Why Masts Sink in the Deck... Especially Tall Rigs
December 9, 2014
The first thing to realize is that all boats get at least some water inside their masts. Rain water especially can enter from the masthead and if there is no drainage at the base of the mast, that water will just collect there. Later boats have mast steps that had horizontal drains cast right into the piece allowing water to drain from the very bottom of sides of the step. They also have halyard exit boxes that allow the mast breath at the deck side of the extrusion. Incidentally, it's not just Catalinas that experience this phenomenon, all deck step masts of different brands are at risk.
So what's so bad about water collecting on the bottom of the mast and why are tall rigs a target? First, since the average Americasailboat in the us goes sailing less than 50 times a year which means that it's fresh water that collects there and freshwater rots wood the easiest. Sure there are layers of fiberglass and gelcoat between the wood and that evil pool of water but all it takes is one small crack to allow the water to enter and the once stiff wooden core and allow it to eventually turn to mush. Then, the weight of the mast alone will cause the mast to visible sink into the deck.
Now how does it get in there? Consider that the mast is a heavy flexible rod that's constantly moving as the boat sails through the water or rides swells at anchor. You can tune your rig drum tight at it still will move around especially with the inertia of a 400 lb rig and a stiff breeze. (Some tall rigs will even pump under certain conditions where as the midsection of the mast moves forward and aft quickly and shakes the whole boat.)
A standard rig Catalina mast has its forestay secured at stemhead that's bolted to the bow and stem of the boat. A tall rig stemhead is basically bolted to a wooden plank with extends horizontally forward off the bow and so when the mast moves, the bowsprit moves some too. Unfortunately, if movement of the mast can cause the sprit to move around some, so the reverse is true. That is, if you anchor a 10,200 lb boat has a rode going over the bowsprit, the sprit is going act like a lever and fix with the swells and amplify the jolting action of the sea state to the mast which are them transferred to the four lag bolts holding your mast step in place. It's these cracks beneath the maststep which allows water to enter and cause problems.
The good new is that the problem is very fixable. First, as far as the repair, it's pretty straight forward, 1) Remove the mast and mast step. 2) Chisel out the damaged area back to good solid material. WATCH OUT FOR ELECTRICAL WIRING!! 3) After allowing everything to dry, add layers of fiberglass and resin to build the area up to the original height. 4) At this point, the area gets filled and should be sanded nice and flat.. 5) Gelcoat or paint can be added to cover the area cosmetically but you can also just skip to install a mast wing plate to hid the repair and further spread the load of the rig. 6) A layer of high density plastic should next be laid down or atleast some electrical tape on the bottom of the aluminum mast step so as to prevent corrosion between dissimilar metals. 7) The mast step is then ready to go back down and is held in place with stainless lag bolts bedded in Lifecaulk. 8) With the repair done, the mast is ready to be restepped and the boat returned to use... after tuning the rig ofcourse. 9) Lastly, a 1/4 drain hole should be drilled into the mast 1" from the base on both the port and starboard sides.
WIth proper care, the repair should last the life of the boat. And just remember, the tall rig anchor roller is meant for storage only. And as always, remember that tail rig boats sail better... way better.