I have mixed feelings about coating wood other than plywood with epoxy. As my mentor has pointed out, wooden boats have been around a long time without epoxy. There are often other ways. Epoxy is not a be all solution. It is a tool and needs to be used correctly. And, sometimes epoxy and cause problems. If water gets to the wood under the epoxy and the wood can’t breath and dry out it can be worse than if you had just left it uncoated. But there are times when it makes sense. In this case, I can’t get to the area behind the tub. So, I will protect it best as I can. I did, after much thought, decide to leave the teak cleats uncoated. Since they are not attached to the tub, but really serve to wedge it in place I thought any coating might get scraped off over time as the tub moves around a little with the working of the hull and the crew crawling in and out of it. If so, the protective layer could be broken could seep in under the coating. Better to rely on teak’s great resistance to rot aided by the air holes through the bulkheads. Such is my rationalization for the day.
15 Apr 12I got a lot accomplished today. I started off by rechecking the temporary cleats I taped in place yesterday. Satisfied that every thing still fit, I took some measurements with a bevel gauge to determine what kind of angle I would need on the permanent Iroko cleats. The angle is necessary to match the tub that isn't square--it gets wider from forward to aft due to the widening of the hull. The angle is 11 degrees. I then all the panels out of the boat and ripped 1"x1" Iroko cleats and then ran them back through the table saw to get the correct bevel. I installed them with 1/4" bolts. It's way over kill given that they will also be epoxied in place but "nothing to strong ever broke" and I can't easily remove the tub if there is a problem . . . so let's not have a problem with it. "P" for plenty as we say when using demolitions in the Marines. Next, I added some additional Douglass Fir cleats to add to the rigidity of the foward and aft panels. Then, I reinstalled the forward and aft panels. I then built templates one at a time to the new cleat system and used them to trace the patterns on what was left of the 1/2" mahogany plywood. When looking for a close fit you get better results if you build each template next to the panel just installed. That way you reduce the chance of a compound error. I used my circle saw to cut the panels from 1/2" mahogany plywood. I cleaned up the edges with a block plane. The panels were a snug fit as I had not cut the bevels to match the 11 degree bevel on the cleats. I cleaned up the edges with my block plane and then used the plane to add the correct bevel checking it with a combination square. I was very satisfied with the final fit. After that is was time to clean up the boat and the shop and call it a day. This week I will start applying epoxy to the panels and cleats and begin the process of "stitch and glue" to connect the panels.
The tub will be about 33” across the aft end and about 27” across the forward end. It will be about 33 ½” long and about 27” deep from floor to top edge. The inboard side will be vertical while the outboard side will have “chines” and generally conform to the shape of the hull. The tub will be made with 1/2” marine grade mahogany plywood. It will be coated with numerous coats of epoxy inside and out to include the end-grain. The inside corners will have thickened epoxy fillets. There will be a removable teak seat in one end set about 10” above the bottom. There will about 40” of vertical clearance between the top of the tub seat and the overhead. The side of the tub towards the boats centerline, the side you step over to get into it, will be faced with vertical v-groove staving just like the rest of the boat. The top edge will be trimmed in raw teak all the way around. The tub will drain into a grey water tank which will be pumped overboard by my manual bilge pump that will be connected to the tank via a diverter valve. The head and pump up spray bottle will be located in a seat locker in separated compartments each with a hinged teak lid that won't be visible when they are not in use. The “user” will sit perpendicular to the centerline with back to the shower tub and feet oriented towards the centerline. This will provide lots of elbow room. The seat will be nearly 35” long (fore and aft) and about 19" deep (less with the hinged lid up) so it will make a good place to sit when getting dressed when using the forward, in-port, cabin. In a perfect world I would have the head oriented fore-and-aft and I spent several days trying to make that work but there simply was not enough room. The best solution was to piggy-back on open floor space already there – the passage way between the saloon and the forward cabin -- for the “users” feet. That gave us the solution for tub and head size we were looking for.
Updated 13 Apr 12: The first thing to do was to install the horizontal and vertical cleats that will support the tub sides. I used 1" x 1" Doug Fir. I cut them to length and temporarily installed them. Satisfied, I removed them and applied two coats of shellac sanding in between each coat. Shellac is pretty good stuff. It is a great sealer and though not as waterproof as epoxy it is a lot easier to work with. It dries in about 20 minutes and can be sanded in an hour. They will never see standing water and in fact will see very little water if any at all. The nice thing about V-groove staving is it provides drainage for water and allows air to circulate. After installing the cleats I called it a day. The next day it was time to work on the plywood sides of the tub. After considerable measuring and too much contemplation I was ready. I picked up another 4x8 sheet of type I Mahogany marine grade plywood from my supplier and also some more door skin ply which I use for making templates. I ripped the door skin into my standard 1 ½” wide strips. I used my hot glue gun and tin snips to cut the doorskin to the proper lengths and glued them together creating the shape I needed for a proper fit. I removed the pattern and traced them on the plywood. For jig saws and skills saws it is best to make the cuts with the good side of the plywood down since most of the blades for these tools cut on the up stroke and it will leave a cleaner cut on the good side of the wood. It’s not very noticeable when you are cutting with the grain but it makes a big difference when cutting across the grain. Then, I temporarily screwed the plywood in place. Satisfied with the work I moved on to the next step.I wanted to use a good rot resistant wood for the cleats that will support the bottom of the tub. So, I milled some 8/4 Iroko. I had to determine the slope of the bottom of the tub. I decided on four degrees, sloping from the bow to the stern. With that decision made I ripped some Iroko into 1 ¼” x 1 ¼” cleats with a four degree bevel. This will ensure the floor of the tub lays flat against the cleats. With that done, I checked the fit by temporarily securing the Iroko cleats in place with some two sided tape. Satisfied, I drilled holes for quarter inch bolts and temporarily installed them. With the end cleats installed I laid a couple of straight pieces of wood across them and used doorskin and the hot glue gun to build a template for the tub center support. I needed it in place to support the template for the bottom of the tub. I cut the center support from a piece of scrap BS 1088 ½” plywood. I hot glued it into place. Later it will get sealed with many coats of epoxy and glassed in place. Next, I built another doorskin template for the floor of the tub. I placed some ½” blocks on the Iroko cleats to ensure the template measures the widest part of the floor (which in this case is the top). This is essential when the piece to be cut will require a beveled edge. I cut the mahogany ply and then test fit it. I spent a little time shaping it for a better fit with a small low angle block plane and a spoke shave. Later, I will trim the floor back even more but not till I am sure where the outboard vertical sides of the tub will join the floor. With this done I called it a day.
Updated 14 Apr 12: We fiddled around and wasted a lot of time today sorting out how to build the sitz tub outboard side panel. To be honest the sitz tub is kind of small though we can't really be sure till we have the seat mounted in it . . . or build a full size functional mock up and bolt it in place and that is not going to happen. I built two different side mockup panels today. The first one did not have a chine. Just a straight angled panel at about a 50 degree slant. We set up buckets to sit on in the tub and different platforms to vary the height. It was OK. Not great. Then, I built another mock up using only doorskin templates (see latest photo in gallery below) and we liked it better as we gained another 3 inches in width at seat height level. The challenge is the vertical inboard face of the tub which can't be changed if there is to be enough room for the head. The vertical panel has an adverse impact on the usable room in the tub. It cramps up your ability to move around. Well, after staring at the thing for too long, making more sketches, and looking around the boat for any other viable option--there were none--we will start building the chined two-panel option tomorrow.