Split Wing

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Post Tue Aug 28, 2007 8:15 pm

It was never obvious to me why a split wing would have advantages over a single wing. I'm just not that technically minded and truly admire those that have that ability to visualize.

I stumbled across an article about bicycle forks, where a dual bladed fork has apparently significant aero advantage over a single bladed fork. (You'll have to look carefully at the picture of the cyclist's bike to see the dual bladed fork)

http://www.velonews.com/tech/report/art ... 170.0.html

The split wing concept suddenly made sense.
litespeed
 
Joined: 28 Aug 2007

Post Tue Aug 28, 2007 10:13 pm

Welcome litespeed.
Thanks for the link to v. interesting article.
So if 2 forks have an aero advantage over 1, then why not 3? Is it a trade-off with weight?

Applying that to F1, why in Monza (high speed, aero setup) testing pics, F1 cars have only 2 plane front wings & 1 plane rear wing vs. usual 3 & 2 respectively?
GTO
 
Joined: 9 Jun 2005
Location: Oil Country

Post Tue Aug 28, 2007 10:36 pm

If I got this right (which I think I did) I think I can explain why they don´t use it on f1 wings :roll:

If you have one fork it pushes the air inside the wheel spokes creating drag but if you add another one on the right position it "catches" the air from the first fork redirecting it, so it doesn´t go inside the wheel spokes

On a f1 car the back is smooth, there arent any parts which the air can run into (like the spokes in a bikes wheel) so the wing can´t create significant amount of drag, but if you still wanna add second plane you´ll get yourself a drag created of the extra leading edge :wink:

Hope this helps :)
I have that Twitter -thingie now!
tomislavp4
 
Joined: 16 Jun 2006
Location: Sweden & The Republic of Macedonia

Post Tue Aug 28, 2007 10:41 pm

GTO:

For bicycles, I would guess that there is a case for dimishing returns. In addition, aerodynamics are not always the most important factor for a bike. For example, cross wind stability is a factor especially on the front wheel/fork, which is why no one will run disk wheels on the front. There's probably some trademark/patents to consider, too.

For F1, I'd love to hear what some of the more knowledgable folks have to add to your question. The aero setup on F1 is so complicated and interesting at the same time.
litespeed
 
Joined: 28 Aug 2007

Post Tue Aug 28, 2007 10:50 pm

Just thinkg about the F1 thing. The additional wing adds force and drag, so you only want to do so if it is beneficial.

On the bike, the drag of the additional wing is more than offset by forcing the air away from the higher drag spokes. On an F1 car, the drag of an addtional wing isn't needed for downforce on a high speed circuit. But, the drag is beneficial for the downforce required on a lower speed circuit.
litespeed
 
Joined: 28 Aug 2007

Post Tue Aug 28, 2007 11:03 pm

The drag is not benficial at all, the thing you need is the downforce.
Thats why the aero-guys want to achieve the best amount of downforce with the least amount of drag. But to increase the downforce you need to alter the angle of attack of the wing and by doing so the drag increases also so the right setup is always a compromise :wink:
I have that Twitter -thingie now!
tomislavp4
 
Joined: 16 Jun 2006
Location: Sweden & The Republic of Macedonia

Post Wed Aug 29, 2007 9:31 am

The concept is similar in principle to a slot gap on a F1 wing but applied differently.

I think you will draw a greater parallel with these kind of developments:
http://www.f1technical.net/development/103

Although the outer edge of flip up there is to create a vortex, the inner gaps appear to be guiding air up and over the wheel, which is rotating against that flow much like the front wheel/fork interaction on the bicycle.

Thanks for the article - I like cycling too! :)
zac510
 
Joined: 24 Jan 2006
Location: London

Post Wed Aug 29, 2007 1:58 pm

A split wing on an F1 car works when large downforce is needed. If a single wing was used instead, it would stall long before it would be able to generate such downforce. What happens in a single wing situation is that at a large enough angle of attack the airflow separates from the lower side of the wing, causing drag and loss of downforce. By splitting the wing, what essentially happens is that a bit of high speed air from the upper surface enters the critical area below the surface, delaying stall. The same principle is used for slotted flaps on an aircraft (turned upside down, of course).
Gecko
 
Joined: 5 Sep 2006

Post Wed Aug 29, 2007 5:29 pm

basically keeps flow attatched for longer :)
PNSD
 
Joined: 3 Apr 2006

Post Thu Aug 30, 2007 3:21 pm

In F1 there are limited volumes in which to position airfoils, especially at the rear. It would be difficult to fit a single optimal airfoil within the rear rule-mandated box. Instead fitting multiple-element airfoils is a better compromise in generating the required downforce. Drag in F1 is always secondary to downforce, so the extra drag associated with multi-element airfoils is something for the engine developers to counter with more horsepower.

Looking (with difficulty) at the forks on the bicycle, it seems to me that the two elements aren't particularly closely coupled, so I'd question whether they are performing as described in the linked article. They also appear quite a distance from the spokes to be having an influence on their aerodynamic performance. Could the forks be designed to help cross-wind stability? i.e., avoiding presenting a blockage to a cross wind.

I wonder if better drag reduction could be realized by shaping the spokes as airfoils rather than cylinders - F1 front suspension style.
Symscape, Computer-Aided Engineering for all
syguy
 
Joined: 22 Feb 2007
Location: USA

Post Thu Aug 30, 2007 3:42 pm

The top level bikes definitely do have spokes with that profile. Even commuters like you and I can buy cheap bikes with spokes like that too these days!
zac510
 
Joined: 24 Jan 2006
Location: London


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