A little Aussie magic

Greg at about 150 watts of power and 11.5 kph

Success! With Aussie Rick Willoughby's help, we narrowed down the source of the speed problems, and it wasn't at all what we thought.

Before I get into that - some additional good news: I finished a 207 km training ride with Chad on Wednesday and my Achilles tendon was fine! It seems to have solved itself, thank goodness! Now I can slowly resume ramping up my mileage.

Rick is from Melbourne, Australia and is visiting Canada with his wife Rhonda. The timing of his vacation worked out perfectly because my human powered boat is basically an attempt to recreate his design - a culmination of many years worth of experimentation, trial and error resulting in what we believe to be the most efficient human powered water craft on the planet for longer distances. I've been having some problems reaching the speeds we should be seeing, and Rick was able to spend a couple of days with me in Calgary trouble shooting.

A single rowing skull is probably faster over shorter distances, and there are a some pedal powered boats that use hydrofoils that are even faster than a rowing skull. The world record for 100 meters is 34.2 km/hr set by a hydrofoil and pedal powered air propeller boat called Decavitator. The current record for the most distance in 24 hours is held by Carter Johnson who paddled his conventional kayak 245 km around a rectangular course on a flat, calm lake. The Surfski kayak that Carter used is very efficient for longer distances, but we believe that our V11 pedal and propeller powered boat has a slight edge over Carter's kayak.

Rick arrived at my house early on Thursday morning with his propeller. He was hopeful that his 'known-good' propeller would make all the difference. Rick was also concerned about the surface finish of my hull, so to test that, we covered the hull with packing tape to smoothen it out. We figured that the combination of the smooth tape covered hull and his prop would get me my 12 kph at 150 watts of power that the boat was designed to produce.

We covered the hull with packing tape

Surprisingly, the speed was a bit SLOWER due to Ricks prop and the taped hull! The CNC machined aluminum prop Manny made for me was actually slightly better than Ricks hand made prop. Rick's prop was grippier because it was designed for power at a lower rpm, but the speed it produced at various power outputs was slightly less than my high rpm prop.

After a few hours of experimenting, the last thing we tried was to remove the rudder. All of a sudden I got a significant .5 kph speed jump! Ah ha. The boat tracked fairly straight without a rudder and I used a paddle to turn. My speed was up to 11 kph compared to 10.3 before.

Rick Willoughby working on the new
flexible shaft and super-thin prop strut

When we got back to the shop, we discussed reasons why the rudder might be the cause of this drag. Rick felt there was some unexpected interaction between my prop strut and the rudder. One difference between my boat and Rick's, is that Rick uses a curved flexible shaft rather than a rigid shaft with a U-joint. Rick calculated that we could temporarily substitute my rigid shaft for a flexible curved steel shaft to test out the elimination of the u-joint. I welded a couple of the shorter stainless shaft sections that I had together and we used a spare bearings tube that Manny made to rig up this very odd prop hanger. This is where the Aussie magic comes in, because if you saw this you would insist that it couldn't possibly work.

The prop hangs from the deck by a 1/16" thick (we're talking cardboard thickness here) by 1" wide flimsy strap of aluminum that has been filed down to a sharp point on both sides. Seriously - you can blow the prop under the hull with a good puff.

The reason this works is that the pusher prop is self stabilizing. When it starts to produce thrust, it maintains a level horizontal attitude and pushes against the angled shaft which forces it to curve up to the gear box. The cardboard prop strut isn't really even required aside from stopping the prop from slicing into the hull during turns.

On Friday morning the lake was calm again and we got some good tests in. The combination of the new flexible shaft and elimination of the rudder produced the best speeds yet of 11.5 km/hr. We put the rudder back in and the speed slowed to just above 11 km / hr. I did a double loop of the circumference of the lake and averaged 11.1 km/hr on exactly 150 watts of power with the rudder in.

The first thing I noticed about the flexible shaft is how smooth the pedalling action was - way better than with the U-joint. Without the rudder, the boat tracked slightly to port, so we thought that a very small fixed rudder would help keep the boat tracking straight. For turning and course corrections, we came up with a dipping rudder idea that would normally be out of the water when not being used. This way, there would be minimal drag when travelling straight forward.

For optimal efficiency, I need to find a very large and sheltered lake where I can plan a huge circular loop consisting of many very small turns.

What next?

I am pretty sure that with some fine-tuning I can get my average speed up to 12 km / hr on 150 watts of power. The hull is now being surface finished by Dave Albreight - a local composites expert who built the University of Calgary solar car. Once I install the new small directional stability rudder, and the dipping steering rudder, and shave some weight off of the outrigger floats, I should be able to maintain 12 km / hr over straight sections.

Here are a few drawings of the dipping rudder idea that will be used to steer about the buoy markers:

The record attempt

I know from experience using the SRM power meter, that I am capable of maintaining power output of 150 watts over 24 hours. If we can achieve the design specifications, then 150 watts will equate to 12 km/hr - or a total of 288 km which would be a whopping 43 km over the current record which is 245 km. Unfortunately, because of power output reductions and slow-downs due to corners, periodic short breaks from pedalling, etc, my real over-all average watts including the 0's recorded when not pedalling, slowly works it's way down to between 100 to 120 watts. I believe that my ending overall average when I set the 24 hour human powered vehicle record was 120 watts, and my average at last summers 24 hour pedal boat distance record was around 100 watts. My 100 watt average speed is 10 km/hr which would equal 240 km (just shy of a record), and my 120 watt average speed is 11 km/hr which would equal 264 km - 19 km over the current record.

Of course, these speed estimates are based on perfectly calm lake conditions with a minimum of speed-sucking turns. This means that I definitely need to find a large, very sheltered, windless lake to make a record attempt on.

I found a database of wind speed averages at the Canadian Wind Atlas web site:

Average wind speeds for Southern Alberta and BC. Click to enlarge

According to this map, my best chances of finding a windless lake is west of the great divide, or West of Banff in the shelter of the Rockie Mountains. Banff, Lake Louise, Field or Golden look good and they are not too far away from Calgary. Here are some photos and basic information for some possible lake venues:

Length: 2 km
Width: .5 km
Facilities: dock, hotel(s) near by

Moraine Lake
Length: 1.25 km
Width: 200 meters
Facilities: canoe docks and Moraine Lake Lodge
Comments: too small

Johnson Lake
Length: 1 km
Width: .25 km
Comments: too small

Bow Lake
Length: 3.2 km
Width: 1.2 km
Facilities: Lodge on the lake
Comments: Big enough, but far from Calgary

Vermillion Lake
Length: .5 km
Width: .5 km
Facilities: town of Banff near by
Comments: Too small and shallow

Lake Minnewanka
Length: 24 km
Width: 1 km
Facilities: town of Banff near by
Comments: Very large, but possibly windy location.

Length: 5.3 km
Width: 1.2 km
Facilities: town of Banff near by
Comments: large, but far from Calgary

Length: 2.8 km
Width: .8 km
Facilities: nothing much near by
Comments: large, but far from Calgary

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