Rick, this is a very good price (OK that is without the high modulus rope ;-) Does the arm lock in vertical position? Apparently you do not advocate an engine pod behind the propeller. Is that because of the increased drag or a heavier moment with the engine weight at the very end of the arm?
Thank you.
Luc

--- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@...> wrote:
>
> It has taken 17 months but we finally have a neat twin electric drive
> system for the 18m proa:
> http://www.youtube.com/watch?v=81tw5Xw4Wdg
>
> The units have been mounted beside the lw hull and ww hull to
> maximise turning moment. They swing up and out of the water
> laterally for sailing. The lifting ropes need permanent attachment
> points and will be thinner high modulus rope.
>
> Since the initial trials with the single Mars 3001 motor we decided
> on much more powerful Mars 1003 motors for the permanent
> installation. These have the simplicity of being brushed DC so could
> be run without controllers in an emergency by direct connection to
> batteries.
>
> The lw unit is not constrained by battery current so it can produce
> 9kW continuously on the 50V battery. The smaller battery on the ww
> side limits power to 6.7kW. We have not measured bollard pull but it
> will be in the region of 6000N with both motors on their current limit.
>
> The testing today was for maneuverability rather than speed test and
> the video shows how the 18m boat can be turned on the spot.
>
> Next step will be to get the hulls clean (again) and do some speed
> trials. The range should be around 9nm at 5kts solely from batteries
> without any extra charging. Decisions are still to be made on means
> of charging but plans are to at least set up some solar panels so the
> batteries can be charged between outings.
>
> Expenditure on the units now totals AUD8,000 in round numbers. This
> is for motors, gearboxes, props, controllers, batteries and aluminium
> housings plus fixings. This is less than the original 60HP high
> thrust outboard installation. Which is now for sale.
>
> The ww unit has ended up mounted lower than planned during design
> stage so it will be modified to get the motor housing out of the
> water to prevent the ploughing evident in the video. The lw unit is
> set at the correct height and wash is much cleaner.
>
> Props are 540mm diameter and prop shaft is 600mm below the surface on
> the lw side. Each drive unit weighs about 35kg. The lw batteries
> weigh 60kg and the ww batteries 40kg. Overall weight similar to
> outboard counting the mounting, starting battery and controls. The
> motor housings have been pressure tested for leaks as they are
> intended to take full immersion.
>
> Time will tell regarding durability.
>
> Rick Willoughby
> rickwill@...
>