Re: [electricboats] New prop 10KW motor

I guess for a 30'-36' monohull, it does not make sense to regen.

Sailing Uma (36') on Youtube has tried, even with a folding prop.

Not much achieved, exept during very long passages.

John, very interesting to help out the drag by a little power applied for day cruises, if a folding/feathering prop is too expensive !

The help of a sudden and available power during tacking (especially singlehanded) is a big advantage of going electric !

Freewheeling without power added seems just like a drag, as the motor is brought to spin.

(There is normally no clutch on an electric boat transmission, as I understand it.)

Best solution for this boat type, if the money is there, should be a big folding/feathering prop, with the feathering as the best.

Bigger prop, at lower rpm => more efficient torque.

Carsten

On Sunday, 10 January 2021, 11:55:45 GMT+8, john via groups.io <oak_box=yahoo.com@groups.io> wrote:

Ryan,

The common experience so far has been that unless you're going really fast (as in catamaran, not Catalina), you aren't likely to be able to get anything out of regeneration - certainly not much that's significant.

John

On Saturday, January 9, 2021, 09:12:44 PM CST, Ryan Sweet <ryan@ryansweet.org> wrote:

I'm curious about this... as I've had hopes of regen. 

I have a fixed three blade. 

Under sail at speed I've tried giving it a little spin - just a few amps, in hopes that it would keep spinning. Alas, it doesn't seem to do so. My assumption has been that I need a feathering prop.  Is there a reference work to read that can help with sorting this out?

On Jan 9, 2021, at 18:53, Bob Jennings <heatnh@gmail.com> wrote:



I'll add to this. You can freewheel your prop @ 0 amps.  

On Sat, Jan 9, 2021, 9:47 PM john via groups.io <oak_box=yahoo.com@groups.io> wrote:

Depending on your circumstances, battery, if you're racing, etc...   It might be cheaper to get a fixed prop, and deal with the drag by simply running the motor at very, very low power (just enough to spin the prop).

One thing about electric boats that is very cool is that when you're sailing, if you apply less than 100W, it's often enough to turn the prop fast enough that you have no drag at all, and you may see your sailing speed go up by as much as a half mph.  (probably not legal if you're racing, but very nice if you're just cruising.)  The amount of power required is typically small enough that a significant battery bank will hardly notice it's there, especially if you're only out for a few hours (or if you have solar you can assist with).

On Saturday, January 9, 2021, 08:04:23 PM CST, Carsten via groups.io <carstensemail=yahoo.com@groups.io> wrote:

Michael, consider a big folding or feathering prop, which will give you far less drag.

Then find the proper ratio for engine rpm and prop rpm.

A toothbelt solution will give you the opportunity to change the ratio.

On Sunday, 10 January 2021, 04:29:08 GMT+8, Michael Blackstock <mdblackstock@gmail.com> wrote:

Thanks for your responses, all. I think I'm just going to go with another stock 2 blade to reduce drag under sail. I plan on utilizing the motor very infrequently, so more speed under sail sounds good to me. 

There are so many resources for Catalina owners, but I thought I would check with you all first. 

I will definitely be chiming back in when I begin my motor and battery install!

Thanks

Michael Blackstock

Cell phone 503-913-8217