DIY Electric Surface Drive

DIY Electric Surface Drive.

Electric Autos have gas on board power so you never are left stranded and no reason why you can not recharge on board to keep batteries well charged even as you motor..
Gas Electric are great in autos so why should boats not have the same.
Better than carrying an outboard spare motor.
Carrying a pair of oars replaces your gym visits.
A sail perhaps is always useful.
What is a bit of extra weight compared to comfort and being able to reach you destination on time.
Main motor, spare outboard, oars, sail have always been on my camping and cruising trips and even using the mast to pole the boat along in real emergencies.There was never any one around to give me a tow home.

 

mydauphin - the batteries have an operating range from 50v to 36v. A 3 mile trip at various speeds brings the batteries down to 47v. A rough guesstimate would be a 10-14 mile range at various speeds with the current setup. The controller logs alot of information to an excel file, at some point ill do something with that. With the 10.5x12 prop I am really just trying to see how fast I can get this thing without burning up the motor. The next step will be to find a prop that gets me the speed id like but keeps the amperage in the continuous duty range.

Tom Kane- I'm beyond happy with it, especially with today's run hitting 25 mph. When I started this I never expected that I would reach these speeds. I just wanted to go faster than the 8.5mph I got with the outboard conversion. In hindsight I should have skipped the outboard conversion and just built this from the start. The drive definitely works in sub-surface and surface piercing mode. I went from 18' to about 8" of water today with no problems, just hit a switch and trim the drive. From here I plan to further refine this drive. I'll pull it once the lake freezes and weld the skeg and protection plate. Put some time into making it look decent. Experiment with some other props. And just have fun until its too cold to be enjoyable.

 

10 to 14 miles is a lot more than I would think. At 10 knots it would take an hour, or half an hour at 20 mph. Irie, to what point can you take the battery down to without damaging them? Also interesting will be to record the temperature of both the motor and the batteries. I believe if you keep them down youm can extend your range.

 

I went and rounded up some real numbers so we could get a better idea of range. These numbers are with the 9x10 prop. At 16 mph the motor draws 215 amps at 41.5v , 8922.5 watts. The batteries are 2kwh each so 4 kWh capacity. They can be drawn down to 36v without damage. So in theory the boat could cruise at 16mph for 30 min continuously and travel almost 8 miles. At least I think that's right. And my initial guesstimate was definitely high. Heat at this power level isn't an issue as the draw is close enough to the continuous duty rating, with the larger prop it becomes more of a concern. The controller records battery + and motor - temps. I'll have to figure out a way to track battery temp.

 

Achieved 25 mph running as a surface drive. 42.5 v, 324 amps. 13.7 kW. I've noticed some bounce in the drive when running at the surface, I'm going to move the actuators back outside the hull to brace the drive.

http://youtu.be/FmWEORpjX6w

 

Cool... bounce.... it is experiencing torque, lift, thrust. It needs to be real sturdy to handle stresses. Keep an eye for deformation and wear. When prototyping things like failures are the norm until you find weak spots. It is better to catch them before they break.

 

Actuators have been moved, they are supposed to be waterproof, but I figured a plasti-dip wouldn't hurt. This arrangement makes the drive far more rigid. The drive is built pretty sturdy. Everything is 1/4" aluminum or thicker. Only the 2 pieces of angle on the inside of the transom are 1/8" and are easily replaced if they show signs of stress. I do see what you mean about finding the weak links and fixing them before they fail

 

So many ways to build a drive for boats and you can never be sure you have got all the best ingredients in your recipe.

 

It is trial and error, break and replace. Then adjust, tune, fix, and start process again. That said one always can not underestimate torque. Torque breaks shafts, splines, joints and bolts. You have to do proper slow testing procedures, and even design break points into the system so that it breaks as intended. Don't mean to sound like your mother, but everyone gets excited about projects and forgets about safety and taking it slow.

 

That sounds like my entire summer. I spent a while stuck at 8 mph, ventilation was my nemisis. So there were a few months of lower speed testing. Initially I had the drive fixed at 15° with no cup in the prop and would ventilate anytime I tried going faster than 8 mph.

Linear actuators were added which allowed me to experiment with different shaft angels on the fly. I found that trimming the uncupped prop down to 20° doubled my speed to 16 mph. Ventilation would still occur at full throttle so I started to consider adding cup.

Since the 9.25x10 prop only cost me $30 and I wasn't going any faster with any other change I decided to try cupping. There's not a lot of information about diy prop cupping but i found a few helpful bits of information and had a go at it. I was definutely surprised by the results in that ventilation no longer slowed the boat but jumped it up to 20mph and reduced the amp draw. At this point I started this thread.

Further experimenting with trim angels has shown me that running the prop on the surface lowered the amp draw and increased voltage/rpm. I'm working on putting this data into some charts since the controller logs it to an excel file.

Its definitely been a slow progression with lots of lower speed shake downs. I'm confident the actuators on the outside will eliminate that "bounce". Should have time to test tomorrow

 

Yes, ventilation should not be a problem on a surface drive. Perhaps you did not have surface props, The lower torque load is why I like surface drives, you can go with bigger propellers since you only have half a propeller in water.

 

I definitely didn't have surface props, still don't. The 9.25x10 was a used Johnson 9.9 outboard prop and the 10.5x12 is from a omc/Johnson v4 or something like that. I don't think either one was ever intended to be run at the surface. That's why initially I ran the drive at 20° so the props would run subsurface. I'd like to try a SS prop designed for surface piercing operation. I'm guessing a 10x14 cleaver would keep my power draw about where it is now. But I have no idea how much pitch was added to the 10.5x12 when I cupped it. What would you say is the most popular spline pattern for smaller HP surface props? Are chopper props made for lower HP applications? Thanks in advance for any insight.

 

Great questions, I don't know... I just bought surface props, mine are like 24" x 24" . They are big and expensive. They are like wedge shape. Not a prop expert. I have noticed that if you use non-surfacing piercing props you get cavitation and destroyed props.

 

Got in a test run yesterday with the relocated actuators. They did stiffen up the drive but introduced a minor issue. The drive will trim up a bit when steering full left/right. Its really only an issue at high trim angles but I think I prefer the actuators mounted inside. I'll move them back after I change the swivel setup on the motor mount.


https://youtu.be/gRGF9anKp4g

I made a few adjustments to the controller settings which actually slowed the boat down a little. So those will be reset before next run. I am also leaning towards putting the 9.25x10 prop back on despite being a few mph slower it offers better all around performance and keeps the amperage closer to the continuous duty rating. And so the tuning continues....

Another hat cam video just for fun.

https://youtu.be/V9J2eDzk-o4

Mydauphin - I bet those props were damn expensive. I took a quick look but couldn't find what surface drives you are running, are they commercial or DIY?

Tom Kane - what did you use for props on your pivotal drives?

 

My drives are DIY, I am redoing them now. Trying to work on getting reverse working better. Very similar to setup used in Atlantic Challenger. The props are Teignbridge they originally cost $12,000 each. I bought both for $400. The original owner left them at prop shop after he bought new ones. Amazingly they fit my shaft and boat/engine/rpm exactly. So having friends in prop shops paysoff. I have also gotten rudders and shaft that I have sold.