Building fairings

I just checked the calc:
http://www.kreuzotter.de/english/espeed.htm

the difference between hands on top and hands on drops is 26% @20 mph.

Huge. And it only gets better the faster you go.

26% more emolis would cost a bit... whereas a fairing would also keep the bugs outta my teeth.

8)



Edit: removed landmine. ES remains independent!
 
Just took the "garbage can lid" fairing for a ride.
While I didn't have any measuring tools, it does help quite a bit.
"Wild Eye Guess": Traveling speed at 60% throttle with "fairing" = about 80%
throttle without "fairing". For about a 25% decrease in power consumpsion.

This is about what Tyler predicted.


Even if only 15-20%, this seem to be big deal. How much $ is 20% of your battery pack?
Seriously, a rectangle garbage can lid :shock:

I try to run a couple tests this weekend.
 
Yup, once on a really hot day I stopped and attached my backpack on my bike's handlebar. Turned out I could then pull 1-2 gears higher over 24. Inner thighs and crotch area got all wet for lack of wind, though.



Aerodynamics of human-powered vehicles - good read.
 
jackatfsi said:
Picked up an OS ZZ off Craigslist...be a couple weeks before I can try it though........
Click to expand...

Great idea! :D

I just searched CL on fairing... looks like mototrbike fairings can be gotten cheaply.

8)
 
Further refinements:

lots of extra flank and windscreen, so folks can trim to their liking
circular relief at the nose, so plastics can bend without cracking
hips in the downtube faces
concave leading edge of flanks
centerline for folding and cutting (symmetry)
pantograph grid for translation to fullsize mockups
 

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That's really neat Tyler. Do you develop the shape by trial and error, or did you have a template to work from? How do you transfer them to the laptop, or is it the other way round?
 
Malcolm said:
That's really neat Tyler. Do you develop the shape by trial and error, or did you have a template to work from? How do you transfer them to the laptop, or is it the other way round?
Click to expand...

I started by holding a piece of paper in the shape of a cone, and drew roughly on that with a pencil. After I cut that out, I opened it flat, traced its outline onto a sheet of paper and scanned it into the laptop.

Then I used a path-tool in GIMP to create the outline for the right half. I duplicate the right half and mirror it to make the whole pattern.

It's all trial and error after that... I make changes, print it, cut it out, tape it together and see where it hurts.

:lol:

edit: GIMP file below!
 
Here's another hare-brained halfbakery:

Use Tyvek in a method similar to paper-mache...

1. Build a positive
2. Cut Tyvek into strips
3. Apply strips using adhesive, like super77

Tyvek is lightweight and has a high tensile strength. It is available at most home improvement stores, and roll-ends can be had for nothing from jobsites.

Fairings could be easily created in unique shapes: bird-heads, t-rex, M1 tank, or...

smooth.


Thoughts?

:?:
 
KnightMB has added GIMP files to our shareables!

fairing file attached.

For those new to GIMP, it is an Open-Source replacement for Photo$hop.
http://www.gimp.org

gimpscreenshot1_144.jpg


THANKS & 3 cheers to KnightMB :!:


:D
 
The "Rubbermaid Roughneck Fairing" report.

Wind: Light
Bike: 60 lbs with 408/4011 (and attendant drag)
Rider: 185 lbs
Power: gravity only
Fairing: A rectangle shaped garbage can lid that measures 21"x14"x4.75", angled @ ~30 degrees = (1.65 sq. ft. Frontal Area)
Speed Measuring Device: Garmin GPS
Dork Factor: High

The Tests:
11th Street Hill: A no power roll down a 2.2% hill for 1100 feet (25' vert.).

Without "Rubbermaid Roughneck Fairing" 14.0-mph @~1100' 14.0 mph Terminal Velocity

With "Rubbermaid Roughneck Fairing" 14.6-mph @~1100' 14.6 mph Terminal Velocity

-----------------------------------------------------------------
4th Street Hill: A no power roll down a 8.3% hill for 1200 feet (100' vert.).

