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jarcher 06-14-2009 10:16 AM

Looking for a dryer boat - desiccant?
Hi all, for a boat with the Nicro solar vents running, is there much point to either a desiccant or a powered dehumidifier? It seems the vents are drawing moist air through the boat anyhow.

I installed 1 vent on the forward hatch and two aft at the rear of the cabin. It still gets stuffy, which I guess is normal, but papers left inside get moist. Is there an effective way to keep the air dryer?

I have shore power available but my boat is not wired for 110VAC, yet.

Mipcar 06-14-2009 10:32 AM

I use those desiccants (I'm assuming you mean those white crystal in tubs) and it helps with my boat. Not some much in cold weather as they are more designed to suck up water vapour.

Fitting one of those solar vents helped immensely plus I fitted more static vents in the hatchway.

I was thinking of trying one of those mains powered (I was going to say 240V but you guys are a bit poor on electricity over there lol.) Wardrobe heaters, they have a ceramic coil and are designed to left on for long periods providing a low heat.. In a closed up boat they would help a lot.
You could just leave the forward hatch slightly open to feed in an extension lead from your shore power.


sailaway21 06-14-2009 11:57 AM

If you use a desiccant, I'd recommend that you use the kind that fit over a coat hanger and hang them in your lockers. You can find them at your local superstore. I think the tubs, used in the cabin are going to be a pain to deal with, and ineffective unless you really button the boat up. You really don't want the watery residue in the bottom container spilling while sailing; it's nasty stuff.

I'm assuming you have the forward fan on intake and the aft two on exhaust so as to set up a air flow pattern. If they are not moving enough air you might want to go to a higher capacity 12 volt fan vent powered off your batteries. I would set it up with perhaps a solar activated relay so that it switches on at sunset and off at sunrise. Your problem occurs because you're not getting enough circulation in the evening hours when the temperature drops to the dew point. If you're down south, you're going to have a certain amount of humidity that is just unavoidable but you should be able to keep your charts from resembling bounty paper towel.

One other thing that occurs to me is that Nicro solar vents do go bad and, in my case, I assumed it was just the battery which I easily replaced. But I found that even with the new battery it would not run for the complete night which is way out of spec. for them. I think you're supposed to get two or three days out of a full charge. Mine did that for awhile, about a summer, before giving up the ghost completely. I can only assume that the motor was in it's death throes, it was a bit noisy, and that it was drawing higher than normal amps as dieing motors will do, and running out of juice over night. In the sun it operated normally. I'd check them out early in the morning before the sun comes up to ensure they've been running all night without a problem. I replaced mine but there is a thread here, somewhere, on re-powering them with a cheap motor from Radio Shack or something.

jarcher 06-14-2009 12:13 PM

Yes, the forward fan takes air in and the aft fans exhaust it. The vents are brand new, and I have seen them running in very cloudy weather and in rain, si I think they are working correctly.

My boat is in Rhode Island, but it has been pretty rainy here of late. So you think I just need more air flow?

Selkirk 06-14-2009 01:03 PM


Originally Posted by jarcher (Post 496200)
.........which I guess is normal, but papers left inside get moist..................

I'd be real surprised if you ever lick this problem. Doesn't mean that you can't enjoy the boat otherwise, though.:)

sailaway21 06-14-2009 01:24 PM

It's impractical to keep the boat air-conditioned which is just dehumidification followed by air cooling. Within minutes of opening it up you're going to have an equilibrium between outside conditions and inside conditions. And even if you kept it buttoned up, it's going to get awfully hot in there later in the summer.

I suspect that the seasonal weather is playing havoc with you. Damp spring air is what cause me the biggest mold and condensation problems here in Michigan as well. Good ventilation is the only really effective way to keep ahead of it. In short, you apparently need more flow.

If you've got good ventilation while you're using the boat, and you button her up at the dock in low humidity conditions the desiccant might keep up with it, especially in the warmer summer water. The cold water against your hull now causes the warmer moist air inside the boat to drop below the dew point as well.

I'd focus on getting more ventilation. I don't think anyone will disagree with me in saying that you cannot have too much ventilation on a boat.

Capnblu 06-14-2009 01:33 PM

I bet Smacky would probably disagree with you Sway, but probably none of the sane people. hahaha

Mipcar 06-14-2009 07:00 PM

Sometimes in the good weather when I am just working on my boat in it's pen I bring down a mains powered portable fan and sit it in the open front hatch.
It draws air in from outside and forces it through the entire boat.
Freshen things up and achieves more air turnover in 30 mins then I'd probably get from half a days sailing with the hatch open.


Maine Sail 06-14-2009 07:25 PM

Keeping your bilge dry will go a LONG way towards a less humid interior. Desiccant won't do beans with a large volume. Sure it works in drawers and somewhat in a closed hanging locker but with 80-90% humidity it won't really touch it. You could put 10 boxes of kitty litter (basically what the expensive marine store desiccants are) in your boat and still have it damp.

Get the bilge dry and you'll see an improvement.

jarcher 06-14-2009 09:46 PM

In the bilge, I always have about half an inch of water or so. The pump is mounted directly to the bottom (I used 4000UV to adhere the pump base directly to the bilge bottom) but it can't pump it completely dry.

I am not sure where the water is coming from. I had the pump out for a few weeks, and I would clean the bilge with a sponge, but it seemed that about half an inch would always come back. That's all, it didn't get any higher. We had quite a bit of rain, and I have some very small leaks yet to fix, but if the water was leaking in why does it not get higher than half an inch over time?

If the humidity inside the boat is the same as out side, is this an indication that more air flow won't make a difference?

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