Demonstrations and information about building a High Capacity DIY Electric Pump for Sail boats. This post includes in-action videos, a close-up video look at the system and advice on waterproofing the container, battery choice, an idea of circuitry, pump capacity and more.
Most of this article quotes Simon from the very useful Goat Island Skiff Group on Facebook.
“The idea for the pump came to me one afternoon when I was out sailing hard and had capsized a couple of times. At this point, I was getting tired from hiking and bailing and it occurred to me that it would be really nice to rest while an electric pump did the dirty work.”
Video showing what a high capacity pump can do to relax a sailor!
Detailed Video of Battery and Pump Setup is further down the page.
Video image can take a moment to load.
No boat has perfect behaviour when capsized or recovering. KNOW YOUR BOAT
There are a number of advantages to boats with buoyancy tanks in the ends. And some for boats with side tank buoyancy.
Boats with End Tank buoyancy are less likely to turn turtle and they have lower freeboard making it easier to get aboard after righting the boat. Also, they are far less likely to blow away from the crew. But they do make for more bailing.
On the other hand, side tank buoyancy has advantages and disadvantages too. The big advantages are that the boat comes up drier but it turns turtle much more readily. The centreboard can be hard to reach and the high freeboard means it can be difficult to get back aboard. And the boat is higher above the water with less boat in the water when capsized. This means it can blow away pretty quickly.
The important thing, whichever way the buoyancy is configured is to actually KNOW what your boat will do. Practice in realistic conditions. Certainly not with the boat tethered as it makes it much harder to get into most boats. Experience means you can plan around problems rather than be faced with the unexpected.
See our article about a DIY Transom Ladder for Sailing Dinghies with Dimensions
Simon Wrote:
Several people have asked for details of the electric bilge pump I built for bailing my Goat in a hurry. I put this little video together to show the basic idea
Careful design planning and precise center of gravity v.s. center of buoyancy calculations, otherwise known as luck came into play with location causing the pump inlet to float deep enough to suck water just fine. Sometimes it’s braced by other gear under the mid seat or I put my foot on it to keep it from bashing about the boat. A flooded Goat is not a very stable thing.
When the water is rough it can be a challenge to keep the boat upright while bailing at the same time. With the electric pump, I can focus all my energy on balancing the boat. This has not happened to me but if I needed to bail in a major hurry, like drifting down on a rocky lee shore, bucket and pump together make short work of getting the boat emptied.
I don’t have a number for the min depth of water needed for the pump to be effective. But, it’s not much deeper than the ply. Maybe 1/2-3/4″. Heeling the boat slightly and placing the pump in the deepest part gets most of the water out then sponge out the rest.
Technical Specs of the DIY Electric Pump for Sail boats
This section gives the basic requirements of the system and explains the advantages and disadvantages of lead-acid vs Lithium batteries for a boat pump system.
LITHIUM BATTERIES ARE NOT RECOMMENDED FOR THE CASUAL USER
See Explanation below.
Just make sure your container is watertight. I ven with a Pelican case the battery box and bilge pump get knocked around. Especially in a capsize and I did not want it popping open.
We do not recommend an Automatic switch for small boat Electric Pumps
I did not use an automatic switch. It’s too easy for an automatic switch to accidentally turn on or get damaged in small boats in an exposed location or not. The magnetic “key” is on a lanyard.
Battery Choice, lead/Acid or Lithium for a DIY Electric Pump for Sail boats
I recommend a small Sealed Lead Acid for those who are not set up to deal with lithium.
A small lead-acid is the way to go unless you are up to speed on lithium. Don’t need anything as big as a motorcycle battery if you are only daysailing or doing short trips where you do not expect to be bailing out many times.
I omitted that because I’m used to dealing with lithiums and am very careful to always start with a fully charged battery..
I would not turn this over to someone without lithium battery experience without adding the protection circuitry.
Even then it can bite you as Samsung is finding out. Maybe you are seeing the balance plug? The batteries shown are 3 cells. The charger uses the balance plug to make sure all 3 cells are kept at the same voltage.
Keep in mind is that lithium batteries are easily damaged by over-discharge. A commercial version of this thing would have automatic battery protection circuitry to limit over/undercharge.
If you have the knowledge and focus to handle Lithium, Current draw is around 3.5A. And I’m using lithium batteries capable of safely sourcing 100A+ so the battery does not change temperature due to current draw.
It gets a bit toasty if you leave it in the sun so I don’t do that. The unprotected model airplane lithium batteries are a fire risk if mishandled.
Circuit for the Electric pump for the Sailing dinghy
The circuit is just a magnetic switch activating an automotive 12v relay and a fuse between the battery and relay.
The switch I used is some generic Chinese manufacturer. Magnetic reed switches are used as window and door sensors in home alarms. Just do a google search and you should have no trouble ordering one.
Oh! In the video, I mention that I can put two of the lithium batteries in the case. The two wires you see are for a second battery, in parallel. I think I have the fuse on the battery side of the relay for maximum wiring length protection.
Video image can take a moment to load.
Pump Rating for a DIY Electric Pump for Sail boats.
A pump rated at 1000l/min would be great. Mine is rated at 1100gph (70 l/min no head). And it empties the boat in about 8 minutes. The Goat Island Skiff has 8ft long cockpit averaging a width of 3.5ft. It has built in buoyancy and floats as shown in the lead photo.
Practice capsizing so you are comfortable recovering and don’t expect a pump to do miracles
I’m quite light so the Goat can get to be a handful in strong winds. Reefing is great but planing at speed is better 🙂. Since almost all my sailing is in warm water I don’t mind pushing the boat and occasionally capsizing.
Capsize is just another maneuver.
If you have practiced!
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