Neat New Electric Outboard


 

Saw an article in a recent Watercraft mag about "rim motors". The electric ones oughta have lotsa torque, since all the power is made out at the rim, and the integral propeller/nozzle eliminates wasted power at the propeller tips. Dunno what happens when the open end of a propeller blade is on the _inside_...

http://www.hy-generation.com/

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John <jkohnen@boat-links.com>
There is no greater fan of fly fishing than the worm. (Patrick F. McManus)


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Jove Lachman-Curl
 

On an aircraft propeller the center of effort is at the 70% radius of the blade. Lift reduces to zero at the hub since there isn't any foil to fluid velocity. From this, I'd assume that there are very little or no tip losses in this design, and it makes a lot of sense to remove the central nacelle of a typical ducted fan design if possible to reduce drag, On the other hand the external nacelle provides a lot of drag surface vs a traditional boat prop. Perhaps fragile if you hit something in the blade tip area.
-Jove

On Wed, Mar 17, 2021 at 3:03 PM John Kohnen <jkohnen@...> wrote:
Saw an article in a recent Watercraft mag about "rim motors". The
electric ones oughta have lotsa torque, since all the power is made out
at the rim, and the integral propeller/nozzle eliminates wasted power at
the propeller tips. Dunno what happens when the open end of a propeller
blade is on the _inside_...

http://www.hy-generation.com/

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John <jkohnen@...>
There is no greater fan of fly fishing than the worm. (Patrick F. McManus)


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David Graybeal
 

Another video on the topic. Looks interesting --

https://www.youtube.com/watch?v=Te_xejpriFM


 

What the Hy-Generation "thrust module". I suppose you could call it, does is combine the propeller with a nozzle. Nozzles do indeed have quite a bit of drag, but they increase thrust. So they're best at low speeds. Fortunately, electric boats go slow. <g>

Earl added a crude sort of half-nozzle to Dr. Petra's gas outboard and liked the result. Increased low-speed thrust and better maneuverability. I can't recall the maker. Earl?

I expect the exposed inner tips of the Hy-Generation blades will have a lot less loss than the tips of ordinary prop blades, but I don't know the details...

On 3/17/2021 3:17 PM, Jove wrote:
On an aircraft propeller the center of effort is at the 70% radius of the blade. Lift reduces to zero at the hub since there isn't any foil to fluid velocity. From this, I'd assume that there are very little or no tip losses in this design, and it makes a lot of sense to remove the central nacelle of a typical ducted fan design if possible to reduce drag, On the other hand the external nacelle provides a lot of drag surface vs a traditional boat prop. Perhaps fragile if you hit something in the blade tip area.
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John <jkohnen@boat-links.com>
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Thanks, David. This is the outfit he mentions that makes rim drive units closest to the size Coots would use:

https://www.torque-jet.de/

I'll bet they'd make more sales if they had an English version of their Web site. <sigh>

On 3/17/2021 3:35 PM, David G wrote:
Another video on the topic. Looks interesting --
https://www.youtube.com/watch?v=Te_xejpriFM
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John <jkohnen@boat-links.com>
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