Dehumidifier crystals and damp

Marakei

Marakei

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The inside of my boat has got rather damp and mouldy this winter [and probably most winters for the past 51 years, judging by the amount of old mould speckles].

I try to air her out but am not in a position to do it very regularly.

Later this month I intend to clear the interior out, so I can paint it and do some varnishing, and I'd like to try and stop the mould recurring after that.

I wonder whether putting some boxes of dehumidifier crystals around is likely to help significantly, and whether anyone can recommend a brand, as there seem to be loads about.

Any other tips welcome.
 
The solution to damp and mould is copious ventilation. If you can't achieve that, the alternative is to hermetically seal the boat and use some dehumidifier crystals, but you may well need a lot of them.
 
pvb said:
The solution to damp and mould is copious ventilation. If you can't achieve that, the alternative is to hermetically seal the boat and use some dehumidifier crystals, but you may well need a lot of them.
Click to expand...

+1 Totally agree with everything pvb is saying. Never understood why people buy expensive dehumidifiers, put inside what are for the most part air leaky boats and congratulate themselves on the amount of water they produce which for the most part has migrated from outside
 
akyaka said:
+1 Totally agree with everything pvb is saying. Never understood why people buy expensive dehumidifiers, put inside what are for the most part air leaky boats and congratulate themselves on the amount of water they produce which for the most part has migrated from outside
Click to expand...
Because it works, and is much easier than fitting a cover with the mast up and leaving the boat open to others, not to mention wildlife.

I use crystals in the cockpit locker, which doesn't connect with the boat. I suspect their usefulness depends on the size of the boat. I used to keep my Sadler 29 fresh with them, but took all the furnishings and electronics home, which I no longer need to, thank goodness.
 
Would echo the above, ventilation is key.
Many do not but I take everything out over winter and fit a washboard for the winter with big vents in it (I don't have power over winter).

Come relaunch there is a little mould I have to remove with standard mound killers but nothing too serious.

The alternative I would consider is leaving everything on board , sealing the boat up and running a dehumidifier all winter.

I have done both.
 
Crystals are a waste of time, maybe a cupful of water in weeks. An electric dehumidifier is what you need. A good litre or so overnight. Boat will be bone dry, warm and with zero dampness or mould. Good Ventilation is the next best thing, and is the answer if you do not have access to shore power, but sealing the boat and putting crystals on is almost as bad as sealing the boat with nothing.
 
Thank you everyone for useful advice.

I can see that the crystals would help in a small space like a locker but might not do much in a larger space.

Improving ventilation via the washboards and fore hatch seems the best option.

I can't run a dehumidifier continually, as my electric connection is shared, but I could seal off the ventilation and use one overnight every couple of weeks.
 
De-humidifier is the way to go.

Climb on board a boat with one on today (February) and its a different world. Dry, warm and smells pleasant, summer never leaves. external canvas dries out really quickly (as it is being dried from the inside) so no creeping green on the canvases. All goes to preserve the resale value and appearance.

Crystals are a waste of time, they are completely overwhelmed in the average boat. On a boat still on the water or kept adjacent to the water the crystal based ones last 24 hours.

Ventilation is the next best option, but the outside roof of my house, the trees in the garden and the fences are all well ventilated and are all green. So whilst it prevents mould it does not prevent flora and fauna.
 
I have in the past used crystals in my Hunter 490 when she lived in a closed barn which reduced ventilation but also produced a surprising amount of condensation. I found that they worked well for keeping in top of condensation - a little water produces a lot of damp smell - but the boat had to be as dry as possible first, so dusty bilges were essential.

Now she lives in an open barn with a good draught and stays bone dry without assistance.
 
Agree that if mains power is available, then a desiccant dehumidifier works well in a sealed boat. I have a barometer / hygrometer on board, and in the lovely damp Scottish winter, it will read 85% humidity. Running the dehumidifier at the middle setting keeps it below 60% and noticeably 'non damp' when I step aboard. I was sceptical myself, but the results prove otherwise.
 
stevie69p said:
Agree that if mains power is available, then a desiccant dehumidifier works well in a sealed boat. I have a barometer / hygrometer on board, and in the lovely damp Scottish winter, it will read 85% humidity. Running the dehumidifier at the middle setting keeps it below 60% and noticeably 'non damp' when I step aboard. I was sceptical myself, but the results prove otherwise.
Click to expand...

Remember that the relative humidity falls as the temperature increases, because warm air can hold more water than cold air, so it may be just the heat output of the dehumidifier that is reducing the RH for you. I have a sooper-dooper Mitsubishi compressor dehumidifier at home, and it's noticeable that just sticking on a fan heater for ten minutes can drop the RH from 85% to 55%, at which point the dehumidifier cuts out. The effect is much more pronounced in colder weather.
 
Yes, I understand that warmer air can hold more moisture, but although the dehumidifier will output air at +10c over the ambient temperature at the full setting, on the mid setting it doesn't seem to have a great effect on temperature. When I stepped on board last weekend, the thermometer was reading 4c and humidity around 58%, so it's not as though it had been heating the cabin temperature up to 18c or anything like that...
 
First thing is to get rid of as much water as possible at source.
That means zero tolerance of rain leaks etc.
Anything that is damp, take it home.
Anything not needed, take it home.
Get those sole boards up, dry everything. Clean it with some sort of anti mould while you are about it.

Ventialation is good, except when the air outside is 100% humid and at least as warm as the boat. That's typical of low-lying places near the water, e.g. your local boatyard.
So opening up the boat whenever the sun makes an appearance is great, but leaving it open afloat is not so good.
Dehumidifier works.
Running the engine up to temp once a week works too.
An eberbasto is the business.
But you still have to get there and run it.

Also don't create water in the boat just before shutting it up.
E.g, steaming bowls of washing up, using the cooker etc.

I used to use those moisure trap things in my lock up, they do help, but will only deal with a small quantity of water. They quickly fill up in an unsealed Pompey lock up with no damp course in the floor.
But if you could dry the boat and lock down all ventilation, I think they would work.
 
I am trying dehumidifier crystals this Winter. I left all the upholstery and sails on the boat and sealed up all the ventilators. I have four large containers, one fwd, one in the saloon, one in the after cabin (with the sails) and one in the engine compartment. I am careful not to leave water or damp things lying about. The boat is not 100% dry, but it isn't getting mouldy and smells fresh. The traps are steadily collecting water and I have had to refill them all with new crystals. I have found that the Kilrock ones (Wilco) seem to perform better than the Kontrol ones from Robert Dyas. Mains power is not always available!
 
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