I think you might want something like the Utility Marathon boats from
the early '90s. Rules limited competitors to 125 pounds of lead/acid
batteries...2 batteries aboard, one ashore for pit-stop change-outs.
The initial marathon ran 12 hours with the winner turning about 72
miles. The next was reduced to 6 hours, but competitors turned up the
amperage wick to run the same distance.
The most successful boats were long slick hulls running 1 hp Bosch
premanent-magnet motors and big slow turning props. The Cloud/Mischke
winner ran a U-jointed shaft to make clearance for a 14 inch peddle-
boat propeller...think airplane prop...that turned at about 300 to
500 rpm. The NOPEC runner-up initially ran a huge marine three-blade
wheel, maybe 10 inch diameter with lots of pitch, and used chain-
drive gear reduction. Later they switched to a custom made tractor
outboard with a three-blade aero-prop. I'll send some pictures off-list
John
On May 19, 2011, at 7:35 AM, F Neil Simms wrote:
> Sorry if this has been discussed before, but most of what I've seen
> here over the years relates to high efficiency running with props
> in the 1k rpm or less range, and motors in the 2kw or higher range.
> With proper reduction, it doesn't seem to be too hard to hit the
> high efficiency 'sweet spot' for such systems.
>
> What I'm looking for is a motor configuration that will drive a
> light, long boat (24' x 2' at WL, under 500lbs all up) at high
> efficiency (90%+ for the motor), with prop speeds in the 300-700
> rpm range. I would like this boat to be capable of both high speed
> (relatively, say 8 to 10 mph) at around 1 to 1.5 kilowatts, and
> long distance cruising at very low power levels - 50 to 100 watts.
> I wouldn't necessarily need both at the same time, so changing
> reduction or even motors and reduction to achieve one or the other
> for a particular outing would be acceptable.
>
> I am able to find DC motors that will operate at 90% efficiency at
> the upper end of this speed range, with appropriate reduction, but
> have been unable to find a motor that will maintain that level of
> efficiency at power levels less than 200 watts, if I'm reading the
> specs and performance charts correctly. Many that do 90% at 1 kw or
> higher appear to do 50% or less under 200 watts...
>
> This boat should be capable of very long runs in the 3 to 4 mph
> range with only modest battery sizing, if I can figure out how to
> get the motor to work efficiently at such low power levels.
>
> Any suggestions?
>
> Neil S.
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
No comments:
Post a Comment