Electric outboards

[Old Forum]

Martin_cartwright
Username: Martin_cartwright

Registered: 04-2008
   
Posted on Saturday, January 17, 2009 - 10:16 am:      
I have been thinking about replacing my rather heavy Tohatsu 6hp with an electric outboard, not only to reduce weight aft, but I also like the idea of silent running and a greener alternative to a petrol engine.
However, I don't like the idea of running out of battery power at the entrance of Southwold harbour or having a huge battery bank onboard.
I have therefore been reading with interest the blogs like this one :- (http://www.geocities.com/Yosemite/Forest/2727/flicka_diesel_electric.html) about hybrid technology whereby you could have a very light electric outboard in the engine well linked to a small diesel generator (positioned where the portapotti was designed to go).
Anyone any views?

[Old Forum]

Roger Parish
Username: Roger_parish

Registered: 03-2007
   
Posted on Saturday, January 17, 2009 - 08:34 pm:      
I have often watched boats entering Southwold Harbour and in the weather conditions prevailing at the time I would not have settled for anthing less than your 6 Hp outboard! You seem quite happy to sacrifice your green credentials to a diesel generator so does it just come down to a weight problem? Can you get away with a smaller Hp and lighter engine? If you have the original WB rudder hanging on the stern then there is opportunity to reduce weight significantly by making a new one.
Just make sure that all work is finished before the TSA Broads trip at Easter.

[Old Forum]

Martin_cartwright
Username: Martin_cartwright

Registered: 04-2008
   
Posted on Tuesday, January 20, 2009 - 06:05 pm:      
Yes. You are right about my credentials. I don't see much merit in being 'green' for its own sake, but I do like efficiency (and I read that a diesel electric drive is a very efficient way of using a diesel engine).

I will certainly look at the rudder which is indeed very heavy. I had alway imagined though that this doesn't add much to the weight as it is largely submerged (ie supported by the water rather than the boat). Am I wrong?

I won't be doing anything before Easter, so we can save the planet together then.

[Old Forum]

David Cawston
Username: David_cawston

Registered: 03-2007
   
Posted on Tuesday, January 20, 2009 - 09:47 pm:      
When I launch Markie, I remove the rudder and when in the water I teeter over the transome rail and lower the rudder vertically into the water. I find it floats about 9 inches below its normal position and very little effort is required to lift it to the correct height to fit the rudder pin. So yes Martin, it is mostly supported by the water. The only advantage in making a lightweight rudder is the ease of moving it when not in the water and reducing the weight on the trailer.

[Old Forum]

Roger Parish
Username: Roger_parish

Registered: 03-2007
   
Posted on Wednesday, January 21, 2009 - 03:16 pm:      
I think it is time to take a bath and contemplate Archimedes Principle! Provided that the two rudders being considered are the same shape and displace the same volume of water then the uplifting forces are the same. The resulting forces acting on the transom downwards will the weight of each rudder. In practice what will happen is that the stern of the boat will lift by a very very small amount to balance. You do therefore achieve the benefit of the reduced weight when the rudder is in position. However because the pintles and headstock castings are so great I think I only achieved a third reduction in weight.

[Old Forum]

Martin_cartwright
Username: Martin_cartwright

Registered: 04-2008
   
Posted on Wednesday, January 21, 2009 - 05:19 pm:      
Over to you David!

[Old Forum]

Roger Parish
Username: Roger_parish

Registered: 03-2007
   
Posted on Wednesday, January 21, 2009 - 07:18 pm:      
Perhaps this explains things better and is an extract from Wikipedia entry on Archimedes.
"Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyant force: 10 - 3 = 7 newtons." If the rocks weight is then reduced by 3 Newtons then the load in the string (pintles) will be reduced by 3 Newtons. QED!

[Old Forum]

David Cawston
Username: David_cawston

Registered: 03-2007
   
Posted on Thursday, January 22, 2009 - 12:23 am:      
I agree with 'Professor' Parish, there would be a very minimal rise in the stern. If the rudder was made too light (whilst maintaining it's volume, got to keep Archimedes happy) it could ride up on the pintles, especially if a wave hit the stern. Now please excuse my long forgotten schoolboy physics. I feel sure the force required to lift Markie's rudder from its floating position to its working position on the pintles is a lot less than 1/3 of the overall force required to hold the rudder in fresh air, so if the rudder is reduced in weight by 1/3rd, surely it would no longer rest on the pintles, but would ride up? Crikey, this is getting a long way off thread but I do enjoy a good 'conversation'!

