Wednesday, October 27, 2010

Re: [Electric Boats] Propulsion Marine 5 KW Electric Drive

 

The prop will create drag.  The effect of that drag depends on several factors.  If the sails are producing enough power to push the boat to hull speed in spite of the larger prop then the effect of the drag is negligible.  I don't have any facts to back it up but after decades of racing sailboats in light air I don't think there is much effect at very low speeds.  It's in the middle speeds that the drag will have the most effect.  There used to a lot of debate about the pros and cons of locking the prop while under sail or letting it freewheel.  
From: Steve Dolan <sdolan@scannersllc.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Wed, October 27, 2010 6:39:57 AM
Subject: RE: [Electric Boats] Propulsion Marine 5 KW Electric Drive

 

 

 

I've got 2 -18" props. When the motors aren't on I'm regenerating. I also have brushless motors which are low drag and direct drive to the shaft, no belts or other stuff adding to the drag. With that said, yes there is a loss, an average of about 1 knot. "Very much" is relevant to your speed. I do a little over 50% of wind speed and admit I have a lot to learn about sail trim. However the regeneration of power while sailing makes it worth while. As to larger than a 12" prop I would think drag would be slightly more to negligible. The thing I never understood, because it's an argument against e-drives, if you got a prop in the water on a diesel it creates the same drag if not more do to the sail drive so why would that figure into the equation?  

Steve in Solomons MD

Does a larger prop create more drag when the e motor is not on? And will this slow down a sailboat very much?

JC


__._,_.___
Recent Activity:
.

__,_._,___
Posted by at

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)