I am in the middle of a few projects aboard my 42ft sailboat. One of which is to design and install a new windlass. Of course with many projects, one project uncovers 3 other issues that need to be done.
As is the case with me, the anchor locker bulkhead is in need of replacement. That in turn, has lead me to find a floor string that is rotted, the plywood subfloor in the v-birth and the hallway just aft of the v-birth leading into the head has become rotted, as well as the bulkhead that separates the head and the settee, has started to rot(and in turn the playwood layers pulling apart). It all seems(still investigating) that it is starting right about where the fiberglass shower pan top butts up against the bulkhead and goes all the way down into the bilge.
That being said, I can't replace the entire bulkhead in one go as its impossible to get a sheet of plywood that large or even get a full sheet down below.
My plan as of right now would be as follows:
1: Pull cabinetry out of head(sink/cabinets/countertop)
2: Remove shower pan
3: Remove subfloor below the shower pan that is also rotted(including flooring from hallway and v-birth as its all connected)
4: Cut above the rotted plywood from the head side(possibly requiring me to remove the head side tabbing to remove the section in one piece)
5: Using removed section to create new bulkhead section
6: Butt joint the new lower section of the bulkhead in place(butt joint will be on the top and potentially side where it leads to a good section of bulkhead)
7: Repeat the process from 1 to 6 for the opposite side of the head where hanging locker exists if needed
8: Using thickened epoxy to smoosh the new plywood section against the existing tabbing structure
9: Tabb it all back together on the head side and put everything back together(while rebuilding any new pieces).
I will be using West Systems Epoxy, will definitely seal the ends of the plywood, but may also sheath the entire section in 6oz cloth(if need/recommened).
I was thinking of using West 405 as a filler for the backside of the ply to smoosh in place(step 8)? Is West 407 (colloidal silica) better for this? What about the butt joint? I was thinking i'd run some sort of tabbing over the joint that would be about 6-8 inches wide on one side to create a mechanical bond while maying adding a small fillet of thickened epoxy in the joint before placing it in as a means to increase strength?
Does anyone have any recommendations, or have they done this on a larger(38+ sized vessel)? What are your thoughts on my plan?