Adding an electric/hydraulic propulsion system to A169 (Kerry Piper) and thought it may be of some interest (attached plan). The mechanical installation is pending completion of structural  work to the hull and bulkheads, but I aim to have it installed during the summer. Bernard Upton (Colchide) is a keen advocate of electric propulsion and my discussion with him during the 2012 AOA dinner got me thinking about this as a serious option. I had originally planned to add hydraulic drive to a 12hp 4 stroke petrol unit thus eliminating the need for a gearbox and the further elimination of fuel combustion was appealing. The Electric Seas forum group was a useful research resource, with many individual (and corporate) technical articles on battery type, amp hour  consumption etc and worth a look for anyone considering electric propulsion. Benefits are: elimination of fuel (and tank space) - compact and versatile installation - smooth silent operation and potentially lower weight (I know - "what about the batteries!" - read on). Downsides for those who do a great deal of motoring are the higher AH battery installation required for extensive motoring, which offsets the potential weight benefit (until Lithium batteries are affordable). The combining of electric to hydraulic as distinct from purely electric drive was my preferred choice. Added attractions (over purely electric) for me are: - smoothness of hydraulic propulsion (minimal mechanics) - instant ahead astern (without overworking the electric motor) -efficient torque delivered from a hydraulic drive and possible use of hydraulics for lifting keels. NB: Vetus offer a ready made electro-hydraulic system for those with deeper pockets. Working out the correct system involves basic calculations like matching the correct electric motor to the hydraulics - my 7.5 kW motor was from a fork lift truck, so the correct pump was already there.  Sourcing the correct hydraulic motor needs a calculation of the required rpm/torque etc. For those happy to keep a fixed prop there is the benefit of charging the batteries whilst under sail with reverse prop rotation - especially effective for direct electric drive systems. Cost wise - about the same as a standard diesel installation, although  clever sourcing can substantially reduce outlay for principal components such as electric motor, tank etc. 

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Chris, thanks for sharing this, looking forward to see how the system works in practice.  I'm planning to install a direct electric drive in Blue Goose but that's still a ways off. Fortunately there are other boats about during this restoration period.  t

Peter Snowdon has fitted electric propulsion on A150 Salizander, because he can't use petrol or diesel where he sails in Austria. He's written about it in a blog here: http://salizanda.blogspot.co.uk/ although it hasn't been updated since 2009. Last time we were in touch he was considering becoming an agent for the motor he's using.

John

An interesting Atalanta project, I recall reading this blog some years ago - I think on the old AOA site. It would be interesting to see Peter's test results for the 2.1kW (3hp)24V system he was installing. Most systems are now based on 48V motors and the smallest output is 5kW.  As Peter predicted in his blog, electric propulsion for yachts has developed apace over the intervening years. A leading player is Electric Yacht (USA)  http://www.electricyacht.com/ with units from 5-20kW . A GRP Folkboat  was fitted with a 5kW version at Sussex YC last summer. I was impressed by the compact design - bit pricey though! Like Peter's system these use a direct drive belt from the motor to shaft (think reversed alternator) and a reverse polarity control  for ahead astern. The electro-hydraulic propulsion system being fitted  to A169 has a reverse flow valve to the hydraulic prop drive for ahead astern, otherwise the electric spec's and batteries etc are the same for both systems. Will be posting the motor installation and restoration of A169 at some point.

A169 Plan attached - Again! Noticed an error on the original - the fluid return is from the valve not the drive motor!

Attachments:

Another source for a ready to go motor, provided you have money bags, is http://www.elcomotoryachts.com/  The

DIY kit from Electricyacht should be fairly attractive to a lot of folks contemplating a conversion.  I have a BionX kit

http://www.bionxinternational.com/bionx-international-north-america...

installed on a standard bicycle that has worked well commuting to work two or three days a week.  The most expensive

component is the Lithium battery as you indicated.  I hope to live long enough to see the price of these batteries come down.  The stator i fixed and the hub rotates, it has 4 levels of assist and 4 levels of charging.  The motor can be used as a brake when charging as you roll down hills.



Chris Green said:

An interesting Atalanta project, I recall reading this blog some years ago - I think on the old AOA site. It would be interesting to see Peter's test results for the 2.1kW (3hp)24V system he was installing. Most systems are now based on 48V motors and the smallest output is 5kW.  As Peter predicted in his blog, electric propulsion for yachts has developed apace over the intervening years. A leading player is Electric Yacht (USA)  http://www.electricyacht.com/ with units from 5-20kW . A GRP Folkboat  was fitted with a 5kW version at Sussex YC last summer. I was impressed by the compact design - bit pricey though! Like Peter's system these use a direct drive belt from the motor to shaft (think reversed alternator) and a reverse polarity control  for ahead astern. The electro-hydraulic propulsion system being fitted  to A169 has a reverse flow valve to the hydraulic prop drive for ahead astern, otherwise the electric spec's and batteries etc are the same for both systems. Will be posting the motor installation and restoration of A169 at some point.

