The Rot Doctor


Subject: A query on Wood/Epoxy/glassed Hulls (rot or not?)
Date: Wed, 04 Feb. 2004

Hi Mate,
Zane here from New Zealand.

I just read some stuff on the Web that you had written about surveying boats.

I have a Wood/Epoxy/Glassed inside & out sailing boat. When I tap along the middle of the Hull at the Waterline I get a dull thuddy sound. A few inches along and heading towards the Bow, well I get a much more hollow sound. Is this anything to worry about? This boat has never been launched, and the builder assures me that she is built to the highest standard using New Zealand's "high modulus" epoxy system.

So are these sound differences normal in Wood/Epoxy/Glass boats? There really is a marked difference in sound. Any advice very much appreciated.

Thanks mate
Auckland, New Zealand


If she has never been launched there is not much chance that the wood has rotted, as long as it has been protected from rain. My best guess is that you are going from an area with just the hull to an area that is backed by a bulkhead or other internal structure. This will change the sound just like rapping on different areas of a guitar will produce different sounds. While the tone can change from one part of the hull to another, there should be a fairly sharp quality to the sound, like knocking on a door. Not the dull thud of someone hitting a punching bag, for example. As long as the sound is fairly sharp, regardless of the difference in tone, I think you are fine.