It is obvious that you know more about electric motors than most of us. However I still have to get by with my limited brainpower. In the KISS department the rule of thumb for electric motors is that the efficiency drops dramatically at loads under 25% of the full load rating of the motor. The Cruise 2 full load rating is 2 KW so loads less than 500 watts are undesirable from an efficiency standpoint. The 801/1003 motors are 1 KW so they can run at loads down to 250 watts with reasonable efficiency. Thanks. Steve S.
--- In electricboats@yahoogroups.com, Joe Grez <joe@...> wrote:
>
> Hi folks, Been following this thread- Agree it's a good one. But while
> efficiency is a useful tool for development, it's varies greatly in
> practice. Look at the Torqeedo efficiency curves here
> http://www.torqeedo.com/us/hn/background-knowledge/performance-indicators.html
> . What
> you see is that efficiency is anywhere between zero and a maximum value even
> with fixed hydrostatic resistance parameters. In reality, there is also
> quite a difference in efficiency from resistance parameters; different
> boats, different loadings, even different weather and sea conditions. So
> it's not surprising to see some customers happy and others unhappy with a
> single product based on their particular set of use-conditions. Inboard
> guys know this and it's why they will go through several props until the
> motor operates within its most efficient rpm range. This is called
> impedance matching.
>
> For example, our Electric Paddle, in a tank that matches the hydrodynamics
> of a Necky 16 ft kayak, has the same efficiency as the Torqeedo 401s stated
> efficiency/ power curve when tested in their tank. If you have a dinghy that
> is shorter and fatter, than efficiency drops. If you point that same dinghy
> downwind, the efficiency goes up even if you account for the wind lift.
> This is a rule of physics and it's reality for all motors and brands. What
> is true is that both Torqeedo and Electric Paddle match impedance to higher
> speeds on more relevant boat hull shapes using advanced technology so they
> are very light for the available power and range. Trolling motors impedance
> match to a bassboat at very low positioning speeds and use lead acid
> technology and that's why trolling motors are much heavier and less
> efficient as main propulsion.
>
> Guess what I'm saying is that the new wave of efficient motors are truly
> well-designed to provide performance but this performance will vary based on
> what kind of boat you use. If you try one and it's not keeping up with your
> expectations, talk to the makers. They should be able to either satisfy
> your needs with a prop change or take the motor back.
>
> I've started a new forum just for electric outboards. The electric boating
> group is expanding and with that it must segment. I hope to make this new
> forum useful to customers and makers of of all brands of electric outboards
> as well as to folks converting gasoline outboards.
> http://groups.yahoo.com/group/electricoutboards/
>
> Joe Grez, President of PropEle Electric Boat Motors Inc. makers of the
> Electric Paddle
> http://www.electricpaddle.com
> 10404 428 ave se, North Bend Wa, 98045
>
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