Shaft horse power (SHP) is what matters when moving a boat or doing any work.
From: "Douglas Kay dougkay8@gmail.com [electricboats]" <electricboats@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Saturday, October 28, 2017 4:52 PM
Subject: Re: [Electric Boats] Re: changing an outboard to electric
5.5 SHP electric = 5.5 SHP internal combustion = 5.5 SHP from squirrels running in wheels
The conversion from the electrical energy source to SHP-hours may be roughly twice as efficient compared to obtaining the same SHP-hours from say Diesel fuel.
The problem is weight of batteries (ie thick plate FLA) to store half the required energy as in diesel fuel is roughly 180 times greater. Furthermore 5.5 SHP is barely going to move your boat when your fuel tank is 180 times heavier. Further furthermore, the batteries do not get any lighter as they get discharged but the weight of the stored Diesel fuel approaches zero as it is burned up so you need less SHP to maintain your speed towards the end of the trip compared to the start.
Regardless of the of the elephant in the room which is the poor kWh/kg capability of batteries, electric boat enthusiasts are trying to improve the efficiency of their electric motors. Helloo, if you are at 90% efficiency with your motor then you can't even achieve 10% improvement because you will hit the big wall built by the laws of physics. "Hugely bigger" than even Trump's wall.
Sorry, if I offended anybody with the basics. Regardless of the of the elephant in the room which is the poor kWh/kg capability of batteries, electric boat enthusiasts are trying to improve the efficiency of their electric motors. Helloo, if you are at 90% efficiency with your motor then you can't even achieve 10% improvement because you will hit the big wall built by the laws of physics. "Hugely bigger" than even Trump's wall.
Ahmet
From: "Douglas Kay dougkay8@gmail.com [electricboats]" <electricboats@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Saturday, October 28, 2017 4:52 PM
Subject: Re: [Electric Boats] Re: changing an outboard to electric
It really depends on what type of boat but 5.5 Hp electric is roughly 12H.p. I.C. so work from there.
On Sun, Oct 22, 2017 at 1:58 PM, danbollinger <no_reply@yahoogroups.com> wrote:
Like others have said, your 5.5Hp electric will certainly move that boat, probably up to hull speed, but not much faster, probably 6–7mph. Keep in mind that you have a planing hull, which adds drag below planing speed. While the 90Hp lower is overkill, as you said, it will swing a larger prop. I'd look for a prop that's as large as the unit will swing (but leaving a 1" space below the anti-caviting wing), and having two, narrow blades.
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Posted by: sv8827 <sv8827@yahoo.com>
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