Using 6kW electric outboard for added propulsion on 39' catamaran

[CaptainPete222]

Originally Posted by Pelagic

I don't know the mechaical components of how Regen works on Electrical drives.
Is it like a brushless alternator driven by prop spin or something different?

If the efficiency of this has improved lately could they be considered as applicable for a Shaft Generator under sail on a boat with a fixed prop and low rpm?

I believe it’s like a brushless alternator driven by prop spin. When the motor doesn’t have power being put into it, it becomes a turbine-like generator when the boat’s forward motion causes the passing water to spin the prop.

[Steve_C]

Forgive me if this is a stupid question, but if you put a giant 3 foot or larger prop on, how do you keep it submerged? Wouldn't you need a much longer shaft?

Sorry if this has been covered, but I have been reading this entire thread on my phone while bored.

[Adelie]

Originally Posted by Steve_C

Forgive me if this is a stupid question, but if you put a giant 3 foot or larger prop on, how do you keep it submerged? Wouldn't you need a much longer shaft?

Sorry if this has been covered, but I have been reading this entire thread on my phone while bored.

36” prop is not an after market that could be added to the EProp. It is something you would use on a motor designed to take it:
Really long leg
10:1 or 20:1 gearing instead of direct drive or 2:1.
1.5-2.0kW max with speed limited to around 3.0-4.0kW.

[ausnp84]

Originally Posted by Franziska

Not trying to be a smart ass here, but 400Watt are 400Watt independent of voltage.

That's why Watt is a great unit for comparing power independent from voltage.

Amperes change with voltage changes...

Fair point. I’m just trying to work out how long our 640W of solar would take to recharge these batteries. The E175 batteries gives 8960Wh at 48V and uses a 220v charger... unfortunately I can’t seem to find any specs for the charger wattage tho (which would make all my calcs so much easier!)

N

[Pelagic]

Originally Posted by CaptainPete222

I believe it’s like a brushless alternator driven by prop spin. When the motor doesn’t have power being put into it, it becomes a turbine-like generator when the boat’s forward motion causes the passing water to spin the prop.

When I bought my boat it already had a Shaft Generator setup.
About an 18" pulley on the 2" shaft and the 24v alternator (50a) mounted beside it for pulley connection.
Previous captain said it never worked because it wouldn't spin fast enough and they would only get a few amps out of it.

My understanding is that these brushless alternators deliver power as soon as they start to spin, so wonder if I should revisit the idea of doing this with a Regen alternator?

I'll start a separate thread on this to see if anyone has tried with brushless alternators.

[jmh2002]

@Pelagic

Check out Beta Marine and Hybrid Marine for a modern take on 'shaft generators'.

They also permit operating in the opposite way with the batteries powering the electric generator/motor, which then turns the shaft and provides electric propulsion too.

It's an interesting package would could work very well for some boats (and not, for some others).

https://betamarine.co.uk/he-hybrid-propulsion/

https://www.hybrid-marine.co.uk/

The disadvantage of your boat is that it is not especially fast so there is low prop shaft speed when sailing in 'regen' mode, so the system needs to be 'geared' at the appropriate ratio just like an alternator - as I am sure you well understand.

A variable pitch propeller helps takes best advantage of a regen setup like this, and this is what systems such as Ocean Volt use on their sail drive type setups for small sailing boats:

https://oceanvolt.com/solutions/systems/

They also have a 'shaft drive' propulsion & hydro generation motor too.

https://oceanvolt.com/solutions/syst...-shaft-drives/

So yes these setups are all available, and yes technically and in theory they work, but to have them perform well the devil is in the detail.

Start a new thread, it could be an interesting topic.

[Shaneesprit]

Originally Posted by CaptainPete222

Not sure why you decided to chime in with those comments. My post about using the excess power from my PV/battery system to push my boat with an electric engine I already use on my dinghy on light winded days in lieu of running my diesel doesn’t seem all that controversial regardless what color Kool-Aid you’ve been drinking.

If you are only using excess solar and not having to run the diesel to top up the batteries then I commend your idea.

Like I said aware the massive prop was not your idea.
I also run diesel, my point was that that using electrical power and then recharging with Diesel is a double negative, (double the losses) better just use the diesel in the first place.

