Looking for Messer-Spit data

[Angus]

Lower wingloading means lower A.o.A. at lower speeds - hence less drag.
But at higher speeds with less A.o.A. it means less and less.

[Knegel]

Hi,

you make the mistake to mix up wingload with liftload!

The needed AoA is of course related to the wingarea and weight, but also to the aspectratio, the airfoil and other wing-construction related features (the Spit-Wing for example was twisted to give a smooth stallbehaviour, but therfor never the complete wing had the optimal position into flightdirection, this decrease the max lift and increase the drag).

For the zero drag (CW0) the wingarea is a main factor. You be right that a higher aoa result in a higher drag in general, but drag= zero drag + induced drag and our planes, in the graph below, still fly around 330km/h IAS, when the DB-Spit overcome the Bf109G. So the test show that the DB-Spit, with 370kg weight-advantage,  have less drag below around 330km/h.

How, do you think, this 3100kg 109G would perform with 370kg less weight in this comparison? It still would have a much greater wingload!

Wingload you only can use to compare planes with same wings!!
If you know that the wings of two planes are not twisted(washouts) and use a rather similar airfoil, you can use this formula to get a better approach to the liftload:
Weight / (Wingarea x aspectratio) = liftload

This explain why the P38, althought very heavy in wingload(242kg/m² 50% fuel), still was able to fly high and turn not to bad and why the Ta152H was a so much better turner and climber in relation to other 190´s, althought the wingload wasnt that smal at all(203kg/m², the heavy 109K4 had 207kg/m² but a much better powerload)!

Greetings, Knegel

[Angus]

I am referring to the same wing with merely different loading.
So how is the mixup?

Still airfoil difference does not allow endless space either. The wings of the Spit and 109 perform very much in the same ballpark.

The only sensible way I have found to compare them is if the power is the same and the weight similar - then extrapolating climb times into Newtons. It won't be completely accurate - but it's a tremendous teaser all the same

[Knegel]

Hi,

as far as i can see you refer to the Spitfire wing in comparision to the Me109 wing(absolute different wings), here wingload isnt a reliable factor. At least the text, you did quote, did refer to the different wings.

If the power and weight would be the same, its relative easy to compare the wings, but we dont have this, the DB-Spit have a 370kg weightadvantage, while the normal Spit dont have the same power. Btw, to use climbtime as value to calculate the wingeffectivety, both planes need the same climbspeed, and best is to have climbresults with many different speeds, otherwise we only know the effectivety for thie one special speed!

Airfoil is not that important regarding lift(at least most WWII planes dont had that bad airfoils, therefor the different was rather smal), but the wingform is (Aspectratio, washouts, eliptical, trapeium, arrowed etc).

A wing which work good at slowspeed, can lose its advantage at higher speeds etc, all this make a comparison very difficult and wingload related arguments dont lead to anything, as long as we have different wings(Spit/Me109).

How, do you think, the 109G would perform in 11000m, with 370kg less weight??  

Greetings, Knegel

[Angus]

My mind was bent on the effect of decreasing or increasing winload of the Spitty in question, - the effect of the 300 kg's of armament you mention.

But cross comparing the two is always a bit fun, - especially if you are playing with the exact same power.
Then the variables are weight, airfoil, and drag basically, right?

[Knegel]

Hi,

ah rgr, i thought you was talking about DB-Spit vs 109G.

Yes, of course 300kg more weight on the DB-Spit would increase the induced drag, cause a higher aoa is needed to keep alt.

"But cross comparing the two is always a bit fun, - especially if you are playing with the exact same power.
Then the variables are weight, airfoil, and drag basically, right?"

Now you talk about 109/spit, right?  
The basic variables are drag, weight, lift.

Weight is clear, but drag and lift are not that easy.

Lift get influenced by the airfoil(smal differents between modern WWII planes), wingarea (big differents), aspectratio (big differents) and other construction related aspects(washouts, slats, combatflaps, the last two dont count while steady flights).

The drag is splitted into zerodrag and induced drag, a subvariant are drag changings due to highspeed problems(shockwaves and other turbulences).

A increased Wingarea increase direct the lift, but in the same way the drag.
A increased aspectratio increase the lift with the factor phi(3,14) x aspectratio, and reduce the induced drag by  1/(3,14xaspectratio). On the other hand it increase the drag at highspeed by a to me unknown factor (shockwafes happen more early) and the structural construction is more difficult(long but smal wing = big leverage on a smal wingroot)
Washouts increase the drag and decrease the lift, but provide a more smooth stallbehaviour.
Slats(if open) increase the drag and the lift and the max AoA(wingarea increasement + a faster airflow over the wing), and give a smooth stallbehaviour, specialy if the slats work seperated. The production and maintance are more difficult.
Different Airfoils have more influences to the zero drag than to the lift.
Flaps are another story, their influences depends to their construction. In general they increase at least the drag.


Greetings, Knegel

[Kurfürst]

Originally posted by Angus
Lower wingloading means lower A.o.A. at lower speeds - hence less drag.
But at higher speeds with less A.o.A. it means less and less.

Keep in mind that at high altitudes, you actually have very low airspeeds (IAS) associated with whatever high true air speed figures.

Ie., the Rechlin test of the 109G-1 shows 640 kph TAS at 10km, but only 367 kph IAS.

[Angus]

Yup Kuffie I know.
And Knegel - yepppers