Trolling motor from wood

The basic idea of this trolling motor is the multi functionality of the cordless drill.
Is the power of a battery drill enough to drive a trolling boat on still waters?
The answer is yes. I made the trolling motor from wood and some other parts in a
Clear design with Clean materials and Cheap. So, the 3 C's.
The outboard is partly inflatable for easy transport. Two nails are locking the hinge
and the steering handle. All the functional parts are there, motor, propellor,
hinge with lift, steering handle with trottle and the square drillhead.
A test with a canoe was convincing although a drill with a low/high switch for getting
the best thrust on the prop is better. Also li-ion battery's give a longer range.
It is all by all a fun project between all the high tech. Ready for some enhancements.
I also used a battery adaptor for connecting an external 12V gel battery of 12AH.
Enough to navigate for a while. Enjoy!!!
Video: http://www.youtube.com/watch?v=rZJTGqmtzBs

Nice idea and very good implementation. My congratulations, Bertoa!

That's pretty darn cool, thanks for sharing!

Nice job Bertoa, and welcome to the board! There is a yearly competition in Britain for electric drill powered canoe's too! Our member Jeremy Harris has competed in it.

I would expect Jeremy won it.

Thanks for your warm welcome on this board. Also thanks for your appreciation of the trolling motor.
I am still working on it; changing the drill and the propellor, for optimalising the thrust. A competition
for drill powered canoe's, that's unbelievable. What is it's goal, speed, originality, or just fun?

liveforphysics said:

I would expect Jeremy won it.

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I read about it on a boat board. He made this elegant gossamer on tubing canoe type boat, and was going to compete in this event sponsored by a drill manufacturer. His execution was superb, as we have come to expect from Jeremy. While his boat was sitting on it's stands waiting to launch, a passerby came up pulled the drill trigger and shattered/damaged Jeremy's custom made prop or transmission (forgot which) in the dirt! I do not believe he was able to compete.

Jeremy's thread on his efficient boat design: http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996.html

Here is his competition boat:


Thread loaded with drill powered boats:
http://forum.woodenboat.com/showthread.php?132054-Beale-Park-2011

Found Jeremy's comment on the competition:

Yes it is, taken before some "kind" member of the public decided it would be fun to see if my prop would plough up the turf and powered it up with the prop resting on the ground..............

The result was a broken gearbox which led to my retirement from the challenge before I'd had a chance to try the boat out - months of work wasted by a few seconds of thoughtlessness. Some people are so moronic they shouldn't be allowed to breed, IMHO

Jeremy

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I see I've been tracked down!

The "cordless challenge" was disappointing, but I've only myself to blame. I should have realised that leaving the drill ready to use on the drive leg was just asking for some brainless pillock to try and power it up whilst I was off having lunch.

The race itself was great, the speed of the winning boat, powered by a single cordless drill and a model aircraft prop, was astounding. I reckon that Tobias (the winner) went around the course at more than 5kts and still seemed to have plenty of power in reserve.

The red boat was specially designed and built for the competition, but I've since rowed it a fair bit and it makes a nice, fast one-person rowing boat. The magazine "Watercraft" have commissioned a 6 page article from me on the build, which is in the next issue, published in a week or so.

There is a video of the cordless drill boats running here: http://www.watercraft-magazine.com/wc_Canoe.html As you can see, it was a typically British affair, full of eccentricity..............

Jeremy

Jeremy Harris said:

I see I've been tracked down! ... the speed of the winning boat, powered by a single cordless drill and a model aircraft prop, was astounding. Jeremy

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Jeremy your too creative to not "follow..." that said, hope you will explain the physics of how the model aircraft prop worked so well in water! I would never have expected that.

A competition for drill powered canoe's, that's unbelievable. What is it's goal, speed, originality, or just fun?

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It is such a pleasure to see that on the Cordless Canoe Chalenge (the 3 C's) there where very original design's and solutions
AND extremely high speed boats AND there was a lot of fun. Yes Jeremy, a typical British affair, that's wat we like so much
here on the continent.

bigmoose said:

Jeremy your too creative to not "follow..." that said, hope you will explain the physics of how the model aircraft prop worked so well in water! I would never have expected that.

