Dave,
I've noticed the same thing with my F-27 trimaran. Since the boat responds so quickly to changing conditions, relating the cause and effect to trim changes and other changes like lifting the motor out of the water can be difficult at times.
Multihulls also have the freedom from the general limitation of hull speed. Chris has reported sailing his 43' tri at more than 25kts, and I've sailed my 27' tri at 17kts.
But a 30' monohull will rarely see 7kts, if ever, and extra drag will slow the boat down in mild conditions. Since there is little evidence of any regeneration below 5kts, that leaves a pretty narrow window of potential regen. As long as you accept that the regen that you get may not cover anything more than house loads, then you you won't be disappointed
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, chris Baker <chris@...> wrote:
>
> 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
>
> On 20/04/2011, at 11:24 PM, Dave Kellogg wrote:
>
> >
> > Chris,
> > I'm wondering about drag while you were making the 18 amps. On your tri that speed isn't much of a problem and the size/weight of your boat shouldn't give you much of an indication of slow down, I'm just curious if you noticed.. Dave K
> >
No comments:
Post a Comment