Airex cores and dark topsides - a problem? - SailNet Community

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Old 10-02-2007
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Airex cores and dark topsides - a problem?

Has anyone heard of a delamination problem with Airex-cored hulls that are dark colors (black and navy). Apparently the heat generated can cause this. Sounds reasonable but I know next to nothing about the properties of Airex.

Bruce
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Old 10-02-2007
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Killarney-

It isn't really delamination but deformation. IMHO, foam-cored decks should never be painted dark colors, especially if the laminate uses epoxy resin. The foams and the epoxy resins tend to soften with elevated temperatures... which is one reason I prefer decks cored with end-grain balsa.

A dark-colored deck, say navy blue, can probably exceed 150˚ or more on a hot summer day. Depending on the construction of the deck, it may soften enough to deform permanently. One one boat I know of, that had a foam-core deck and was made with fiberglass, kevlar and epoxy composite, the deck deformed and you could see one of the crew's footprints in the deck material afterwards. Granted, the crew member in question is a huge guy, about 300 lbs... and he was carrying a cooler filled with ice, beer and soda at the time..

Several of the companies that make epoxy-based composite rudders and such have warnings about painting them in dark colors for just this reason.

If the deck is polyester or vinylester resin... it would take some really wicked sun to do this..since they deform at much higher temperatures than most of the epoxies do.
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I assume Killarney is referring to the topsides and not the deck. In theory, fiberglass never totally cures resulting in the possibility of hull deformity but not sure that's really true given the myriad of top-of-the-line (read most expensive) boats built in just this way with either dark colored gelcoat or dark painted hulls over Airex cored innards. In fact there are virtually no contemporary boats built with other than hulls cored with something, often Airex. I wouldn't worry too much about either a new or older boat constructed that way as the new one will be guaranteed and the old one would have long-since demonstrated any ill effect.
Although a matter of personal opinion, I don't think there is anything prettier than a sailboat with good lines and a dark hull color.
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Old 10-02-2007
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I often hear about this on the net but a few years back I contacted both WEST System Epoxy and MAS epoxy and asked about this issue. WEST had test data that they fowarded (MAS may have as well) which suggested that the impact of heat in the range that we are talking about (typically less than 200 degrees) was really negligable. They concluded that dark colors had no impact on the strength of the boat overtime.

Jeff
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