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Thanks for the kind words.

The physics of props is the same whether they are running in air or water (at least for the case when both fluids can be considered incompressible, which in essence means sub-sonic speeds). Because aircraft are limited in terms of the weight of engine that's practical, a lot of effort went in, right from the time of the Wright brothers, into making propellers as efficient as possible. For example, the props on the Flyer were very good, over 80% efficient, but they had to be as the engine only delivered around 12hp. On the other hand, ship and boat propeller design seems to have been largely empirical at first, followed by little in the way of change for many years as shipbuilding is a fairly conservative business, quite resistant to new fangled ideas. One consequence of this is that it is rare to get a boat propeller that's better than 60% efficient, even now; boat builders just fit big engines and waste a lot of power. The exception to this are boat propellers that have been designed for electric and human power, where the same need for efficiency (due to low power availability) that drove the Wrights to work hard on their propellers has caused some people to re-think.

There are some practical problems with using high aspect ratio propellers on boats though. The diameter will be large for a given thrust, which impacts on the draft of the boat and makes it need deeper water than a more conventional boat propeller. The propeller rpm has to be limited, or else the blade loading will increase and the prop may cavitate due to the low pressure induced on the lifting face of each blade. This low rpm means gearing motors down a lot, which in turn increases losses if a high rpm motor is used. Also, long, thin, blades are more easily damaged if they hit something, plus they tend to get tangled up with weed more easily. Making the blades fold back reduces the probability of impact damage and also reduces the weed fouling problem (if a bit of weed gets caught the blade will naturally fold back under the drag load causing it to slide off the end of the blade). The downside to the folding blade design is that it makes going astern very difficult, if not impossible (the blades fold as soon as the prop is reversed, from the reversed thrust load).

There is some evidence that boat propeller design is starting to change, because, apart from anything else, boat designers are starting to look at the way model aircraft propellers perform in comparison to conventional boat propellers and are realising that they are missing a trick. A look at the cordless challenge video illustrates pretty well how all the boats with model aircraft props were pretty fast, all those with conventional boat props were pretty slow.

If you want a stark comparison of the performance difference a high aspect ratio prop can give, then a chap on the Boat Design forum, Denny Wolfe, did some careful testing with an electric outboard and a handful of mods. He nearly doubled the range of his boat by simply changing the prop to an APC model aircraft one, adding a fairing and hub spinner and changing the crude resistive speed controller for an ordinary brushed motor PWM one. Here's a link to Denny's posts where he details his final test results: http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996-17.html#post305142

Jeremy

Bertoa said:

A competition for drill powered canoe's, that's unbelievable. What is it's goal, speed, originality, or just fun?

Click to expand...

It is such a pleasure to see that on the Cordless Canoe Chalenge (the 3 C's) there where very original design's and solutions
AND extremely high speed boats AND there was a lot of fun. Yes Jeremy, a typical British affair, that's wat we like so much
here on the continent.

Click to expand...

Thanks, it was a lot of fun, even though I didn't get to race myself.

Apart from the fast boats, one of my favourites was the paddle boat. It was amphibious and drove down the slipway into the water under its own power, then drove back out again and across the field to the parking area afterwards. It wasn't fast, but was a remarkable contraption, with spliced rope drive belts and four cordless drills (all of different types) connected together with pulleys. I have a feeling that only a certain type of Englishman could spend tens of hours in a shed building something like this!

Jeremy

Thanks Jeremy! I never would have "intuited" that result. Would have thought viscosity, Reynolds No., etc. all that stuff would have made the designs different. From the post Jeremy cited here are the astounding results of using a plane ol' model airplane 10x6 prop:

Adding the PWM controller and adjusting 'throttle' to give 4.3 mph speed:
-Standard (boat) prop pulled 330 watts; range 1.7 hrs, 7.3 miles
-10x6 (model airplane) prop pulled 260 watts; range 2.2 hrs, 9.5 miles
-10x6 (model airplane) prop plus fairing and spinner pulled 190 watts; range 3.2 hrs, 13.8 miles.

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