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fairing test and 10 mph!

Because I realize that dealing with some wind for most of the afternoon during the 24 hour distance record attempt is going to be a given, I decided to test out a fairing. At 10 km/hr, an aerodynamic fairing won't help very much, when when I am pushing CP3 10 km/hr into a 10 km/hr head wind, my apparent speed is actually 20 km/hr, and at 20, the advantages of a fairing could be substantial.


The fairing was easy to make - just a thin PETG clear plastic sheet curved over a curved plywood bulkhead. I had a few large sheets of PETG in the shop from when I was making canopy domes for Critical Power streamliner. Both the front and rear fairings took me a total of a few hours to make.



The test was the same loop I did at the reservoir on Friday at 150 watts and my average speed was 11.5 km/hr. This is .1 km/hr faster than without the fairing. That's only about 2.4 km over 24 hour and only 1.2 km if half the day is calm. It was typically windy with some calm periods. I would say periods of 10 to 15 km/hr winds with patches of calm.



At this point, I can't say for sure that pursuing this fairing is worth it. I will experiment with additional fairing to fill in the area behind my seat and possibly some additional covering for the sides of the cockpit. Over 24 hours including some calm periods where a fairing would not help at all, I would say the weight of the fairing which increases the displacement could result in a SLOWER over all average.



I can still set the entire boat up at the car in the parking lot and carry it on my shoulder down to the dock.




Here is a video of me hitting 10 miles per hour (16 km/hr) in CP3.
I'm not sure why the image is so washed out.


I decided to maintain 400 watts as I approached the dock and got Gary to film this. I hit 16 km/hr then the prop flexed up so high it struck the hull. I've done 15 km/hr before and the prop clears the hull - I guess 16 is the limit for now unless I lower the angle of the shaft and gear box. I think I could hold 400 watts for about 4 minutes which means it might be possible for me to average 16 km/hr for 1000 meters.

Mixing it up with the rowers

My buddy Gary was with me and here's a photo of him taking CP2 for a spin. The fairing might not help the speed all that much, but it sure looks cool! It would look even better if it was painted silver with a giant Critical Power 2 logo on the side.


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6 Responses to “fairing test and 10 mph!”

  1. # Blogger "the Dude"

    an 'out-there' comment (my favorite kind): rather than the typical full fairing, or partial, would it make sense to consider something quite different, a bunch of loose feathers.

    At speed, a fairing pushes air around, while feathers would dissipate the air into numerous small microturbulent breezes which are easily penetrated.

    Get my drift? Feathers is probably the wrong word, but some way to break the solid flow of air against you into weak diffused breezes. There must be an analogy, I'll think on it.  

  2. # Anonymous Anonymous

    Greg,
    I hope you're considering that the fairing will have considerable crosswind drag (or thrust depending on your tack) in a crosswind. 'the dude' may be suggesting that you could pivot the fairing to use it as a sail. In any case you should check the rules to see how much (if any) of such assistance is permissible.

    NickHein
    Morgantown, WV  

  3. # Blogger "the Dude"

    nick, no not a sail, rather a diffuser. Maybe keep the fairing, but add, at the trailing edge of the front fairing, some sort of porous screen or net that allows some air flow through but pushes about half above you.

    Basically, compare a wind blowing against a solid wall to a trellis (or windrow?), the wall gets the full force while the trellis partially offsets the force.

    Right now, the cockpit area still has turbulence, with a diffuser the turbulence will be minimized.

    It may not be worth the effort at human-powered speeds though, and cross winds may be more significant.  

  4. # Anonymous certifiable

    Skip the fairing as it will only serve as a distraction and give Carter an excuse to later claim he could have done better if he had used a fairing too. If crosswinds hit, you will deepen the leeward pontoon's draft and raise the windward pontoon to catch more air. This will cause more roll induced drag and need to oversteer as the boat flops side to side.

    You will also slip sideways a little. Don't think it matters? Tie the boat sideways to the wind and measure the crosswind force with a spring scale in both faired and unfaired versions while you are seated in the boat.

    The fairing can't be wider than 9 inches, but your recumbent position would still have hips at 14(?) inches wide and shoulders at 18(?) inches wide. That is alot of overhang out both sides of the fairing's potential slipstream, which probably obviates any benefits.

    What if a fairing was to break partially loose during your attempt and serve as a dragging sea anchor or wind drogue? What if you flipped and had to right the boat yourself? Would the fairing become water filled ballast? Have you even tried flipping and righting to see how to deal with this situation, however unlikely it might be?

    I would also be concerned with proper lower body cooling being blanketed behind a fairing on a hot windless day when the fairing would be just extra weight.

    Ditch the fairing!  

  5. # Anonymous charlitos way

    Greg,
    You have in your hands the best of both worlds. I don't know if it is allowed to use the fairing in a windy condition and to take it off at night when the wind is calm but would be something to consider.Any distance gained even a meter would make the diference between breaking the record or not.  

  6. # Blogger JD Schaefer

    In the photo "mixing it up with the rowers", why are you going backwards?  

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