Chris

I am interested to see your plans for electrical propulsion, and particularly interested to see that you intend to fit hydraulics in the drive train. I heve contemplated electrical drives on a number of occasions but have always dismissed them as being impractical for the use I make of a boat.

The electrical drive taking its power from batteries will I suppose be quite OK if a boat is to be kept in a marina (where the batteries can be recharged between outings), and where the planned use of the boat is for day sailing and perhaps occasional weekend trips.

 

The BIG problem that anyone will face when installing such a system is the cost of replacing the batteries every three years. Battery technology has changed little since 1890 - there have been minor improvements - but no major technological breakthrough. The "G Whiz" car seen in london costs about £7000 new, and is worth very little after 3 years - why? Replacement batteries cost £3000 and they need replacing at 3 year intervals. There is no way around this problem.

 

Of course the issues of running out of charge in an electric car have been humourously highlighted on "TopGear" - and the same issues are relevant to a boat. With a deisel engine the range is limited only by tank capacity - and when it is close to empty it can be refilled - then you can motor on again for the full tank capacity. With battery power the remaining charge will have to be monitored, flattening the batteries will wreck them, and you will run the risk of having no power left to enter the marina if you run them flat. So the boat becomes a deffinite AUXILIARY sailing boat.

 

Hydraulic drives have been used in boats for many years, and the major drawback when used for propelling small craft with low horsepower engines has always been that the hydraulic system absorbes lots of power itself. Quite a few horse power actually. When there is a big engine driving it it is less of an issue. The main use of hydraulis systems in boats (commercial ones especially) is for anchor windlasses and winches such as pot line haulers. High torque low revs remote from the engine - in otherwords. Not really going to help in the main propulsion system. I think you are actually going to reduce the range significantly by using hydraulics. I dont see what the potential gain is. Electric motore reverse easily, and can be speed controlled in low and high tech ways. The right motor aught to make a good match for a direct coupled drive.

Berrnard has hydraulic drive of course - but then it is driven by a small deisel and only really used for leaving and entering harbour, so maximum speed and efficiency are low priorities in this case.

So while it seems a good idea to fit an electrical drive I do wonder how it will work in practice, and if it will actually make a boat difficult to sell?

I have every confidence in the advantages of electric drives for those who don't tend to motor for hours and hours at hull speed.  The lack of oil in the bilge, through hull fittings, exhaust, noise, self sufficiency, and component weight are all qualities that lead me toward this type of propulsion.  That said, I have always been the type to shut off the motor when the wind picks up (and sometimes even when it doesn't).  Battery technology will continue to advance at a rapid pace because there are many applications and that always brings the cost down eventually.  The lithium battery I use on my bicycle has seen over 500 deep discharge cycles and it still maintains the same capacity it had after the initial drop from new condition.  At my current rate of use I will reach break even in two to three months on the battery cost from gas savings, although the exercise benefits are more important. I can't really claim any carbon footprint high ground because my other vehicles are a 2 stroke motorcycle and a truck.  The forces to propel a bike vs. a boat are quite different but the electric drive systems installed in boats with displacements much higher than Atalantas seem to be working quite well.  In regards to hydraulics, it's an interesting energy experiment with the higher torque electric motor for the main drive.  I prefer to avoid oil on board as much as possible but I'm still very much interested in the performance aspects.

I share Tim's view regarding the future for electric propulsion also my use as an auxiliary to sail i.e.mostly  entering/leaving and docking. My choice to opt for the hydraulic drive (as opposed to purely electric) is based on expected low use and the further option of  hydraulic keel lifting as an add on the drive system.  I did research the power loss/efficiency issues at some length and had a lengthy discussion thread on the Electric Seas website. A very useful site http://www.electricseas.org/ a (US based) site for anyone considering or using electric propulsion. It has contributions from hundreds of electric users with many season's stat's to peruse. Back to my hybrid - the 7.5 kW motor has sufficient over-capacity to allow for any transmission downside, and with super efficient torque delivered by the hydraulic motor has some upside to offset this (torque being the key - no pun intended!) for an efficient prop. There are a couple of further benefits to hydraulic drive such as the simplicity of the drive system; few mechanical parts to fail (i.e.no pulley or belt drive); eliminates the need to reverse the electric motor for astern; and of course the luxury of a flexible installation. A169's hydraulic motor will drive the shaft at the point it exits the rear of the bay, thus removing a few feet of heavy prop-shaft. Even with the comparative massive 7.5kW electric motor and batteries there is still a large amount of free space below the cockpit - as with most electric installations. You also lose engine sea-cocks, exhaust system, fuel tank (although A169 will have a 10L Hydraulic tank). Personally, I see electric engine installations as at worst neutral and at best an attraction to the after sales market.

I have added a further file showing some of the kit  - taken on board today in between re laminating holes!. 

Attached - Motor details

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