Does a thicker wing act the same as a thinner/larger wing?

[niner555]

For the same given cross sectional area and airfoil shape, will a thicker wing act the same as a thinner wing in relation to generating lift?

Here's the example:

part 1
* wing area of 300 sq. in.
* 8% wing thickness
= 24 sq. in. of cross section for the airfoil

part 2
* wing area of 200 sq. in.
* 12% wing thickness
= 24 sq. in. of cross section for the airfoil

My question is, will these two airfoils theoretically generate the same amount of lift? The reason I ask is that I am trying to build a scale sized jet (Su-11), but it has a very small wing area and I am not happy with the high wing loading. I was curious if I could simply build this small wing with thicker % airfoil to get the lift I will need. If this would work, I could maintain proper wing dimesions for a scale look and not take a big hit in the aerodynamics area.

Thanks

[nmasters]

The strake really makes the airfoil section a moot point. If it works as intended the vortical flow that it generates increases CLmax more than any airfoil feature

--Norm

[niner555]

Forgive me for my ignorance, could you please explain that in simpler terms for me?

Thanks

The strake really makes the airfoil section a moot point. If it works as intended the vortical flow that it generates increases CLmax more than any airfoil feature

--Norm

[JetPlaneFlyer]

I think Norm is referring to the vortex lift generated by wings of high leading edge sweep.. To be honest I don’t think this is completely relevant to your original question because vortex lift only occurs at very high angles of attack and when it does occur is creates so much drag that the model often would have insufficient power to maintain level flight... It’s good for landing approach though where the extra drag is a benefit. During most flight conditions a delta wing like the Su-11 generates lift in much the same way as any other wing.

Back to your original point... No; a thicker airfoil will not generate more lift. Lift generated really has little to do with airfoil thickness, camber is more important. Certainly the cross sectional area of the wing has no direct relationship to the amount of lift produced. Generally, other than for the really large scale stuff, thin airfoils work better on models because of the low Reynolds numbers small/medium models fly at.... Bottom line; don’t thicken the airfoil.

What is the type/size of model you are building?

regards
Steve

[nmasters]

could you please explain that in simpler terms for me?

Oops, sorry about that. I must not have actually read the question. :o Somehow I decided that the plane in question was an SU-27 which does have a large strake (LERX is the currently fashionable acronym). No mater, my previous statement applies equally well to simple deltas, just substitute "LEV" for "strake". The bump in the lift curve due to the Leading Edge Vortex is at 7 or 8 degrees. Below that AoA a delta has a very shallow lift slope but it becomes much healthier (though still about half of normal) after that and the new slope continues up to +30 degrees. Oddly enough the sustainable CLmax isn't much higher than for an unswept, high AR, wing because of the shallow lift curve slope. If it weren't for the LEV deltas would never get off the ground. The Soviets were fond of wing devices. A wing designed to have aerodynamic devices probably won't fly very well without them so reproduce anything you find near the leading edge. The pictures I found show an unusually clean wing for a Russian plane of that era. The missile pylons have the same effect as vortilons so it would be a good idea to keep them.

Here's a page with some polars showing the influence of the LEV (http://adg.stanford.edu/aa241/highlift/sstclmax.html)

Build light
--Norm

[niner555]

Thanks for your thoughts, very informative! I purchased the Profili airfoil software and have been having fun scratchbuilding.

I am currently on my third scratchbuild and starting to design number four. I have an 800watt minifan set-up that I want to put into something unique. I really like the Su-11, it's a classic "Soviet" looking interceptor and I have not seen it modeled much. Based on some initial measurements, it looks like something around 50" long with a 31" wingspan. I prefer to hand-launch my planes, so keeping the wing loading in a reasonable range is prefered.

Thanks again for the information


I think Norm is referring to the vortex lift generated by wings of high leading edge sweep.. To be honest I don’t think this is completely relevant to your original question because vortex lift only occurs at very high angles of attack and when it does occur is creates so much drag that the model often would have insufficient power to maintain level flight... It’s good for landing approach though where the extra drag is a benefit. During most flight conditions a delta wing like the Su-11 generates lift in much the same way as any other wing.

Back to your original point... No; a thicker airfoil will not generate more lift. Lift generated really has little to do with airfoil thickness, camber is more important. Certainly the cross sectional area of the wing has no direct relationship to the amount of lift produced. Generally, other than for the really large scale stuff, thin airfoils work better on models because of the low Reynolds numbers small/medium models fly at.... Bottom line; don’t thicken the airfoil.

What is the type/size of model you are building?

regards
Steve

[BMatthews]

All else being equal a thicker wing section will tend to stall at a slightly higher angle of attack. This lets you develop more lift per sq inch before it actually stalls. But something as extreme as you wrote up won't be the case. Your 200 sq inch option will stall at a higher flying speed compared to the 300 sq inch option regardless of airfoil thickness. Model weights being equal of course.

The true key to small wing performance is a light wing loading. Oddly enough if it's lighter it'll fly faster as well since it doesn't need as high a lift coefficient at any speed to get the job done and that means less induced drag at any speed.

Remember... Lighter if Righter.... :D