A bilge-full of condensation?

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dustysheehan

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Hi all,

I’ve left my boat afloat for the winter in Sweden and will be away from it for 2.5 months total - left it mid December and will be retuning end of Feb / beginning of March. I found myself concerned that over the course of those few months condensation from the inside of the GRP hull, which flows down into the bilge, might fill the bilge to overflowing. I feel the risk is probably minimal - bilge is at least a couple hundred liters and so would require a minimum of 3 liters of condensation run off a day - but wanted to get some feedback from others. Just looking for a simple “Nah dude - no chance in hell there’s that much condensation” or “it’s well within the realm of possibility”.

Thanks all.
 
More likely to fill the bilge from leaks than condensation. The list of possible places to leak is almost endless, whereas a naturally ventilated boat will be at little difference in temperature inside the boat and outside, so little condensation will result. Placing heaters or dehumdifiers alters this balance and can increase the flow of moisture into the boat and cause other problems like the units catching light.
 
It's the occupants that normally create the condensation. As stated above, if adequately ventilated, condensation isn't normally an issue.
 
If the boat is sealed up and unventilated the H2O contained within will be free to evaporate in warm weather and then condense onto internal surfaces when outside temperatures are cold, in a constantly recycling system with no additional water being present. If you are on board, obviously your breath will add some water-vapour to the environment. In a sealed environment like this, some form of either mechanical or chemical de-humidifying will remove the water.
On the other hand, you could make sure that the boat has a reasonable through-flow of air to provide ventilation, which will ensure that your upholstery, soft furnishings, headlinings etc., will not be negatively affected by water-laden air. Bear in mind that the winters in Sweden tend to be colder and dryer than the mild and wet ones that we experience in these islands. Constant air-changes, consisting of cold dry air, will be much better for your boat than keeping it sealed up like a drum.
Threads on this subject come up fairly frequently on the forum. A quick search should reveal some advice on ventilation; such as fixing temporary covers over hatches, ports, etc., in order to leave them open while at the same time preventing the ingress of rain, snow or pests
 
Theory aside, what's the weather like? Is it even above freezing? Icicles are a bigger risk maybe?
 
One advantage of properly cold winters is that, once the humidity that's there has condensed and frozen, things tend to stay pretty dry - sub-zero air just can't hold much damp. The trouble will come when it gets warmer and rainy, but not enough to sink the boat unless the rain or the sea is getting in.
 
Bear in mind that an auto bilge pump is only a good thing if you have a way to keep the battery topped up or have a very good non return valve. Often the pump will drain the bilge into the outlet pipe, which will then seep back in via the valve until it triggers the bilge pump again. It doesn't take a lot of this to drain a battery since raising the level of water by a metre or so is a lot of work. Needless to say, short pipe runs help here too but that's not always a choice.

But back to the original question, no, it's a non issue. We use our boat most weekends over winter and still don't have much moisture in the bilge with us all breathing.
 
Great. Thanks all - I appreciate the feedback. It sounds like the condensation shouldn’t be a problem. Really grateful for the helpful!
 
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