[Old Forum]

Julian Swindell
Username: Julian_swindell

Registered: 03-2007
   
Posted on Monday, April 27, 2009 - 10:24 am:      
I'm getting seriously interested in an electric outboard. I have always been concerned that you could get caught with a flat battery, but have suddenly realised that every year I am caught out with a @#!**! outboard that cuts out or won't start when it's needed. Even one that was practically new. The fact that I had enough fuel on board for 10 hours motoring was irrelevant, the engine just wouldn't go. So maybe a limited battery charge is not such a limitation after all. Has anyone had any experience with the (very expensive) Torqeedo outboard with the clip on battery? It had a very good review in PBO a couple of months ago.

[Old Forum]

Martin_cartwright
Username: Martin_cartwright

Registered: 04-2008
   
Posted on Friday, May 08, 2009 - 10:25 am:      
I still like the idea of an electric motor and the Torqeedo seems to be the one to go for if it wasn't so expensive! I am hoping that battery technology will continue to improve and prices will continue to come down so that it will be a realistic proposition in about two years time!

[Old Forum]

Barend Nieuwendijk
Username: Barend_nieuwendijk

Registered: 08-2008
   
Posted on Thursday, September 10, 2009 - 11:13 pm:      
Hi,
Last weekend in the Netherlands we had the HISWA boat show and I had the opportunity to try the Torqeedo. The motor was mounted on a RIB.
It was the Cruise 4.0 model. This model is de top of the range but can be compared with the cruise 2.0 (of which I was thinking of).
Well: it makes noise, to much noise I think. Only in the lower speed the sound is acceptable. Half throttle is very noisy. With full speed the sound drops a bit.
All together is my conclusion that I will not buy this motor.

I now orientate myself on an other type of motor: the so called POD see http://www.etd-net.nl/Aandrijvingen.html
They are expensive, but at this moment in some parts of the Netherlands you can get subsidy
(euro 1500), so may be I can arrange something.
Will be continued.

[Old Forum]

George Billington
Username: George_billington

Registered: 12-2009
   
Posted on Tuesday, December 08, 2009 - 06:26 pm:      
Greetings Good Sailors,

Just joined the Forum, having recently bought a Winklebrig. Noticed your comments about Electric Motors - don't know if it is too late, but I've been using one for a time. My previous boat was about 150kgs heavier than a Winklebrig, and I used a 55lb thrust Flover motor - very quiet and easy to use. However, be aware that you will need a big battery - about a 100amp hour leisure battery - not a car battery. That will give about 3hrs running, but if it's greater than a Force 2 wind, you will struggle. One of my fellow Club Members actually has an array of photo cells on the cabin roof, and this gives power without the need for a battery - but still you have the wind strength problem. Hope that gives some food for thought

[Old Forum]

David Cawston
Username: David_cawston

Registered: 03-2007
   
Posted on Tuesday, December 08, 2009 - 11:27 pm:      
Hi George, welcome to the joys of WB ownership. Hope you find the forum useful.
So from your experience, a motor like the Minn Kota Riptide 101 lb electric outboard should have reasonable power to move a WB even in slightly adverse conditions. Obviously there is then the problem of battery storage as touched on earlier as this motor requires 36 volts.

[Old Forum]

George Billington
Username: George_billington

Registered: 12-2009
   
Posted on Wednesday, December 09, 2009 - 09:10 pm:      
Greetings Young man, and thanks for the welcome. The motor you mention seems to have plenty of umph, but as you note, as you need an awful lot of battery power - possibly three batteries at 12volt - some weight, plus where would you secure them? I chose my current motor 'cause it was light to carry about, and only needed one x 12volt battery. The other thing was that on the technical bits web site, it is suggested that the motor will push along a boat up to 21 ft LOA. One other advantage to me is that I kept my previous cruiser on a mooring, so the motor was a welcome alternative to rowing! For this I used a 12volt gel filled alarm battery - relatively light! One thing to watch though - an on/off switch in addition to the throttle control is desirable - when fastening the engine to the rowing dinghy, nearly lost a leg several times when we caught the throttle without realising it! Hope that helps anyone reading this - but if you can wait till next April, once I put the baot in the water, I can tell you how this engine performs on the WB

[Old Forum]

Martin_cartwright
Username: Martin_cartwright

Registered: 04-2008
   
Posted on Monday, May 24, 2010 - 07:22 pm:      
I would be very interested to hear from George and Barend how the electric motor 'trials' are proceeding.