Would anyoe know where to look for flat blade spokes? I am wanting to do a build but cant find them online at all.
Any help will be appreciated.:thumbsup:

Thanks
John

Do a google search for "Sapim CX Ray Spoke"

they shouldn't be too hard to find....

What is the advantage to them? Do they tend to be lighter? Are they more aerodynamic?

is the claimed advantage.

IMO, it's an advantage that, if real, can only be measured in the lab, and will never be measurable on the road in the form of a faster speed or time.

A practical advantage is that you will know if your spokes have twist.

A complication is that the hub must have a hole with a slot so the bladed portion will pass through.

A complication is that the hub must have a hole with a slot so the bladed portion will pass through.

Actually, no - the ovalized spokes (Sapim CX-Ray, DT Swiss Aerolite) do not need a slotted hub.

Other more truly bladed spoke (like the ones used in Neuvations or Ksyriums) do require a slotted hub, but IIRC tests seem to indicate that these are likely less aerodynamic than the ovalized ones (hence why zipp, reynolds, etc. uses oval spokes rather than fat blades...)

is the claimed advantage.

IMO, it's an advantage that, if real, can only be measured in the lab, and will never be measurable on the road in the form of a faster speed or time.

A practical advantage is that you will know if your spokes have twist.

A complication is that the hub must have a hole with a slot so the bladed portion will pass through.

Aero is a relatively small part of the advantage to the Sapim CX-Ray and DT Aerolite. Any 'bladed' spoke doesn't acheive an aspect ratio sufficient to make a meaningful improvement aerodynamically, particularly at those sizes. (Aerodynamics don't scale linearly.) Perhaps more importantly than the supposed 'aero' benefit, they have additional strength compared to a round spoke of similar amount of material, as a result of the forging process they undergo.

They DO NOT need slotted hubs. Hubs have holes slightly larger than the diameter of common spokes, to allow the bend to fit through. These spokes make use of that fact, having a maximum width that will fit through a standard spoke hole. (There could be some problems in a straight-pull hub, though I'm not certain which ones would / would not be affected.)

There are also the old-style flat-bladed spokes that are wide enough to need slotted holes. You don't want them. They are relatively weak, twist horribly, and are close aerodynamic cousins to cinderblock. Their hard square edges mean they don't cut through the air any better than a round spoke, and as soon as the wind is slightly off-axis (as it usually is) they are considerably worse.

At the Re# that a spoke would see, a 2 to 1 aspect oval has a Cd less than half that of a round shape. CX-Rays and Aerolites have a 2.5 to 1 aspect. In addition it should take a pretty strong cross-wind before the angle of attack is so great as to cause a stall... ie I expect they will produce some lift which will further reduce drag. So... .9mm x .5/1.5mm= .30... so only 30% of the drag of a light round spoke.

Forging the blade adds nothing to the strength. This isn't where spokes break.

There are lots of straight-gauge oval and bladed spokes available that are too big to fit in standard hub holes and require slotting or special hubs. Most of them are fine aerodynamically, and they are stiffer than CX-Rays, but suffer the same fatigue issues as other straight-gauge spokes.

Thanks for all of your input guys. Now to search and decide.

Sorry, I didn't make myself clear. I'm not dissing the aerodynamic qualities of CX-rays. I only meant that as I see it, their other contributions to a wheel build are of greater importance.

I was using 'strength' colloquially, as in 'builds a longer lasting wheel,' rather than the engineering use of the word, applied to the discrete component. You are of course correct that forging doesn't increase the ultimate yield or change the failure point. I don't believe there's a disagreement that as compared to weight-equivalent Lasers, Rays will build a wheel that's longer lasting and should take the hits better.

Aerodynamically, there seem to be small differences in our analyses. At these Reynolds numbers, frontal and surface area have a higher relative importance WRT to Cd. As compared to first-gen flat blades, by being closer to round the ray will decrease surface area. It will also present less frontal area in off-axis conditions, which are more common than dead air on the bike, and more important to the aerodynamic qualities of a spoke when built into a wheel.

