Graeme - I think the propeller is 16" with a pitch of 15" but could not swear to it without going back through emails.  It is definitely two bladed and not folding or feathering, Arne.  I wonder if the two bladed aspect explains the cycling of the regen, as the prop is close behind the keel.  The reduction is 2:1. I am not sure about efficiency and do not have the monitoring equipment or expertise (or time and interest, if I am honest) to measure accurately, but I did a ton of research and calculations when I was setting up the system three years ago and 8amps (400W) for 2.5 knots is close enough to my expectations that I guess it must be acceptably efficient.

Horst - I have not even (hangs head in shame) connected the battery temperature sensor yet, never mind thinking about a sensor for the motor.  For the light usage I am giving it, the motor has never felt more than slightly warm to the touch, but I have not yet had it running for more than an hour or so at low draw. I think your solution sounds good - I had also considered a sail drive solution, but decided to stick with the shaft drive that was already there.  I tried to get a Kiwi prop on Finn - the Norwegian Gumtree - but sadly missed it! From what I have read, they are a good choice for an electric setup, though it may take an extra lift out or two to get set up correctly.

Arne - I shouldn’t admit this, but I had not even considered using an outboard instead of a generator - it is a good idea.  The Tohatsu 6 Sail Pro that I had on the IW 31 was surprisingly capable as an auxiliary.  Once you add a generator into the system and have a fossil fuel aboard anyway, there is no reason not to consider an outboard and as an added bonus the outboard is out of the way - the generator takes a fair chunk of floor space in the aft cabin. You don’t happen to know where they got the rails from on that Norlin, do you? Although I can picture how it may look, I do not remember seeing anything like that when browsing the online chandleries.

I also agree with your comment about gung-ho sailors and I would generally include myself in that group - I am much less likely to reach for the start button than many of the people I sail with.  I had underestimated how different that is when family sailing, though.  Although the boys enjoy sailing and are keen to come along, we generally have a target in mind when we go out together and they are less accepting of light winds, low speeds and flexible destinations than I am. I certainly do not want to dent their enthusiasm, as I am hoping they will be crewing for me (or I for them) into my old age!

Thank you for sharing your experience here Mark!

I'm also in process of changing the propulsion to electric. Even though a good part of the needed hardware is on board already it still will take me a long time to finish the project.

I will go with a 10kW water-cooled motor from Golden Motor on a Yanmar Saildrive. Also the controller is prepared to be water-cooled. It is a little effort (time- and money-wise) to build such a small fresh water cooling system and it also would be nicer to avoid the water but I want the system working also in really hot conditions.

Do you measure the motor temperature? What are your readings at maximum in summertime?

I bought Winston batteries from Hong Kong and paid 190USD for a TSWB-LYP160AHA. The price includes delivery and all costs arising because of the import to EU in my case. Perfect service and communication with the shop in Hong Kong but the packing could have been better.

I'm planning to use my old Kiwi prop with 16" diameter and an adjustable pitch between 18 and 24°. The reduction of the Yanmar saildrive is 2.64:1. I also could use a 17" Kiwi prop which I found in the garbage bin recently (!)..

Horst

Keep it simple; add an outboard engine...

Frankly, I don’t think it is a good idea to replace an internal combustion engine with a 100% electric installation on a small boat. Small boats are inefficient in terms of kWh per ton-mile, much unlike bigger ships. A small boat needs a power of 2-4hp/ton while a 10000ton ship is very happy with 10000hp. The exception may be the British narrow-boats, meant for the low speed on the English canals.

Changing to electric propulsion for a motor boat will only...

• ·         .. turn a big fortune into a much smaller one, in particular if sufficient solar panels are to be fitted to keep one independent of shore power.
• ·         ..delay the project and keep one high and dry for a good while...
• ·         ..give one range neurosis...

Pure electric power is only useful as aux. power on a sailboat if the sailor and his/her crew are gung-ho sailors who sail in most conditions and only use the engine in and out of crowded marinas.

