T-Pain Is On A Boat: Re: [Electric Boats] Folding Prop and Regen

Thursday, June 6, 2019

Re: [Electric Boats] Folding Prop and Regen

Hello Martin,

That video is a very simplified view of the Oceanvolt regen capability. They do not lock the blades in open position. What happens is the button pulses the motor at a high speed to get the prop to open while sailing. Then the centrifugal force of the water against the blades and the motor continuing to turn at an optimum speed keep the blades open. If you look closely at the video you see the blades open fully and then relax a bit. What Oceanvolt has been able to do is an algorithm in their programming that continually tunes the speed of the motor to keep the prop open. It may speed up or slow down depending on if the boat is against a slight current or has a lift and sails faster. What gets the power flowing back into the motor (remember the motor is turning to keep the prop open), is when the boat sails faster than the speed at which the motor is turning to keep that prop open.

This is the layman's explanation. There are much more technical details which I can't begin to go in to. All I can say is that yes, you can do regen with a folding prop. Some are better than others. Flexofold is very good and Gori is even better. 2-blade is good, but 3-blade is best. However, if you really are wanting as much regen as possible then use a fixed 3-blade prop.

Regen can be done with a folding prop on a shaft drive system as well. The keel configuration has a lot to do with whether you can get regen though. The best is a fin keel boat with a spade rudder. That way there is plenty of water flow on the prop. Here is the video of the Danish sailboat owned by the CEO of Clean eMarine (formerly ASMO Marine) showing regen with a Flexofold 2-blade prop.

https://www.youtube.com/watch?v=Zljhl89Rc54 The Thoosa systems are manually controlled to achieve regen unlike the more automated Oceanvolt systems. I also know that Electric Yacht has regen function much similar to the Thoosa systems. We have no data or experience with the regen from a Thunderstruck kit.

Bottom line - regen is a gift! It will offer some power storage (amps) back to your battery bank after a longer period of sailing. For day sails you aren't likely to get much regen due to tacking and a shorter time on the water. Good regen means getting the great beam reach where your boat is sailing at its full potential and holding it over several hours.

Sally Reuther

Annapolis Hybrid Marine

On Thu, Jun 6, 2019 at 9:27 AM Martin Thacker martythacker@gmail.com [electricboats] <electricboats@yahoogroups.com> wrote:

Yes I've seen the information from the ocean volt system that uses a folding prop for Regen,
here is a video of it: https://www.youtube.com/watch?v=OPSruoTjLZU
They are pushing a button which takes the prop out of the folded mode and must set it into a locked mode where it becomes a turbine.

It seems you would need some control on the folding mechanism to over-ride its natural tendancy to fold up when under sail.

I am also interested to know if anyone has used a folding prop setup to do regen on a shaft based electrical motor . (not sail drive)

thanks

On Thu, Jun 6, 2019 at 1:48 AM 'Gennaro Fazio' gfazio@rochester.rr.com [electricboats] <electricboats@yahoogroups.com> wrote:

I have a 10.5Kv thunderstruck and a non folding 3 blade prop – it starts spinning at 4.5 kn to give me -1.5 amps.. Folding props do not have the same resistance in the water – unfortunately you will not have any regen. Gennaro

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
Sent: Tuesday, June 4, 2019 6:18 PM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Folding Prop and Regen

Anyone using a folding or feathering prop and able to regen? Im converting my NY 36 from a volvo md7a 13hp to a 10kw thunderstruck sailboat kit. I have a folding prop and i was wondering if it will spin up for some regen underway.

Thanks
Gary S.