Cycling aerodynamics

[FuzzyDice]

Ok this is not really a topic about racing car aerodynamics its about racing cycling aerodynamics.

Its just a tought i got while riding my bike, one have a lot of time to think as he rides

All pro and some amateur shave their legs and arms because they say it helps improve their aerodynamic properties among other things. So lets stick to the legs, or better just the under knee section of it. If you think of a tennis ball its fuzzy and thus creates turbulent flow around it making flow separation to accour later and it has less drag.

So my question is...from aerodynamic point of view is smooth leg really better? taking in conideration relativly slow speeds at wich cyclist travel...lets say 10m/s

[Ian P.]

10 M/sec is around 36 k/hr which is a reasonable speed for a recreational cyclist.
What you also need to consider is that the lower leg while having an average velocity of 10 M/sec, has an effective velocity considerably higher. You need to consider the lower leg going forward at the top of the pedal stroke and back at the bottom. Since the drag force is influenced by V squared, you need to adjust your effective leg speed upwards.
Just based on simple terms, it works out around 1+ minutes in a 40 K time trial.
15 minutes with a razor (and 15 with bandaids) is the easiest and cheapest speed you can find on a bike. Besides.....it just feels different.

[Ciro Pabón]

I think cyclists (at least the ones I know, and I was one once) shave their legs because of:

- furuncles (specially in the, ehem, upper part of your legs)
- road rashes (they're easier to cure if you don't have hair)
- to allow for better massages (perhaps the main reason)
- and finally, believe it or not, to avoid ticks clinging to your leghair when you ride in the woods.

Aerodynamics have nothing to do with it. On a side note, you'll look professional and you know how men are when it's about beautiful legs... So, there you go, none of these reasons have anything to do with less drag.

I can attest that if you ride a horse for some time (and I have ridden a horse for days in this God forsaken land while building roads!) your legs hair will, well, form small hairballs that give you the pains of hell at the end of the day, when you realize you have had a depilation, but without wax. I imagine the same thing could happen to the parts of your body under your cycling shorts, which, I also imagine, are made of lycra to avoid this very painful and incredible happening (yeah, I know, nobody will believe me, but try to ride a horse for a full day with corduroy pants: you won't do it twice).

Even if you don't believe those are the reasons, you're right: unshaven legs (at least, hairy ones, like mine, manly in its ugliness) would give you less drag. We have had like one thousand threads on the subject, here you have the best post I've known about that matter (the author writes in a peculiar style... ).

So, to put it mildly, I think Ian P. is wrong (sorry, Ian, I'm just trying to spice the conversation and, hopefully, made this an endless thread). Perhaps Alonso should have shaven his beard to get the third WDC... or did he? You know, the helmet allows the air to get inside, so, if we consider the equations...

BTW, I'm moving this thread into the Chat Forum by popular request, it's a little off the ball for the aerodynamic forum.

[czt]

There is plenty of scope to explore aerodynamics in cycling.

There is a company run by an ex F1 aerodynamicist which now specialises in analysing a cyclists riding position using a wind tunnel. They also compare what power output you can produce in the various riding positions, to ensure that what you gain in aero you are not losing through not being able to put as much energy into the pedals.

http://www.veloscience.co.uk/
http://www.drag2zero.co.uk/

Maybe you can move this back into aero now Ciro?

[Ciro Pabón]

Well, czt, I agree with you: there is plenty of aerodynamic research in cycling, from the shape of the frame or helmets to the shape of wheels.

However, the aerodynamic forum goes into "Formula One > Aerodynamics". So, in my infinite wisdom, I'm moving this thing into "Other racing series" and that's final. Yeah, I know, somebody will point out that this is the forum "Automotive > Other racing series", but what the heck. I'm hereby defining that bycles are self-moving vehicles, period.

Now, please, talk about shaved legs, it's the fourth request I receive today about "wrong forum threads". Oh, man, we need some form of racing, I tell you. March is like a year away when measured in "moderator months"!

I'm tempted to open a thread (in the "Useless Chat Forum", of course, a forum that hasn't received the proper attention from Tomba) with the subject of "When will everybody agree on something?", but I'm afraid there will be a strong disagreement about that.