Without "Rubbermaid Roughneck Fairing" ~21.5-mph @~800' 24.6-mph @~1100' 24.6 mph Terminal Velocity (Edit: terminal velocity due to being switched on to "4011")

With "Rubbermaid Roughneck Fairing" ~23.5-mph @~800' 30.3-mph @~1200' Terminal Velocity not reached, still accelerating at bottom of hill!
---------------------------------------------------------------------
Math:
@~14 mph
14.6/14.0= 104%

@~22 mph
23.5/21.5= 109%


Conclusions:

Below 15mph: very minor help (4%)

At 20 mph: minor, but helpful (8-9%)

25-30: major help (15%)(ediited to reflect new tests)

30-40: Holy Cow, Batman

If the "Rubbermaid Roughneck Fairing" can produce these improvements, What can a real "Fairing" do?

I want to try one of Tyler's next.
Tyler, Can you give me some idea of a length of the width or something in your patterns? If so, I can make it to scale in CAD and then
produce a "Scaled PDF" for everyone's printing ease.

Can anyone Say "Aero Disks"?
 
The "RRF" is priceless. The report did not indicate time of day... Under cover of night perhaps?

Hysterical... yet the data is remarkable. Kudos.


I'm clueless about how big to make the thing. For my bike, It will get major revs, but I haven't decided if I'll try to get it in front of / below the pedals...

In the attached image, I pasted the paper profile shot onto my bike and scaled it to get an idea of relative sizes. I'm not sure if a roughneck lid looks any more dorkish that this... (so far)

(Keep in mind, this is something that I occupied myself with while sick in bed. I mighta been feverish...)

A rough guess might be 48" from nose to wingtip, but whatever seems good to anybody... this is open game...
 

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Believe me, The "RRF" is very high on the Dork meter.

I rather like your round lines.

But with all that side windage I be scared here in "Windsurfing Central", the Columbia River Gorge. (Remember, wind doesn't blow, it sucks!)

While I beleive the rap-around sides will help lower drag, I wonder just how much?

That's why I wanted to start with something simple.
To see just how far it makes sense to go with the Progession to the Ideal.

Next, I think I try a modified version of Tyler's latest.
I'll cut back the sides quite a bit.

Later
Kyle
 
30-40: Holy Cow, Batman
Click to expand...
Cracking data Kyle, can't wait to see what results you get using Tyler's template :)

So if I attach two dustbin lids to the front of my bike do I get twice the efficiency improvement or just twice the dorkishness?
 
Front and side views of the RRF as Requested.

Strap one on and take it for a spin.
You guys who go faster than 25mph will see remarkable gains.

BTW, the bike @ 60 lbs.:
408/4011
48v x 6 amp/hr nimh

Top unassisted speed: 22-23 mph
Range (with pedaling): ~18 miles@ ~18mph

I'll see what I can get out of it with the RRF.
I'm hoping for 25 miles, as that is how far the closest MircoBrewery is.

Later
Kyle
 

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Saw a guy on a road bike this past winter with this exact same setup except he had a crazy carpet strapped between the drop bars & tied to the tip of the front fender. (do they call them crazy carpets in the States or is it wacky carpet?)
I think it was more for keeping the cold off him than for speed.
 
That's a nice looking bike! Even with the lid it still manages to look the business. (at least from the side :lol: )
 
Excellent. Major geek points.

It makes me wonder how small an area you could use and get a major improvement.
 
Thats Crazy

Ha ha wicked, Im thinking it prob makes you less efficient though? I think on a bike a true bike the only real way you can easily do it and still look half normal is on a recumbent bike, full bike fairings are only really practical on fully motorised bikes like Malcolms where you can tuck down.

There is a great thread on here about wind resistance being futile and so is peddling past a certain point in to a head wind, I find on my bike and I know this from looking at my watts up meter that I use far less power than I can put in by sitting up and peddling by simply tucking in really tight and getting really low and tight, I can go further and faster than If i sit up and peddle some.

I think if wind drag is your bag then deffo go for a bent with a tail and wear some lycra!! you can make a rocket and go along at high speed with hardly any power.

Power to you for riding with the lid like that, just tell people its a new solar panel or something.

Cheers

Knoxie
 
The only problem with a bent bike is you lose the handling advantage of a regular bike, plus there's the convenience issue if you commute. A 1/4 faired upright won't be far off a bent w/ fairing in terms of drag.
 
Now THAT is one Sweeeeeeet fairing...









bike's cool too.

8)

If that lid makes 20% improvement @ 20mph, a well-designed fairing could be as important to ebiking as safe lithium batteries.
 
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