Desiccants for keeping boats damp-free

[johnpye]

Does anyone have any experience of using desiccants in bags to keep the boat dry over winter?

We've been doing some tests that are encouraging for smaller boats, but would be very interested in any practical experiences.

Currently we are thinking along the lines of a 1kg bag for a boat up to about 30ft. Could be handy where there is no mains power available for a dehumidifier.

 

[Rafiki]

Dessicants

Yes I have used these over the last 4 winters, but mind you I have also removed all upholstery, clothes books etc , and to provode more ventilation I've put a temporary washboard with a bigger grille in place, opened teh vents and even removed a couple of the blakes seacocks ( they need to be re-greased each year so might as well come out for most of teh winter) you will of course have gathered that teh baot ais out of teh water for the winter.

I now buy a tub of the dessicant (2 kg?) and this lasts all winter. I split it into two containers which were boaght with bags of the stuff and change it about every 6 weeks.

It works for me but as I say I pretty well strip out the boat in the winter.

 

[Cantata]

We leave vents cracked open bow and stern that ensure a flow of air through the boat. We never take cushions etc home but do stand them up on edge. No dehumidiers, no heating, no dessicants...and never had any problems with damp.

 

[reeac]

Our first boat came complete with desiccant containers so I used them for a couple of seasons and then gave up. We use an overall cover with good ventilation plus a winter washboard with lots of holes in it, log transducer withdrawn, upholstery tilted on edge and all storage spaces left open. I bring all the upholstery home in the Spring for a quick sponge over followed by a few days for it to dry. No heater or dehumidifier and no problems whatsoever with damp or mould.

 

[maxi77]

At the end of the day there is no substitute for good ventilation

 

[oldsaltoz]

When we owned a 30 footer we used to hang a stocking over the galley sink filled with the crystals from large transformers.

Worked well, but you do need a lot. Just put them in the oven to dry them out and re use.

Avagoodweekend......

 

[pheran]

We have always used plain, ordinary cooking salt rather than fancy desiccants. Available from supermakets in large bags for very little money. Place a large soup-type dish*, half full, in each of the main cabin areas. Water collects on top of the salt so you can see what has been extracted from the atmosphere. Renew the salt at least once during the winter or when it becomes saturated. Worked for us, ashore or afloat, for the past 30 years and we have never had to take upholstery etc home.



* best use plastic (tupperware container?) or old dishes because the salt may harm the glaze on posh dishes.

 

[entrecour]

To ventilate or not with dessicants?

Should one seal the boat if working with dessicants or keep it ventilated?

If the boat is kept ventilated won't more damp air be able to circulate?

 

[johnpye]

Thanks for the useful responses.

 

[Ifraser]

are you drying the boat or the world..??

Yes I have used these over the last 4 winters, but mind you I have also removed all upholstery, clothes books etc , and to provode more ventilation I've put a temporary washboard with a bigger grille in place, opened teh vents and even removed a couple of the blakes seacocks ( they need to be re-greased each year so might as well come out for most of teh winter) you will of course have gathered that teh baot ais out of teh water for the winter.

I now buy a tub of the dessicant (2 kg?) and this lasts all winter. I split it into two containers which were boaght with bags of the stuff and change it about every 6 weeks.

It works for me but as I say I pretty well strip out the boat in the winter.

From readig a lot of previous threads on this topic... if you are ventilating the boat then a dehum or crystals are a waste of time as they are just sucking moisture from the atmosphere... personally I rely on ventilation but I'm just relaying what I've picked up on these forums before... cheers Iain

 

[Poignard]

From readig a lot of previous threads on this topic... if you are ventilating the boat then a dehum or crystals are a waste of time as they are just sucking moisture from the atmosphere... personally I rely on ventilation but I'm just relaying what I've picked up on these forums before... cheers Iain

I agree with that. Dehumidifying machines and crystals will only succeed if the space is completely sealed , otherwise you are attempting to dehumidify the world's atmosphere.

Plenty of ventilation is the best answer, with air moving throughall parts of the boat.

When did you last see condensation in a bus shelter?

 

[srm]

In the days of wooden boats designers and builders knew that ventilation was essential for the well being of the boat and its contents. Plastic boats generally rely on opening hatches and windows, so when closed up for security, or to keep the rain out, they soon build up a humid atmosphere ideal for mould and rot to flourish.
The simple answer is permanent water trap ventilators that will allow a sensible air flow from bow to stern. Proper 'Dorrade' type vents are required and not those silly little dish types that have such a narrow slot for air to get through that none does unless there is a big pressure difference. With good ventilation interior cushions etc can be left on board provided they have not been impregnated with salt as salt will soak up any moisture in the air.

My approach is good ventilation plus a low level electric heater if mains power is available. I use the low wattage tube type just to keep the chill off, but ventilation alone will work.

If you do go for desiccants or a de-humidifier your boat needs to be hermetically sealed so as to be 100% air tight, otherwise your system will be trying to dry the global atmosphere as it seeps in and out through cracks around hatches and the odd token ventilator that the builder may have fitted and thus is doomed to failure.

Hope this helps.

 

[johnpye]

Should one seal the boat if working with dessicants or keep it ventilated?

If the boat is kept ventilated won't more damp air be able to circulate?

I would have thought yes, so you theoretically should seal up if you are dehumidifying, and that is the view of desiccant air drying specialists I have spoken to. The amount of moisture that can be absorbed by a kilo of desiccant is fixed, so it makes sense to try to control the atmosphere inside the boat without bringing in possibly moist air from outside.

But there may be a down side, and it is partly to get the experience of others that I thought it worth 'airing' the subject.

When did you last see condensation in a bus shelter?

On foggy days, I think you can see condensation everywhere - even in bus shelters

So maybe it rather depends on the weather and where you are located....