Mark Harrington, Ananke, #166
The tabernacle is my solution to both the sinking deck, bending beam problem, and my wanting to be able to lower my mast myself. I also found (after ripping the mast base out when pulling the mast) that the dip in the deck had caused water to puddle, the aluminium base had corroded, and water had seeped in through the 6 (yes, six) holes through the deck and rotted the cross beam. The mast base had stainless lag screws (1/4"), one on each side, penetrating the beam about 2", and 2 short machine screws fore and aft threaded into the fiberglass. In the middle was the hole the builders made for the original mast wiring, and one the yahoo who owned the boat before me had drilled straight up through the beam, mast base, etc. for part of his wiring.
What I ended up doing is making up a full scale model out of 1/4" hardboard, so all the welder would have to do is unscrew the model, lay out the parts, cut them out and weld them up. I started out by trying to jack the dip in the deck up from below. I through bolted 2 2x6's to the fore and aft sides of the support posts about 2' down, set a ten ton bottle jack across the 2x6's (way way to big, but it was all I had on the truck) and cranked it up to the middle of the beam. I was actually just positioning it by hand, you know how you just grab the pump with your hand and crank it up till it's firm enough to hold itself before you grab the handle to start jacking? Well, as i was going wocka wocka on the pump waiting for back pressure, the beam lifted off the posts, and the deck was still deformed. As i still had plenty of bottom work to do, i left a little pressure on for a couple of days to try and let everything shift back.
In this process i realized that there is esentially no fastening between the posts and the beam except a few finish nails through the plywood bulkhead, and they were all rusted out because they were just mild steel. The beam does have 1/4" stainless bolts fore and aft holding the two halves together.
No joy on the shifting back part, and since my boats name is Ananke, which means "it is what it is", i pulled the jack and started from up on deck. I took a lathe (3/4x3/4" wood strip), and standing on the ends to get the curve of the deck, i found the most foreward position a plate could lay. It ended up just aft of the little raised areas for the hatch hinges. I checked the line in relation to the forward hatch coaming to make sure it was perpendicular to the centerline of the boat, and drew a line on the deck, and then found the exact center of the boat side to side, and marked that on the line.
This next part was the hardest. since I wanted the new mast base to conform to the original deck shape and transfer the load to the tops of the posts, i needed to make the base 32" wide and get the curve. I layed the lathe on the line on deck, standing on both ends to get the curve over the dip, and then traced the curve on a strip of the hardboard, which gave me my foreward curve. My mast is a 3 1/2" by 6" sort of oval, so the base plate I made 7" wide. so i moved back 7" on the boat and repeated the above.
I then assembled the model. Since you can't edge screw hardboard, i screwed a 3/4x3/4" cleat to the curve on the foreward flange, did the same on the aft flange, and then screwed the 7" x 32" base to each. This gave me the stainless beam to spread the load. I then set the two cheeks 4" apart (4" clear inside to give room for nylon spacers and a fudge factor) and 12" high with a 1/2" hole in each down 3 1/2" from the top for the through bolt.
As the old turnbuckles were screwed down tight, opening them completly gave me 3 1/4", and the old mast base was 1 1/4" high, it looked like i had 4 1/2" vertical to play with, and i wanted the foot of the mast high so the mast cleared the foreward hatch when lowering (not catching that its the pivot point that matters, not the base), i set a plate in 4" up from the bottom for the foot of the mast to rest on, and the welder added a 1/8" neoprene pad to eliminate stainless to aluminium contact.
I finished off with a series of 1/2" holes in the aft flange for turning blocks. In hindsight I should have put holes in the forward flange too, as the main halyard will be better positioned there.
I filled in the deck dip with approx 3/4" of fiberglass and epoxy resin (after grinding down past the gelcoat) and threw on a coat of epoxy primer.
>From below, i mounted 1 1/2" wide by 1/4" stainless ell brackets to the posts with two 5/16" through bolts each, and then through the ell drilled a 3/8" hole up through the deck on each side. I then marked and drilled the tabernacle, gushed a whole tube of 5200 on it and the deck, and bolted it down to the ell brackets.
If i had it to do over again, i would make sure to drill for turning blocks in both the fore and aft flange.