Re: [electricboats] Electric Motor for 40' Sailboat

Good additional feedback on regen.

The sailing Uma indeed have doubled up. Impressive kit. They also are doubling up to get reliability and because they have upped their power use to that of the upmarket western home. They mentioned several times that they had found batteries had fully charged enroute with just one motor.

Anyway the props used on their kit appears to be uniquely set for regen. Anything else will indeed be disappointing. Large thin props also optimise drag reduction . 

As I said the industry is still in bleeding edge mode and maybe it will start to settle in five years and be stable in ten

Best regards

Lee Eldridge

0427874796

On 4 Jun 2025, at 23:03, gsxbearman via groups.io <gsxbearman=yahoo.com@groups.io> wrote:



To Lee

I think of regen more like a wish than a requirement.

 

All the manufacturers tout the regen of their models but all the customers seem to be upset with how little is actually generated.

 

Most of the companies don't tell you that you need to be going at least 6 knots to get ANY power from regeneration and 7 knots to get any real power from it.

 

And even if they do tell you this, 7 knots? Really? How much wind does it take to make your boat go 7 knots? Now how much more does it take to make your boat go 7 knots while overcoming the drag of spinning the prop with a load on it. How often does the wind blow that hard? What will that sea state be at those wind speeds and how much abuse can you (and maybe more importantly, the others on your boat) stand with the wind at that speed.

 

I think some of this issue is because the traditional props on sailboats are not very efficient. They usually have small blade area, some even only have 2 blades. This is what you should want on an auxiliary engine, that is not meant to be primary power, so that the drag is reduced during sailing.

Contrast sailboat props to power boat props and you will see way more blade area on a power boat.

More blade area equals more drag on a sailboat but better regen potential. So do you want more sailing performance or more regen?

 

Uma transitioned to an electrically adjustable pitch prop a while back (with more blade area than the mechanical folding one they had) strictly because they weren't happy with their regen. Just recently they have added a second identical saildrive and prop, again strictly because they  were still not happy and want more regen.

 

I would still rather have regen than not but it's not a deal breaker for me.