Science Buddies: "Ask an Expert"

Please help.
I've to many different websites and forums and I haven't been able to find the answer for my questions.
You see I'm doing a project over winglets and I'm not sure whether there's a certain height or angle that a winglet should have. For the height I was wondering if the height of the winglets should correspond to the length of the wing or chord.
For the angle people have been telling me that it should be a 90 degree angle or a 60 or 50 or 40 degree angle, and I'm just utterly clueless about everything winglets.
If there are other requirements a winglet has to follow by please let me know.
Thank You.



p.s.If there isn't a certain requirement I could definitively use that as another experiment.

Chinwe wrote:I've to many different websites and forums and I haven't been able to find the answer for my questions.

Welcome to Science Buddies. The experts here probably can't answer your questions as stated; however, we can probably help you to construct a Science Fair project and experiments that will allow you to investigate on your own.

Chinwe wrote:I'm not sure whether there's a certain height or angle that a winglet should have

First, have you researched winglets and figured out their purpose? If not, you need to read up on winglets and why they were invented. Here is a reasonable definition of their purpose: http://en.wikipedia.org/wiki/Wingtip_device
Aeronautical engineers "play" with designs using computer modeling and wind tunnels to investigate these kinds of questions. Bottom line, the characteristics of the base wing design and the fuselage and the relative airspeed all affect how any wing tip modifiers behave.

Do you have access to a wind tunnel and smoke/fog to visualize the turbulence? Often it is much easier to experiment with a differnent fluid, water. The results obviously won't match air; however, the experimental process is similar and it might be easier to do the experiments.

Ok
well I've built a wind tunnel already and i know what winglets are and what they do
I just wanted to know how do Aeronautical engineers know which design and angle and height and ect to make a winglet according to the wing.
What exactly are they considering and looking at while making the winglet.
for instance what sort of winglets would you put on a wing with a rectangular planform?

Sorry, was hoping that an actual AE would respond.

Aeronautical engineers typically investigate the addition/modification of winglets to improve an airframe/wing in some specific way:
1) reduce drag at some air speeds
2) reduce turbulence at some air speeds
3) decrease fuel cost at some speed
4) increase stability under some conditions
5) reduce wing span needed

Winglets increase the cost of the airframe/wing design so there has to be some benefit to the total platform performance to add them. On most commercial aircraft applications, a winglet modification will be used to reduce the wing span needed, low speed air turbulence, reduce cruising speed drag, and decrease fuel costs.