You're right, John.
Size matters !
For a shaft drive, there might not be much space left.
However, an extended shaft could solve the problem, if there is enough space for that.
My so-far favourite of motor is the Thunderstruck 18 KW (12 KW at 48V) watercooled.
Does any of you have experience of that motor ?
I intend to let the existing freshwater cooling system for the diesel cool this motor.
I have a saildrive. The fixed 2-bladed prop for my 10 HP diesel is 14", and there seems to be space for a bigger prop.
Choosing a 16" or 17" 3-blade feathering will turn it into luxury high torque slow rpm propulsion !
I'm considering an Autostream 3-bladed, feathering. I read lots of good reviews.
According to Autostream, the distance of blade tip to hull should ideally be 15% of diameter, min. 10%.
I am now even more convinced, that converting my Volvo Penta 100S drive is THE solution.
It is rated for 24 HP max.
Remove the gearbox and clutch, and extend the vertical shaft through the housing top.
This will make it possible to fit a toothbelt drive to a vertical mounted motor.
There are quite some interest on the net for converting saildrives to electric propulsion, but as far as I know, no one has done it yet...(?)
With the diesel tank placed aft gone, I can fit the motor aft of the saildrive there, leaving lots of room for batteries, where the stinking diesel was. The cooling water inlet/outlet will be downward, so no wetting problems to the motor, if anything of the cooling system leaks.
I hope to begin my project this summer, if covid and airline flights allows me to get home.
I can mount an outboard at the stern while the conversion goes on, and then still be sailing ;-)
Cheers,
Carsten
On Sunday, 10 January 2021, 14:58:55 GMT+8, john via groups.io <oak_box=yahoo.com@groups.io> wrote:
The other consideration on prop size is the limitation of available space. There's only so much physical clearance between the prop shaft and the hull. You'll need to leave at least an inch of clearance. I wouldn't be surprised if the existing prop wasn't at least within range of the max allowable diameter before hitting something.
And yes, being able to hit the throttle for a little more "umph" when tacking in light air and/or single-handing is another nice benefit of electric!
It's like using just a little just to keep the prop spinning when cruising. In theory, you could do that with a gas/diesel engine - but you'd have to keep the engine running, burning a LOT more fuel than would be worth it, and suffering the noise, etc. Electric motor sailing, on the other hand, is pretty nice!
On Saturday, January 9, 2021, 11:25:26 PM CST, Carsten via groups.io <carstensemail=yahoo.com@groups.io> wrote:
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.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!ThanksMichael Blackstock
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