formulaben

Is it OK if I quote DocRay on aerodynamics?

DocRay

It's often just common sense, even my Cervelo has some BS aero: Cervelo goes on about the main tube being a tapered airfoil, but then they use a round airfoil shape for the downtube, which is pointless, because it doesn't see clean air.

I'd like to see some independant testing of the efficacy of most aero parts, but I doubt any manufacturer would sponsor this.

timwat

The PF Flyers of road biking. Buy aero - you'll run faster and jump higher.

gcasillo

If true about bladed spokes, why can't the same be said for aero tubing such as that on a Cervelo Soloist?

DocRay

read two posts back. The front downtube does see cleaner air, as does the seatpost. But the seattube on the Soloist contradicts the design on the P3s. In other words:looks cool, but really means nothing.

krazyderek

I personally like them for the looks, i'm not going to sit here and say that i can feel the difference since i can't base it on facts, even if i could setup some controlled test instead of "me and my friend.... ", the difference is so miniscule, that as soon as your can think you sense the difference, you start to think you feel the difference more and more, a phenomenon more commonly known as bull****.

I will say this for a fact though. My rear bontrager race rim actually broke as the bladed spoke ripped thru the rim (i guess it had to much tension or something, no clue what that rim's deal was), but the bladed spoke never broke. A week using my friend's spare wheel and i break 2 spokes on it, they where round. So bladded is stronger, weathre this is a good thing or not would be a case by case thing

timwat

FWIW, Garcia says as much on his web site, one paragraph reads:

"The spoke shown is Wheelsmith's XE14 bladed model. These spokes are similar in weight and stiffness to a 1.5mm thick round spoke such as the Wheelsmith XL14 tm* or DT Swiss Revolution tm*models. They have much better tensile strength as the result of the forging process used to create them. The significance of the aero benefits of bladed spokes is somewhat debateable, but the strength advantage is not. Simply put, these will carry more tension load compared to an equivalent weight round spoke."

Cable43

to answer the original question- yes.

trayer350

I suppose many do have tails, but the original phrase was "old wives' tales," I believe.

53-11_alltheway

I've read that Pdf before, but I thought that is why Zipp uses oval and not large bladed spokes like the ones on the Kysrium SSC SL.

It's early in the a.m. (I'm not awake yet) and I'm going by memory. I actually have that pdf book marked and have used in my previous threads though.

badkarma

Right, airplane wings are made to create lift - BUT their design also has a low drag coefficient. Why is this? Wings are designed to keep the flow separated to the wing surface. Often you'll see tripwires at the leading edge of the airfoil to trip the flow turbulent which will keep the flow attached to the surface longer due to the effect that turbulence pushes more momentum to the surface, thus why it stays attached longer than a laminar boundary layer.

When flows become separated from a surface, trailing vortices in the wake and contribute heavily to the pressure drag (the largest component of aerodynamic drag in our case). As a result, with airplane wings having the shape they do, the flow stays attached longer, thus creating a lower drag profile, and not to mention, MUCH more lift.

badkarma

I assume when people say "clean air," they really mean a laminar flow.

johno

Some personal experience...

I have had three aero style wheelsets - Rolf Vector Pro with 30mm aero rim and heavy bladed spokes, Campy Zonda with 30mm aero rim and mild bladed spokes, and Zipp 404 with 58mm aero rim and round spokes.

Without a doubt, the Zipps are the fastest downhill, with the Zondas and Rolfs pretty much even.

The figures I've read tend to back this up - spokes constitute a fairly small portion of overall wind resistance in a wheel, with the rim creating the bulk of wind resistance. Bladed spokes are more aero, but the reduction in wind resistance is fairly small. They do look cool, though...

ExMachina

Regarding spoke shape, I was just reading some figures on this last night. The results of the several laboratory tests I've read all show bladed spokes to be more aero than round. Oval/elliptical spokes also faired very well and were even superior to bladed in off-angle airflows. Round spokes always made a poor showing, sometimes producing close to 100% more drag than bladed/oval.

So like 53-11 said, oval spokes are the most efficient *overall*--bladed only edges (ah-hem!) out elliptical spokes when the airflow is coming nearly straight-on, from the front (and here you have to wonder how many wheel sets have their blades perfectly aligned anyway)

gcasillo

Yes, I'm sure that's what he meant to say.

53-11_alltheway

Yeah seriously you have to wonder how true that is.

I had some drag tests from tour magazine that showed sapim cx-rays made 30% less average drag (from all yaw angles) than round spokes in the same wheel.

Of course I have to assume they were being compared to straight guage spokes. Something like a DT revolutuion with a small 17 guage center would no doubt have much less drag than a straight round spoke.

Fox Farm

My Rolf Vector Pros are flad bladed aero spokes. I don't know if it is the flad blade or the minimal number of spokes which really makes the difference but they are faster in my experience than 32 hole round spoke wheels.