Repairing a Delaminated Deck Part 1: Tapping a Deck

Removing a damaged core section

When we bought Cups, she had teak decks, which was one of things that sold us on her. Teak is certainly beautiful, but does have a few shortcomings - as we found out after being aboard a few years. It is heavy and adds considerable weight; it gets quite hot in the tropical sun – so much so that we often needed to wear deck shoes when walking on it; and it requires a fair amount of maintenance to keep the caulked joints in good repair. The biggest problem, however, was due to the 3,000 or so screws that attach it to the fiberglass deck. Over time, especially as the boat flexes with the motion of the seas, moisture works its way under the teak, finds its way to a few of those screw holes and eventually migrates into the core. The core gets wet, possibly causing the layers to weaken the bonding and separate – also called delamination, which is very hard to detect under the teak. The water continues to work its way downhill until it finds an opening in the lower layer of fiberglass, perhaps dripping inside the boat.

Once in Colombia and once in Panama, we carefully removed sections of the teak, cut out a section of fiberglass, repaired the core, and then put it all together again. When it started leaking in yet another place, we decided it was time to remove the teak entirely, repair any damaged sections of the core, then fare and paint the decks. It turned out quite nicely, but a few years later, we discovered a few other sections of the deck that also needed repair. We repaired the worst of them in New Zealand a few years ago, and another couple of areas in Fiji, intending to get the last of them when we had the time and opportunity. Well, now is as good a time as ever to finish that job up before we officially begin marketing her.

The decks on most fiberglass boats – Cups included - consist of a top layer of fiberglass laminated to a wood core, which is then laminated to another layer of fiberglass on the bottom side. The wood core stiffens and reinforces the two layers of fiberglass while adding minimal weight. When moisture makes its way into the core, it sometimes causes the wood and/or the bond between the fiberglass and wood to deteriorate. If the deterioration gets bad enough, the deck will begin to weaken and flex, and eventually become spongy.

The next few blogs will describe how to find and repair deck problems. This week, I'll describe how to detect problems in the deck. The method involves tapping the deck with a small hammer or mallet and listening carefully to the sound the hammer produces. An area of delamination will have a very different sound than a good section of deck. Check out this YouTube to see how I tap a deck.