Propellor for charging batteries using electric motor

[john61ct]

I do not think anyone is thinking regen power would contribute any significant proportion of the energy required for propulsion.

Similarly with solar input,

both would require either

a purpose-designed custom boat as a technology demo / PR stunt, unsuitable for most of our needs, or

an owner who had zero schedule, was happy to wait for days and weeks gathering enough electrickery for a few miles propulsion at a time.

Ideally both.

[wingssail]

Your profile says Olsen 40. This is a very light sailboat with an easily driven hull (low drag). Extracting power by spinning a propeller will add a lot more % drag on this boat, than, say, a heavy cruiser.

Do not put a fixed propeller on this boat. Stick with Martec or a MaxProp or other folding/feathering propeller. I think you will be disappointed in the power generated vs the speed lost of you try to use regen while sailing.

[Brewgyver]

Originally Posted by KTP

(snippage)
It is coastal cruising where I see the need to carry a small generator for emergency....the eu2200i will do perfectly and is 47 pounds....not really "massive".

If you think carrying a Honda or the equivalent to go along with an electric drive motor is a working solution, I think you should check out the "Sailing Wisdom" YouTube channel. That's what they did. They were happy they had plenty of food, water, and stuff to read!

[john61ct]

Yes, living aboard happily in one place with no worries whether it takes a week or two to top up the propulsion bank, gives lots of flexibility to use low kW sources, even solar.

Many have panelage that puts out more than one of those Hondas. . .

But not **that** different from back in the day waiting for winds.

Most owners would prefer to not be limited that way.

[hellosailor]

"Any experience in other low-drag props and regeneration?"
You want a fixed three-blade (or 4) prop for regeneration. You need HIGH DRAG to create enough force to spin the prop up and give you regeneration. A low drag prop will spin less--if at all--and not turn your shaft, so there's no regeneration.

Two contradictory goals.

[gmakhs]

For me the only way electric propulsion makes sense is a secondary motor in a form of outboard that can push your boat when no winds and can regenerate when under sail, the regeneration part I have test it by firing my wind generator on the outboard and it works .
Pushing the boat I need to get my hands on the electric motor first .
If I had to remove my diesel I would do it only to be able to use the space for different purposes not to make the boat heavier adding gen batteries or if not heavier more complicated .
If you want to use the regen from the other hand go with a 3 blade fixed propeller.

[u4ea32]

Thanks for the comments so far.

Normally for day sailing, there is no need to charge the batteries. Shore power works great.

I am hoping to use regeneration for multi-day to multi-month cruises.

I love having zero fuels of any kind on the boat. So generator is not a consideration. All the internal combustion related crap represented 10% of the total displacement, and easily 50% of the total parts, and 90% of the spare parts and fluids etc. And best: NO DIESEL STENCH. It is truly transformational.

The Olson 40 sails at wind speed (9 knots in 9 knots of wind) so battery charging should be possible, given an appropriate prop. The current folding prop (Martec elliptical 2 blade 15d x 14p) does not work for regeneration, at least thus far. More experiments to come of course, but so far I have seen zero amps coming back in, just does not work. Also, the prop is too large diameter and too poorly balanced. This is a 35 year old prop!

I am strongly considering a MaxProp 3 or 4 blade, adjusted to maximum pitch underway: manual says 30 degree pitch is possible, while normally supplied adjustment is 24 degrees. High pitch angle seems important, based on what works for propellor-like hydro generators in dams, etc.

I would love to hear first hand, or second hand, experiences.

[wingssail]

Originally Posted by KTP

Actually passage making is probably the area where we would least likely need an electric motor. If you figure a 3000 mile passage, you are going to run out of fuel on a diesel with 2500 miles to go...if you carry a massive fuel tank.

It is coastal cruising where I see the need to carry a small generator for emergency....the eu2200i will do perfectly and is 47 pounds....not really "massive".

I don't think that a eu2200i will provide enough power to move the yacht at any useful speed.

The OP's motor is 11kw. The honda is less than 1/5 of that, and there will be losses in the conversion to the battery.

My engine is 27kw, so for my 43' boat the honda provides 1/13th the power my engine does.

