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Re: Getting Into Electric Power Catamarans

Posted: Nov 01 2021 3:00pm
by ZeroEm
Good eye. Did not see that at first.
by Voltron » Feb 09 2021 1:38pm

It looks like the strut is being used as a hydraulic adjustable belt tensioner.

Re: Getting Into Electric Power Catamarans

Posted: Nov 13 2021 10:41pm
by bobkart
The 6kW motor arrived last week, and we got out on the water with it today.

It worked well; good power and speed. But we experienced ventilation (also referred to as cavitation) approaching top speed.

Transom could be a bit lower. Also, ePropulsion makes an 'anticavitation plate', so that's another option.

On one run I saw over 20km/h, so around 13mph. Assuming that holds after fixing the ventilation problem, that's right in line with my estimates.

Re: Getting Into Electric Power Catamarans

Posted: Nov 14 2021 8:21am
by SlowCo
That is a very decent speed :thumb:
Maybe also try different props to get better efficiency?

Re: Getting Into Electric Power Catamarans

Posted: Nov 15 2021 7:43pm
by bobkart
Hi again SlowCo!

The motor comes with two propeller, differing mainly in pitch. I'm using the higher-pitch propeller, due to the pitch involved being more in line with my expected top speeds. The lower-pitch propeller has about 30% less pitch, so would likely only achieve around 10-11mph. I could see that propeller coming in handy if I was able to carry enough load to drop the top speed of the higher-pitch propeller down below that number, or perhaps if I was towing something heavy.

Re: Getting Into Electric Power Catamarans

Posted: Nov 16 2021 5:57am
by SlowCo
The cavitation would indicate that a different prop could bring even higher top speed without the ventilation and be more efficient. I would hook up a watt meter to see how much amp draw there is at different intervals/speeds. And try an even larger/higher pitch prop to see the difference.

Re: Getting Into Electric Power Catamarans

Posted: Nov 16 2021 9:28am
by bobkart
SlowCo wrote:
Nov 16 2021 5:57am
And try an even larger/higher pitch prop to see the difference.
Unfortunately, there's only one other pitch of propeller available, and it's lower pitch, not higher.

The control for the motor includes an instantaneous watts readout (and speed). I will definitely plot those two values at various wattages (1kW, 2kW, ...). I did notice that I was able to achieve the same speed as the top speed of the 2.2kW motor (11km/h) at lower wattage than 2.2kW. Due to a more efficient propeller than is on the smaller motor, no doubt.

Re: Getting Into Electric Power Catamarans

Posted: Nov 25 2021 8:35am
by SlowCo
There must be higher pitch/faster (aftermarket) props from different manufacturers that can be made to fit?
In the trolling motor world there are guys making their own props or using model aircraft props with surprising results (higher speeds @ less amps so longer trips):






Re: Getting Into Electric Power Catamarans

Posted: Nov 26 2021 2:24pm
by bobkart
I'm all for going faster/further on the same power/energy. Unfortunately, my searches for aftermarket propellers for the ePropulsion Navy 6.0 Evo don't reveal any sources.

Of course someone could measure the mounting pattern and integrate that into a new propeller design, but that someone would not be me.

I also feel like 13-14mph is the right speed for the 6kW power level and this boat. This is based on other quoted speed/power points.

I got the transom lowered by almost exactly one inch (as much as will fit the current parts). Just waiting for a dry-and-not-too-cold day to test it.

Re: Getting Into Electric Power Catamarans

Posted: Dec 02 2021 4:35pm
by bobkart
We got out on the water a few days ago with the transom lowered one inch. At first it would still ventilate at top speed, then I trimmed the motor in five degrees and that pretty much cured it.

It was windy and rough, as can be seen in this rear-facing video:

https://www.dropbox.com/s/kmsuo94jgmygkeq/GP010001.mkv

I saw 20.x km/h on the readout, so about 12.x mph.

Here is a photo that shows the trim angle:

https://i.imgur.com/NwvLsaF.jpg

It would still ventilate in the worst of the waves. I'm pretty sure the so-called Anticavitation Plate would cure the problem the rest of the way, and probably allow me to go back to a straight-ahead trim angle, and maybe even allow raising the motor back up to the original height.

Re: Getting Into Electric Power Catamarans

Posted: Dec 02 2021 4:49pm
by SlowCo
Very good speed!