I think a hybrid solution is better. If Mark’s boat were mine, and in its present state, I would use it as it is, but then add a 4-stroke  6 or 9.9hp outboard on the stern, reserved for extending the range on those days with no wind. The stern of the Maxi 95 can easily take an outboard which goes up and down on a pair of rails. I have seen a Norlin 34 (similar transom) with an outboard like that: The diesel had just gone on strike right before vacation, so the dinghy’s Honda was pressed into service. That worked very well. Access to the outboard on a Maxi 95 may not be good, but it is only meant to extend the range, not for harbour manoeuvres. The powerful electric engine, with the controls at the wheel, is better for that.
By running the fuel through an outboard, one makes better use of it than when running it through a petrol generator+inverter+charger+electric engine.
Edit: In addition, the propeller of the outboard does not drag in the water when not in use. Does the inboard engine have a feathering propeller?

This solution is much quicker to fit, Mark, and it lets you spend the winter doing better things than acting a boat electrician. I am sure you can find a useful second-hand ob. unit on FINN.NO.

Good luck!
Arne

Nils wrote: I can't easliy see the connection between electric motors and Junk Rigs...

It doesn't suit everyone, of course, but in this article in the JRA archives, the writer describes quite a nice relationship between junk rig and electric motors.

(I should add, I realise I have been a bit selfish in cluttering the forum with these recent threads on electric motors. It really has been (and is) beneficial to me to learn from other JRA members who know a lot more about these things. I thought maybe there would be some other people interested, and I had assumed anyone not interested would just skip these threads. I hope it has not been too tiresome and if it has, I do apologise.)

Anonymous wrote:

My experience with motors suggests that DC is  significantly more efficient than AC.  It has a maintenance issue however with brushes and commentators that wear out over time.    AC operates via induction instead of brushes and commentators and offers long term virtually maintenance free operation.........BUT it requires that DC be inverted to AC and transformed to the optimal voltage..... or the voltage must be produced by series and parallel topology of the battery pack.   3 phase AC has the wonderful feature of being variable speed simply by varying the frequency...... if the motor is designed to accommodate it.

Umm, I think that all motors require AC or switched current. That switching is done either by electronics or brushes. This is the first time I have heard of "DC" motors being more efficient. Though you do mention "AC" motors use induction so perhaps you mean AC induction motors as opposed to AC motors in general, though there have been advances in induction motors as well. Most AC motors used for motive power are permanent magnet AC motors which are at the heart of pretty much all the brushless "DC" motors out there (including the $1 specials in your computer). A DC brushless motor is an AC motor with an electronic switch or controller.

    All of this calls for some fairly complex costly electronics, some components of which is failure prone... such as electrolytic capacitors.   Most DC motor systems vary speed by electronics also.... using pulse width modulation, though DC voltage could be varied using series parallel connections to change speeds, limiting the sensitive electronics.

PWM controllers are no less pron to failure as any other motor controller... less so than brushes though. Electrolytic Caps come in various grades and can last a long time if good grades are chosen. Most AC motor controllers that offer speed changes and power control are PWM controllers as well. They do not put out a sinwave but rather pulse width modulated square (for some definition of square) pulses that provide a sine wave of power to the load. Varying DC voltage either requires complex switching (probably electronic like PWM) or series resistance which wastes power (by the time the series resistance equals the load impedance, one quarter power, efficiency is less than 50%). It would be possible to tap power off of only part of the battery but that would mean uneven charge and discharge.

 I would assume cars that use AC motors use much different frequency than 60 cycle.

Continuously variable dependent on speed (the same as brush motors). Most do not use induction motors though but rather permanent magnet motors with the magnets on the rotor. In some cases the rotor is outside of the field for greater torque but most of the 10-20kw units used on boats have the field outside.

  I personally own a couple of pieces of equipment that operate at around 10,000 cycle, and vary the frequency depending on the circumstances to regulate output.  The transformers are tiny, compared to what would be required at 60 cycle, and generate a fraction of the heat.

400hz used to be common for portable equipment that needed greater than battery voltage, mostly transievers with valves in them. 40k to 48k is pretty common these days though as it and it's most annoying side bands are outside hearing range. I think 10k would give me a head ache :)  But yes for a motor controller that is in the ball park.