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A bit faster, but not there yet


It was the perfect day - high of around 18 degrees C and dead flat calm during the morning. I finished all of my little fixes to the boat yesterday, and headed out to Glenmore Reservoir early this morning to test the boat again.



I climbed into my seat, kicked her off the dock and started to pedal when the the new U-joint that I had just welded onto the shaft snapped in two! Luckily I always ride with a paddle and was able to make it back to the dock. I drove home, picked up my old shaft with the big fat draggy U-joint on it and drove back to the lake. I installed the old shaft and headed back out.


Disappointing speeds again. Faster than Mondays test, but still not as fast as she needs to be to challenge the current 24 hour human powered distance record of 245 km.

I need to make something clear because I am getting a lot of advice (thanks - it's always appreciated) about what to do and what not to do, etc. There is almost zilch 'research' on this project. I am building a COPY of Rick Willoughby's V11 human powered boat. He has spent years doing the concepting, building, testing, and experimenting. I don't need to do any of that. All I need to do is copy exactly what he has already built and I *should* be able to match his performance numbers.

Here is a YouTube video of Rick pedalling his V11 to 16 km / hr !!!!



Rick's V11
100 watts = 10.4 km / hr

My V11G (on Monday)
100 watts = 8.8 km / hr

My V11G (Today)
100 watts = 9.2 km / hr

My cruising power for a 24 hour event is 150 watts which should equate to 12 km / hr and my current speed at 150 watts is 10 km / hr - 20% slower. If I were to maintain an overall average of 100 watts for 24 hours straight, I could cover about 250 km in Ricks V11, but that would equate to only 220 km in the current state of my V11G which would be 25 km short of Carter Johnson's record.


We need to figure out why my V11 is slower than Ricks. My V11 isn't *exactly* the same, so lets take a closer look at the differences and see if there are any clues to my missing speed:

1. My V11G is lighter than Ricks because the hull was made from Carbon. The weight of the hull with the seat and everything is 39 lbs (the 24 foot long hull alone is lighter than moat racing bikes at 19.5 pounds!). The outriggers are an additional 7 pounds for a total weight of 46 pounds. This means less displacement which should result in FASTER speeds, not slower!

2. My seat position is higher than Ricks. At 11 km / hr, the boat should balance on the center hull with the outrigger just lightly skipping on top of the water. Since I have yet to reach 11 km / hr, I can't seem to get my hull to balance on the center hull. To compensate for my higher center of gravity with the higher seat, I extended the outrigger arms to 8 feet (from 6 feet). This made it a bit easier to balance, but I found that I was still sort of rocking from one outrigger to the next. When it was super calm and flat out, I was able to get a few rides that I felt were very light on the outriggers, but it didn't make an appreciable difference to me speed. The reason my seat position is higher is that I have had foot numbness issues with a lower seat. When my heart is above my feet, I don't seem to get the numbness.

3. Rick is using spring steel for his shaft and no U-joint. We designed my version of the boat to use a U-joint and stainless steel shaft because in theory it should be slightly more efficient than the spring steel. That said, I could see and feel some pretty wicked vibration in my shaft under the water. This doesn't seem right and it seems that there would be efficiency losses through this vibration. The shaft vibrating is also shaking the prop around, and I can feel this vibration in the boat at higher speeds. It might be worth a test to place a support on the shaft at mid point to stop the vibration, and perhaps an angled fin to better support the prop.

When I spin the cranks and turn the prop when the boat is out of the water, the shaft and prop vibrate and shake wildly. Rick says this shouldn't happen under the water because a pusher prop is self stabilizing. When spinning the air, there is not enough resistance for the prop and it doesn't self stabilize. During my observation of the prop spinning in the water, this does not seem to be happening, as the prop and shaft are still vibrating - not nearly as much as in air, but still, something is definitely different with set up. Perhaps it is with the stainless shaft and U-joint.

Rick has a prop that doesn't have a strut! The prop is so stable that it pushes the boat against the spring steel shaft alone!

