Leaving resin/glass exposed over winter

Actually Coopec & PaulRainbow, you’re both right in a way.

Polyester resin isn’t UV stable, but it can be made UV stable with additives. The clear panels Paul refers to will almost certainly been manufactured with a stabilised resin system as there is no UV protection applied, but many other products that aren’t transparent probably won’t have the stabilisers added to them.

The OP believes that his boat was manufactured with a isophthalic resin system. As the manufacturer spent extra on a good quality resin, for a product that will spend most if not all of its life outside, it’s likely that they also spent a bit more to ensure that it was UV stable, but there is no guarantee of that as they may have felt that a stabilised gel coat or paint was sufficient protection.
 
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Well this certainly got a bit heated. Either my ignorance has been exposed or there are some generalisations made here which are not accurate. As I understand it usually gel coat is simply the same resin to be used in the matrix though usually with pigment added. It is applied and allowed to gel, ie not hard but not runny such that when the next layers of resin with glass is applied it gets a good chemical bond while the gel coat is hard enough to cover the glass strands. Now things certainly may have changed over the years certainly with different resin systems etc but I imagine OPs boat is old and polyester so no worries about exposing glass layers. Although I find it strange that he has removed the gel coat perhaps only in patches. ol'will
 
William

No! Gelcoat is not "simply the same resin to be used in the matrix though usually with pigment added"

The gelcoat has multiple functions, one being UV protection. (The alternative to a gelcoat is an UV stabilised paint.)
Please note 1576456615482.png prof patent pending post #21 above

" Gelcoats are specialised resins. Gelcoats differ from resins in that they contain pigment and usually contain less filler to give the most durable surface possible. When choosing a resin to form the base of the gelcoat, the resins with superior properties are usually chosen. The gelcoat is usually the first layer applied to the mould and its purpose is to:
  • provide an attractive finish to the surface of the product
  • act as a barrier against absorption of water or chemicals
  • act as a barrier against UV radiation from sunlight which can degrade the part
  • provide an abrasion resistant surface
  • act as a screen against protruding surface reinforcing fibres"
Polyester Resin and Gel Coats | Composites Australia
 
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Do we need a punch-up forum, to which arguments that produce more heat than light can be banished?

The bottom line, as far as the OP is concerned is that his boat won't suffer for the layup being exposed over winter. Nor if it sat for the next summer and winter too.
 
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