Hi All!
The article mentions commingled terms relating to “cracks” somehow conflating ‘gelcoat cracks’ and ‘stress cracks’ as if they are the same thing…. They are not.
It’s funny folks griping about ‘thin’ fiberglass and ‘stress’ cracks…. Have they ever looked closely at a similar vintage Boston Whaler or Grady White??? Next time you’re at the ramp, marina or used boats take a good serious look at the back transom to side gunnels corners and near the engine mounts as well as the included angle deck corners of whatever suffices for a cabin. On all the similar vintage ones I’ve looked at, especially on white gelcoat kept uncovered outdoors, I’ve observed “gelcoat” cracking which some have erroneously called ‘stress’ cracks.
NOTE: There is a BIG difference between a gelcoat crack and an actual structural stress crack!
As some already know Gelcoat is a ceramic filled resin coating designed to inhibit Ultra Violet (UV) light from penetrating and damaging the fiberglass bonding resin. UV damages the resin by breaking (cutting) the molecular resin bonds. Gelcoat is nice as it is thick and a generally more durable lasting protection for fiberglass structures as compared to UV blocking paints. (Aside: On fabric cover aircraft a coating of aluminum filled dope (paint) is applied to the natural or synthetic fabric before base priming and finish coatings to inhibit UV degradation of the fabric.)
As gelcoat is a ceramic filled resin top coat it inherently doesn’t have much actual tensile strength (are inherently brittle) so they tend to develop cracks over time, UV exposure and flexing of the fiberglass resin substructure... This does not mean the underlying fiberglass strands and/or bonding resin has cracked. Gelcoat cracks by themselves
are not actual structural damage.
On the aspect of an actual ‘stress’ crack the structural fiberglass strands and bonding resin have actually suffered physical damage and separation weakening the actual structural integrity. Actual ‘stress’ cracks
are structural damage.
Polymer paints tend to be substantially much thinner than gelcoat and more elastic … at least in their early exposure life. The thinness of the paint in most cases allows the polymer paint to stretch with flex action of the underlying material structure. If/when crack do occur in polymer paint films they are by their very nature shallower than gelcoat would be and hence less noticeable. Eventually the thin polymer paint film degrades and wears out due to UV exposure as well as physical wear sooner than a relatively thicker gelcoat.
Now one aspect that Rodger could have spent a bit more at time of manufacture and ensured a much thicker gelcoat was applied …. This would have been very much appreciated by current owners especially on the top shell and flat high exposure & contact wear surfaces… at least we would have!
…. Such as it is……
Best Regards,
Over Easy
. After all, we don’t want to be confused as Puffin owners, do we 
