PS Advisor: 10/06

Change your soundproofing before it crumbles.

I am sending you this sound-proofing sample to consider for your next report. It was purchased in 1997 from BoatU.S., or possibly from West Marine. I don’t remember the brand. The enclosed sample is unused and was stored in my garage. The sample is what remains of die panels I installed in my Hunter 27 engine compartment. The entire installation was reduced to this disintegrated form. In researching suppliers for replacement panels, I found that different foams are used. Which should I choose for longevity? I cannot use the fiberglass panels because of allergy problems.

Edward Carney Sr.
Sarasota, Fla.

While the exact composition of the foam used on your vessel may be a mystery, its breakdown is a relatively common occurrence, particularly with foam insulation from this era. Incidentally, polyether and polyester are urethanes, which comprise most of the currently available flexible, foam-like engine room insulting materials. Polyester foams are slightly stiffer. Urethanes show poor resistance to, among other things, acetone, most hydrocarbon fuels (diesel and gasoline), chlorine, alcohol, formaldehyde, many acids, turpentine, and boiling water. With repeated exposure to heat, fuel, lubricating oil and coolant vapors and ozone (created by electric motors and alternators), many foams show the signs of disintegration you’ve experienced. Aging also appears to have a significant effect on many varieties of engine room insulation such as the one stored in your garage (inset picture below). Not only is this disintegration unsightly and messy, the sloughed off material can be sucked into alter-nators and engine air intakes, leading to serious mechanical problems. An insulation manufacturer PS spoke with said foam formulas have improved over the past decade, so past performance may not be indicative of what you might expect from today’s products.

Disintegrated insulation blankets a reader’s alternator. He sent us a sample, inset, for review.

Heavier facing material appears to add considerably to a foam’s longevity. These facing materials are available in reinforced, aluminized polyester films, perforated vinyl, urethane film, vinyl im-pregnated cloth, and polypropylene. The non-perforated varieties offer greater liquid resistance. Be sure the foam—usually open cell—is installed so that it terminates well above the highest expected bilgewater level. All exposed foam edges and seams should be sealed with proprietary tape. Avoid insulating aluminum fuel tanks. The slight acoustical advantage is easily offset by the potential for corrosion that exists if the foam were to become wet. Highly hydroscopic materials such as acoustical foam set up the perfect environment for poultice corrosion, which occurs when aluminum remains continuously wet in an oxygen-depleted environment (the stagnant water trapped within the foam is quickly robbed of its dissolved oxygen).