Efficient electric boat

[portacruise]

Originally Posted by MCDenny

Porta, It's a little dicey using the graph at very low power levels as measurement inaccuracies can be a greater proportion of the total result.

It is true though that very little power is needed to move a boat slowly. At the WoodenBoat Show last summer I was easily able to row a 19' sail boat with 3 men and all sail up (in zero wind and current) at least 2 mph.





That 2mph is hard to maintain over long distances with very short hulls, especially with additional resistance when using super stable inflatable pontoon fishing platforms. The lengths run to over 12' but a motorized "porta" travel version under 6' takes a bit more consideration and energy.





I wanted to see if I could find a prop that would unload the motor enough to get decent range with the resistor control at WOT and avoid the cost of a PWM controller. A 10x3 showed some promise but I didn't get conclusive data. APC props are not available in pitches lower than 3 in appropriate diameters. If your friends want to try this on their dingy witht the resistor control they should try both a 10x3 and and a 10x6. The 10x6 will produce more speed but at much higher amp draw and commensurate short range. They will want to get a letter V drill (0.377") to bore the prop to fit the .375" MK shaft. Using a 3/8 drill will give a very tight fit - difficult to get on and off.





Thanks for these tips. Fooling with the PWM probably doubles cost and time to modify, plus electronics are vulnerable to shock and corrosion due to wicking in salt water atmosphere, IMHO. The original connectors should probably be soldered if the resistor control will be retained and the basic unit is kept. For speed control, I have used a submersible sealed series-parallel switch with 2 batteries in the past that has been bulletproof. That gives the options of long range or short burst of power for emergencies. For more power on big boats, the small MKs can be overvolted to 24v as I posted previously. The overall speed range is defined by the APC selected.

I have also worked out a fitting/adapter on my longtail arrangemet that allows use of APC directly without any drilling. Props can be switched out in 10 seconds. The props remain unmarked and those unsuitable are refunded by my hobby shop.



Another note about the final graph. These tests were conducted in modest wind, maybe 5 - 8 mph blowing against the current. I assumed the added drag caused by the 3" - 6" chop wouldn't matter very much and the wind effect would be cancelled by taking the speed average over two way runs. Looking at my data from a few days earlier I now see I was wrong on one or both counts. Two days earlier in very calm water I was able to achieve 4.3 mph with 30% less input power to the same motor setup. I now realize that since the wind drag varies with the square of the speed, averaging up and down wind runs is not the same as conducting the test with no wind. In the final test my speed, relative to a 5 mph wind, was -2 mph downwind and +11 mph upwind. That's quite a bit different from the +3 vs. +6 mph apparent headwind I would see at zero true wind speed.

The conclusion that the prop and controller allow big improvements in range is still valid, but as they say YMMV.




Yes, especially in Michigan area, cold weather and YMMV ( your milage may vary) to the downside.





Another thought on the fairing. I learned today that the round shaft has a Cd of .47 while the teardrop fairing has a Cd of .09. Even considering the shaft is 1.125 thick and the fairing is 1.5" thick, that means the drag coming from the shaft is reduced by a factor of 4 - tha'ts a lot when working with such small power levels. Also, it think the fairing helps the prop work more efficiently (no proof, though) because the round shaft leaves a turbulent wake and a lot of air right in front of the prop. The fairing smoothes out this flow.

The fairing may not work as well when turning the motor is used as a form of steering. I have used "shark fin" adapters with trolling motors before and find steering to be very twitchy, requiring constant correction. The cruising speed on most of these inflatable pontoons is probably closer to 2 mph so the fairing may not be such a factor.

Still it's incredible what you did with the Cd on the shaft and thrust with the APC!

Porta

[Submarine Tom]

On the contrary, I think the steering will be great.

It should take very little angle to produce yaw providing the cowling is coupled to the shaft, otherwise steering will still be good due to directional thrust or vectored thrust, whatever you want to call it.

Tom

[portacruise]

Reference to running 12v troll motors at 24v for double power listed in above responses is listed in "Batteries" section forum posts 279-283. Sorry, cannot return PM directly from this computer.

Porta

Originally Posted by portacruise

The fairing may not work as well when turning the motor is used as a form of steering. I have used "shark fin" adapters with trolling motors before and find steering to be very twitchy, requiring constant correction. The cruising speed on most of these inflatable pontoons is probably closer to 2 mph so the fairing may not be such a factor.

Still it's incredible what you did with the Cd on the shaft and thrust with the APC!

Porta

[MCDenny]

If anyone is interested the brushless outrunner motor I had wound for a Kv=117 so it could turn an APC prop in the water at a reasonable speed on 12v, its here:

http://cgi.ebay.com/ws/eBayISAPI.dll...=tab%3DSelling

[portacruise]

What kind of speed control, where do you get it, and how is it hooked up? I see 3 wires in the picture....

