Wing sections--same area, same lift?

[zolotiyeruki]

I'm in the process of making a super-efficient plane that will cruise at around 1675m/s at an altitude around 25km. Right now, the design uses a pair of structural wing Type A's, which are 2m wide at the back and 4m long.

So here's what I'm wondering:

--If I were to replace them with a Wing Connector Type C (2mx2m square), how would that affect the lift and drag of the wings?

--Is the lift calculated based only on angle of attack, surface area, air density, and speed? or,

--Does KSP account for the sweep of the wing?

From this post, it kinda sounds like wing sweep and aspect ratio are ignored, which leads me to believe that aerodynamically speaking, the Type A Wing would have identical performance to the Type C Connector.

Does anyone have any experimental data to back this up or refute it? Or deeper understanding of the KSP aero model?

- - - Updated - - -

Well, I shoulda gone one link further. Yes, lift is based off wing area, regardless of actual geometry.

Edited October 12, 2015 by zolotiyeruki

[Wcmille]

I believe that sweep is not considered in stock. You can verify this for yourself with using a simple mod like NathanKell's AeroGUI to show you the in flight numbers.

[NathanKell]

For wings that share the same plane (i.e. all are rotated at the same angle) total lift is proportional, absolutely linearly, to the sum of all the lift ratings.

So yes.

[Skalou]

I protest sir!

I was asking a few months the same question, and so tested it myself:

first, here is 2 pictures that show most of the test:

i tried to keep the sames parameters for the 2 crafts (infinite fuel, same part , altitude, time, static margin: distance COM-COL,...),

the only thing i tries to change is the wing orientation, rotated of 90°.

As you can see there is a small difference in the speed limit (after 4 hours of flights).

My suggest:

the wing as a thickness, and so the "wide wingspan" show a bigger area facing the relative velocity direction direction that has a bigger drag coefficient (the side faces have a lower drag coeff).

Is it a good explanation?

But it is going in the opposite IRL rules for the wing shapes in sub-sonic ( aspect ratio).

But i don't find it armfull because, the error is small (but additive with a patchwork bigger wing!), KSP is a space game first, and there is FAR solving it for perfectionist ( i don't use it myself anymore, stock is sufficent for me).

Edited October 13, 2015 by Skalou

[Red Iron Crown]

Skalou, in the first pic the control surfaces are deflected more than in the second, which may affect the overall lift and drag values.

[zolotiyeruki]

Skalou, from the reading I've done, it sounds like KSP ignores parasitic drag for lifting surfaces (excluding Mk2 fuselages), so having a wider higher aspect ratio wing wouldn't make a difference.

Red Iron Crown is right--you have a significant difference in control surface deflection between the two craft. You'll notice that the control surfaces on your main wing are further astern in the second craft. Were the control surfaces set up so that each only controlled one axis? (elevators on the tail, ailerons on the main wing)

[Skalou]

yes, the control surface on the main wing only control the roll (i maybe disabled them completely for the test but i don't remenber, it was a long time ago),

putting control surface during this test was a bad idea, i should have tried without anything on it.

As you can see, i asked an auto pilot to keep the plane at 6000m , the difference in the angle of attack, control deflection of control surface,... for me are a consequence of an other balance state(weight= lift, drag=thrust,...). the faster you go the lower your aoa will be to keep the same direction.

zolotiyeruki

the control surfaces on your main wing are further astern in the second craft.

do you mean extern? ailerons only control roll, so it doesn't matter.

or on the rear?( it's the dictionary definition: sorry i'm not an english native),

By keeping the same static margin i think this effect is taken into account, and so my main wings are a bit more on the front than if there wasn't ailerons.

control surfaces are taken into account for the blue marker (kind of center of pressure).

In fact the main problem here is KSP do'"t show the drag, lift,... parameters for wings!

Edited October 13, 2015 by Skalou

[DancesWithSquirrels]

Astern -> towards the stern, towards the back. It's naval terminology.

I would suggest running the test with no control surfaces on the wings whatsoever, just to remove that factor.

[Skalou]

Astern -> towards the stern, towards the back. It's naval terminology.

I would suggest running the test with no control surfaces on the wings whatsoever, just to remove that factor.

Thank you.

yep, as my test is now public, i will maybe redo it, do you have other test suggestion guys? i think about this:

-more wings: to demultiply the effect if there is a difference, somthing like this?

- Maybe doing the test with a vertical launch also? add tons of radial wing on a rocket, and compare how high the 2 crafts are going. it will tell us if there is a drag difference for 2 differentscraft. (it's not the original question but it will help to understand it or to choose how to cheat place our wings)

-no control surface on them.

-use of a rocket engine even for a low speed plane, to avoid the "engine velocity curve" artifacts. a custom engine with a custom flat ISP and thrust curve?

Edited October 13, 2015 by Skalou

[Claw]

i will maybe redo it, do you have other test suggestion guys?

Your rocket idea is the most solid, if you want to test drag on the wings (vice lift rating).

However, as someone with firsthand knowledge, I can say that a lift rating of 10 is a lift rating of 10, regardless of what kind of wing pieces you used to get there. Wing drag is tied directly to lift rating and is not affected by wing shape. All of the stock wing pieces should be pretty close in lift per wing surface area ratio, so there isn't really much of a lift/mass or lift/size difference either.

I explain in detail in the two links posted by the op. However, that doesn't mean you shouldn't test and explore. There is still a lot to find buried in KSP aero.

Cheers,

-Claw

[Skalou]

Ok, i' ve made the drag only test:

Javascript is disabled. View full album

there isn't any significant difference in my opinion, and so no drag difference. and was wrong in my previous test (bad test craft?).

Nice link claw, i didn't noticed them at the first reading.

so if there isn't difference in drag, and with claw explanation, i think there isn't lift difference too.

need to test it later.