I've been thinking for a long time about adding an auxiliary electric motor, and with my new boat, I might just do it.
The PRIMARY purpose would be to silently add a couple of HP while under sail to make motor-sailing a pleasant and efficient process.
Secondary functions would include using the high torque of the electric motor in close quarters maneuvering and possibly as a get-you-home backup.
With my new boat (Nauticat 40) I have copious battery capacity, and space for more, and I have a 6kw diesel genset. 6kw happens to be about 8HP, which if you follow the formula of 0.5hp/tonne to get to 80% of hull speed, means that in theory
an electric motor coupled to my 6kw genset could
push me at 80% of hull speed. But that's not the primary purpose. Really what I want is to silently add a few HP under sail, and as far as getting me home, I could sail (or electric/motorsail) to the marina and use the electric motor in close for docking.
Here's what I'm imagining for how to connect it. I could use a high grip shaft collar, coupled to a sprocket and motorcycle chain. The use of roller chain (motorcycle chain) would eliminate the side loads that trash out bearings.
The sprocket could be attached to the coupler with very little imagination I would think.
What I would need is some kind of clutch (electromagnetic?) so I could engage or disengage the setup when running the main engine. I also haven't figured out the best motor to use, though there are coutless options
Does anyone have an idea what kind of clutch I could use to attach this sprocket setup to an electric motor? Any ideas on hooking it up to some kind of throttle (resistor?) Any other comments or criticisms?