I ave also noticed that the prop when pushing water, seems to twist a bit to push to the starboard side. It is hard to observe this because the lake water is very cloudy, and it could be an optical illusion, but it appears that as soon as I start pedalling and spinning the prop, that it starts to twist the strut and rather than thrusting directly back, it pushing slightly to the right. When I am moving in a straight line forward, it feels like the boat is tracking slightly to the right. If I let the rudder go, the boat does a slow turn to the right. If the prop was pushing slightly to the right, then it would be pushing the back of the boat to the left which would cause the bow to make a slow right hand turn.

Perhaps providing a support for the shaft will resolve this, or maybe i need to add another triangulated strut to the prop bearing tube.

4. We had Manny at Rhomec Industries here in Calgary CNC machine a custom aluminum prop for me. In theory, this prop should be more efficient than a hand made stainless version because it is almost perfect (it is a true work of art!). Maybe the aluminum is too soft and it is warping under the water. My prop was designed for my cadence of 90 rpm at 150 watts compared to Ricks prop at 80 rpm for 150 watts. This means that my prop is spinning faster. Maybe there is something unexpected happening with that higher rpm? Like some unforeseen cavitation issue or something - I don' know. It would be worth it to exchange the prop for my old stainless hand-made prop from WiTHiN. I believe the rpms were the same - need to check that.

5. Water temperature Warren found this for me regarding the difference in drag of 30 degrees C water temperature: 0.8 KPH with a 30 degree temp spread (20.3868 KPH at 0 degree C to 21.1104 KPH at 30 degrees C). Rick's V11 was tested in the warm Australian waters near Melborne where he lives, and the ice on Glenmore reservoir just melted. That could account for maybe 1/2 kph which is fairly substantial.


To top it all off, my Achilles tendon started to get sore after only 2 hours on the water yesterday! Ugh! It used to take 5 hours at easy effort to cause pain, and now it's down to 2 hours. I have been really taking it easy on the Achilles over the past 10 days. I've been using my ultrasound and applying anti-inflam cream every day. It would seem that the reduction in activity is counter productive to recovery.

The other problem I had at the lake yesterday was repeated chain derailments! I hate those! Luckily, it's an easy fix, but I need to add a chain guide.

I also ran aground yesterday! That is a freaky feeling. The water level in the reservoir is still low and there is a large area to the west where the river feeds into the reservoir and it can get very shallow there. I hadn't realized how far to the west I was when my prop suddenly struck the dirt! Yikes! Luckily, I had my paddle on board and I was able to paddle east and back into deep water. I need to check my prop for damage.

Well, I've got some work to do. I'm planning on getting as much of these changes done today as possible and getting back out to the lake this afternoon. It's supposed to be in the mid 20's today, and I have to take advantage of this weather.

Stay tuned...



Manny from Rhomec made me these neat little brass busings for the rudder.
Plus, I filled and smoothened in the welds



This is the narrower, less draggy u-joint. Good in theory but it failed
immediately at the ball bearings joint




You can see a small pulley on my frame used to tension the steering cable.
It worked very well.

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11 Responses to “A bit faster, but not there yet”

  1. # Anonymous Frank

    Greg,

    I would think your speed issues are all related to the prop. It shouldn't move other than spin. Any other motion is not only a waste of energy, it is also counterproductive and will slow you down.

    Re, your achilles, see my previous posting. A bit of vibration and cream is not going to solve this. You need some serious anti-inflammatories and strengthening exercises, and you need to back off a bit on the cycling. You don't want to rupture this tendon.

    --Frank  

  2. # Anonymous 25hz

    3 things that I would humbly suggest, but it may be too late for a couple of them.

