condensation in sealed amas

[jedkins]

Is it possible for condensation (water) to form in trimaran amas that have been completely sealed and that are water and air tight? Thanks for any advice

[Chris Ostlind]

Originally Posted by jedkins

Is it possible for condensation (water) to form in trimaran amas that have been completely sealed and that are water and air tight? Thanks for any advice

Yes, and it wold be especially possible in a climate like the one in which you live. You have considerable ambient humidity. That humidity (water vapor) is contained inside the hull of the ama when it is sealed. Sitting out in the the hot tropical sun, the contained air and water vapor rise in temperature and the water condenses out of the air and settles first on the interior sides and then drools down to the bottom. This effect is enhanced by the fact that the air in the contained interior volme will also experience a rise in pressure from the expanding gasses.

Limber holes in the interior bulkheads and a thoughtfully placed drain plug system will allow you to drain off the condensed water vapor and keep your amas light in weight and as buoyant as possible.

Really big amas might require you to install removable deck plates for access and make a routine inspection of the interior and siphon the water off manually or electrically.

If you are talking about a wooden multihull, then sitting water in the amas is asking for a rotten core as water will, eventually find its way into the wood and just sit there creating huge problems for the future.

Chris

[jedkins]

Thanks for advice. I do get what I suspected is condensation in my current boat, a catamaran with vents that encourages air flow. THe problem seems to be improved somewhat if I store cushions and other absorbant materials in the hulls. I guess they act as a sponge.
I am now building a tri and I wonder if there is a purpose built material or product that collects condensation by the same principle, I guess a bit like the material that you find in some pill bottles that is there to protect against damp.

,

Originally Posted by Chris Ostlind

Yes, and it wold be especially possible in a climate like the one in which you live. You have considerable ambient humidity. That humidity (water vapor) is contained inside the hull of the ama when it is sealed. Sitting out in the the hot tropical sun, the contained air and water vapor rise in temperature and the water condenses out of the air and settles first on the interior sides and then drools down to the bottom. This effect is enhanced by the fact that the air in the contained interior volme will also experience a rise in pressure from the expanding gasses.

Limber holes in the interior bulkheads and a thoughtfully placed drain plug system will allow you to drain off the condensed water vapor and keep your amas light in weight and as buoyant as possible.

Really big amas might require you to install removable deck plates for access and make a routine inspection of the interior and siphon the water off manually or electrically.

If you are talking about a wooden multihull, then sitting water in the amas is asking for a rotten core as water will, eventually find its way into the wood and just sit there creating huge problems for the future.

Chris

[sailrjim]

Originally Posted by Chris Ostlind

..............the contained air and water vapor rise in temperature and the water condenses out of the air and settles first on the interior sides and then drools down to the bottom. This effect is enhanced by the fact that the air in the contained interior volme will also experience a rise in pressure from the expanding gasses.

Chris

Chris, I understand everything in your post except the quoted part. My expectation is that the water vapor will condense (first on the interior surfaces) only when the temperature of the interior surfaces of the ama drops below the dewpoint of the air/water vapor mixture.

In addition to the pooling of water in low places, another effect that I think would be of concern is that water vapor is forced into the core as the internal pressure increases much above the external (ambient) pressure. Mass transfer (water vapor) is driven by pressure differential.

Do I misunderstand? Would you please clarify?

Just my $.02.

[sailrjim]

Originally Posted by jedkins

................. I wonder if there is a purpose built material or product that collects condensation by the same principle, I guess a bit like the material that you find in some pill bottles that is there to protect against damp.

,

You might try searching on the word desicant. Silica Gel in crystal form is one commonly used when shipping/storing electronics products. Most disicants seem to work in one of two ways. Some are crystalline materials that dissolve by absorbing moisture (water vapor) while others absorb the vapor and remain in a solid state (crystaline form). The latter can expel the vapor when exposed to higher temperatures and can thus be regenerated for reuse. And then there are those who place a few grains of raw rice in the salt shaker to prevent the salt caking. By my experience and by reason, such products are most practically used where the amount of vapor is limited, i.e. in an enclosed space.

Beware: some desicants may contain strong agents such as acids that can damage surfaces upon prolonged contact.

Jim