Need proof that tin boats "sweat" - forming condensation?

[DaleH]

Imagine if you will, that your original tin hull maker, or you in a modification, made an entirely enclosed compartment in your boat that was filled with foam. It would create water by natural occurrence of condensation inside that compartment, forming on the interior surfaces of the aluminum skin.

Maybe this is the reason some brands, e.g., Tracker, are notoriously known for having water-logged foam in their hulls. As even US Composites, who sells premium 2-part 'closed cell' foams, states that ANY closed-cell foam can ingest or absorb water if allowed to be immersed in it continuously.

The picture shown is the amount of water - from condensation - that built up in my livewell that is up on the forward/raised bow deck of my 16' tin skiff ... in 5-days (of no rain at all either!). I had added a known water-proof hatch over the top so the compartment was completely sealed. I used a dry sponge to wipe out the water and squeezed it out over the plastic cup as shown. The picture of the well doesn't show it well at all, no pun intended, but there was actually standing water in the lowest corner of that livewell compartment.

Note that since adding a vent (used a 3/4" IF thru-hull) at the top of the livewell (now my dry storage compartment) that goes out to the vertical bulkhead of the well ... it now remains dry. The only condensate I've seen since was in a small plastic storage box placed in their.

Goes to show us that boats and their bilges need to 'vent to the atmosphere' to stay dry ...

 

[momule]

If the enclosed compartment is actually totally sealed off from the outside air it will only "create" as much moisture as is present in the material in the compartment. If the compartment and foam are 100% totally dry there will be no condensation occurring.

 

[PsychoXP18CC]

We fish the white bass spawn every winter on the Sabine River here in Texas. Two of my buddies run 15' and 16' jons, Alumacraft and G3 respectively, and both of their boats condense moisture like crazy on days that the conditions are right. I assume mine does too, but my Xpress has full decks and floor so I can't see it forming on the inside of the hull. I know there's flotation under all of it so I can only assume that mine is at least slowly taking on moisture.

It highly unlikely that we'd be able to seal a compartment off to where no moisture intrusion could take place so I think fighting with condensation would be a futile effort. I see it as the cost of doing business. My two buddies run smaller rigs than I, but they have the advantage of accessing their foam much easier than I can. When the time comes dealing with mine will be a PITA.

 

[turbotodd]

Have fished the White River in Arkansas quite a bit. Same deal. You can visibly see water condensing on the inside of the hull, basically any part of the hull that is at or below the water line. The conditions are almost always "right" for this to happen. Water temp in the 50's. Air temp in the 90's and 100's, with a dewpoint in the upper 70's and low 80's. Yes, it sweats inside the boat. After an 8 hour trip, I usually get close to a couple gallons out of the bilge, mostly condensation with a little bit of fish drip if we catch anything.

When the dewpoint is that high, it doesn't take much cooler water to make the boat sweat.

 

[KMixson]

I work as a mechanic at an airport on aircraft fuel trucks and the fuel farm. The fuel tanks and trucks are sumped out every day because of the condensation that builds up in them from sitting overnight and the cooling effect that takes place. The truck tanks are aluminum also. By law they have to be sumped from the tank low point before we can use that truck for that day. We also have sump separators on the bottom of the filter vessel that collects water if it passes into the vessel before making its way to the plane. Your air compressor in your shop has the same issue. It is good to drain the water out it often or it will start to rust inside and then get a hole in it. The trucks I work on have an air compressor system that have desiccant air dryers installed in the line as the compressed air leaves the compressor to keep the air lines,valves and other parts in the air system as dry as possible. Condensation is a big issue where I work.

 

[richg99]

Interesting discussion. I've never thought about it, since most of my prior boats were fiberglass. No doubt, the fiberglass boats "sweat" too. But, since they have ..some..insulating qualities in the 'glass, they might not sweat as much.

Another factor that would have reduced my observed condensation was that most of my boating was in Texas flats saltwater in the Summertime. The water temperature was normally in the high 80's to 90's.

Even with the very high humidity, and high air temperatures, my differential between water and hull wasn't very much.

You boaters in Northern climes have chillier water temperature/differentials most of the time.

Looks like a good reason to add some venting though, no matter where you live and boat.

Thanks for posting. richg99

 

[Al U Minium]

In time fibreglass, resin, epoxy all absorb water. If the enclosed compartment is air tight, made of aluminum, there will be no water absorption from atmosphere or submersion.

 

[DaleH]

In time fibreglass, resin, epoxy all absorb water. If the enclosed compartment is air tight, made of aluminum, there will be no water absorption from atmosphere or submersion.

I hear you ... but why then is soooooooo much foam in tin boats water-logged? 10X more than in frp boats, by my rough guesstimation ...

 

[DaleH]

If the enclosed compartment is air tight, made of aluminum, there will be no water absorption from atmosphere or submersion.

Doesn't make sense #-o ... that livewell that was converted to dry storage is fully sealed and water-tight, or as water-tight as the thick O-Ring seal allows it to be. I can literally spray down the hatch with a jet spray and ZERO water enters that compartment.

But until I added the vent ... she'd "make water" as KMixon's post says happens to aluminum storage tanks, 'every' day' to boot ...

 

[KMixson]

Actually Al U Minium is right. Air tight does not mean water free. There is water in the air you breathe. It is called humidity. You can't see it until in condenses. If you have an air tight compartment there is water in it. It will not receive any more moisture if it is sealed air tight. You can dry it as much as possible but there is still water in it. Even if you put desicant cartridges into the compartment it transfers moisture from the air to the cartridges. The moisture is still there but moved to the catridges. When you open the hatch humid air fills the compartment again. You can minimize the water content but can't entirely get rid of it. Nitrogen gas is used in a lot of applications where you want a compartment free of as much water as possible. Nitrogen is considered a dry gas.

 

[ADIBOO]

KMixson pretty much nailed what I want to say. If any amount of outside air can get into it at any point, their will be humid air in it.