It's doubtful that the cross-section of a ray will develop meaningful lift, but to the extent that it may in some conditions, it's not a good thing. Any positive lift vector would be accompanied by a much larger perpendicular component, a force that would need to be counteracted to keep the bike on the road and on line. While those corrective forces wouldn't necessarily be aerodynamic, they would still be losses. To turn lift into a net positive, the foil would need to be canted towards the relative wind a bit, which obviously causes build difficulties. Not to mention the need to change to your left-handed wheels at the turnaround :)

And I was only talking about the first gen flat blades - the type that have long been aerodynamically refuted, yet 'look' most aero and still appear appallingly often in lower-end 'aero' prebuilt wheels. But you know far more about the spoke market than I, and I'd accept the idea that there are spokes in between these two points that are aerodynamically superior to Rays. I simply haven't given them much thought. I'd believe that something just a bit more oval - ie, just slightly outside of fitting thru a normal spoke hole - could do a bit better. Whether that gain would be 'worth it' is a separate, convoluted discussion that I'd prefer to avoid. You know how those discussions can get.

so only 30% of the drag of a light round spoke.

Is this significant on balance using the same rim, spoke count, and lacing? Would the use of CX-Ray or Aerolite spokes contribute more of an aero benefit vs going from a 24 mm to a 30 mm rim?

Is this significant on balance using the same rim, spoke count, and lacing? Would the use of CX-Ray or Aerolite spokes contribute more of an aero benefit vs going from a 24 mm to a 30 mm rim?

Some day I'll put together an "analysis" of the Tour data regarding round spokes vs aero. It is difficult because the rims and hubs are changing also... ie no direct comparison between spoke shape without other variables mucking things up. Still, you can see that aero spokes are better in the overall trend by plotting the drag of round spoked wheels and steel aero spoked wheels vs rim depth.

Regarding the 24mm vs 30mm rim... it depends. Some 24mm (Shimano wheels for instance) rims are as good as 30mm rims... shape matters too. Some like the Ksyrium are awful. One other advantage to the deeper rim is that you can use fewer spokes and still have decent stiffness.

IMO if you are going to be spending the money for a nice set of wheels and you care about aerodynamics at all (ie you would like to have a ~1% speed boost on the flat) then it makes makes sense to use a deeper rim and aero spokes. The weight difference is so small that you'd have to be climbing a really steep grade before the shallow rims would "win". The spokes are pretty expensive (adds maybe $80 to the wheelset price) but the rims don't cost any more.

Of course having lighter (shallower) rims can make your bike feel more responsive and some people prefer this even though it isn't quite as fast.

I just think bladed spokes are cooler than round. Good enough for me.

What is the advantage to them? Do they tend to be lighter? Are they more aerodynamic?

Flat-bladed spokes tend to be slightly heavier and stiffer than most double-butted spokes, but have more side push in cross-winds. Also easier to see if bladed spokes are twisted (stressed). But not fun to hit your knuckles against bladed spokes when your tire lever slips ;(

Aero issue probably doesn't mean much to non-racers. I have multiple wheelsets inc. round and bladed spokes, but not on same rims so can't claim I can tell a difference.

I've done some internet searching to help decide on a new wheel build. It's hard to find good direct comparisons of spoke aerodynamics because most tests are either poorly designed or change more variables than just spoke design (different rims, # of spokes, etc.). Seems to me that most tests suggest flat-bladed spokes are more aero than round but not as good as oval (like CX-rays). But differences are probably minimal under 15-20mph or so (except for side force in cross winds).
Zipp website has some good discussions & data about wheel aerodynamics, inc. spoke design. From their wind tunnel testing they state "Bladed spokes are more aerodynamic than round spokes at most every possible condition, however, they do add some side force to the wheel in a cross wind, whereas oval spokes tended to yield an aerodynamic improvement and reduced side force". Another comment accompanying a "Watts vs Wind Angle" graph (30mph wheel speed done at Texas A&M in 2004)-
"Perhaps the most noticeable feature of this graph is the very high wattage of the round spoked 46mm deep wheel. Requiring more than 10 additional watts to spin when compared to the almost identical bladed spoke 46mm deep wheel." That is the most direct aero data of bladed vs rounded spokes I know of. Not sure what it all means to me since I rarely hit 30mph except on a good downhill ;)
Still- interesting comments from a high-end wheel maker who is NOT pushing bladed spokes; they switched to oval spokes about 10 years ago. I'll prob invest the extra $$ on CXray spokes for my next wheels.