Chris,
The statement made about not being able to tell the difference was what I expected and wanted to hear. The heavier the boat the less likely anyone would be to tell exactly the cost of the re-gen prop in the water... I have sail craft from 400 lbs. to 22,000 lbs. and as I go up the ladder in weight I have no feeling or measurement difference in speed when drag from either the propulsion re-gen or an alternative generating device.. To me, this means I'll take what I can get and be happy to put something back in my batteries for later use.. The more efficient I can make my Generating device and the means to turn it the better result I should have. Thanks for the reply..
Dave K
PS: I love your boat... actually I've looked at some Tri's, drooling...
From: chris Baker <chris@currentsunshine.com>
To: electricboats@yahoogroups.com
Sent: Wed, April 20, 2011 4:38:51 PM
Subject: Re: [Electric Boats] Re: hydro generator
Hi Dave,
Its really difficult to tell what it is. I've tried to do some tests sometimes but its really a guessing game. I've rarely been able to keep my bat sailing at a really steady speed—I find that the speed is always fluctuating just slightly by a fraction of a knot, up 0.2 here , down 0.3 and so on. And so when I do raise or lower the motor, its not clear whether changes that I see have come from drag, or from slight changes in wind, or boat directional changes and so on. It could be half to one knot.
But this difficulty of measuring raises an interesting point. If its so difficult to tell how much drag there is, what does it matter?
I'm mostly never in a hurry to get anywhere, after all it is a sailing boat, and for me the enjoyment is as much in the trip as in getting there.
And another aspect of this is the advantage of this in fickle winds, such around Pittwater (Australia) where I have the boat, and where the waterways are fiord-like and can generate fickle winds on the narrow creeks. When the prevailing wind is say 10 knots, the wind at water level can be 5 to 15 knots and changing from moment to moment. Then by running the Torqeedo at a low speed, say 150 watts, it is enough to help her through lulls and knocks, and to keep her going through a tack, especially with just the jib up. Then when the wind picks up to over 10 knots it will be regenerating. So this kind of sailing is "for free" in that the power used in the lulls can be won back in the gusts. As well as being much easier to sail cos she doesn't keep stalling, and just as quiet :)
Cheers
Chris
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