Mould while cruising

We use mocrofibre cloths for that and change every couple of days. The condensation on windows is expected and the only moisture on the boat.
Personal hygiene is non-negotiable, this is where we live so we have to have showers. Its nothing like a week long cruise where you can choose to be dirty, this is every day life, we have no house.
Ventilation simply doesn't work, it makes the boat cold and damp and the problem worse as moisture then collects on things.

Sounding like the only sensible option is not to cruise Scotland for very long 🤣
 
Also, no sails or paddleboards etc. in the boat, we have a very large cockpit locker for that kind of thing.
 
lustyd said:
We use mocrofibre cloths for that and change every couple of days. The condensation on windows is expected and the only moisture on the boat.
Personal hygiene is non-negotiable, this is where we live so we have to have showers. Its nothing like a week long cruise where you can choose to be dirty, this is every day life, we have no house.
Ventilation simply doesn't work, it makes the boat cold and damp and the problem worse as moisture then collects on things.

Sounding like the only sensible option is not to cruise Scotland for very long 🤣
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What about fitting an extractor fan in the shower compartment/ heads ?
 
Boathook said:
What about fitting an extractor fan in the shower compartment/ heads ?
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The windows work pretty well in there and we keep the door closed after showering and sponge the walls and floor dry but I’m sure some moisture makes it into the cabin.
I guess one option is leaving the heater on 24x7 which we do in winter, but would be nice not to have to in summer. Its almost warm in Scotland today so perhaps summer is here and the problem wont be so bad 🤣
 
I think that all you can do in practice is take the sort of precautions mentioned, and give the boat a full airing in the odd half-hours when the sun shines.
 
Yes i think thats probably the conclusion. Its good to know I’m not missing anything and I’m hoping that the next few months remain warm enough to keep it at bay. Current plan is to head towards the tropics at the end of this season as i want some warm weather and swimming (without jellyfish!!)
 
I suppose the Hornblower solution of standing on deck whilst someone pumps sea water over you doesn’t appeal?
 
It does not 🤣

Ive probably made it sound worse than it is. The boat isnt really damp and theres no damp smell going below or anything but its definitely a problem we need to solve
 
johnalison said:
I think that all you can do in practice is take the sort of precautions mentioned, and give the boat a full airing in the odd half-hours when the sun shines.
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That's a common practice but based on wrong beliefs :( Warm air can hold a lot more water than cold air, with bright sunshine open everything and fill the boat with warm air at its relative humidity, when night falls close the hatches, then as temperature drops there will be condensation everywhere because colder air can bear lower relative humidity and the excess condensates. Google psychrometric diagram to compute amounts, it can be several grams per cubic meter.
 
Roberto said:
That's a common practice but based on wrong beliefs :( Warm air can hold a lot more water than cold air, with bright sunshine open everything and fill the boat with warm air at its relative humidity, when night falls close the hatches, then as temperature drops there will be condensation everywhere because colder air can bear lower relative humidity and the excess condensates. Google psychrometric diagram to compute amounts, it can be several grams per cubic meter.
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I can see that this applies to the volume of air, but there is also the matter of moisture adherent to all the surfaces in the boat, not to mention that contained in the soft furnishings, bedding and clothes, and possibly small collections of actual liquid. I have no idea how you would calculate the relative amounts, but my experience suggests that the boat seems drier after being aired. It can also seem that the salinity affects the dampness, to use a different term than humidity. Somewhere like Dover can seem perpetually damp, while we always found a marked change as soon as we entered the Baltic, even though the water was presumably just as wet.
 
