T-Pain Is On A Boat: Re: [Electric Boats] Re: why not a golf cart setup?

Thursday, June 11, 2009

Re: [Electric Boats] Re: why not a golf cart setup?

G'day
i have been observing this re generation debate for such a long time..
one aspect which has not been mentioned....and MAY be a solution to a
number of issues discussed on here
how about variable pitch props....??
would seem to have the following advantages............PLEASE SOMEONE
CORRECT ME IF INCORRECT

# often can use some in complete fold position for more or less drag
free sailing
# can more easily adjust your speed/power input to match the conditions
# use for sail assist as very low power inputs to get the extra knot
of so at low or variable wind speeds
# buy experimentation with the blades (possibly set to reverse ?...)
to get the maximum regeneration
# all with the same propeller....i understand they are more
expensive......but may be the answer to lots of the issues raised here....

i am a little surprised no one has raised their potential use
before......??..........maybe they have i i have missed it...??

i had a friend who sold these for ICE and all his customers were very
pleased
as in theory were ideally suited for low power ICE but maximum
performance over a range of situations

hope this adds to the discussion.....

George

constancedraper wrote:
>
>
> I've been impressed with Mark Stafford's comments on electric drives.
> Clearly, he knows what he's talking about, and I don't.
>
> But ignorance has never managed to silence me before, so...
>
> Mark, I'm not sure that Keith's analogy with golf cart wheels is such
> a great analogy. With carts, you get regen only when you are braking.
> With a sailboat, you're turning that prop 24/7 so long as you are
> under sail.
>
> People pay nearly $800 for a 100 watt solar panel and it's only really
> effective about 8 hours a day.
>
> I do believe that you're right about props being optimized for
> propulsion -- and at maximum RPM and power output at that. So, how do
> you optimize a prop for regen?
>
> >From the bit of reading I've done, I think you want to maximize
> diameter. I don't know about pitch.
>
> One outboard site said ï»¿"Houseboats and cruisers care more about
> efficiency at displacement speeds, therefore they require a lower
> pitch to achieve low-end power and the largest diameter their lower
> unit can handle."
>
> Intuitively, I think I want the prop to be spun readily at low speed,
> because most of our sailing is going to be done at low speed. (I've
> read some reports of units not regening until sailing at nearly 4 knots).
>
> Permanent magnets seem the way to go, but if you had wound fields, it
> would seem that a controller could adjust the resistance to shaft
> turning to optimize regen? I'd rather miss opportunities to max regen
> output at high speed in favor of getting some juice out of it when
> you're barely coasting...
>
> I'm grateful to have stumbled into a forum where so many knowledgeable
> folk are posting.
>
> Best,
> md
>
> --- In electricboats@yahoogroups.com
> <mailto:electricboats%40yahoogroups.com>, "Mark Stafford"
> <mstafford@...> wrote:
> >
> > Keith, Mark Stafford always appreciating your real-world numbers.
> Your almost 100watts regen @ 6knots.... what prop size/pitch? 12x8?
> The other problem with regen: most props are optimized for propulsion,
> not for braking.
> >
> > Great traction analogy with golf-cart wheels vs propellers.
> >
> > Mark Stafford
> >
> >
> > --- In electricboats@yahoogroups.com
> <mailto:electricboats%40yahoogroups.com>, "aweekdaysailor"
> <aweekdaysailor@> wrote:
> > >
> > > Most of the systems in use are in fact derived from golf-cart
> parts. But we typically use more efficient PM (permanent magnet)
> motors instead of the older series wound motors common in the used
> market. So it definitely can be done and I think a few on this board
> have examples. The drive and controller are only about 1/4 the total
> cost of a system so it's not really a great place to skimp.
> > >
> > > As for regeneration - it's one of those things that sounds great
> in theory but isn't really practical. Consider that all 4 tires on a
> golf cart are gripping the road with several thousand pounds of
> stopping friction - vs all that water easily slipping by a very small
> prop.
> > >
> > > So golf-carts get great braking, and a few watts of power - on a
> boat you just get more expensive electronics. I have a system that can
> regen and I get less than 100watts sailing at 6knots and then only
> when I carefully feather the controller (though I think the controller
> can be programmed to do this better). It's not impossible to boost
> this, but it's a science experiment, not a proven tech.
> > >
> > > Regards,
> > >
> > > -Keith
> >
>
>
> ----------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.339 / Virus Database: 270.12.62/2168 - Release Date: 06/10/09 18:30:00
>
>

--
George Burrows

Address:
Black Snake Inn
650 Old Main Road
South Granton
Tasmania
Australia 7030

Email:
george.burrows@keypoint.com.au

Phone home:
+61 3 6263 4219
Phone mobile:
+61 418 350 001

[Non-text portions of this message have been removed]