Re: [electricboats] Electric Drive Installation - Some Data

All good Questions Carsten.  And good suggestions.  I have done the gopro on a stick at the dock to inspect the bottom.  I loose the wifi connection after it's about a foot underwater but it keeps recording. 

I have tried a bit of reverse then to neutral to get the prop set the other way so it will feather while still moving forward.  I have had mixed results.  But I have only been at this for a couple weeks so I need to do more experimenting.  One problem is be the vagueness of the feel of the lever control.  The neutral detent in the throttle unit is hard to feel from the lever in the cockpit through the Morse cable connection.   So its a bit too easy when shifting to neutral to skip over and into the opposite direction. 

 

Yes, adding a bit of power to tack has been handy.  I have only done that in light (4-7) wind with chop conditions which are a bit troublesome for tacking.  I also used a little bit of motor to maintain 4-5 in those conditions rather than 2-3 I would get with just sail.  Worked well.   But adding the power instantly with the feathering prop still requires that you mind the wind up of the motor until the prop blades are fully rotated on the hub.  The acceleration curves of the controller will help with that. 

I may have overstate the Volvo idle.  Probably more like 800 looking back at my notes.  And I may have set it there to get past the vibration at very low RPM.  Mine was a 2 cyl Volvo MD11.   My notes on speed vs rpm started at 900.  I may have skipped the lower RPM in recording that.   That is still a lot faster than the slow speed you can run the electric at. 

I will probably switch that that same hose I used for raw water which is basically the auto type but with a marine rating (Trident).  I will add that bleed valve at the controller inlet and I may re-mount the controller lower on the bulkhead so there is more space above it in the fill hose to get the coolant level higher above the high point in the system (controller).  I will also look into adding a sight tube that is OK to 100C so I can monitor for bubbles.  In the mean time I'll keep the power down to keep temps under 65C.  And that seems to be under 6 kts.  That's where I would operate normally anyway. 

Another thing I probably should have had was a drain valve on the coolant system.  It might help to keep from making a mess when re-configuring the system.  But I was really trying to keep the parts count to a minimum to honor the R=1/P relationship I try to live by. 

R=1/P
R is reliability
P is number of parts

The goal in design should be less than one part.


Dan Pfeiffer

On 2021-07-25 3:47 am, Carsten via groups.io wrote:

 

Dan, I envy you to just go for a sail !

For feathering, perhaps set sail, rev the motor up to 6 knots and set it to neutral. Then it should feather.

 

Does it begin to spin in short surges (unfeathers), if it is already feathered at higher speed, and you slow down ?

 

Another thing, when you tack, you can use the instantly available motor to keep up the speed, so it doesn't "die", when turning through the straight headwind. My boat dies easily in light winds, so I am looking forward to that.

Keep the motor running up to 6 knots, and set to neutral  for feathering. Just an idea.

 

If you want to check what's going on underneath, you could mount a Gopro with Wifi on a stick (aluminum tube), and see what happens on your smartphone :-)  See Youtube for connecting to wifi.

Also nice for checking growth.

When sailing, of course you'll need to secure the stick properly !

 

My MD6A Volvo idles at 600 rpm. 1100 seems a lot ?

 

You can use automotive hoses for the cooling system, and I think you already used that for the raw water ?

At the top inlet (the blue) hose of the controller, you can insert a valve to release the air trapped there.

Run the pump a bit when topping up, so it circulates.

Again, just an idea.

 

Carsten

 

 

 

On Sunday, 25 July 2021, 13:13:46 GMT+8, Dan Pfeiffer <dan@pfeiffer.net> wrote:

 

 

I have a little more info on props and performance in general.  I got out for an excellent sail today in 15-20 kts.  While sailing at a sustained 7.5 knots I checked the propeller and it was not spinning so it found its way to being feathered all on its own.  All I did was put the motor control to neutral.  At slower and more typical sailing speeds of 3-5 kts it seems to spin in short surges.  So there is more to learn about the prop behavior but it is able to fully feather and stay that way with more boat speed. 

And another thing about how the boat handles now compared to the diesel.   I can operate the electric at very slow speeds.  The diesel could not do that.  It idled at 1100 rpm which translated to 550 prop RPM and a bit better than 3 kts.  I can operated the electric at much slower RPM.  The steerage suffers greatly so it's debatable how useful that is but it is a distinct difference. 

Also I will need to upgrade the hoses I used for the cooling system.  They turn out to be rated for only to 65C and that isn't enough for high powered operation.  That's only 15C beyond the set point to turn on cooling.   I used Trident reinforced water hose.  I'll need something made as a heater hose.  The transparent hose was very handy in chasing bubbles out of the system.  But keeping the hoses from melting will be more useful. 

Dan Pfeiffer