Re: [electricboats] Pocket Trawler Electrification

I would double check on reversing motor direction by swapping phase wires. I don't think you can do that with these motors/controllers.   I think you need to do that in the controller.  I did it by swapping two wires on my throttle at the advice from Thunderstruck Motors where I got my kit (Sevcon controller and Motenergy ME1616 motor). 

As for power expectations, I have a 6 ton monohull with 28.3 ft of waterline,  At 5 kts I am using about 2,200 watts.   You have less displacement but less waterline.   5 kts is 0.7 of hull speed for me.  That's a better way to look at it?  I get to 0.7 at 2,200 watts. 

I swapped props last season from 3-blade feathering 14" pitch, to 2-blade folding 12" pitch.  I get about the same power consumption at the same speeds but at higher RPM now with lower pitched 2-blade.  Can't get to hull speed at max RPM anymore.  I will re-gear my reduction drive to compensate ($50 belt + pulley swap).  Seems though that while there are some efficiency differences ( The 2-blade has better blade shape, the 3-blade has a lot more area), it takes a certain amount of watts to go a certain speed whether that's from motor or sails or whatever.  And to get the same watts delivered to the water by my 2-blade prop takes more RPM.  But the load on the motor is about the same? 

On the props, you can swap LH and RH any time you want to evaluate relative performance in real application. 

My installation:
http://dan.pfeiffer.net/10m/electric_drive.htm

I need to update with the 2-blade performance data....

Your boat looks like a great choice for the Trent Severn. 

Dan Pfeiffer

On 2026-01-29 9:49 am, maaseidvaag via groups.io wrote:

That's interesting that the control software monitors wattage.  I doubt I'll ever see 6000 watts, and after testing may even use the option in the software to set the maximum output to a lower wattage under the assumption that that will give me finer control at the lever if the full range no longer represents 6000 watts.  We'll see once I'm on the water.

 

I'll give the folks in Canada a call on that LH prop.  I was planning on carrying a spare prop, so I guess I might as well try the LH prop, subject to finding out what the price becomes after whatever tariffs are applied.  My understanding is the rotation direction is reversed by swapping the outside two phase wires on the controller.

 

If I do manage to get my hands on the LH prop, then the next decision is which way to rotate them.  They will be fairly closely spaced on either side of where the existing prop sits now, so I expect there will be some interaction of tip vortices (if that's the right term?).  So, do I have the props spinning downward on the inside edge of their circle, presumably drawing water downward at the centerline of the hull and creating a lower pressure zone between the props and the hull (this feels right) or the opposite, having the tips spinning upward at the middle.  I'd love any thoughts/experience others have on the topic.

 

Thanks - Lars