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Prevention and Maintenance of Deck Leaks
by Tom Neale

Fortunately there are products to help with deck leak control. While it’s always theoretically better to remove and reseat any deck components with leaks underneath, these products allow a little successful cheating. We’ve used Capt Tolley’s Creeping Crack Cure for small cracks around port lights and windows. We’ve found Liquid Life Calk to be helpful to fill in larger voids. In our experience, Life Calk, if squeezed out from under the deck hardware that it’s sealing, will be degraded by UV. But if you carefully use just enough so that it’s covered by the deck hardware and not exposed to the sun, we’ve found it to work very well. Silicone products, we’ve found, are less likely to be degraded by UV when exposed, but don’t seal as long as Life Calk when used to seal a piece of hardware fastened to the deck.

No matter how hard you try to keep on top of things, there will always come the time at the beginning of a week long monsoon when you’ll discover a new leak. If you know where it is, you may be able to fix it, even in the rain. One possibility is---yes, duct tape, if the leak source is on a reasonably flat surface. One partner stands by with a strip of tape, cut from the roll and ready to go. Keep the sticky side dry. The other dries the offending area with a fluffy towel, bending over it as he does so, to shield it from more rain. As soon as it’s dry, slap on the tape. Quickly press down hard over its entire surface. This will probably stem the flood for the duration. Remove the tape as soon as the sun comes out so that it won’t leave residue. If it does, remove it with a product like Goo Gone.

There’s yet another trick. Because Life Calk (and similar products) is designed to bond and set up under water, I’ve been able to successfully smear some of this, during rain storms, into an area where a new leak has developed. I try to dry the area with a towel as well as possible first. This will probably leave a mess, but you can usually clean that with a product such as Acetone. (Read and heed all the warnings on the label and never store this or similar products below decks or in unventilated areas.)

When you make (or discover) a hole through a cored hull, especially with balsa, scoop out the coring material between the two layers of fiberglass around the hole. The extent of the void you make depends upon the size of the hole. It usually should be at least a quarter inch for small holes (such as Bimini fasteners) and perhaps up to an inch or more for large holes such as those for bolts. Then fill the void with epoxy or other suitable material (read product literature at the marine stores), let it harden, and re-drill. This not only keeps water from migrating into and through your core, it also adds needed strength to the deck section through which you’re mounting your component, and helps prevent rot or other disintegration.

We only use sealants that are designed to remain flexible when installing or reseating an object on deck. Anything that cures to rigidity will probably work loose during stress flexing. Most marine sealants are designed to remain flexible. When you’re using these, remember to tighten down the bolts or screws most of the way when you do the job, but not completely. Don’t torque down all the way until AFTER the sealant has had a chance to cure. This is usually around 24 hours. This method avoids pushing all of the sealant out while it is still wet. Follow instructions on the label of the sealant.

To read more about deck leaks, go to the Tom’s Tips section under “Tom
Neale’s Cruising for You” on


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