T-Pain Is On A Boat: Re: [Electric Boats] Propulsion Marine 5 KW Electric Drive

Tuesday, October 26, 2010

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

It will usually make sense to use the electric drive while sailing. It takes very little power.

Dan

--- On Tue, 10/26/10, Rob Johnson <dopeydriver@yahoo.com.au> wrote:

From: Rob Johnson <dopeydriver@yahoo.com.au>
Subject: Re: [Electric Boats] Propulsion Marine 5 KW Electric Drive
To: electricboats@yahoogroups.com
Date: Tuesday, October 26, 2010, 4:10 PM

Just to go off on a tangent slightly.

Assuming we have a motor sailer with a hybrid diesel of 50hp diesel , and 10hp electric .

Under sail , wouldn't we get maximum value from the electric motor , turning the large prop ?.

The motor isn't so much driving the whole show , as contributing , and instead of there being prop drag , there is prop drive .

What I envisage is an electric drive contribution for most sailing time .

Does this make sense ?.

Rob J.

From: James Lambden <james@toolboat.com>
To: electricboats@yahoogroups.com
Sent: Wed, 27 October, 2010 6:49:02 AM
Subject: Re: [Electric Boats] Propulsion Marine 5 KW Electric Drive

Dick,

That would be true. More propeller area means less propeller slip and higher efficiency.

However, you can accomplish the same thing by having a larger propeller turning slower. ( A larger propeller will require a higher reduction gear ratio )

James

On Oct 19, 2010, at 10:34 AM, Dick B. wrote:

Jim:

You said:

< < However, as an electric drive consumes more power, the thrust per kilowatt decreases. This is because the propeller gets less efficient the faster it turns, which is a result of more propeller slip. Also, the electric motor becomes less efficient as it creates more power.>>

This would indicate that a more efficient electric drive system to power a boat would be to have several motors running at a fraction of their max output driving several peopellers turning at slower speed. Is this true?

Dick