I have recently been following a couple of threads where wet deck core is being repaired by cutting off interior or exterior skin and full replacement of the core. Two years ago I thought that I was in for the same on my 1988 Catalina 30. I found a crack in the deck that was weeping brown water and a moisture meter showed that the starboard side of the cabin top plywood core was saturated (40% +) from the mast back to the cockpit. When I removed the traveler, about 1 gallon of water poured out of the through-bolt when I removed it. The traveler had not been properly bedded with the boat was built in November of 1987 and the gap between the deck and fiberglass headliner had been filling ever since.
At that time another member of my sailing club was repairing the deck core on his boat so I could watch the process but was not thrilled by the prospect of losing the molded nonskid. If I ever decided to sell Papillon anyone who looked at her was ask “what happened” and it would probably reduce the base value of her as a result.
As an engineer with a minor in physics I theorized a different plan. I knew that I could not dry the core with it encapsulated in glass because drying wood requires air flow. I briefly wondered if it might be possible to blow air through the core to allow drying but dismissed the idea. Then I came to the realization that the only way to get the water out was to boil it out so that it could be removed as a vapor.
It would not be practical or possible to heat the deck to 212º but if I lowered the boiling temperature of the water… Basic physics lesson, increase in pressure causes boiling point (BP) to increase which is why we use pressure caps on radiators. Decrease in pressure causes BP to decrease which is why an air conditioner needs to be evacuated before recharging the system. Theory: if the deck can be put under vacuum the water will boil at room temperature and will come out as a vapor.
I purchased an AC vacuum pump from Harbor Freight for $100 dollars and used ¼”ø plastic tubing and aquarium fittings to connect to every hole in the wet area to the pump. The first day I got 1 quart of water which decreased every day. I ran the pump all day long any time the sun was shining for the whole summer. At the end of summer my moisture meter showed the core to be from 0% to 12%. I then used the same system of ports to infuse the deck with ultra-low viscosity epoxy. It pulled in about 2 quarts and then quit pulling any more.
Two years later the deck is still dry and very solid.
At that time another member of my sailing club was repairing the deck core on his boat so I could watch the process but was not thrilled by the prospect of losing the molded nonskid. If I ever decided to sell Papillon anyone who looked at her was ask “what happened” and it would probably reduce the base value of her as a result.
As an engineer with a minor in physics I theorized a different plan. I knew that I could not dry the core with it encapsulated in glass because drying wood requires air flow. I briefly wondered if it might be possible to blow air through the core to allow drying but dismissed the idea. Then I came to the realization that the only way to get the water out was to boil it out so that it could be removed as a vapor.
It would not be practical or possible to heat the deck to 212º but if I lowered the boiling temperature of the water… Basic physics lesson, increase in pressure causes boiling point (BP) to increase which is why we use pressure caps on radiators. Decrease in pressure causes BP to decrease which is why an air conditioner needs to be evacuated before recharging the system. Theory: if the deck can be put under vacuum the water will boil at room temperature and will come out as a vapor.
I purchased an AC vacuum pump from Harbor Freight for $100 dollars and used ¼”ø plastic tubing and aquarium fittings to connect to every hole in the wet area to the pump. The first day I got 1 quart of water which decreased every day. I ran the pump all day long any time the sun was shining for the whole summer. At the end of summer my moisture meter showed the core to be from 0% to 12%. I then used the same system of ports to infuse the deck with ultra-low viscosity epoxy. It pulled in about 2 quarts and then quit pulling any more.
Two years later the deck is still dry and very solid.