Electric Propulsion Part 1

We have removed the old broken diesel engine from our Contessa 26 and are replacing it with an electric motor.  This post discusses how we came to that decision.

We sailed all last year without a working engine, which was fine as we were based on a swinging mooring out on the river Orwell.  Picking up the buoy with shallow water, flukey wind and lots of other boats around was sometimes exciting, but we survived.

The main thing which held us back without an engine was being unable to manoeuvre in small spaces like marinas.  This also put us off visiting some places like the river Deben where there are (apparently) strong tides and narrow channels.

What Are Engines For?

Sailors basically use their yacht engines for four different things:

  1. Manoeuvring in and out of harbour.
  2. Going along when there is no wind.
  3. Motoring or motor-sailing when the wind is unfavourable.
  4. Generating electricity.

People’s definition of “in and out of harbour” varies wildly.  Some people seem to arrive off Harwich and think “well, that’s the real sailing done, lets just motor the last five tedious miles up the river Orwell,” whereas we sometimes spend an afternoon just sailing up and down those same miles!   For us, the final manoeuvring under power is only likely to be a few hundred yards in most places.

Being able to go a long way when there is no wind is occasionally useful.  We once motored all the way from Falmouth to the Scillies at the start of a long period of high pressure, which meant we got a great week of settled weather once we were there.  If we’d had no engine we would have missed out on this.

Even when we had a working engine, we didn’t tend to motor into wind much, partly because we like the sailing and partly because the engine was so feeble (even once we’d fixed the overheating problem) that sailing was faster and more comfortable than motoring.  Our boat is definitely from the days when yachts had an “auxiliary engine” rather than a motor which would power you through anything.

Charging batteries is a useful by-product of running a diesel engine.  Virtually no-one sails without a host of 12V powered equipment these days, including lots of safety-critical items like navigation lights and radios.

The Plan

We are installing an electric motor powered by a 4.2kWh bank of Lithium batteries.  Data on how far this will get us is hard to find, but it should give us at least an hour of motoring at a decent speed, which should be sufficient for manoeuvring in and out of most harbours.

For longer passages (like motoring to Scilly in no wind, or traversing the Kiel Canal) we will run a small petrol generator which will power a battery charger.  This should allow us to run almost indefinitely, although the noise will be annoying.  Depending on how much power is being drawn by the motor, we may be able to stop the generator periodically every few hours and motor on silently from the batteries for a while.

We will charge the batteries from:

  • Mains power in marinas.  We should be able to go from empty to full in about 3 or 4 hours.  Maybe we’ll start visiting marinas more often!
  • The petrol generator, while motoring along (or if we are away from everyone in a remote place, or in a really noisy port I guess).  Again, should charge the batteries completely in 3-4 hours unless we are motoring hard at the same time.
  • Solar panels.  When we are sailing for the weekend every couple of weeks this might be enough by itself.  If we are living on board and sailing every day, it will probably need supplementing.

Our 12V lights and instruments will be powered from a separate 12V battery, charged by the existing wind turbine.  We will also be able to switch over to power everything from the propulsion bank as a back-up.

Man Power?

Before committing to the electric route, I built a Yuloh (sampan-style oar) which pushed us along ok for short distances, but we only really used it once.  It was very long to store on deck, and the mounting pivot got in the way of the tiller.  We decided that it wasn’t very practical as a means of propulsion, particularly as we are planning to transit the 100km-long Kiel canal, so the yuloh sadly became firewood.


We were originally planning to use an outboard motor for the long passages rather than a petrol generator, but:

  • A decent long-shaft outboard costs nearly £1000, whereas a petrol generator costs about £250.
  • The outboard motor would have been very heavy to lift on and off the transom, dangerously-so in any sort of sea.  It would therefore probably have lived installed on the transom where it would stick out getting in the way and incurring extra berthing fees.
  • The outboard would have required a large bracket to cope with our very overhanging transom.   The push-pit was also in the way of any motor-tilting mechanism.
  • The outboard’s propellor would have been quite shallow so wouldn’t have worked very well in waves, and it wouldn’t push any water over the rudder like the built-in propellor does.
  • The petrol generator will be a lot more flexible -for example we could use it to recharge the batteries in a remote anchorage if required.
  • The noise of the petrol generator will probably not be much different to a petrol outboard.
  • We’ll arrive with our battery bank full rather than empty.


We’re really looking forward to motoring silently into harbours under electric power.  We’ve already enjoyed the amount of engine-related plumbing, exhaust piping, seacocks, grease and spares that we’ve been able to remove along with the engine.  I’m looking forward to having a clean engine bilge with no grease and no stink of diesel.

There isn’t much information out there about this type of project, and it is all fairly experimental so we don’t know how practical it is going to be.   It is hard to estimate how far the batteries will take us, and how annoying the petrol generator will be.  But we survived all last year with no motor at all, so hopefully it will be an improvement on that!

Self Steering Part 1

I am attempting to build a wind-vane self-steering gear based on the “Quartermaster” design from the 1960s.

This is probably the simplest class of self-steering gear: a trim-tab on the main rudder actuated directly by a vertical-axis wind vane.  It was designed for a Folkboat, which our boat was derived from, so hopefully it will work on Lizzie.  This report from 1966 includes a description by the original designer, H K Wilkes who seemed very pleased with the performance.

One of the nice features is that it all just clamps onto the rudder stock, so you can remove it when you don’t need it without leaving lots of ironmongery sticking out of the back of the boat like most self-steering designs.

I’ve come up with a design based on the above report and two photos that I found on the internet.  I’m having to guess all the dimensions and some of the inner workings, so I expect that it might require a few iterations to get right.

So far I’ve ordered the following parts:

  • 10mm diameter 316 stainless rod for the main shaft
  • 25mm x 1.5mm square-section aluminium tube for the shaft housing
  • Plastic end plugs for the housing, which I’m going to drill out as shaft bearings
  • A sheet of 10mm RG1000 plastic for the adjustment dial
  • Fibreglass to cover the water vane, which I’m going to carve out of plywood

The plastic arrived yesterday and I’m now waiting for the other parts.  I just received a very unhelpful text from Fedex saying that they are going to deliver something today, but no indication of what, when or from whom.

In case it is useful to someone trying to Google Quartermaster wind vanes, the “Building Your Own Vane” section on this page is basically describing a Quartermaster vane without using those actual words…