Agreed that weight is an issue, but then so is hull form and planing area. You say your 7m, "skinny" boat has a low-drag hull. That is true for displacement craft, but not necessarily true for planning hull forms. For the same weight, longer hulls are require more energy to plane than ones with a lower aspect ratio. His 16' boat, all things being equal, is going to plane at a lower speed than your 7m boat, and therefore will need less energy to do so, and of course won't have to carry as much battery weight. Agreed that weight is an issue, but then so is hull form and planing area.
--- In electricboats@
>
> At 08:40 AM 3/02/2010, you wrote:
> >Has or does anyone know of a 16 foot Jet Boat to electric conversion?
> >There is no transmission or reverse needed so it would be direct.
> >I'm looking for a 4000--6000 rpm motor, simple set up. Any info
> >very appreciated.
> >
> >Thanks, Ernie
> >vacationdoc@
>
>
> G'day Ernie
>
> The Australian Maritime College - Vessel Propulsion Lab vessel
> "greenliner" is a jet boat, but a low speed one, not really
> efficient. We have had it up to 11 knots at 96 volts - it normally
> runs 48V and no more than 6.5knots. With 120V and a lighter battery
> it should plane at about 16 knots - that is what it did before with
> the internal combustion engine. Run time will become an issue then,
> as it'll be running probably about 20kW, so at 120V about 160 amps,
> so a 200Ah lithium battery would be about 200kg (down from 250kg now)
> and give just over an hour, and that is in a skinny, low-drag hull -
> 7 meters, so longer than your 16 foot.
>
> The motor is simple enough, pick your lump of DC motor from ADC,
> warfield (warp), High torque electric or others, (google 'em will
> find 'em), also through a number of EV parts suppliers. Depending on
> your setup you could use a 2 or 3- step 'rectactor' controller, 24V,
> 48V, 96V, consisting of four or five contactors and some honkin'
> great diodes, no electronics to throw a 'hissy' when it gets damp. 3
> electric speeds plus the variability of the bucket should be enough.
> Add four 24 volt chargers and good to go.
>
> Only trouble is, your really going to need to look at Lithium
> batteries to keep the weight under control, so as to have more than a
> few minutes of fun (run) time, so battery management system, all that
> other guff that goes with it.
>
> How deep are your pockets? If you can throw a good chunk of dollars
> (or whatever currency is legal tender in your country) at it, then
> easy, have fun. If you are 'on the cheap', then maybe a jet boat is
> not so practical. What do you want to use the boat for? If a short
> run across a fast river, then it may be OK with lead batteries -
> although a bit embarassing when you try and sneak an extra trip and
> get caught out halfway.
>
> Regards
>
> [Technik] James
>
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