Typed "regen" in the search box and got 857 post, starting in 1999.
Good information for the most part, with a very common line of thinking.
A few comments that matched my thoughts, feed just enough power to the prop to neautralize all drag and get a zero loss or gain, but here you lose a certain amount of power to friction in bearings, stuffing box, gear reduction system, and losses in a big motor not designed for trickel charging.
My solution will involve some designing and machine work, but build a prop that can be de-coupled from the propeller shaft and that has a small generator in the hub section that deals in miliamps up through maybe 500 watts or more. It can then work between a range of slight power to the prop all the way through a regen of several hundred watts or whatever compromise one needs to make, based on situation.
There are several ways to design this, so I will refrain from details and someone else might jump straight to a better method.
Ron
--- In electricboats@
>
> Hi Larry,
>
> Something I didn't mention in my earlier post was that the drag tests
> I did were on a motor on a lifting carriage - so when the motor is not
> needed for generating power it was pulled up through the hull. So
> there was no drag from any of the paraphenalia of prop, motor and
> supports.
>
> Another point worth making is that I found it very difficult to get a
> good estimate of how much speed is lost. Because my boat is very
> light (about 3000kg) but carries a lot of sail (75 sq m), it is very
> lively and changes speed easily with slight changes in wind speed.
> After pulling the motor in and out if the water a few times I guessed
> that the drag was in the range of half to one knot, but even that
> range has a low confidence rating.
>
> Dave K's comments confirm that on heavier boats the effect is less.
> So its likely my estimate of cost of drag is at the high end of the
> range. I also suspect that the closer to hull speed you are sailing,
> the less the effect would be as well.
>
> What I think would be nice would be a controller that would allow you
> to dial up as much or as little drag/power as you want at the time.
> Some days when the batteries are pretty full, it would be nice just to
> have a trickle to keep them topped up and if it cost a quarter of knot
> to get say 50 watts that would be fine for me. On other days I'd want
> every watt I could get and wouldn't mind how many knots it cost me.
> If I could get 500 watts at a cost of 2 knots of boatspeed, even that
> could be acceptable when I have a big amps deficit.
>
> So even on the same boat the needs would change from day to day.
> Where I am right now in Ku-ring-gai chase national park, I've been
> cruising around here for the past 10 days. Many of the days have been
> overcast and rainy and the solar panels have barely provided for my
> domestic use. The inlets are steep sided and narrow, and difficult to
> sail against the wind because so much tacking is involved, as well the
> wind being very fluky. So we often chose to motor when the wind was
> contrary. So one day I ran the generator to top up the engine
> batteries while we were motoring. If I could have had some regen to
> do this it would have been nice - and because we are just cruising
> around the inlets here, there is no rush, and it would be
> inconsequential whether it took 2 hours or 3 to sail to another inlet.
>
> Cheers
>
> Chris
>
>
>
> On 12/03/2010, at 3:35 AM, gramplarry wrote:
>
> > chris, dave, myles.
> > cris you mention 200 watts per hour and being nirvana and 100 wats
> > per hour as being acceptable. There is no free lunch so what drag
> > sacrifice would be acceptable to you. e.g.1/4 to 1/2 knot?
> >
> > I have to agree with Myles. Originally i thought that only racers
> > would be interested in feathering or folding propellers. The around
> > the world cruisers i have talked with(The company has a booth at the
> > Annapolis boat show every year)quickly sorted that out for me.
> > Cruisers have even more interest in low drag. A 1 knot difference
> > can add an extra day or two to a week long passage. It makes sense
> > if they can average say 5 kt then a 1 kt drag will add 20% more time
> > to the passage.
> > But is there a break even point for watts vs speed? and what about
> > the comfort and convience factor. Many cruisers enforce very strict
> > power conservation rules while making a passage. how much is it
> > worth to relax those rules?
> > larry
> >
> > -
>
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