Keeping the Water Out: Mast Boots & Chain Plates

Keeping the water out – now there’s a topic dear to any sailor’s heart! In the olden days, before each passage we’d put all our clothes and bedding (and anything else we wanted to keep dry) into plastic bags-double plastic bags if we wanted to be sure. But over the years we’ve learned how to make boats watertight.

One part of this success has been due to creating structures which do not move under load. The other part of the equation has been using the correct sealing system.

For deck hardware we’ve had great success with GE 5200-providing you don’t ever want to remove the fitting (unless heat is present). As with all caulking materials, it works best to have plenty of caulk in place, and then only partially tighten the fitting initially. Once the caulk has started to set up final bolting pressure can be applied.

A system we’ve also used with good success is to create gaskets of 1/4″ neoprene rubber-wet suit material-and then place these gaskets under the hardware. This works particularly well with windows, and under cover plates on top of chain plate deck penetrations. When you tighten up the fitting or window, the neoprene gasket forms an “O” ring around fasteners, and of course around the edges of the hardware.

Mast boots are more of a challenge. The first issue is that masts tend to move around a lot-even those which are chocked firmly. So the system used needs to be flexible. BEOWULF’s main mast was a real challenge. It is subjected to very high velocity spray when the she is reaching at speed. After some experimentation here is a system which we found works well.

The first step is to clean the mast and deck collar. Next, a neoprene (wet suit) boot is glued into place (using special neoprene adhesive) with an extra reinforcing patch over the butt glued joint. The top and bottom of this neoprene mast boot is then clamped into place, top and bottom, using multiple wraps of 1/4″ shock cord. The shock cord contours to the mast and collar faces. We use five complete wraps top and bottom. The edges of the neoprene are then sealed using silicone.

The next step, and this is critical, is to wrap the entire gasket with self-amalgamating rigging tape. This is available in 2″ widths from West Marine. We use one entire roll for each mast boot. This layer starts a couple of inches above the neoprene, and ends at the bottom of the mast collar.

The final layer is a fabric cover to protect this entire assembly from sun damage.

And these boots do not leak!

Posted by Steve Dashew  (January 20, 2003)

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