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GEEKMOBILE


Ya, I know. What a dork huh?

I met my buddy Bryon Howard at the Heritage Park docks at Glenmore reservoir to help me launch the new floating geek-mobile. I chose the Heritage docks because they are usually fairly deserted aside from a few guys trying to catch fish from the dock. I seriously did NOT want anyone to see me in this! Especially the competitive rowers and kayakers that I race around the reservoir all the time.

I knew it wouldn't work and it didn't. My average speeds were way down due to the weight of the silly fairing contraption. It was pretty calm, but there was a section of the lake that was windy and my speed decreased just as much as it usually does when I passed from the sheltered area to the windy area. After a few loops we tore off the fairing and did another couple loops unfaired as a control. Results below:



With fairing @ 150 watts = 11.2 kph
Without fairing @ 150 watts = 11.5 kph
Wind: calm sections, 5 kph sections

I know that the benefit of the fairing should really only be for moving into head winds, but from these tests, I think that the weight of the fairing during calm waters would defeat any benefit the aerodynamics of a fairing would offer for the windy portions of the ride. My gut feeling at this point is to focus on weight shaving rather than wind shielding.

That said, our calculations still predict a net overall gain if the full fairing weighs less than 10 lbs. I think this could be possible with an aluminum wire frame/mylar covering. But, I think the gain would be very small and might not worth the time or effort.


Here is a photo of Rick Gritters streamliner HPV. The photo shows it with a heat shrunk mylar covering, but I think Rick used aircraft Dacron wing material as the final cover. He says the bike weighed in at 40 lbs, so I would guess the fairing itself might be about 10 lbs.


-----------------------------------
Friday, July 25th report and a comparison to last years record attempt:

I was on the lake for 3 hours today. The objective was non stop and to maintain 150 watts. It was fairly windy - 10 to 15 kph and quite wavy for most of the 3 hour ride. My SRM battery died after an hour, so I don't know what my ending power average was, but it was probably between 140 and 150 watts. My speed however was very low - 10.5 kph. There were quite a few stops due to weeds collecting on the prop and wrapping around the bow. These stops were probably responsible for .5 kph of the average. Still, without these stops, I would really only have been at an average of 11 kph. 10.2 kph is record pace. Calm water is a very important factor.

I looked back at last years blogs to see where I was during training for last years pedal boat record attempt. On May 18th I finished a 10 hour day on Glenmore reservoir. I reported that it was very windy at times, and dead flat at times. I was pedaling an early version of WiTHiN which is based on a double kayak with a recumbent seat, pedals and a propeller. I finished the 10 hours at 7 kph average speed which was right at the 168 km record I was training to break. This compares now to an entire day spent on the water with CP2 and ending with an average of 11 kph (I am using the average speed from my 5.25 hour training day because it included both calm and windy periods just like last years comparison training day) which is 264 km in 24 hours, which is 22 km over the current record of 242 km. This is encouraging.

WiTHiN-24 from the 2007 HPB record attempt

To summarize, my long training day average speed from last years boat WiTHiN was right at the record pace, and this years long training day average speed on CP2 is slightly over the record pace.

Also, here is how both boats average 150 watt speeds compare to their respective records they were design to break:

WiTHiN 150 watt speed = 9.2 kph
24 hour record = 173.76 km
Theoretical 150 watt 24 hour distance = 24 hours * 9.2 kph = 220.8 km
150 watt efficiency over the record = 127%

CriticalPower2 150 watt speed = 11 kph (average water and wind)
24 hour record = 242 km
Theoretical 150 watt 24 hour distance = 24 hours * 11 kph = 264 km
150 watt efficiency over the record = 109%

CriticalPower2 150 watt speed = 11.5 kph (calm water and wind)
24 hour record = 242 km
Theoretical 150 watt 24 hour distance = 24 hours * 11.5 kph = 276 km
150 watt efficiency over the record = 114%

CriticalPower2 150 watt speed = 11.8 kph (mirror flat)
24 hour record = 242 km
Theoretical 150 watt 24 hour distance = 24 hours * 11.8 kph = 283.2 km
150 watt efficiency over the record = 117%

As you can see, this comparison shows that it will be more difficult to break the 242 km record in CP2 than it was to break the 168 km record in WiTHiN. However, my training day average now shows a higher average speed relative to the respective record than last years training day average.

"At some point you have to put the calculators down and just go for it."
Greg Kolodziejzyk


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7 Responses to “GEEKMOBILE”

  1. # Anonymous Anonymous

    Greg,

    Just two comments today:

    1. It looks like at least one of your small hulls will always be touching the water. They never carry much weight though. It seems like the ones you have could be narrower and that would reduce their drag above and below the water. Maybe Rick could give you a design with minimum drag at 11kph while producing 5 pounds of floatation. Of course the hull would need to have reserve buoyancy, but it would be designed to operate at 5 pounds. Or maybe using a helper and a fish scale you could figure out how much flotation you really do need. Replacements would be pretty easy to test.

