electric motor with regen

[flybynight]

Hello everybody! Another question from the learning wannabe sailor.

What's the inside scoop on electric motors with regen? They say - you need at least 16" propeller with 4-5 blades for regen - at speed over 4 knots under sails. Any advices and tricks? Scary stories?

Can you recharge batteries also from solar batteries? I don't know - gym bicycle? (just fantasizing)

Thanks!

[StuM]

Regen is useful if you have a fast boat and sail a lot in good winds.


They will give you little or no energy until you get over 5 knots and will provide a noticeable speed reduction unless you are making close to hull speed.


Regen from exercycles etc has been discussed here several times. The bottom line is that you have to be very fit to produce more than 100 W for any significant length of time.

[zloitapok]

Originally Posted by StuM

Regen is useful if you have a fast boat and sail a lot in good winds.


They will give you little or no energy until you get over 5 knots and will provide a noticeable speed reduction unless you are making close to hull speed.


Regen from exercycles etc has been discussed here several times. The bottom line is that you have to be very fit to produce more than 100 W for any significant length of time.

All above is correct.
In addition: I using a 250W solar panel at my boat, it provide me additional +12..15 km of range each sunny day at slow speed (4-5 km/h). Boat is 25 ft, 2300 kg full weight.

[a64pilot]

Taking a propulsion propeller and reversing the water flow through it is much more inefficient than using a prop designed from the beginning to be drug through the water and power extracted from it.
If you desire to use the sails of your boat to generator electrical power, a tow behind generator would make much more power and slow the boat less to do it, however you don’t see many of them being used.
Reason is the the average cruising boat will be slowed by more than most are willing to accept to get a little “free” electricity.
Or cruisers are just an ignorant bunch and don’t know any better, it’s one or the other.

[seandepagnier]

Originally Posted by StuM

Regen is useful if you have a fast boat and sail a lot in good winds.


They will give you little or no energy until you get over 5 knots and will provide a noticeable speed reduction unless you are making close to hull speed.

It is possible to generate power at lower speeds.

I achieved 0.5 amps at 2.5 knots tidal current at anchor using 18 inch 2 bladed 3d printed repeller (generating prop) It has 2 stage belt gear up to get higher rpm to generator.

There are designs which fly what looks like a glider anchored to the bottom in figure 8 using control surfaces. A generating prop on the glider produces power since it's apparent speed in the water is several times the speed of the current. This can generate significant power in slow currents of less than 2 knots.

Regen from exercycles etc has been discussed here several times. The bottom line is that you have to be very fit to produce more than 100 W for any significant length of time.

100W is not much. I can produce 200W for basically all day but I have to eat more food.

Originally Posted by a64pilot

Taking a propulsion propeller and reversing the water flow through it is much more inefficient than using a prop designed from the beginning to be drug through the water and power extracted from it.

This is correct. I use 3d printer to make perfect generating shape then glass over it.

It's also possible to design a propellor which is equally bad at regen as propulsion.

You can also design propellors equal in forward as reverse propusion, but this is a completely different propeller as well.

If you desire to use the sails of your boat to generator electrical power, a tow behind generator would make much more power and slow the boat less to do it, however you don’t see many of them being used.
Reason is the the average cruising boat will be slowed by more than most are willing to accept to get a little “free” electricity.
Or cruisers are just an ignorant bunch and don’t know any better, it’s one or the other.

The amount of drag does not slow the boat much if it is already overpowered by sails.

Tow generators are well known, and reliably make significant amounts of power.



Look for gearless electric bicycle hub motors. They are already very low rpm, efficient and quiet and come with regen controllers. These motors also can push most cruising boats up to 40ft at 2-3 knots in a calm using 36-48v batteries drawing 10-15 amps which you may find useful.

[StuM]

Originally Posted by boat_alexandra

It is possible to generate power at lower speeds.

I achieved 0.5 amps at 2.5 knots tidal current at anchor using 18 inch 2 bladed 3d printed repeller (generating prop) It has 2 stage belt gear up to get higher rpm to generator.

There are designs which fly what looks like a glider anchored to the bottom in figure 8 using control surfaces. A generating prop on the glider produces power since it's apparent speed in the water is several times the speed of the current. This can generate significant power in slow currents of less than 2 knots.

But not with a workable propulsion motor propeller

100W is not much. I can produce 200W for basically all day but I have to eat more food.

That I'd like to see. You must be very fit and have a very efficient generator setup.

[GordMay]

Greetings and welcome aboard the CF, flybynight.