T-Pain Is On A Boat: Re: [Electric Boats] Prop notes - diameter, & pitch

Saturday, December 19, 2015

Re: [Electric Boats] Prop notes - diameter, & pitch - for EV

Had to look up venturi.. https://youtu.be/Qz1g6kqvUG8

Dirk

Westsail 32

On Dec 16, 2015, at 5:07 PM, Bill and Ai Qiu hopen billhopen@yahoo.com [electricboats] <electricboats@yahoogroups.com> wrote:

I've heard surrounding spinning prop with a cowl or duct with a venturi crossection can make slow knot boats 20-30% more efficient; efficiency drops off as you try to push the venturi/duct surround through the water at more than 10 knots

Bill Hopen - www.billhopen.com
Hopen Studio Inc - 227 Main St., Sutton WV 26601
304 -765-5611 billhopen@yahoo.com

From: "'cal' h20dragon@centurytel.net [electricboats]" <electricboats@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Tuesday, December 15, 2015 8:24 PM
Subject: [Electric Boats] Prop notes - diameter, & pitch - for EV

From research I've done a "square prop" seems to have the best balance in performance. From the Dave Gerr book, and my EV outboard that is a 12 inch, by 12 pitch prop. I decided on a 12" by 12 1/2 pitch as the one best fitting my outboards opening, and a stock 2 to 1 reduced rpm stock lower unit. Will see when the warm weather gets back up to Oregon, not over 34 deg. in last week. If more oomph is needed then is the time to cup the blades a bit, works wonders for water grip. That cupping should allow fine tuning of push to amps needed at specific throttle openings.

Also having a custom built skeg in stainless built to cover the larger prop size. In the engineering of this we are adding enough to provide a "kick up" situation if the lake gets a bit too shallow. Saving even one prop pays for that easy, even if I do have a super prop tuner in the area, it is a pain to have happen.

Later, Cal


From: mailto:electricboats@yahoogroups.com
Sent: Tuesday, December 15, 2015 4:19 PM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: Arrival of Motor and Controller

<Quote>
"The best way of arriving at the correct propeller for EP at this time is by looking at boats that are currently working with EP."
</Quote>

Some sort of crowd-sourced data accumulation is in order. Not sure if this is the proper forum to take that forward. Lots of variables are in play but ultimately, data will show the way. A big gorilla in the room is bottom condition (at least where I sail).

I'd think CANbus-based (and perhaps other) systems would lend themselves to data accumulation and sharing. Not sure what data to capture and how to analyze it but fortunately, the Internet is full smart folks.

Full Disclosure: I'm an Electroprop customer.

--Bob Moriarty