    1) The SRM crank arms are wide enough that you could relocate the holes and shorten the cranks to 145mm which I think would be more efficient and easier on your knees. You could fill the concave in the back of the arms with your TIG. They'll be more than strong enough because you can't apply as much force in the bent position as you can while standing on the pedals hammering while weighing 200+ lbs - which is what they were designed to take. This would also reduce the pressure/tension on your achilles tendon because your knee would not be bent as much, nor would your ankle, when you start applying optimum power.
    2) If you made an oval chainring with about 10% ovality, you could actually increase the tooth count, make the dead spot easier and increase the speed. Installing a small spring loaded idler would take care of the minimal chain tensioning duties required with the oval chainring.
    3) For your achilles tendon, modify some shoes so you can move the cleats back closer to the center of your foot. This will also reduce the tension on your tendon and and maybe stave off a serious injury/tear.

    These changes would feel a little different but you would adapt very quickly and quite likely surpass even your best scenario distance.

    Good luck dude :)  

  3. # Anonymous Anonymous

    fliming the prop with a strobe light you will be able see what it is doing  

  4. # Blogger "the Dude"

    Stay hydrated thoroughly, drink a yummy fluid (water-gatorade etc.) and keep drinking.

    Why? Internal lubrication and "engine" coolant. It won't prevent injury or pain, but will improve it by transmitting trapped heat away from the body core, rather than letting it build up locally in tissues.

    get wet within.  

  5. # Blogger Adventures of Greg

    25hz: My SRM cranks are custom made 150's - already fairly short. I've been using the 150'2 since the 24 hour HPV record and love them. I'm not sure if an additional 5 mm would make much of a difference to my achilles. ??

    The cleats on my shoes are always set back as far as they go. Recently, I drilled holes in the shoe and mounted the cleats WAAAAY back such that the pedal is now directly over my mid-foot (arch area). I've been training with this for a couple of weeks and my achilles has been getting worse. I don't think that is working at all.

    The oval chainring is not a bad idea and something I have looked into before.  

  6. # Blogger David Tangye

    1. I suppose this is obvious but: How is your total power to weight ratio compared to Rick Willoughby's?, ie add your personal weights + weight of craft. on identical craft you need something like power squared /weight to get the same speed.

    2. Sounds like there is a good 10% loss in your shaft and prop setup, ie the vibration and in countering the 'natural' turning circle as currently observed. I would guess 4% in turning drag, 6% in inefficient prop thrust.  

  7. # Blogger "the Dude"

    {Off topic}

    This video inspires me, but not enough to cross the Atlantic on it. Nice piece of marine engineering:

    human powered water skiing

    We're having our annual human powered Kinetic Sculpture Race festival in Eureka & Arcata, Cal. on Memorial day weekend. The bike-car-boat crafts cross mud, water, dirt, asphalt on a ~20 mile trek over the weekend, many are incredible designs, some are nuts. I've got a friend at the kinetic lab working now on them.  

  8. # Blogger David Tangye

    Also: I guess the prop must be right-handed: spins clockwise looking from aft. The lower half of the spin is in deeper, so denser, water than the upper half, so works more efficiently. So it tends to paddle-wheel the prop outwards, and the strut is allowing a little of this to happen. If the shaft were on the port side of the craft, then at speed the prop would tend to shift under the craft, and the turning effect would tend to disappear at speed, increasing efficiency at speed. Alternatively, reverse a gearing and spin a left-handed prop.  

  9. # Anonymous Koen (Belgium)

    Hey Greg,

    I'm no engineer at all, but I was thinking about the following.

    I guess the reasons of the lower speeds are to be found in the shaft, prop, automatic turning.

    If you can lead the shaft through the hull directly to the prop (no u-joint), maybe it is possible to do so without the support you need the have now and the shaft can't move around that much.

    Koen  

  10. # Anonymous charlitos way

    Get twin props.  

  11. # Blogger biff

    As a competitive water skier, I can tell you that I can feel the difference in speed and acceleration between different waters. There is a huge difference between Okanagan Lake and Duck Lake (around Kelowna) for example. Duck lake feels like slow motion, compared to Okanagan (probably the fastest water I have skied on), and Duck isn't the slowest I have been on. Stagnant mirky water (hense usually warmer) is slower, how much more energy it uses I can't say, but I would bet that it is at least part of your equation.  

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