Computer 12 fans for better airflow

[slawosz]

Hi,
the condensation on my boat is unbearable and I am thinking about employing 2 computer fans connected to the battery (which is connected to solar panel) to create air flow.
1 fan would bring air in, second would bring air out. Only during time ashore. Is it a good idea?

 

[LittleSister]

Should be possible to sufficiently ventilate to avoid problem condensation without fans, but fans might be cheaper than more vents.

Is your cabin roof insulated?

Make sure the boat internals are cleaned of dirt and especially salt (rubbed off clothing etc.). Take wet oilies, etc. home with you.

 

[ctva]

I'd just go with one fan to extract in the forward part of the boat and allow the natural airflow from the main hatch work. Computer fans shift a large amount of air.

We have one solar vent in the forepeak which keeps a 34' dry and fresh.

 

[tudorsailor]

Do you have Dourades? I ask as I have just (3D printed) made a gizmo to hold a computer fan inside the tube of the dourade. My aim is to get some airflow when it is hot and there is little wind. I will wire into the light supply but use a wireless remote to turn on and off.
TS

 

[Roberto]

Hi,
the condensation on my boat is unbearable and I am thinking about employing 2 computer fans connected to the battery (which is connected to solar panel) to create air flow.
1 fan would bring air in, second would bring air out. Only during time ashore. Is it a good idea?

It might be even better if they only worked at night, in order to fill the boat with colder night air and keep it there during daylight.
It might seem counter intuitive (as many people fully open the boat during sunny, warmer winter days to change the air for example, then close everything at sunset), but cold air can keep a lot less moisture than warm air.
If one fills the boat with warm air, it will contain relatively more moisture, during the night the temperature drops, humidity will condense and the boat fills with water. Example, take 100% relative humidity, saturated air at 30°C will hold about 32 g/m^3 of water, if one brings it to 10°C saturated air will be able to hold only 10 g/m^3 --> you have 20 grams of water droplets.
Viceversa, bring in 1 m^3 of saturated air at 10°C, then bring it to 30°C and you have a very dry 30% relative humidity.
Search "psychrometric chart" for examples with RH different from 100%, the principle is the same.

 

[oilybilge]

This has been tried already and it's said to work. I hope so anyway, as it's on my to-do list for this year.

Due to the set up of my boat, I'm going to install one computer fan near the bows under a mushroom vent, and another in the main cabin. Both will be set to extract. The idea is the air will enter amidships through the passive vents in the heads and the hanging locker, and exit by way of the powered vents. And if that doesn't work it'll be easy enough to experiment with other configurations. You just have to turn the fans upside down to reverse the flow.

 

[dankilb]

Do you have Dourades? I ask as I have just (3D printed) made a gizmo to hold a computer fan inside the tube of the dourade. My aim is to get some airflow when it is hot and there is little wind. I will wire into the light supply but use a wireless remote to turn on and off.
TS

I’d be amazed if any boat with dorades had serious condensation problems! (Although the idea of a fan to aid ventilation for comfort sounds great)

 

[V1701]

Assuming you mean when you're on board producing the condensation they will help but I doubt be sufficient to do away with condensation altogether. For that you'd need to use a dehumidifier and close all the vents. Some will tell you that successful use of a dehumidifier necessitates hermetically sealing your boat and that unless you are able to do this you're attempting to dehumidify the earth itself and it's a waste of time & electricity. This is not the case - dehumidifiers make a huge difference to comfort aboard. You should choose the dessicant type if it's for use in winter, compressor dehumidifiers are not very effective at low temperatures. When the boat is left if you leave vents open you shouldn't have much of an issue with condensation because everthing will usually be at the same temperature hence little opportunity for it to form...

 

[FairweatherDave]

Interested in this computer fan idea and have heard about it before. Bit confused that a computer fan from a 240 volt mains supply would work on 12v. Also what sort of control do you use so that it would cut in and out and not drain the battery. (Apologies for not googling)
The condensation in my forecabin recently is the worst I have seen....no dehumidifier or heat and boat ashore with same vents open. I m not aboard.

 

[oilybilge]

Interested in this computer fan idea and have heard about it before. Bit confused that a computer fan from a 240 volt mains supply would work on 12v. Also what sort of control do you use so that it would cut in and out and not drain the battery. (Apologies for not googling)
The condensation in my forecabin recently is the worst I have seen....no dehumidifier or heat and boat ashore with same vents open. I m not aboard.

Computer fans are typically 12v. They also draw little current, and are happy to run continously, and cost less than a tenner. But yes, eventually they'll drain your battery, so you'd probably want a solar panel to top it up.

 

[tudorsailor]

I’d be amazed if any boat with dorades had serious condensation problems! (Although the idea of a fan to aid ventilation for comfort sounds great)

Yes the fan is for comfort in hot weather. Something to while away the time while not sailing was to make the surround for a standard computer fan.

TudorSailor

 

[dslittle]

Assuming you mean when you're on board producing the condensation … dehumidifiers make a huge difference to comfort aboard. You should choose the dessicant type if it's for use in winter, compressor dehumidifiers are not very effective at low temperatures. When the boat is left if you leave vents open you shouldn't have much of an issue with condensation because everthing will usually be at the same temperature hence little opportunity for it to form...