    2. This is a little more work to test and harder to back out of if there are problems, but it should help in rough water. The latest thing in sailing catamarans and a few experimental power boats is wave piercing. The idea is to minimize the impact of hitting a wave by going through, or under it. You have the advantage that your total weight will be nearly constant during your record attempt and your CG location doesn’t move, so you don’t need a lot of reserve buoyancy and stability. If you lowered the forward deck so that it started just above the water line at the tip of the bow and then angled very slowly upward, so that the deck height increased an inch or so for every two feet back from the bow, I think there would be a lot less additional drag every time you hit a wave. It might be good to shape the deck so that the water that comes over the bow would naturally flow off the sides and back into the lake.

    OK, a third comment. I agree that weight is critical. Essentially the more weight the more drag. It’s not quite linear though. If you design a boat with twice the weight, the drag only approximately doubles. But, a 10% weight reduction gives you apx. 10% less drag at constant speed. Unfortunately, drag as a function of speed is approximately a square function, which makes power a cube function. A full 10% weight reduction would only give around a 3.6% speed increase. That’s around 8-9km further if you are right at record pace. Do you or Rick have something better than my guesses? You have numbers to show the power increase with speed. Adding weight and seeing how much you slow down will tell you about how much saving weight would help.

    Peter Raymond  

  2. # Anonymous Certifiable

    As I had stated in the past, "Ditch the fairing!" It is a distraction that will only waste time and divert you from concentrating on what I will now go on record as being your biggest problem: WEEDS! As you pointed out in this blog, you estimated that you lost at least 0.5 kph in average speed due to stops to clear weeds from your bow and prop. This is what will be your ultimate downfall. If you do not COMPLETELY avoid weeds getting caught on your hull or prop, no amount of weight saving or streamlining will ever make up for the weed factor. Either you find a weed free venue or you get two powerboats with a weighted thin wire strung between them to clear a 10 meter wide by 2 meter deep swath over your course several days before your record attempt. This way the chopped off weeds have time to drift to shore. Weeds, like remoras on sharks, will suck speed out of your efforts when you don't know they are stuck on your hull or prop.

    Carter's record breaking kayak had a weed shedding bow that curved gently down and back. Do your hull and pontoons have square like planforms that catch rather than shed weed? If so, you might consider changing their planform to better shed weeds. If this is too difficult or too late to do, see the weed cropping suggestion above. Avoiding weed increases speed!  

  3. # Blogger bl

    Weight does not increase drag, more vessel contact with water does. Get your vessel out of the water.
    Hydrofoils provide stability and provide lift to reduce and eliminate drag. Design your hull like a wing to provide more lift when your hydrofoils lift your vessel out of the water.
    ("It's cheating, it's cheating!")  

  4. # Anonymous Matt Weaver

    Not that simple with hydrofoils at lower power to weight ratios. The necessary wing grows to enormous size, the induced surface wave effects directly above the wing similarly grow to substantial proportions (from negligible for hour/sprint power to weight ratios). Never mind weed issues.  

  5. # Blogger Adventures of Greg

    Matt is correct. Rick and I have looked at the whole hydrofoil issue and at these low speeds, a displacement hull is more efficient.

    Regarding the outrigger floats and their width, again, the floats were designed for the exact flotation that I require. They happen to be wider (and heavier) than design because of expanding foam and they are being rebuilt right now.

    Weeds are a problem - I know. I will need to pay careful attention to my course to ensure that there are no weeds.

    And aero vs. weight and displacement - Rick has done all of the calculations: basically, the lightest boat we can make would be .2 kph faster than a heavy, bloated boat. Not much there. A good fairing would also give me .2 kph, but would increase the weight. All in, we would be talking about a .3 to .4 kph increase in speed. Over 24 hours that might work out to about 7 km (probably less because the fairing would only be effective during the windy portion of the day).  

  6. # Blogger "the Dude"

    Using hydrofoils to get the vessel out of the water is not an option, energy cost is way too high. My recomendation for hydrofoils was not for big wings (nor the Bucky Fuller picture style), but for small fins, whose main role was to provide slight lift & lateral balance (reducing the need for floats and their associated drag.), with the additional benefit of weed clearance from the prop. I just don't like the "bicycle with training wheels" effect once the ride is underway. Better to gain equilateral stability with small fins at very slight energy drag cost, than flip-flopping side to side across the lake at full speed. Can you imagine riding the Iron Man with training wheels alternatively touching the ground?

    I'd ditch the front and central fairing immediately, but the rear fairing only if cross winds are bad. And the float fronts should definitely not catch weeds at all.
    Luckily the lake waters won't have cross currents, so that's not an issue. Again, I'm just working conceptually, your the one getting wet and tired, so your say counts.  

  7. # Blogger Bryon Howard

    Greg,
    The boat is VERY stable with the two pontoons.

    It probably does not need to be so stable.

    I agree with one of the above comments ... where you could probably narrow the pontoons.

    Would having just one pontoon be an option?

    ... or ... what about no poontoons .... but holding a pole with floation ... that you would 'lean into and float' when required.  

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