Thanks Han,
From: han <gcode.fi@gmail.com>
To: electricboats <electricboats@yahoogroups.com>
Sent: Sun, Jan 12, 2014 5:30 am
Subject: Re: [Electric Boats] EV comparisons was: RE: Tartan 30 Sailboat
Including the vendors - much appreciated.
There is no comparison - because one would be hard to do.
Most (voluble, at least) members are from the US- thus most products are from the us.
There is a lot of marine engineering involved - or not, in going to an ev.
This is easy - or not. Depends no your engineering know-how, and interest in same.
For example;
You may nor may not have a thrust bearing that comes off with motor/gearbox.
Having one is critical (bigger boats or bigger engines) or not (small boats-under 9 m is small).
Making one is easy (for a machine shop) using old as template - or not.
It can cost several thousands for an industrial solution (workboat quality).
Or several thousands for a crappy yacht pos, gold plated, from an overpriced marine store (weak, poor materials, far too light).
Or about 200 in parts for same industrial quality (add old steel).
How do you compare ?
Marine stuff is expensive-or not. A new generator is 50.000$ plus for bigger boats, installed.
Some users plan to save 200 in components. Some spend over 2000 on cables. The gamut is wide.
A throttle assy may be 2000$ - or 20$. Both will control a motor on a boat. So how do you compare ?
Battery cost is highly variable for the same tech depending on marketing and packaging. Ie 20.000$+ for 6 kW, or under 8000$, in li-ion technologies.
Controller cost is highly variable.
More expensive is not necessarily better, today, for leisure boat stuff in general and EV in particular.
Also, motor power truly needed is very small, especially on efficient, longer boats.
For many reasons, typically a much larger system is chosen, partly because the cost is practically the same.
My opinions on conversion options;
Most kits sold seem to work well. Users are happy.
Power stored.
Users are happy with whatever they have chosen, from li-ion to agm to gold cart to std batteries.
My opinion on the right choice.
Use li-ion tech from your preferred vendor.
Use about 1/3 to 1/4 of old gas engine power - or about 1 hp or 700W per metric ton of displacement.
A very heavy full displacememt trawler like Williard, in the 10 m size range, uses about 7-8 Hp, or 5 kW, of power to travel at 6 knots.
Sailboats are lighter, and need less.
*Change your prop* to a bigger one if at all possible. 3 sizes larger would make more difference than anything else.
It is probably likely that you cannot easily change your prop - but this would help a lot.
For example, a 70 tons, 24 m long, full displacement trawler in steel, of a friend, has a 100 Hp (high torque) industrial engine.
It is vastly overpowered, and the prop cavitates without the least effort.
As only about 1/4 the power is ever needed, and props are expensive, the choice has been to do nothing.
One (small) gas tank last all summer, with minimal observed use of gas.
-- -hanermo (cnc designs)
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