Soss Hinge
This type of hinge (for cabinets, folding doors, and shutters but not regular doors) is named after its inventor and is for situations where you want a hinge that is completely concealed. The Soss hinge is mortised into the door edges, and when the door is closed, you can’t see any part of it.
Soss hinges are very strong, but they are very difficult to install. There is simply no room for error; they must be lined up directly opposite each other right on the money. They are also expensive.
This type of hinge (for cabinets, folding doors, and shutters but not regular doors) is named after its inventor and is for situations where you want a hinge that is completely concealed. The Soss hinge is mortised into the door edges, and when the door is closed, you can’t see any part of it.
Soss hinges are very strong, but they are very difficult to install. There is simply no room for error; they must be lined up directly opposite each other right on the money. They are also expensive.
Indeed they are expensive at $25 + each. I was glad I had invested only $8 for some Naval Jelly in my efforts to clean up and free up the old ones.
There had originally been six used on the table, so replacement, if I could find the right size, would have been $150! There was one hinge missing and one hinge had missing parts and was not functional, leaving two for each side of the folding table. Because the hinges are under no load at all with the table folded or unfolded, I think two per side will be perfectly adequate. A nice small-scale example of how the Salar is over-built. If I ever decide the other hinges are needed I can add them easily enough. To clean up the old hinges, I first soaked them for a couple of days in some old wine vinegar I had in the kitchen that was too old to use in cooking. Vinegar (dilute acetic acid) dissolves rust slowly. It helped, but I decided to follow it up with a soak in Naval Jelly (phosphoric acid) rust remover/converter. In between, I wire brushed them and tried to work them free. Three of the four could be moved, albeit stiffly. To make sure I had completely neutralized the acids, I gave them a brief soak in a bakng soda solution. That was followed with a couple of days soaking in PB Blaster, a spray for freeing rust-locked nuts. That freed up the fourth hinge and made the rest move much more easily. A spritz of WD 40 and they all worked smoothly.
Retesting the leaking ports showed that the silicone caulking I added around the glass had sealed the glass fine. 
I replaced both rubber gaskets with solid square-section rubber and retested.
I replaced both rubber gaskets with solid square-section rubber and retested.
One port was fine; the other leaked. The difference was the joint where the two ends of the gasket material came together. The recommended way to deal with this joint is to cut the ends at a diagonal. I opted not to do so because I didn't think I could get the angle of both ends straight and exactly the same. The simple right angle cut was pretty easy with a razor blade. I tried to make the cut such that the ends would be squeezed together when the hatch was clamped down. I succeeded in one, failed in one. Rather than use another couple of feet of gasket material and re-do it, I decided to try adding a bit silicone to the faulty joint and retest. It worked.To repair the gouges in the table, I decided to cut a rabbet along the entire edge and then glue in a replacement strip of teak. Because I don't have a jointer or even a router table, I had to cut the rabbet on my table saw. The only problem was handling the somewhat large and awkward table on edge. To guide it while I made one of the two necessary passes through the saw, I screwed a piece of plywood to the saw fence and used shims to align it perfectly vertical relative to the saw table.
While not as perfect and precise as it would have been with the right tools, it was close enough to finish off satisfactorily with a little sanding and planing. I glued in the replacement strip I had cut and sat around drinking a glass of wine and watching the glue set.
While not as perfect and precise as it would have been with the right tools, it was close enough to finish off satisfactorily with a little sanding and planing. I glued in the replacement strip I had cut and sat around drinking a glass of wine and watching the glue set.
A couple of days later I trimmed off the ends of the new teak strip and spent a hour or two sanding off 35 years worth of old and darkened varnish. I have so far laid on three coats of polyurethane varnish (sanding between coats). Another coat or two and it will look great. You can just see the end of the replacement strip in the lower right corner of this photo:
This weekend I'll be back at the boat hoping to finish reinstalling the doghouse skylight and perhaps removing the old teak hatch covers so I can start refurbishing them.
On our way back to Sacramento, we stopped to check on Circadian and have lunch. While there, I removed the saloon table so I could bring it back to the shop to remove and refurbish the unique two-way hidden hinges that let it fold up neatly. After 35 years, they had corroded and gummed up with varnish to the point where attempting to fold up the table resulted only in damage. Even in the shop I had to use my whole bag of tricks to remove the screws and get the hinges out of their recesses. I'll be soaking them in paint remover, vinegar and all sorts of caustic nasty stuff to try to get things freed up. Then, lubricants and rust-
In the meantime, here are few photos from our holiday....
That night I fabricated the new bracket and reassembled the skylight with new plexiglass (smoked instead of clear) bedded in marine silicone sealant. The plexiglass is not fastened to the frame, but rather ‘floats’ within the assembled frame in a bed of sealant. The aluminum framework, in turn, is screwed onto a fiberglass flange on the doghouse roof. Below the frame on the underside of the doghouse roof is a teak trim surround.
Trial fits on the boat on Sunday confirmed my suspicions. It took quite a bit of grinding away of old sealant and some fiberglass to get the assembly to fit in place.
Even then, it was obvious some of the bolt holes did not line up any longer and will need to be redrilled. I was out of sanding disks to finish the trimming, and there wasn’t time left to start on the big task of rebedding and re-bolting the skylight in place. Instead, I sanded the teak trim around the opening and put a coat of epoxy on it. 
Before I left I managed to get all the proper gaskets for the forward hatch and the Ta Chiao portlights. I replaced the gasket in one of the Ta Chiao ports and did some more leak testing. They leak around the glass mount as well as the gasket, so I'll need to try staunching those with silicone. I see more gasket replacement and leak testing in my future!