[WhiteBlue]

Perhaps we can agree on "We need a longer racing season". For the fans a six weeks brake over Xmas is surely enough. I would love to have 25 races with several holidays over the season like a month in summer and several three week brakes to compensate for fly aways with one week spacing.

[czt]

I was only winding you up Ciro, I know it's F1>Aero

Seriously though, the world of cycling has transformed technically since I used to ride about 10 years ago. there are some fantastic examples of engineering to be found these days, whether it be in the design/materials of the bikes themselves or methods of develoing the whole package such as the wind tunnel work shown above.

There are a fair few ex-f1 people working in the industry now - I wonder if people will start moving the other way any time soon?

[FuzzyDice]

First sorry for misplacing the thread

I know that aerodynamic doesnt really have alot to do with shaving the legs and there are better reason to shave but many will say that they "feel" faster and sometimes "feel" is good, you know, mind over mater.

i was just curious if that principle would apply on the cyclist legs. now i know for sure that they "feel" wrong

and i agree in many sports at high end level of competition we have alot of engineering seen at work. human potential is coming to its limits just take a look at swimming and their suits which are banned now. they were brakining world records by are margins of few seconds

[Ciro Pabón]

Don't worry, FuzzyDice, it was just that you did it at the same time that other three guys... Talking about coincidences: it must have been the "Misplaced Thread World Day". It's OK, czt, I took it tongue in cheek as almost anything here can be (and should be, if you ask me, given the kind of jokers we are) taken.

Actually, the swimsuit thing is a very good example: those suits, as you probably know, have the same kind of "fuzzy" coat shark skin (and your legs) have. We have posted pictures of shark skin elsewhere.

I find very interesting that a human being is a marvelous endurance runner: humans are built to outrun nearly every other animal on the planet over long distances.

According to the research, it happens because you, humans (and perhaps some of the other aliens in the forum, like me) have an excellent sweating system. The way we cool our body is outstanding (it might explain why we have been called "the naked monkey", besides the obvious pleasure of watching "naked girl-monkeys"). This could have evolved as a way to hunt down prey.

"Over long distances and under the right conditions, (humans) can also outrun just about any other animal on the planet—including dogs, wolves, hyenas, and antelope, the other great endurance runners. From our abundant sweat glands to our Achilles tendons, from our big knee joints to our muscular glutei maximi (note by Ciro: in english, your buttocks), human bodies are beautifully tuned running machines. 'We're loaded top to bottom with all these features, many of which don't have any role in walking'".

I wonder if it has something to do with the shaving of hair of long distance cyclists... you could call it "The Pabon theory of leg shaving": you might feel it right because (maybe) it helps you to cool your body more efficiently. I don't know how important is hair in aerodynamic drag, but certainly hair is made to block thermal transfer.

Anyway, it's very important to keep the heat of your body under control, if you are into long distance racing. Humans can do incredible things when racing. For example, check this amazing contest:

Man vs Horse Marathon (no, I'm not talking of racing against some particular horse-faced ex WDC Formula One driver, altough it would give a new meaning to the "Cavallino Rampante" shield)
[youtube]http://www.youtube.com/watch?v=s_otWXz7vU8[/youtube]

No chance, you would say: a man beating a horse? Well, keep reading.

The first time a human beat a horse was in 1989, when Tim Gould, in a bicycle, beat the first horse by three minutes.

The first time a man on foot beat a (mounted, I concede) horse was in 2004: during the 25th race, Huw Lobb beat the horses in 2:05:19. In 2007 the same thing happened (and by 11 minutes!)

So, incredibly as it seems (I have never read about it), perhaps, maybe, it could be that shaving your legs could help you with this incredibly sweating system you have. Next time a hyena hunts you, well, start running!

Finally, I read some time ago that a man in a bicycle is beaten only by a bee as the most energy efficient animal on our beloved Earth: so, if shaving your legs help you somehow, be my guest. Anyway, I wonder if I should call you "SmoothDice", instead of fuzzy one...

