AeroAirheads

[HammerTime2]

I propose a sister board "AeroAirheads", with a singular focus on bicycle aerodynamics, to include aerodynamic stiffness. Weight, function, durability, maintainability, and ability to support power output must not be considered.

[Privateer]

Perhaps not a sister board, but maybe just a thread.

Here are a few for starters:
1. Does anyone have a link to the Velonews article that did a wind tunnel comparison of different wheels? I can't remember where I saw the reference to it.

2. Does anyone know how to translate grams of drag into watts of power? The Hed website has an interesting wheel comparison graph (http://www.hedcycling.com/aerodynamics.asp), but i don't know how to translate the differences to real-world performance. The graph, for example, claims that there's an 80 gram difference at 10 degrees of yaw between a Stinger Disc and Zipp Sub-9. Taking this at face value and assuming no wind and a constant 300 watts, what would difference (if any) would this have on speed?

3. Just how much difference is there in aerodynamics of different discs or 90mm section rims? There is substantial variation in the weights- in discs, for example the Hed Stinger disc is a claimed 1,130g, Zipps are around 1,000g and carbonsports claim that one version of thier discs only weighs 780g. Are aero differences between brands substantial enough to offset a 200g weight advantage on the slight rises and accelerations of a typical TT course?

4. Has anyone had a session in the wind tunnel with Drag2Zero?

[Dalai]

with a singular focus on bicycle aerodynamics

http://biketechreview.com/forum/1-general-discussion

[Dalai]

Does anyone know how to translate grams of drag into watts of power?

Found this on slowtwitch - http://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/Drag_differences_(watts_or_seconds_per_40k)_for_different_bottle_set_ups_P2570287-3

0.1 lbs (50 g) of drag (at 30 mph) = 0.5 s/km = 5 W = 0.005 m^2 CdA = 0.0005 Crr

The above rule-of-thumb (which refers to changes) is based on various assumptions/rounding everything to a 1 or a 5, but is fairly accurate and hence quite handy when doing in-your-head (or back-of-the-envelope) calculations.

[freemyheel]

As far as grams of drag equating to watts saved, I believe the simple math is a 10:1 ratio, so 100 grams of drag saved equals 10 watts fewer needed to achieve the same speed. I think the real math is more complicated, but its one of those cases where the simple math is close enough.

[Privateer]

Thanks, that's really useful.

Hed's claim that their disc has 160g less drag than Zipp's at 15 degrees of yaw is a pretty big one then. 16 watts? Really?

[djconnel]

Harumph. Grams are not a unit of force. Harumph.

Hats off to Tour magazine for getting this right.

[rustychain]

So how aero is Sparticus?

[HammerTime2]

Perhaps my idea for an AeroAirheads board was ahead of its time when I proposed it 16 years ago. But the time seems right now.

Although Watt Weenies does sound classier.

Note: This is in Road because there was no Cycle Chat at the time.

[tarmackev]

Wow! 16 years ago. Great name as well. That fact that you’re still here 16 years later espousing the virtues of the same thing is amazing.
I for one salute you!
Hopefully the all powerful ones will consider it.


Sent from my iPhone using Tapatalk

[jih]

What is a gram of drag anyway? Never understood this unit. Newtons of drag seem obvious, but how do you translate mass to a force? Is it equivalent to the force acting on a gram of mass under earth's gravity?

[spartacus]

What is a gram of drag anyway? Never understood this unit. Newtons of drag seem obvious, but how do you translate mass to a force? Is it equivalent to the force acting on a gram of mass under earth's gravity?

I'm assumung it's 1g multiplied by gravitational acceleration, kind of like pound-mass (I know, don't even start with me) versus a slug.

[spartacus]

I'd like a forum to learn more about aerodynamics besides people blindly repeating various tests and adding together "watt savings". There needs to be some kind of validation process IMO but I dont have the time or energy to come up with one. I guess there's the chung test which might be the best we have but it's still tough.