Well, I finally did it. I waited as long as I could and then procrastinated for a week and then I cut a hole in my boat. A lot of people weighed in with opinions and suggestions and good wishes and I thank all of you. I attached a few pictures to document the project so far.
This is the guide block on the right side. I put them down with 1" pin nails through 3/4 wood. This let them stick in the cabin sole just enough to resist side pressure and still pull out easily.
This shows the guide block on the other side. By now I'm sweating. Gone too far to stop but really wondering what's wrong with my thinking.
Then it's across the passageway. I set the blade about 1/6 above the beam. (used the smaller hatch as a guide) I knew I might have to finish it with the vibrating tool
This is the vibrating tool. I'm sure it has a real name but it's a vibrating tool. I used it to finish the corners where the circular saw couldn't go. And I used it to cut the final 1/16" the circular saw didn't get. Well, almost.
This is the new hatch reluctantly coming up. It took another couple of minutes with the vibrator (oh baby) and a couple of whacks with the deadblow hammer and I could pull it all up. Almost.
When I got it up I had a pad of delaminated plywood. One 1/16" layer and about a half cross layer. Another couple of minutes with the vibrator and I had a hole in the boat. If I had lived a better life this would have been neater and I wouldn't feel guilty about cutting up my boat.
Oh god, now that I have access I wish I didn't
Is this Calcutta? It's sure as hell a black hole.
Full of interesting plumbing. Like this reduction from 1 1/2" sanitation hose to 1" water hose to a pump to drain the tub. I'm going to install a 20gal grey water holding tank and have the showers and tub drain to it. Then everything will drain by gravity and the tank can be pumped overboard. I think overflows from the shower caused the delam. I'll know more when I get there
This is looking straight back at the lectra-san system lurking under the passageway steps. How did they get that in there? The godless heathens must have used a child. It's still 18" to that fitting!
You can see the delaminated plywood under the guest head. The one where the shower leaked through. I'll have to get back there and check for rot but so far the boat is remarkably dry. Any suggestions on how to deal with the delamination are welcome
This is the hatch plug. As you can see, it's really delaminated. I'm going to strip off the plywood and leave just the top 1/16 layer to hold the teak and holly together. Then I'll bond it to a piece of 3/4 plywood that I sand the top 1/16th" off. I'll square it up and band the edge with a wear layer. I'll find a hatch pull and route out a space in the center.
Once I have the hatch finished I'll use it to square the hole and make a good fit. I'll route out a 3/4 X 1/8" lip and finish it with hardwood to match the existing hatch. More later.