moisture trapped between two gelcoat layers

[tappers]

My Westerly Longbow has a rash of small blisters on the topsides, just above the waterline. They are hard and won''t pierce.

I am told that she developed these as a result of being overloaded and kept on the same tack for long periods during a transatlantic trip.

I am also told that they are caused by moisture forcing itself through the outer layer of gelcoat, then hitting a second layer which it can''t penetrate. Apparently, Westerly used to lay up boats with a double layer of gelcoat in the late 1970s.

Has anyone else experienced a similar problem? Even better, has anyone cured it - simply and economically?

Thanks

Phil

[AGott]

My Cape Dory (1977) has the same problem... It is tough to fix, from what i hear, and I have been told to leave it alone, since it is kind of hard to see anyway...

[Jeff_H]

I think that it is unlikely that Westerly was using a double layer of gelcoat. At least in the 1970''s and on into the 1980''s, Gelcoat is simply dyed, unreinforced polyester resin. Typically, Gelcoat is the first material that would be applied in the mold. On better boats of that era the next layup would be a resin rich layer of light weight mat which was intended to reduce the amount of ''print through'' from the folloing layer of mat. Ideally this layer of mat would be applied quickly after the gelcoat had ''gone off'' in order to get proper adhesion between the gelcoat and laminate without sanding or other prepwork. Occasionally, for one reason or another there would be two long a lapse between gelcoating the mold and laying up the resin. When that happens there is poor adhesion between the gelcoat and the laminate. I owned a boat with just such a problem. While this is far less of a problem than osmotic blistering, the failed bond between the laminate and gelcoat can allow water to reach the laminate after which the repair in much more serious.

In my case I used a wood chisel to remove the loose gelcoat. It acually peels away quite easily where it is not properly bonded. I ground out the area to provide proper tooth and had a boat yard respray the area with new gelcoat. The boat yard was able to get an excellent color match and frankly was not that expensive. If you have good glass working skills, or are less concerned about aesthetics or plan to paint the boat anyway, it is not that hard a job to do yourself.

Good luck
Jeff

[BigRed56]

Ahoy blister sufferers and Jeff_ Water trapped between layers of glass will try to get out (Osmosis) Pour quality control in manfacturing is the primary reason. (Workers sweating in a hot factory and dripping in the lay up is a fact you won''t hear much about but then again you''d have to be there.)
Several technical differences as well Gelcoat if far from being just unrienforced poly resin. Second, time between layers is generally unimportant except if the mold is drug outside in the sun for a month. The over use of wax in gelcoat is the primary concern for proper bonding with the initial mat application. No type of gelcoat or resin needs to be sanded between coats and if you ever tryed it (where wax was not used to get a hard cure) you would know that it is a gummy impossibility to sand. It is this very adhesion property that allows strong multi- layer bonds. The correct second layer would be a bi-axial or woven layer which will leave a print. Often core-mat is used in critical areas (hull sides) where visible finish is more important. As to the blister question pop the fill them and re-gelcoat the area. IF you suspect the initial problem is an inside to out problem but if water got in through a stress crack and builtup over time and somehow sealed itself so that it could blister ?? I seriously doubt it. Does it bother you then fix it. Big red says If it ain''t leaking faster than the bildge pump who cares? OHH yeah Jeff_ if water reaches the laminate its a more serious problem ... if gelcoat is the same a poly resin whats the difference? Do you seriously think a boat with no gel coat would sink? Stick to your area of expertise, or make you bones in a factory like some of us. Big Red 56

[Jeff_H]

There is difference between high moisture content in gelcoat and high moisture content laminate. In the case of high moisture content in laminate water is able to wick though the laminate and is more likely to cause structural levels of osmotic blistering. Obviously, since there is no reinforcing in gelcoat, damage to gelcoat does not recult in structural level blistering.

While you are correct that laminating resins remain tacky until deprived of oxygen, gelcoats are often formalated so that if left long enough (over a weekend) they will entirely go off to the point that preparation between the gelcoat and structural laminate. My family was in the boat building business and we experienced these problems first hand. Big Red, what is your area of expertise?
Respectfully,
Jeff

[BigRed56]

Ahoy, my friend Jeff, I see our spats have drawn some bad press. I grew up on and out of wooden sailboats from 1963 - 1987 on the Chesapeake. I''ve worked in a production boat factory for 4 yrs @(200) boats a year,and have owed my own custom fiberglass business for 7yrs. I have designed and built the plugs and molds for many projects including a 16'' planing hull dinghy of my own design, planter liners for the lobby of Westin Hotels, 9'' double sink photography lab countertops, etc. I have reparied everything from blisters to a sunfish lost off a roof top on the Washington Beltway, to a complete deck glassover of a 30'' power boat just to name a few. I can sail any boat anywhere anytime , heck I could sail a power boat if I had to. I''m a master plumber as well as a general contractor for 20 years so my real hands on skills and business skills are extensive. My sailnet bio lists the variety of boats I own and sail. By my estimates I''ve spent four years of my life on the water and another twelve in the fiberglass /boatbuilding business. I ''m semi retired bouncing back and forth from SW Florida To Philadelphia, depending on where the sailing is good. I''m on my second marriage(9 yrs) with four daughters and one grandaughter (all very attractive) . My varied accomplishments and sucess with boats,women and business are a matter of fact. I have built this experience without benefits of family money or formal college education. Those that can, do, those that can''t, sell boats. I don''t race for the simple reason that I believe racing should be fun and class racing isn''t very nice. I don''t think that boats in excess of 100,000 are morally fair to the poor slobs who ruin thier bodies for a paupers wage in building them and the snobbery of those who buy them. This industry and your steadfast opinions notwithstanding need to get real. I sir am the real deal. I love the smell of resin(stryene) in the morning and I could care less is my boat is slow or ugly or inexpensive. I don''t need fancy industry buzz words to prop up an empty life. Big Red 56. Pirate.

[HGSmith]

Big Red 56

Arrrr. I enjoyed your reply, but I''m still trying to figure out the leap between fiberglassing and success with women.

HGS

[BigRed56]

Ahoy, HGSmith, the connection is the personal effort and satisfaction of a job well done with what you have and the guts to keep trying no matter what happens. In many ways I have depended on women and boats to keep me sane and afloat. Of course there are other more racy similarities between resin and women but I think decorum has me tied up at the wharf. Thanks for the support and in the future and for the record IF I had a son I would like him to be just as smart and driven and professional a man as Jeff_ , no matter what I may say to him , I say it out of respect and love. Big Red 56 weeping in his cockpit.

[VIEXILE]

Man, I''m getting scared here . . .

[Jeff_H]

Holy mackerel, Well Thanks, he says blushing over his keyboard.

Jeff