We lived on board for five winters in the UK. The above ensured that we never had condensation over that time.
Mind you, the BEST solution is to move away from cold winters!!!

 

[Neeves]

The term computer fan is slightly misleading. They come in a variety of sizes from around 3cm square, maybe smaller, to at least 12cm square - the bigger the fan the higher its amp rating - they are all 12 volt. The smaller ones can be a slightly different design to the larger ones that all have a square housing. The small ones were common in older laptops - I've not tried to recycle a lap top recently - so don't know what they are like. Tudor Sailor's round fan, or the round housing - I've not seen before. How quickly the fan drains your battery - depends on the size.

We don't have condensation problems but have the fans wired for the fridge/freezer.

We sit on a swing mooring or at anchor consequently the bow largely points to windward and we have used ducting to draw fresh air from the bow, the bow locker, to the rest of the boat. We have a fan drawing the air in and then 2 individual fans (within the ducting) to direct the airflow over the fridge and freezer compressors and we have an extra fan drawing the air from the back of the fridge. The fans are wired into the fridge/freezer circuits so only operate when the fridge is in its 'on' cycle. Most, many, monohulls might have difficulty installing ducting from the bow locker (easier on a cat) but maybe through the bilges? and then up 'into' and through the cabinetry?

We have a couple of larger fans wired to allow plugging into a cigarette sockets for hot weather - but we seldom use them.

Jonathan

 

[HissyFit]

You just have to turn the fans upside down to reverse the flow.

Assuming that the fans are secured in place, reversing the polarity on the connectors would be simpler.

 

[V1701]

Interested in this computer fan idea and have heard about it before. Bit confused that a computer fan from a 240 volt mains supply would work on 12v. Also what sort of control do you use so that it would cut in and out and not drain the battery. (Apologies for not googling)
The condensation in my forecabin recently is the worst I have seen....no dehumidifier or heat and boat ashore with same vents open. I m not aboard.

As pointed out they run off 12v (computers also usually actually run off somewhere between 12 & 20 volts not 240). I have one running 24/7 venting my home made separator loo to the outside, it works very effectively negating any smells (and it does smell with the fan off so they really do work). Buy a good quality one not the cheapest you can find, still should only be a tenner or so each unless they've gone up a lot recently...

 

[oilybilge]

Assuming that the fans are secured in place, reversing the polarity on the connectors would be simpler.

That doesn't work with computer fans. They have brushless motors that can only turn in one direction

 

[FairweatherDave]

So I need to brush up on my amp hours calculations, but I could probably install a fan from an old pc and leave it on 24/7 and if the battery is topped up with a 50w solar panel (in a UK winter) then no need for a timer switch?

 

[HissyFit]

That doesn't work with computer fans. They have brushless motors that can only turn in one direction

Brushless DC motors can be turned in either direction. It is just a matter of timing which poles are energised in which order. Even if the computer fans run in one direction in their usual intended application, they can be hacked with the right control circuitry.

https://studyelectrical.com/2015/06/how-to-change-direction-of-dc-motor.html

 

[dancrane]

Slawosz, I thought for a long time about fitting a solar-vent for my Achilles...

...but the better solution by far, was simply to stop the rain getting in.

The big lazarette lids on my A24 were loose, as probably yours are too, held in place purely by gravity. I discovered that hard rain hammering down on the aft deck would bounce up into the cracks between the locker-edges and the lids, and some would drip into the lazarette below...

...and there's no structural division between the lazarette and the (lower) bilge beneath the cabin floor, so the leak in the stern caused damp in the cabin.

After several seasons finding and trying to eliminate other leaks, I put a small tarpaulin over the aft deck, and then had dry bilges (and no condensation) for months at a time.

There's no shame in an Achilles having leaky windows and stanchion bases, and nor is there any universal solution - at least, the owner's group hasn't heard of it...but a big source of rainwater ingress is those loose lazarette lids.

Also - there had been no attempt to seal the significant crack between the steel mainsheet traveller, and the glassfibre deck surrounding it, behind the cockpit seating. Really poor build-quality (probably home-built), but not a difficult thing to improve.

On my Achilles, the three-section square-profile tubular traveller also leaked, so I caulked the joins. If you have the same shape of traveller, the design forms a gutter and rain dribbles gradually but inevitably to port and starboard, from where the 40+ year old sealant may be letting water inside the tubing, and straight through the deck.

 

[oilybilge]

Brushless DC motors can be turned in either direction. It is just a matter of timing which poles are energised in which order. Even if the computer fans run in one direction in their usual intended application, they can be hacked with the right control circuitry.

https://studyelectrical.com/2015/06/how-to-change-direction-of-dc-motor.html

Right. So it's NOT a simple matter of reversing the polarity, as you claimed in your first post.

Yes, you might be able to hack into the control circuitry and reverse the direction of the motor. But I'm sure your hasty googling also revealed some of the other problems which might then occur.

OR ... you could undo four nuts and flip the whole unit over, a job that would take maybe a minute.