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3 hr fairing test


This is what the wind sees

I spent 3 hours on the water Monday non-stop at 150 watts with the front and rear fairings on and my overall ending speed average was quite disappointing. I ended up at 145 watts and 11 kph. The wind was very calm for Calgary - long periods of very calm with pockets of 5 kph wind and ripples to 10 kph gusts with a bit more roughness in the water, but over all a very good example of a calm weather day - probably about as good as I could expect for an entire 24 hours.

I don't think the fairing did a thing, but it is hard to say for sure. Compared to the last 5 hour non-stop run where I ended at 160 watts and 11.4 kph average. The first 3 hours were very calm like Mondays test and my average was at 150 watts and 11.3 kph average - this compares to 11 kph from Monday in the same conditions, but with the added weight of the fairing shell on CP2. All that said, it is still hard to say for sure because I was continually pulling weeds off the prop. My speed can slow down by up to 1/2 kph or more when there is a weed on the propeller. There are sections of the reservoir where large patches of weeds are growing right up to 6" of the surface. It's a major pain.

I need to clarify a few of the reasons regarding testing of a fairing, as I've been getting quite a few emails. I know that at low speeds of 10 km/hr, the aerodynamic drag reduction from a fairing won't provide much additional speed. I am also aware that my fairing only went half way in creating a really good, smooth airflow over the cockpit because it stops abruptly before the pedals and starts again right behind my back. The reason why we think it could help is mostly due to reducing the effect of pedaling into any head wind. This is the same reason why WiTHiN human powered ocean crossing boat is fully faired. When I am moving forward at 10 km/hr into a 15 km/hr head wind, the apparent speed of the hull through the air is 25 km/hr and at 25 kph, a fairing is very effective.

For those of you reading this who aren't aware of my previous project, I did play a large role in the design and development of Critical Power human powered vehicle where I set a 24 hour distance record of 1041,24 km by circling a 1/2 mile oval race track in Eureka, California in the summer of 2006. When Ben and I designed the fairing shell for Critical Power, we ran various shapes through CFD software to test and refine the shape.


Also - about comparing my faired human powered boat performance to Carters unfaired effort, I don't see any reason why a fairing would be considered cheating or some kind of unfair advantage. One of the advantages of pedal/propeller power over paddle power is that we have the option to encapsulate the driver because there are no large paddles or oars that extend out from the boat that need to be allowed for. A large benefit of the pedal/prop platform is that it is more aerodynamic to start with due to the lack of the draggy paddles, so why not build-on that as a feature? I mean, that is the whole idea behind my pursuit of what can be accomplished using human power and some open minded innovation.

Hopefully technology that we develop and demonstrate will inspire new attitudes toward pursuing energy efficient boats and vehicles. Human power is about doing more with less rather than our current gluttonous attitude of doing more with more.



My buddy Gary takes CP2 for a spin

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5 Responses to “3 hr fairing test”

  1. # Blogger Paul Bell

    Totally off the wall but it would be cool to see Critical Power bolted to the boat(minus wheels of course).

    For sure you would need a safety boat if you capsized.

    How much weight would you add. You would be loosing the wheels on the bike and the seat and frame etc on the boat. It could be mounded easily enough via the front and read drop-outs on the bike to a simple light bracket on the boat.

    Just need more time huh :(

    Good luck,
    Cheers,
    Paul Bell  

  2. # Blogger "the Dude"

    No weed guard in front of the prop?

    What's up with that?

    I'd have put on a finned hydrofoil weed guard in front of the prop that adds lateral stability and enough lift to bring the draggy side-floats above the waterline once in motion.

    Alternatively, based on a strange pic I saw in a magazine, just sharpen the prop blades, then double rev it, it'll chop 'em like lettuce in a lawn mower.

    did i actually say 'feathers'? man the things that pop out of my brain sometimes!

    Just blabbering, good to see you're doing it in real-time.  

  3. # Anonymous Russell

    Greg, have you given any thought to trying the boat with only one of the fairings at a time to see what effect it has. I built two fully faired recumbent bikes some years ago, and the problem was always the extra weight vs the reduction in air drag.
    As the boat is a displacement craft you have to displace the all up weight of the boat and crew every time you travel one boat length, ie total weight say 80 kg, every time you move the boat one length thats 80kg of water to displace. If the fairings weigh about 2kg thats an increase of roughly 3% of displacement. So the fairings have to make up for that plus add a little more speed to justify themselves, a hard task at relatively low speeds.
    Thats why I would try the fairings individually to see which has the greater effect, if any, and go with the one that gives the best speed increase.
    I'm sure none of this is news to you, good luck, I'm going for 249.88km in the comp' Russell  

  4. # Anonymous Matt Weaver

    Hi Greg,

    I don't manage to read too many of your posts lately, but I'm excited about your latest plans to break the water record! I was looking forward to you doing something like this knowing the potential of building a faster non-ocean-crossing-worthy craft.

    I noticed the "fairing test" and had to take a look! I know aero doesn't amount to much save that winds are present, and regardless - the airspeeds you are likely to find point strongly towards "splitter plates" if anything at all due to the very low reynolds numbers of the flows. Look up Sighard Hoerner's classic Fluid Dynamic Drag (I'm sure you have it!) for a primer on splitter plates. Love to say more bug I don't want this comment getting too long. All the best!!!  

  5. # Anonymous Matt Weaver

    Hi Greg,

    Pardon I haven't even read about your fairings yet. I just saw the photo. I'm sorry but I'm not sure they'd help.... I've seen plenty of lowracer fairings that have landed in similar turf. The flow just does not follow the form and the form instead ends up introducing more separation zones and vorticies. Look into Splitter Plates... there's a chance of some improvement over nothing there...! The other one is surface textures if they can be positioned to trip an otherwise known seperation zone - but those are very speed-specific - getting impractically rough as the speeds get lower and lower.
    Best,
    Matt  

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