[a64pilot]

You would not most likely need or want a course pitch, you would want a fine pitch.
Look at a wind generator for example or talk to anyone who has auto rotated a helicopter.

Of course fine pitch will speed up the prop. But also increase drag.

A driving propellor and a driven propellor are somewhat different things

[u4ea32]

Originally Posted by wingssail

I don't think that a eu2200i will provide enough power to move the yacht at any useful speed.

The OP's motor is 11kw. The honda is less than 1/5 of that, and there will be losses in the conversion to the battery.

My engine is 27kw, so for my 43' boat the honda provides 1/13th the power my engine does.

I get the same speed at 5KW as I did full throttle from the 20kw Yanmar 3GM30FC I removed: same prop, same shaft log, same strut, same shaft.

Maneuvering, the electric puts out MUCH more thrust. At 3 knots, the electric motor uses 330watts.

[Oceanride007]

Use to work on DC ships. Sure any DC motor can be a DC generator, thats what they said back then. But now think modern DC motors have permanent magnet rotors, maybe it could work, but to get around any electronic box, thats now getting awfully complicated. Sorry may have missed it is your motor a variable speed or fixed.

[a64pilot]

Originally Posted by wingssail

I don't think that a eu2200i will provide enough power to move the yacht at any useful speed.



The OP's motor is 11kw. The honda is less than 1/5 of that, and there will be losses in the conversion to the battery.



My engine is 27kw, so for my 43' boat the honda provides 1/13th the power my engine does.

I don’t think that is the idea of how to use the Honda, I took it to be that the Honda is used to recharge the batteries if needed. A Honda can make I’d guess 1600W or so continuously, I think if you pulled that much power out of a prop it really would slow the boat, and may not be possible, and to get that kind of power out of Solar would take a really large array.

We keep running into this reality with electric propulsion, the fact that it’s likely brilliant for day sailing, but for long distance cruising, it’s going to be really tough to recharge that bank, real tough.

We have a member that is actually long distance cruising, without a Diesel. He is a smart guy too, nobody’s fool. He tried electric propulsion and gave it up for a sculling oar, and obviously sails.

[john61ct]

I would think the vendor outfit that supplied the drivetrain would have at least some data and suggestions, if it is at all practical

[KTP]

Yes sorry I meant the 1800 watt continuous EU2200i could be used to put some power back into the battery bank in an emergency situation where you *have* to motor.

Take for example our boat with our 18kWh lead acid bank (48V @ 350AH from twelve Lifeline GPL-31XT batteries). Eventually we will switch to lithium and maybe even larger bank but right now we can motor for about 5 hours at 4 knots drawing 2000 watts from the bank. If we were to run the EU2200i while also drawing the additional 200 to 300 watts needed from the bank we could motor for about 55 hours at 4 knots.

If we sent 3800 watts to the motor, the bank supplying 2000 watts and the EU2200i supplying 1800 watts, we could go about 5 knots for 4 hours. Probably 6 knots for an hour and a half or two hours. Running flat out 10kW to the motor with lead acid, our bank would probably only give 45 min but we would be doing 6.8 knots. Lithium would improve that a lot.

I'd rather sail. It does take a lot more time and planning though than just turning the key and becoming poor excuse for a motor boat.

[KTP]

So this is our current 3 blade prop on our 1989 Pacific Seacraft 34. It is being driven by a 10kW Thunderstruck electric motor kit with a 3:1 reduction.

At 3,000 watts input to the motor controller at dockside with the boat attached to a 400 pound limit digital scale, the motor spins at 1900 rpm (prop at 633 rpm) producing a thrust of 180 pounds. On the water this amount of power to the motor controller usually moves us about 4 to 4.5 knots.

If I only care about regen and prop efficiency, and noting that our 3:1 reduction is pretty large, what options might I have for increasing our prop size under the assumption that a larger prop would have more surface area to the water and would produce more regen at lower speeds. With this prop we are seeing about 50 watts at 4 knots regen.

Here is a picture from our last haulout. I guess what I am asking is exactly how close can you have the tips of the prop to the rudder gudgeon? It looks like there are several inches clearance right now.