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(I posted this on another board without any gel coat gurus responding. Perhaps someone on Canoe Tripping is gel coat knowledgeable)
I’ve worked on boats with great factory gel coat jobs, and others with not so good gel coat work. More specifically some boats, usually thicker gel coated hulls, had lots of spider cracks and missing gel coat chips and chunks, and some others, while heavily used and scratched with thinner gel coat had fewer issues.
I have noticed that some earlier gel coat was applied noticeably thinner than on later models of the same boats from the same company/factory, and the thinner examples seem less prone to spider cracking. It makes sense (I guess) that thinner gel coat would be more flexible, and less prone to splintering on an impact flex, but I don’t do much gel coat work provided there is an alternative.
At the same time that thinner vintage gel coat has also proven less prone to busting off chunks; maybe it takes an unattended spider crack to get those missing pieces started flaking off. That also, to me, makes sense, and may be a reason to attend to spider cracks before broken pieces break off entirely.
I’m thinking of a friend’s hard used and abused early fiberglass MRC Explorer I first rehabbed 20 years ago, and the ’75 Hyperform Optima I am currently working on, both with thinner, more flexible gel coat, both largely sans spider cracks or missing chips.
The glass Explorer has a very stiff bottom, the Optima is more flexible, so I’m guessing it is not entirely the hull flexing on impact.
The 46 year old Optima has 1,000+ scratches on the bottom, but zero spider cracks, only a few tiny pieces of (thin) gel coat missing. On the other side of the vintage gel coat coin a similar age hull from a different manufacturer had the thickest gel coat I’ve ever seen; it was easy to gauge the depth, large slabs were missing.
Curious if anyone has an explanation for gel coat variances. Maybe a “just right” thickness on gel coat, not too thick, not too thin? Was it factory prep work, process, technique, chemistry? Was there some superior gel coat used in the ’70’s & ‘80’s that fell out of favor, became too expensive compared to a lesser alternative, was banned by OSHA for toxicity or etc?
Or are some hulls just outliers, made by a careful shop with skilled employees, and some made on Friday afternoon by sloppy folks ready to call it a day?
I’ve worked on boats with great factory gel coat jobs, and others with not so good gel coat work. More specifically some boats, usually thicker gel coated hulls, had lots of spider cracks and missing gel coat chips and chunks, and some others, while heavily used and scratched with thinner gel coat had fewer issues.
I have noticed that some earlier gel coat was applied noticeably thinner than on later models of the same boats from the same company/factory, and the thinner examples seem less prone to spider cracking. It makes sense (I guess) that thinner gel coat would be more flexible, and less prone to splintering on an impact flex, but I don’t do much gel coat work provided there is an alternative.
At the same time that thinner vintage gel coat has also proven less prone to busting off chunks; maybe it takes an unattended spider crack to get those missing pieces started flaking off. That also, to me, makes sense, and may be a reason to attend to spider cracks before broken pieces break off entirely.
I’m thinking of a friend’s hard used and abused early fiberglass MRC Explorer I first rehabbed 20 years ago, and the ’75 Hyperform Optima I am currently working on, both with thinner, more flexible gel coat, both largely sans spider cracks or missing chips.
The glass Explorer has a very stiff bottom, the Optima is more flexible, so I’m guessing it is not entirely the hull flexing on impact.
The 46 year old Optima has 1,000+ scratches on the bottom, but zero spider cracks, only a few tiny pieces of (thin) gel coat missing. On the other side of the vintage gel coat coin a similar age hull from a different manufacturer had the thickest gel coat I’ve ever seen; it was easy to gauge the depth, large slabs were missing.
Curious if anyone has an explanation for gel coat variances. Maybe a “just right” thickness on gel coat, not too thick, not too thin? Was it factory prep work, process, technique, chemistry? Was there some superior gel coat used in the ’70’s & ‘80’s that fell out of favor, became too expensive compared to a lesser alternative, was banned by OSHA for toxicity or etc?
Or are some hulls just outliers, made by a careful shop with skilled employees, and some made on Friday afternoon by sloppy folks ready to call it a day?
