posted 01-08-2006 06:04 PM ET (US) 17 bodega relays his frustration in the lack of good information available on the cause of 'spider cracks', or 'stress cracks' in classic Boston Whalers. It is a great question as to why they occur. We have this awesome boat that just cannot take enough of a beating, but the gelcoat in some spots seems to 'craze', or 'spider web'. I think the question, or topic even evolved to 'quality years' of Boston Whaler manufacturing.![Boats Boats](/uploads/1/2/6/4/126426279/590865929.php)
There are so many reasons why gelcoat developes spider cracks. It is very hard to pinpoint the cause to one finite reason because they occur on any fiberglass boat for very different reasons.
- Gel coat stress cracks frequently and most cases are related to structure; but not always. In some cases it can be related to thickness, age, and quality of application of the gel coat, too. Boats move and flex; Gel coat can be extremely brittle.
- If the cracks on your boat were caused by impacts, such as around rub rails or where a heavy object was dropped, move on to Step 1. If, however, the spider cracks appeared at an attachment point or in a high-stress area, there's a good chance they'll simply return after you fix them.
As we all know, even the best built and well designed fiberglass boat flexes and moves a bit while underway or docked. Gelcoat is a marine finish that cures hard just like polyester and epoxy resin. The gelcoat is primarily a cosmetic coating, it has no structural strength on it's own, just like epoxy or polyester resin.
Progress tracking and illustration of almost completely rebuilding a boat to remove and repair rotten wood found in the transom, in portions of the decking, and at least one main stringer. Franks adventure 4 hacked. Repairing Stress Cracks - 1988 Glastron Boat Restoration Project.
The very basic reason for stress cracks in a gelcoat finish is the hull or surface that the gelcoat is bonded to flexed or moved an amount beyond the point that the gelcoat can flex, so it just cracks, because the gelcoat has no structural bearing attributes.
A fiberglass layup that is too wet, or has too much resin will crack also. The resin does not bear strutural loads well either. It is the 'right' proportion of resin an fiberglass that gives the greatest strength. Aol downloads free gold.
So, if there is spider cracks, there are typically two reasons.
The gelcoat was applied too thick at an area that does flex. Gelcoat will tolerate a bit of flex. But as the coating gets thicker, the less it will tolerate flex.
The underlying fiberglass structure is not adequate, and the gelcoat cracks due to insufficient laminant layup or structural support during the molding process to support the gelcoat.
The only way to know the cause of the stress crack is to grind along the stress crack with a dremel type tool until you hit fiberglass. Grind the cracks out and pay attention to gelcoat thickness and the general binding of the gelcoat to the fiberglass layup. Also look for failure in the fiberglass.
The problem with opening up stress cracks and repairing them is that it will more than likely be a cosmetic problem due to excessive gelcoat. Making a repair that will match, and will not crack again, will probably look worse than the original stress crack.
I really don't think that a vast majority of true stress cracks alow water into the laminate. I do think that most stress cracks are a minor cosmetic problem.
Now on a real old classic don't confuse stress cracks in the gelcoat with 'crazing' of the gelcoat. I think most of the reports of 'cracked' or 'crazed' gelcoat on 30-40 year old hulls is ultraviolet rays from the sun damaging the gelcoat over time.
To sum up, the only way to determine the cause of a stress crack, especially a minor one, is to grind the gelcoat off to evaluate the structural integrity of the fiberglass substrate.
Stress Cracks On Boats Youtube
Usually it is not a productive action in grinding them out, filling and re-gelcoating the area so you do not see the cracks.
Hope this helps Steve. It is one of those things with boats that you will not know the cause of until you start grinding, absent a major gore in the gelcoat. If you have the San Andreas fault in the gelcoat you know you have problem, and water will be getting in there. Very fine lines here and there and there is probably very little if any water gettting down to the glass.
Stress Cracks On Boats Images
Rich