Porta

Originally Posted by MCDenny

If anyone is interested the brushless outrunner motor I had wound for a Kv=117 so it could turn an APC prop in the water at a reasonable speed on 12v, its here:

http://cgi.ebay.com/ws/eBayISAPI.dll...=tab%3DSelling

[MCDenny]

Porta, I'm using a Castle Creations Mamba Max. There are many others that will work. Just depends on how much power you need.

Tower Hobbies has a huge selection of brushless controllers and excellent service. You need a controller for a model car if you want forward and reverse.

The controller will have two input wires to connect to the battery, three power wires to the motor, a three wire flat cable to connect to the receiver (use a servo tester to generate the throttle signal, Tower has an Astro-Flight model for $25) and an off-on switch.

I'm just selling the motor. I'm keeping the controller for my trolling motor project.

[Guest625101138]

I have been looking at what sort of motor controller combination you would use for a reliable, long-lasting electric drive. Something that has continuous rating rather than the RC burst type motors and controllers.

I found Kelly Controls are now covering a wider range. They have a nice little PMSM:
http://www.newkellycontroller.com/pr...roducts_id=509
Not a lot more expensive than the bigger RC motors. Probably better efficiency and certainly more robust if a little heavier.

They also have a reasonably priced controller:
http://www.newkellycontroller.com/pr...roducts_id=503
I gather is has reversing switch because there is a reversing alarm.

Rick W

[MCDenny]

The Kelly products are sensored so probably have smoother operation at low speed.

I have to say, though, my bench tests with the Hyperion motor and Castle controller (sensorless) showed it to be smooth and quiet at very low speeds. These are both high end brands in the RC world so maybe that explains the differences between this and the results Jeremy reported many pages back.

[Guest625101138]

Denny
I have been asked about an electric outboard equivalent to the smallest ICE outboard - these are 2HP. So I have been looking at what would be used for around 1kW electric swinging a more efficient prop.

The Hobby City stuff is OK for fiddling with but the durability is suspect. Like Jeremy has found, most users find they have to re-glue magnets and fit more durable bearings to get reliable operation.

If you look at the better made RC motors then they are typically more expensive than the new Kelly range. Hence for this particular application I am looking at this stuff. There is a weight penalty but it is not excessive for a boat.

One important factor is the kv of the Kelly motor I linked to. With a 2:1 rightangle gearbox it allows a decent size prop. Other advantages are ability to reverse and a selectable current limit.

I bought my Mars motors and controllers from Kelly and was very pleased with the service.

So my interest in the electric drive is a little bigger than you are doing and I would like something more robust as it will be pushing a boat that will have high windage in a good breeze.

Rick

[blisspacket]

A while back I wrote MinnKota and asked why they weren't producing something advanced like the Torqeedo. Now I have to reconsider. Listening to all the motors on UTube, I have to say a submerged brushed motor has the quality of power that I see as essential to electrics: total quiet. Somewhere around the hitech corner there might be an oilfilled brushless that will bring us totally quiet efficient power. I'm waiting...

[MCDenny]

Jay, The small Torqeedo motors use two planetary transmissions in series to get an 11:1 reduction ratio. The noise comes from the gears, not the motor. I'm told the new larger Cruise models do not make the noise. I fooled around with a Torqeedo 401 at a boat show running in a barrel. You could hear the gear noise but it was not as bad as I thought it would be from listening to the youtube videos.

I have a EPIC whisper OB working as a pod motor on my second Harmony 25 launch. It is a brushelss AC motor running at 72v but direct drive to the prop. It is just as quiet as the little MK motors.

[portacruise]

2 ways I have used to gear down for quiet, low rpm, electric efficiency- cogged belt drive OR overdesigned nylon spur motor gear. Oil fill viscosity causes losses and will not always stop whine which transmits via metal to metal contact.

Porta

Originally Posted by blisspacket

A while back I wrote MinnKota and asked why they weren't producing something advanced like the Torqeedo. Now I have to reconsider. Listening to all the motors on UTube, I have to say a submerged brushed motor has the quality of power that I see as essential to electrics: total quiet. Somewhere around the hitech corner there might be an oilfilled brushless that will bring us totally quiet efficient power. I'm waiting...

[joco]

jeremy harris any new improvement on your project.?

mabe found something that could be use in that project to.

i will use it on mine..might or or might not..but its fun to try.

i founfdin my basement a little tanaka 1.2hp or a 1.5hp outboard.

i will take the motor off...the muffler that goes down off the boat brakcte off..so the only thig that will be left that alminium tube and the shaft inside and the lower unti/prop that men mabe 4 pound max..mabe even less.

not sher what kind off motor i will use taugh.

did like the little motor you post in the first few treads.

i was thinking eltric drill..but need to many batterie to last at least 4h..unles i get a 12 volt drill and put it on a 12 vold batterie.

but wen i was looking at the lower end you did wit that drill thing.

and looking at this lower unti..m sound not to bad.









joco

[wardd]

curious here.
what would be the advantage of a genny connected straight to the motor, no controller?

with cpp

[joco]

there could be a controler..just not on the motor.

itself...could be a wire that goes to the motor and control frome the seating area.

no pro here in electricity...

just a taught

joco