DIY Electric Surface Drive

Some people are so lucky to have so much to spend on their boats.
Just a few hundred dollars was all that was available for me over many years and everything had to be recycled to try new ideas.

 

Very impressive planing performance, smooth drive and wake. Have you considered running a comparison test using a trolling motor to cover the same distance at approx 4 mph? The relative efficiencies would set a real standard due to your near laboratory conditions. Ideally you would choose a trolling motor thrust rating to give the chosen speed at one-half throttle, since ISTR best efficiency for trolling motors is reported to be at the mid point tiller position.

Designing an electric boat knowing planing speed vs trolling efficiencies would be a godsend.
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Mydaupin - I can definitely see the benefit of having friends in prop shops. Sounds like a great deal there. How was reverse before you started redoing them?

Tom Kane - I noticed in some of your videos the props look to be home built. Have you used them in the water? If so how do they perform?

Skagit gadget - thank you. I had not considered a comparison test but I could look into doing one. Ive got a 35# and 55# but I don't think either would get the boat to 4 mph.

 

My props had to be cheap because where I did my boating the water was full of sand and debris and it is easy to make a prop from flat steel plate just strong enough to propel the boat but not strong enough to damage the drive if large rocks were hit.

I used second hand props which I had to modify to suit my needs.
A local marine Engineer used to cast Aluminum props which I also used, he patented and sold a tunnel surface drive called HydroDrive which sold in USA an image is on this website if you search that name.


They worked as well as other props and there was not any surface piercing props available anyway and not many boating people or dealers new anything about surface propulsion anyway.

I only ever damaged one prop in all my boating trips in the shallows.
http://www.boatdesign.net/forums/at...aeration-tunnel-charlie-crow-s-hydrodrive.jpg

 

> Ive got a 35# and 55# but I don't think either would get the boat to 4 mph. [Irie]

I bought a pair of Newport 46s for the sake of redundancy and smaller size. So if your transom can mount both then use whatever speed seems appropriate. I've yet to try mine. The nautical world awaits your data. 8^)
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Reverse is like 25% of a regular setup. The problem I see with surface props in some applications like mine is the difference in thrust between reverse and forward in use for docking with twin screws. It has to do with as much with stern design as props. Looking at building some tunnels on the side of props to help direct water in reverse. Not 100% sure what the exact design is yet.

 

Tom Kane - that's pretty awesome! All thanks to your pivotal drive? Seems like a great system for shallow water. What got you into surface drives way back then? Just trying to get certain places?

Mydauphin - 25% sounds challenging! How much improvement do you think the tunnels would give?

Skagit gadget - I have a little data coming in a minute.... PC had to restart. At 4 mph it burns 114 amps at 11.6 volts.

 

The chart corresponds with the first run in this video. https://youtu.be/gRGF9anKp4g

The controller was set to peak amp mode which allows 460 amps as long as the controller is below a certain temperature. I usually have the controller limit maximum amps to 350 but I wanted to see what 460 max amps would do. Speed data was imported from GPS.

I apologize for any shortcomings of the chart. Its been a while since I used excel, still knocking the rust off.

 

I spoke with someone that had the same design as me, and had the same problem. His tunnels made his boat usable increasing reverse to 50% reverse power.

 

Very nice work on your drive and data! Do you have any idea of the boat weight?

OCB

 

Tunnel hull with surface drive

Did the guy start with a tunnel hull? Has anyone installed surface drive with tunnel hull to testing before?

Any info on that setup will be very helpful?

I just got a Penn Yan tunnel drive hull to test with. I'm hoping for better reverse?

OCB

 

Hi Irie,

in your graph is the battery current shown eaqual or lower than the motor current. Physics says that is not possible. Did you mix them up?

 

Fitting tunnel propulsion to boats in NZ made the boats seem as though they were running on rail lines and boats did not want to turn and they operated similar to water jets in that they needed big HP and little forward action until high RPM.

Alright for full throttle work but not good in a bad seas or just cruising at economic speeds.
Reverse was always a problem.

 

No, the boat is a planning hull with a transom at 45 degrees except where drives go into stern. The problem is when you put one drive into reverse and the other one forward the backwash is a disaster. You can dredge the bottom and nothing happens.

The idea is very similar to image below


Though in my setup propellers are ventilated and above the water when boat planes. I use exhaust from engine to fill tunnel with air.

 

Ocb - Thank you, it has far exceeded my expectations. I dont have an exact weight yet but estimated weight is 580lbs which includes operator. Its been tested with an additional 230 lbs on the bow, and achieved 17 mph with the 9.25x10 prop. I have not had a chance to test that load with 10.5x12 prop.

Heimfried - hello, I double checked the chart and source data, it is exactly as the controller logged it. At 100% throttle battery volts and amps are exactly equal to motor volts and amps. At 99% throttle the battery current is slightly lower than motor current. I can make the excel file available. I unfortunately don't know much in the way of physics or how the controller works its magic.

Mydauphin - that looks very similar to the setup in the diy tunnel drive thread. Anyone know if he ever got it to plane?