 as an apprentice in 1965 as the era of wooden boats was drawing to a close.
Certified by the National Association of Marine Surveyors in 1972, he has conducted over 5,000 pre purchase surveys in addition to having conducted hundreds of boating accident investigations, including fires, sinkings, hull failures and machinery failure analysis.
Over forty years of knowledge and experience are brought to bear in following books. David Pascoe is the author of:
- "Mid Size Power Boats" (2003)
- "Buyers’ Guide to Outboard Boats" (2002)
- "Surveying Fiberglass Power Boats" (2001, 2nd Edition - 2005)
- "Marine Investigations" (2004).
In addition to readers in the United States, boaters and boat industry professionals worldwide from over 70 countries have purchased David Pascoe's books, since introduction of his first book in 2001.
In 2012, David Pascoe has retired from marine surveying business at age 65.
On November 23rd, 2018, David Pascoe has passed away at age 71.