[Pelagic]

Originally Posted by jmh2002

They also have a 'shaft drive' propulsion & hydro generation motor too.

https://oceanvolt.com/solutions/syst...-shaft-drives/

So yes these setups are all available, and yes technically and in theory they work, but to have them perform well the devil is in the detail.

Start a new thread, it could be an interesting topic.

Thanks for pointing me in the right direction.
I'll contact Oceanvolt next week with my setup to get their advice and start a new Thread

[jmh2002]

Originally Posted by Pelagic

Thanks for pointing me in the right direction.
I'll contact Oceanvolt next week with my setup to get their advice and start a new Thread

Torqeedo is the other major competitor to Ocean Volt. Not sure if they have a 'shaft generator' variant though: https://www.torqeedo.com/us/en-us/products but all these companies seem to offer custom solutions over and above their standard product line.

Integrel is another variation on the theme - it's not quite what you are looking at but might be a useful to have an overview when considering what is available now: https://integrelsolutions.com/

Hope that helps. Even if it doesn't work out it's still interesting to see the new variants of this tech.

[Simon.Sails]

Originally Posted by CaptainPete222

My Lagoon doesn't get close to the speed necessary to have meaningful power production from the outboard, so I won't be doing that. The engine will be out of the water when I'm clipping along, which, for me, is 6.5-7 knots. That would only produce around 250W/hour. Not worth the drag and reduced speed, especially where my solar system is so much more productive.

Where your boat is sleek and light, the regen capability could very well come in handy, particularly if you're seeking to minimize the cost of panels and if you have relatively minimal energy needs.

I have thought about using the regen for my Corsair F31 that routinely sails above 10 knots (16 knots average top speed this summer for 3 hours!). Regen is particularly attractive on a fast tri because (1) there is so little space for panels, (2) I wouldn't want the full time windage of an arch slowing me down, and (3) I can charge my 1000W battery--which is all I need on that boat to run my lights, charge/run electronics, and power my fridge--just by dragging the outboard behind the boat for an hour.

I'll install the Navy 6.0 on my Dragonfly 920 trimaran this winter, will report back in spring how it performs.

[merrydolphin]

Yes, as others have said. Prop is very important as is reduction ratio.
In addition to pitch, diameter is very important. The OB must be geared and proped correctly for it to work. Power is just ONE faction. Another factor is the leg length. Is must be deep enough to stay underwater when pitching.

[mcarthur]

There's quite a bit of work on surface-piercing props too, so not all props need to be deep underwater. Closer to the surface can also be useful for lowering draft.

[Adelie]

Originally Posted by mcarthur

There's quite a bit of work on surface-piercing props too, so not all props need to be deep underwater. Closer to the surface can also be useful for lowering draft.

Surface piercing props is a high speed boat thing. EP is anything but high speed unless you are doing competitive electric hydroplane racing.

[mcarthur]

Nope, plenty of research on low-speed surface-piercing. US Navy got 70-80% efficiency at 6.5kn (old research, not modern). Good speed, although still high, for many electric yachts

[pelenter]

Originally Posted by CaptainPete222

The goal of my experiment is see if I could obtain the same propulsion from my dinghy's 6kW electric outboard as running one of my 29 hp Yanmars at 2200-2400 rpm. I usually run a single engine when the wind is light and the sails are pushing the boat less than 5 knots and in moderate breeze when trying to make my way to windward. The 6kW engine is now mounted on the port ama transom (see attached picture) and the boat will splash in a few days. I was going to post the results of the experiment for anyone interested after trying out the engine with the boat under sail, but I thought it might be interesting to hear from those far more knowledgeable about propulsion what your guess would be for increased boat speed if the engine is run at 5kW and based on varying sail-driven boat speeds, say, 3, 4, 5 and 6 knots.

Hi,

Need to replace my 2T Mercrusier for my Highfield CL 340 dinghy.
It´s just for short trips between the CAT and beaches/ports. MAximum 1 hour per day.

- Any tips regarding electric outboard motor brand and size?

- If I want to to go for a larger electric engine to eventually do wakeboard and water ski using the dinghy, how many KW are needed for a 80Kg person?


Thx,