wave activated bilge pump

[sarabande]

Seeing the Orkney marina pictures, and wondering what one could possibly do in such a situation, I remembered this (or a similar) device which might have helped.

All hands to the pumps

I recall that a Scottish Bishop was developing a similar device about 30 years ago.

 

[nordic_ranger]

Have used one of these for a number of years on a moored dinghy. They do work well and are very efficient in removing rain water. I do not think they would be much good in a storm, not sufficient pumping capacity.

 

[sarabande]

Then, do you reckon there is a need for a self-powered bilge pump, which could deal with more than rainwater ? I'm thinking of using a boat's motion in the vertical, or side to side planes.

 

[nordic_ranger]

I would be worried about useing the pump in any boat that has a stern tube or skin fittings but I guess if you get a large leak from any of these and you are not onboard your doomed anyway. The pump which I still have was used when on a mooring and would be absolutely useless in a Marina.
What were your plans ?
I developed to prototype stage a wind pump that did a similar job and in many ways was more effective than the wave pump. My theory was that most times when you need a pump working it is also windy with rain and if no rain it still worked with wind.

 

[sarabande]

This is going to be a bit of an unstructured chain of thought posting !

Like, I guess, many boat owners, I have an electric bilge pump on a float switch for dealing automatically with largish amounts of water ingress, and a switchable pump as a second line of defence.

When I get on board, the first thing I do is check the battery levels, then run the second pump for about 15 seconds to clear the bilges.

To cope with non-attended times, I was thinking of using the "free" energy of a boat's movement in the pitch and roll axes (relative to the outside water level) to operate a small non switched pump to deal with any leak, whether minimal from e.g. rain, or from the extreme conditions shown in the Orkney photos. In the latter case it's a wild guess but would 20l/min have made a difference to keeping the boat afloat ?

You made a good point about leaks being most likely in adverse weeather conditions, and when there is a lot of free energy available from wind, but I am thinking of the times that one can have a calm, yet the boat can be moving around in a residual or incoming swell. Wind energy requires some form of rotational device to convert a linear movement (air) to another linear or rotary movement at the pump.

The "green energy" people have invested zillions of squids into extracting energy from wave movement, and there must be a number of designs which could be scaled down to produce a form of energy suitable for moving water from the bilges back to the sea.

Presntly, I am looking at a "column of air" device which, by movement of wave or boat, compresses air to operate a rotary or rocking bilge pump, through an intermediary air tank. The idea being that air pressure is gradually built up (or quickly in rougher conditions) in the tank which, when a sufficient air pressure is reached, operates the pump. I came across an 18th century water pump in Versailles which used air pressure to power it, but the amount of energy used there is outside boating conditions.

The aim is a nil maintenance, long-life device, with a very low potential for failure.