msu2001la

As far as the sailboat analogy is concerned, there isn't a sailboat in existence that is generating power when pointed just 15 degrees off the wind. Most normal sailboats cannot sail efficiently any higher than 40-45 degrees. Some race boats can sail as high as 30 degrees. At 15 degrees, the boat would be stopped, or going backwards.

A sailboat has huge stationary sails that are optimally shaped to generate power, and if it struggles to do so at anything less than 30 degrees, how is it logical that a spinning disc wheel on a bicycle (which is not an optimal shape for generating power from wind) would be generating power from wind at 15 degrees?

If the answer involves suggesting that I take a course in fluid dynamics, please don't bother.

patentcad

Does DocRay ride and/or race his bicycle, or does he simply exist to raise the Stupid Bar on BF on a daily basis?

Cromulent

This is the most sensible post in the entire thread.

Rutnick

probably the one post in this thread that actually makes the most sense to me.

patentcad

On the other hand, the BF Good Sport Award does go to DocRay for putting up with all my persistent abuse and not whining to the Mods. Credit where it's due.

gcl8a

It's quite straightforward, actually. The sail may still be producing thrust at 15 degrees, but the drag on the hull is greater.

In addition, note that the thrust component of the Zipp wheels drops to zero at 18 degrees. The two are optimized completely differently. But the basis of the analogy, that a disc wheel generating thrust is similar to a sailboat, is qualitatively sound.

patentcad

You guys are friggin rocket scientists. Good God man, just shut up and ride your bikes.

gcl8a

Correct.

It's dark out, and I already did 80 km today.

PS. How much would it cost to draw up my sketch in AutoCAD? I'm thinking I should copyright it and get rich on the royalties.

waterrockets 

I think a logic course would help more.

One issue: what does a "15 degree yaw angle" mean? I assumed it meant apparent wind, not absolute wind angle. Sailboats can make forward progress a much steeper than a 30 degree apparent wind angle.

The reason a sailboat can't go forward in a headwind greater than 30 degrees is because the windiage is too great for the lift to move the boat in a forward direction. As the angle steepens, the lift is the same, but the vector applied in the forward direction goes down. In addition, rigging, deck, crew, and hull all are getting hit by the wind and adding no lift, so they are pure drag, proportional to the amount of wind. The sail will continue to provide lift at steeper angles, but the lift degrades to the point that the windiage is greater than the forward force, so the boat goes backwards.

The big difference here is that a sail is exclusively a means of wind propulsion. If your goal is to go steeply into the wind, a sail is not the solution, and the entire mast should be removed -- row or motor from there. On the bicycle, we already have a wheel regardless of using it to harness the wind. We also have propulsion to move us steeply into the wind, independent of any sail effects. In a steep wind, we can't just remove the wheel. However, if an airfoil can be created such that some forward force is generated, just like in the backwards-moving sailboat above (whose sail is still generating forward force), then there is a net gain.

A better analogy would be motorsailing. You will go faster with the sails up while under motor power, as long as you can keep them trimmed. Even if you're beyond the wind angle at which you could sail w/out a motor, the sails are still providing enough lift to contribute under motor power.

gcl8a

Værsgo:

https://www.windpower.org/en/kids/intro/energy.htm

It looks to be about your level.

Rutnick

I have no freaking clue whether or not those zipp wheels do what they claim but they sure look like the new sexy to me. Doc Ray is using an outdated ISIS bottom bracket in his bike. I believe that would be called...nuff said. I can get a titanium spindled square taper bb with ceramic bearings. Still means they belong in the vintage forum.

new sexy vs old and busted.

Man, I bet nobody ever would have thought a MIB reference would crop up in this thread.

chzman

If you drive by a kid selling lemonade on the side of the street, you stop and buy a cup. Always.

ElJamoquio

+2. Everyone is an idiot.

waterrockets 

You'd love my bike then. It could be on the Vintage forum, or the Why Can't You Keep Up? forum. Just because standards change doesn't mean the older stuff is outdated. There has to be an actual improvement for something to be outdated. For example, I think steel rims are outdated. There is no performance gain to be had from any BB other than potentially weight on a climb.

Rutnick

I remember when all you use to need for a date was a van and some chloroform.

M_S

Look like fun in a crosswind.


I wonder if we'll eventually see them on fixies once the aeorspoke thing wears itself out?

vic32amg

science:

my tubular zipp wheels help me go faster most of the time. the clincher version of the same wheel helped me go faster except on the hills. most importantly they look sharp. like dressing a razorblade in a black tux.

vic

mollusk

Correct.

However, an improperly torqued crank onto a square-tapered BB can lead to a ruined crank. It is much less likely to happen with a "modern" BB.

patentcad

In that case, as much as it pains me to say it, the correct thing to do would be to simply...

shut up.

Hocam

Judging by your previous technical opinions on things like carbon fiber only being strong when the fibers are running in one direction, I'm going to go ahead and believe zipp.

Terex

And if you're a true follower of H. Simpson, you will remember the remark about "speed holes", a few weeks before the concept was detailed in a scientific journal. The aforementioned H. Simpson, and his associates, are obviously much more knowledgeable than you in the area of boundary layer fluid dynamics. Harrumph!

formula4

If the time savings from this feature is so small that it is arguable that it even exists, it's not worth buying it.

2manybikes

The dimples are to get people to discuss them on the internet. Then others will hear about the wheels and they will sell more.

Mission Accomplished.

I want some.

Rutnick

then I guess you missed my lengthly post about the different BB and cranks I have used in this thread. The FACT that I could see and hear the campy square taper flex. Something I wouldn't have noticed if I had not used the current generation equipment. I guess you also missed that I was friction shifting 9 speed until feb 06.

For the record, my touring bike STILL has a square taper BB AND it still is friction shifting. It still has a place, just not on a modern road bike. My touring bike is early 80s vintage. I am also restoring my 1982 road frame which I rode until this year.

sac02

It is amazing how unwilling some people are to admit they may be wrong, even in a field they know nothing about. That someone had to draw out a vector diagram to try and explain it even makes me laugh, just a little.

I may not have stayed a a Holiday Inn Express last night, but I am grad student designing the aero package for this year's FSAE car...