Condensation

[talbot]

Can't say I wasn't warned. Last week during a dull drift with no wind I opened my cockpit sole inspection ports to find several inches of water in the bilge. Took quite a while to pump out. I thought the boat seemed a little low in its berth...
Opening all inspection ports (I have them in the seat backs as well) pretty well dried the bilge in a few days. I assumed it had to be a CB leak, but no, apparently just several months of condensation. I had been leaving the side ports open, but that wasn't good enough. If any of you who wet-sail your boats haven't checked the bilge in a while, take a peek.

[jeadstx]

I originally thought that water on my boat was coming in from the centerboard bolt, but later found that it was coming thru the cockpit floor inspection ports. I determined it after a rainstorm when the boat was sitting on the trailer. Before the storm, the inner hull was dry, afterwards it had water in it. Check those inspection ports for leakage.

John

[talbot]

Could you determine if the problem was the O-ring seal or the installation screws? My cockpit ports are all new last year, even the originals. (They were cracked, so I recut the holes and installed new ones.) I am reluctant to crank down on the ports, because they can be hard to unscrew, but I'm not sure how tight is tight enough.

[GreenLake]

Where do you have the O-rings? As a seal between the ports and the deck? I embedded my inspection port with sealant, but, of course, I've not tested it for water or in this case air tightness..

I read in another forum about someone who swears by butyl tape for bedding any hardware. Silicone free and also forming a thicker layer when squeezed.

[talbot]

My ports have o-rings bedded in a channel above the female threads. They get brittle with age. I can relate. The outer housing is through bolted with silicone sealant ( only type approved for ABS).

[GreenLake]

Ah, the O-rings are part of the fitting, not how the fitting is bedded to the deck. Can you get replacement rings?

I can relate. I just replaced a rubber part today that had gone far beyond "brittle" and reached a stage of disintegration best described as "cratered"or "eroded" (as craggy as the Dakota badlands).

[talbot]

Sure. See, for instance,
http://www.iboats.com/Beckson-O-Rings-f ... w_id.48324

[GreenLake]

In that case, I'd install the new O-ring. If the problem persists, you'd need to re-bed the deck plate.

[talbot]

True, but in my case, all the ports are new, and that wasn't the problem. I was sailing last night, and the ventilated bilge is now dust-dry. The whole problem was condensation, and my story is that in four months, you can condense as much water in a DSII bilge as you would take on by launching with the drain plug out.

[GreenLake]

OK, that is surprising.

At 100F and 100% humidity, there's 4% of water in the air, by weight. (Less, much less, at lower temperatures, and proportionally less at lower humidity).

To get a pint of water you need 20 pounds of air. That's about 16 mols, or a volume of around 95 gals of air, 99gals of air saturated with water.

That volume would displace about 825 lbs of water, so it's probably more than all the air in your hull.

If you see even that amount of condensation, your hull would have to be ventilated - (moist) air has to constantly be circulated into your hull, condensate its water there, and then be replaced again by moist air.

If your outside air is only 85F and 90% humid, you'd need around 1850 gals of moist air for the same pint of water.

Either your bilges are exceptionally well ventilated (and I think they are not supposed to be, because then they won't keep you afloat when you capsize) or there's water coming in after all - perhaps not from below, because you didn't notice any after sailing.

[talbot]

Here is what I think is going on: In a misguided attempt to dry out the hull, I opened the side vents. Because of flotation (flex tubes) stuffed behind the seats, the vents did not allow much circulation; not enough to evaporate the bilge. It was enough, however to provide a steady supply of moist air, which then condensed against the hull where it was cooled by the surrounding lake. When I did leave the side vents closed, the nylon ditty bags that attach to the inside of the ports came out dripping wet from condensation. This is the first season I've had the boat in the lake for five months, and I think that if you do the wrong thing--even a small wrong thing--for long enough, it will eventually have an effect.

[GreenLake]

If your lake water is cooler than the dew point, or if you have low enough temperatures each night that stuff condensates underneath the deck, then your method would seem ideally designed to transport water from air into the boat.

If your hull does not leak and is essentially air tight, then keeping the vents closed should cure the problem.

BTW, I don't think it's just the tubes, if the lake water is cool, then bilge water is also cool and will not evaporate as readily.

[Moose]

I agree, If water is not getting in through a leak you are letting it in by keeping the ports open and allowing moist air in.