[noname]

I wonder if it has something to do with the shaving of hair of long distance cyclists...

as a former triathlete I will add my few cents, as in the past I was trying to find out why cyclists do this.

the first obvious answer was aerodynamics, but I got some study saying there is not much profits. however on the top level every little piece counts.
from my experience I can say you do feel better (smoother) with shaved legs, so even if it's only psychological effect it's worth to do.

second reason is hygienic related. scars and brushes recovers faster when the skin is smooth (no hairs and much less dirt goes inside). do not forget for pro cyclist crashing is almost everyday experience.

the last reason I would mention is purely psychological. shaved legs are (as I found) the way of showing the world you belong to the cyclist family, you are not the "sunday rider" but someone taking it seriously. kind of uniform, I would say.

[FuzzyDice]

well hair on your body definitely warms you...when you are cold and get chills your body hair errects and thus keeping the warm layer of air to your skin.

as for endurance there is an native american tribe that can run very long distances without geting tired. i cant remember tribe's name right now but i'll look for it.

edit: well they are not navtive american, they are from mexico

http://en.wikipedia.org/wiki/Tarahumara

anyway i didnt make this topic because i have dilema...to shave or not to shave...im gonna keep my natural look

as for the nickname...its another coincidance...i wasnt thinking about fuzziness and boundary layer separation when i was reging to this forum

[Ciro Pabón]

I apologize for insisting on this: a fuzzy coat will give you better times. On the other hand, as noname and FuzzyDice point, there are medical and psychological reasons to shave legs. noname told us that every second counts (and I think he's right). So, is there any kind of garment for cyclists that improves boundary layer separation, you know, like the swimsuits? We could make a fortune... I ask any person with the serious intention of developing a better garment (if it hasn't been developed already, please, post anything in that respect) to contact me by PM. We could ask for the forum help if nothing is for sale. This is what I imagine:

- Inner lycra lining for comfort (or perhaps even a better material for avoiding friction of joints and skin with the fabric).
- A layer to allow transpiration to move out (right now I cannot remember the name of the very popular material used in winter clothes, but someone will tell me, I hope).
- A layer resistant to abrasion, to protect cyclist from road rashes.
- An outer layer with a hairy surface, to minimize drag.

It seems a very good idea to me. Right now, when a cyclist falls, is out of the race: a full body, low friction, thermal optimized, rash protecting, drag minimizing light suit would be ideal for professional racers (gloves and elbows included and some useful padding in the outer side of your legs and in your kneecaps, if I have learnt something from my own falls!).

I find funny to see the Tour de France cyclists opening their shirts to allow some air inside for cooling off (while the clothes flap in the wind: let's talk a little about wind resistance and "every second counting"!). I know that track cyclists (and some cyclists in against time stages) use low drags suits and that they are for sale everywhere: however, I find no suit that brings cyclists the last two phrases in bold of the previous characteristics I imagine a road cycling racesuit should have: excellent thermal control and rash road protection.

I propose (again, if hasn't been invented already) to name this the Noname Fuzzy Cycling Suit, of course... We should hurry to patent this... "having doubts about leg shaving? Use a Noname Fuzzy"...

[manchild]

Forget the aero if you don't have good grip and traction.

[noname]

So, is there any kind of garment for cyclists that improves boundary layer separation, you know, like the swimsuits?

you(we) may be a little bit too late as lot of money were spent already. I am not a specialist and I am a little bit busy at the moment to perform a search but the idea behind the suits is similar to what is applied in the golf balls. I do not know if they (suits) are so advanced to take into account all of the aspects mentioned by Ciro, would have to dig deeper in the topic.

similar approach is also used in regards to wheels design. I know Zipp patented its "dimpled" rims.

I am not 100% sure if it's true but I remember article about suits made for British track cyclist and used by them during the last Olympic Games (I think Adidas made them). they were regarded to be so advanced that, to protect all the "magic" an science behind them, after Olympic Games they were destroyed.
It's worth to mention British Cycling Team almost destroyed opposition.

[FuzzyDice]

here you go ciro, your suit idea is dead

1N5. Jerseys must be worn in all races and shall cover the shoulders. Sleeveless jerseys are allowed only in non-international MTB races. Skin suits may not be worn in Pro gravity events per UCI rules. No additional equipment, whether worn over or under a rider's uniform, which has the effect of reducing wind resistance is permitted, except in the case of inclement weather, additional covering designed solely to protect against precipitation or cold may be worn. However, shoe covers are permitted in any conditions.

thats from usacycling.com