johnalison said:
I have no idea how you would calculate the relative amounts, but my experience suggests that the boat seems drier after being aired.
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It does seem drier, because warm air can hold more moisture; but if you trap that air inside the boat (closing openings etc when temperature begins to drop, hey ho it s getting colder close the hatch/companionway) then every further decrease in temperature will condensate inside moisture into water, to a varying extent.
Likewise, let night air come into the boat, then keep the hatches closed during the day while the sun warms the boat, the air inside will be a lot (relatively) drier with no condensation whatsoever. Who does that? :)
 
johnalison said:
I can see that this applies to the volume of air, but there is also the matter of moisture adherent to all the surfaces in the boat, not to mention that contained in the soft furnishings, bedding and clothes, and possibly small collections of actual liquid. I have no idea how you would calculate the relative amounts, but my experience suggests that the boat seems drier after being aired. It can also seem that the salinity affects the dampness, to use a different term than humidity. Somewhere like Dover can seem perpetually damp, while we always found a marked change as soon as we entered the Baltic, even though the water was presumably just as wet.
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Yes, the crucial concept is that of dew point. Which is the temperature at which the water in the air will condense out (similar to crystallisation from a saturated solution). A surface that is warmer than that should lose any moisture, though that process will extract (latent) heat from the surface and add to the humidity if there is no ventilation. Thus it may eventually cease to be warmer than the dew point and evaporation will stop. This is how evaporation and condensation interact.
 
We cruised Scotland full time, at anchor, including winter, for a couple of years during the COVID lockdowns and had few problems.

I think the most effective measures were:
  1. Thick insulation
  2. Good heating
  3. Good ventilation, even when raining hard
  4. Little gas cooking
  5. No leaks, or water in the bilge.
 
Roberto said:
That's a common practice but based on wrong beliefs :( Warm air can hold a lot more water than cold air, with bright sunshine open everything and fill the boat with warm air at its relative humidity, when night falls close the hatches, then as temperature drops there will be condensation everywhere because colder air can bear lower relative humidity and the excess condensates. Google psychrometric diagram to compute amounts, it can be several grams per cubic meter.
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Following on from your (correct) comment: In Holland it is common practice in the winter to ventilate the house every day in cold weather - open all the windows when the house is warm, letting the damp warm air out, and cold dry air in - then close the windows again. The walls and everything in the house remain warm, so the air is soon up to a pleasant temperature again when the windows are shut. I believe the Germans do the same, and even have a word for it (which I can't remember)

I tried (and failed) to find a switch than would run a fan based on humidity outside vs inside, for a solar log kiln - something similar would be good on a boat too I think. Anyone on here clever enough with electronics to make one?
 
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lustyd said:
Dehumidifiers aren’t practical and airing doesn’t work.
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We decided to bring ours when we cruised in Scotland last summer. We'd go to a marina every couple of weeks and dry out the boat properly. That plus ventilation seemed to do the trick.

Much more of a problem here in the warm humid south (currently ABC islands). Relative humidity outside 100% most of the time, and definitely no affordable marinas within hundreds of nautical miles. So, we do the best we can with ventilation and vinegar. But it is a constant battle. I'm hoping that once our new solar panels arrive, we might have the surplus to occasionally run the dehumidifier through the inverter.
 
Thats depressing, i was hoping moving to the tropics would fix it 🤣 at least when we move south we can ditch a bunch of excess clothing so we’ll have less stuff cluttering the place up
 
KevinV said:
Following on from your (correct) comment: In Holland it is common practice in the winter to ventilate the house every day in cold weather - open all the windows when the house is warm, letting the damp warm air out, and cold dry air in - then close the windows again. The walls and everything in the house remain warm, so the air is soon up to a pleasant temperature again when the windows are shut. I believe the Germans do the same, and even have a word for it (which I can't remember)

I tried (and failed) to find a switch than would run a fan based on humidity outside vs inside, for a solar log kiln - something similar would be good on a boat too I think. Anyone on here clever enough with electronics to make one?
Click to expand...
Lidl recently sold this product by Auriol that claimed to assist with exactly this problem; the "Ventilation Monitor" part of the description. Not sure yet how effective it is...
Customer Service & Help - Lidl Great Britain
 
KevinV said:
Following on from your (correct) comment: In Holland it is common practice in the winter to ventilate the house every day in cold weather - open all the windows when the house is warm, letting the damp warm air out, and cold dry air in - then close the windows again. The walls and everything in the house remain warm, so the air is soon up to a pleasant temperature again when the windows are shut. I believe the Germans do the same, and even have a word for it (which I can't remember)
Click to expand...
Reinigensiedashausmitkalterluft.
 
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