Small wings/high wing loading of German fighters

Tony Kambic said:

I was surprised to learn his design philosophy was a single main spar. The 109 is clear evidence of that. Maybe a smaller wing because of that?

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The increase in wing loading is required by aerodynamics. A higher wing loading allows to increase the maximum speed at the same power. Indeed, there is an optimum. The Soviet paper from 1942 was quite good, the problem was the manipulation of numerical data to discredit the I-185 project. But in principle the article describes the phenomenon correctly. Theoretically, a higher wing loading can also result in the reduced airframe weight, but the additional high-lift devices can compensate this reduction and even increase the airframe weight.

There is a lot of "stuff" going on with the change from biplane to monoplane and things can rarely (if ever) reduced to a single sentence.
Lockheed was flying this thing in 1931.

Wing loading was about 14.9lb/sq/ft.
You could get rid of the upper wing but now you needed to make the wing strong enough to do without the bracing of the upper wing. (or lower if you made a high wing monoplane) and for light weight that meant a thick wing. Much thicker than most biplanes ever used.
Unbraced monoplanes go back to WW I.

Semi-braced?
WW I

Arguments about parasol and bracing aside even the D. VIII had low (lowish?) wing loading of 11.6lb/sq/ft.
Which with the thick airfoils used the above examples did not allow for large gains in speed. Worthwhile yes but not the gain the later monoplanes would get.
Please note that all 3 planes had some rather large contributors to drag aside from the wing type/size/airfoil.

In the early 30s the engine makers were moving away from water to Prestone which allowed radiators to be smaller.
They were also designing better fairings for air cooled engines which much less drag.
The airframe makers were moving to retracting landing gear (or at least fairing it or streamlining it better).
They were putting brakes in landing wheels instead of a depending on skid plowing a trench in the ground to slow the airplane down on landing.
They were putting flaps and slats on wings to allow the wing to be configured for both high speed and high lift/drag for landings and take-off.

They had to get a number of things to work together to get the planes up to the high 200s and into the 300mph range.

Canaus said:

During the 109 production run much effort was made not to disrupt the production line so the wing did not appreciably change over production run.

But as the war progressed the lack of wing area would have been a drawback to performance as the increase in dry weight increased due to increased armament & equipment. The 109s small and tight packaging of the complete aircraft certainly was a detriment in trying to find room for more fuel tanks.

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It was possible to increase the wing area, it was done in the Bf 109 T model. It was produced, though I admit i don't know if the limited run (60 or 70, sourvces differ, produced by Fieseler) was delaying other license production from Fieseler? According to this web page Me 109 T the span was 11 meters. according to wiki it was 11,08. An increase of a little more than one meter may not be much, but it happened early war.

Ten Bf109Es were converted to Bf109T configuration before the 60 manufactured.

In addition to extended wings, they also had longer slat spans as well as an increased flap extension.

I'm late to comment on this thread and am surprised that no one seems to have mentioned range and altitude advantages of larger area wings, especially high aspect ratio. Here are some thoughts to broaden the discussion.
Note that most bombers and all transports utilize that layout. Early war Axis fighters emphasized raw speed, ground support and short range tactical bomber protection. Japan had several years advantage with their war against massive China and SoPac expanses, while Germans and Italians were fighting a short range war, operating from just behind the rapid advance. Camm and Mitchell's lower wing loading philosophy held with the mainstay Brit designs, which wound up being more flexible in the long run.
Note that when the escort weaknesses got challenged by the longer ranges against England, the longer wing Me110 came into play.
Americans had many high wing loading designs in the late '30s, but seemed to realize that range was going to be a big factor, which predominated in P-38, P-47, P-51 and Naval fighters. That wound up serving them well in the long run, and the P-47, and Naval fighters did not suffer from lack of maneuverability ... the P-51 did have some laminar airfoil compromises. What's amazing, is that one of the most maneuverable aircraft was the massive P-61, which with spoilers as well as ailerons, had a faster roll rate than single engine fighters. There are tales of 1945 Pacific mock dogfights with Jugs and Mustangs, that amazed the single engine guys.
Note that WWII was a "shoot down the high altitude observation planes" air war, which influenced generals to avoid static positions, and emphasize fast hitting armor and attack aircraft. Too many of the generals and designers were still bound to the last war in their thinking, and the early sieges in Spain and China kept them tied to that likelihood.

Shortround6 said:

Bf 108 first flown in 1934. Willy and the boys were using very modern developments and were ahead of much of the competition.
But short span slats are not magic and the Willy and the boys were not using them as magic. They were using them in combination with the flaps to get desired results.

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That is common sense, I haven't seen/heard that neither Willy nor his boys has ever used the term magic, but...

"In the early/mid 30s there was a lot of transition. It there was also a lot scheming to get around patents."

It could be, but not in this case, certainly...
According to one old HoHun post: Vann's "Willy Messerschmitt" confirms that there was indeed a 16 May 1928 patent on the single-spar wing, invented by Messerschmitt, and also the trade of patents (slats -monospar wing) between Messerschmitt and Handley-Page, which was agreed-on between Willy Messerschmitt and Frederick Handley-Page personally.

And generally, the story of slats is guite interesting one - as it should be - and includes even Ludwig Prandtl, personally .. but no scheming

blau said:

That is common sense, I haven't seen/heard that neither Willy nor his boys has ever used the term magic, but...

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Willy and boys never used the term magic but it seems that a some post war writers or a lot of modern internet "experts" seem to think they are "magic" and confer turning ablities well beyond what physics would allow for.

blau said:

"In the early/mid 30s there was a lot of transition. It there was also a lot scheming to get around patents."

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Didn't mean to imply that Willy and boys were doing anything wrong.
But there was a lot of interest around the world to get the benefits of Handley-Page/Lachmann slats without having to pay royalties.
Wing washout was one way. The slightly twisted wing stalled at the root before it stalled at the tip preserving aileron control, but at the cost of higher drag at all times.
However it also made the wing cheaper to build and lowered maintenance costs.
I don't know where fixed slots (letter box slots) fall legally, wither they were covered by the Handley-Page/Lachmann patents or not.

A bit like the multiple types of flaps that came out in the 1930s. Truly better? parallel development? patent get around?
How many are still in use?