I'm doing an experiment using two airfoils of the same dimensions except for the camber. I am getting results in which more lift is produced using the smaller wing. Is this correct or are my results incorrect?
Thanks
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2 Answers
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When you say smaller wing, I assume you mean less camber? Because you say they are the same dimensions, which I take to mean wing plan.
Here is one explanation, it all depends on the regime the wing is designed for.
I am sure you know most of it already though, sorry.
If an airplane is being designed to fly at low speed (0 - 100 mph), it will have a different camber than an airplane designed to fly at supersonic speed (760 - 3,500 mph). In general, low to medium speed airplanes have airfoils with more thickness and camber.
Greater camber gives greater lift at slower speeds. At faster speeds (supersonic) and at higher altitudes airfoil shapes need to be thinner, so you reduce the camber to delay the formation of a shock wave. I don't think this applies to you.
There are NASA sites which have calculators for total lift on them.
NASA lift calculator. If they don't cover camber, keep searching, their should be one site that does
So unless you specify the speed regime, it's not a yes or no answer.
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$\begingroup$ Thanks for the reply. You're right that I should have specified the speed regime. The air speeds that in dealing with are between 20 and 50 km/h. $\endgroup$ Aug 24, 2016 at 23:26
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$\begingroup$ And the wing plan is exactly the same, it is just the camber that is less on one wing than the other. I can't give you a definitive answer, but I need to clear this up for the person who does know. So 2 wings, everything about them the same except the camber, right??Then you know for that speed regime only the one with less camber is better. Your speed regime sounds like a model, or have you a drone with wings : ) $\endgroup$– user108787Aug 24, 2016 at 23:36
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$\begingroup$ yes the dimensions are exactly the same except for the camber. And it is an airfoil made from styrofoam with clear vinyl adhesive film covering it. Thanks for the answer! I'm really glad there's nothing wrong with my results! $\endgroup$ Aug 24, 2016 at 23:38
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$\begingroup$ Try and find a site with a input box for every parameter, you might try a few other sections with less camber. I am no expert, but it seems to me you should try and find out why this happening. Is greater camber giving more lift ( it kinda should, that's what worries me) but also producing even more drag than the "good" wing. That would make sense. Best of luck with it. $\endgroup$– user108787Aug 24, 2016 at 23:46
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$\begingroup$ Alright, thanks. I was also thinking that - the big camber just creates greater drag, reducing the effect of the big camber on te lift. $\endgroup$ Aug 24, 2016 at 23:49
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The way a wing produces lift is by turning the air through a deflection angle without the flow separating from the wing (stalling).
By curving the wing, that angle can be greater.
Lift is proportional to the deflection angle (actually the sine of the angle) and velocity squared (and wing area, of course).
Drag (induced drag) is proportional to those same things.
When an aircraft such as a jet transport wants to fly at slow speeds, it compensates by increasing the camber and the wing area. It has leading edge slats, and trailing edge flaps, which are extended for this purpose.
Read this great ebook, and take one or two flying lessons. Call your local airport, or google "flying school near me". It's fun and not expensive. Then you'll have a much better understanding of how wings work.
answered Aug 25, 2016 at 12:43
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$\begingroup$ Thanks for the answer. Funnily enough, I'm actually halfway through my PPL training :) $\endgroup$ Aug 25, 2016 at 13:38
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$\begingroup$ @Gabriel: Good for you. I've got 100 hours and 300 landings, but other things got more important as I was finishing up (job, family), so I'm sure you'll do better. $\endgroup$ Aug 25, 2016 at 13:48
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$\begingroup$ Hi, I hope you will see this, but in the ebook link you posted, when I click on one of the titles in the table of contents I just get an error. Would you by any chance have a functioning link? $\endgroup$ Oct 29, 2016 at 15:16
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$\begingroup$ @GabrielAaron: Something messed up the link. When I put in an additional "htm/" it seems to work: av8n.com/how/htm/#contents $\endgroup$ Oct 29, 2016 at 15:33
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$\begingroup$ Induced drag is proportional to velocity squared? You should know better. $\endgroup$ Nov 2, 2021 at 14:02