Biplanes for ww2: where could've these still mattered?

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Way back in the Windows 95 & 98 days I found that site and figured it was gone today. With little computer memory and even less computer ability than today, I printed much of his data and made notebooks. Thanks for the site update.
 
tomo pauk said:
Thank you for the excerpt.
The aircraft of the 1940s will hopefully be using more modern wing profiles than what is shown there :)
Click to expand...
I am not sure that is a bad airfoil. A wing section must do three things...
  1. Generate lift, generally equal to the weight of the aircraft
  2. Generate minimum drag
  3. Work as an efficient structural section.
That third item became particularly important when cantilever wings were developed during WWI. A thin wing section is a functional structure if the wing is a set of short cantilevers supported at both ends. If all the attachment and support is at one end, the wing must be way stiffer and stronger. Early cantilever monoplanes needed to be very light, so the wing sections needed extra structural efficiency. They needed to be thick. A thin cantilever section must be heavily constructed. On a 400mph aircraft with 1000+HP, this is manageable.

BernoulliAirfoil.png​

Thick airfoils were not well understood back in the day. The figure is what I call a Bernoulli airfoil I analysed it at zero angle of attack, using Bernoulli's equation. It works. For an aerodynamically efficient shape, you need to round off the leading edge, and move the top of the curve to about 1/3 chord. You wind up with something that looks a lot like a Clark_Y airfoil. By WWII, newer, more symmetric airfoils that could not possibly work by Bernoulli's principal, were developed empirically in wind tunnels.
 

As above - the designer of a biplane even for the second half of the 1930s will not choose the wing profile from ww1.
 
It is not the wing profile itself.
The drag of a biplane was considerable. The two wings interfere with each other.
Consider the Gladiator and the Hurricane. The Gladiator used the RAF 28 airfoil (wiki?) and that airfoil has a max thickness of 9.8% at 30% of cord. Practically a razor blade compared to the Hurricane. However the Gladiator has 323 sq ft of wing area for a 4600lb airplane. The Hurricane has 257 sq ft of wing for a 6400lb plane (MK I ?)
The Gladiator has got about 25% more wing area for surface drag.
Gladiator had a best landing speed of 57mph (not stall speed)
Hurricane had a best landing speed of 67mph.
Gladiator is not getting a lot of lift from that wing area.
But if you throw in all the struts and wires on the biplane the drag really starts to build up.
If you try to use a 250 sq ft biplane wing you need a thicker wing = more drag. Maybe not a lot thicker, Soviet I-15 used a 11.7% air foil (?) and 236sq ft.
At the speeds most biplanes flew they were not running into compressibility problems.
The wakes from the wing interfere with each other creating induced drag.
 
Admiral Beez said:
How about swapping out the Arados on Bismarck and Prinz Eugen for a fast biplane fighter to dissuade the Stringbags? It's a one way trip until the Germans are within range of France.
Click to expand...
Given the Bf109s landing characteristics, this might have been a good idea. What they really needed was a carrier version of the Fw190.

How much of the Fairey Fulmar's success in combat was due to it facing Italian biplanes?
 
If asking where they could still have mattered, its probably best to look at where biplanes endured and why. In these cases all the way from '39 to '45

In the RAF and FAA, aside from things like the de Haviland Moths who were still providing sterling service in the training squadrons, there were front line aircraft such as:

#1 Fairy Swordfish. Not sure why escort carrier service is breezily dismissed as not worthy of discussion, as it illustrates both a capability which was an important contribution to the final victory at sea (and fundamental to keeping both the UK and Russia in the war), and one which no monoplane aircraft was capable of performing as effectively (or at all).

#2 Supermarine Walrus; From 1935 to 1945: As a spotter plane for capital ships and cruisers. For air-sea rescue. And until the advent of rugged, reliable helicopters with a modicum of performance, it was supplanted and superseded by the Supermarine Otter.

Biplanes offered low wing loading and excellent low-speed handling - the latter in a simpler package that did not require slats, flaps and other comparatively complex mechanisms that also made them lower maintenance. Being a generation behind most other designs, they also tended to employ simpler manufacturing techniques which seems to have made them simpler to repair in the field.

In the case of both swordfish and Walrus/Otter and their final roles, it wasn't really the monoplane that finally made the biplane finally and completely obsolete as a design - it was the helicopter.

The simplicity aspect in terms of airframe had other advantages - austere operations in places like Malta and Greece showed how Gladiators had certain advantages from a maintenance aspect, as well as an ability to operate from barely prepared short fields. As long as you were prepared to ignore the limitations of speed, biplanes were generally more manoeuvrable, structurally lighter and able to lift more for their own given unladen weight.

I can imagine that an adaptable, rugged and versatile airframe with short field similar capabilities to the Antonov AN-2 might have been very useful in remote and challenging theatres of war for a whole variety of purposes. Perhaps a repurposed Swordfish with some of the modern attributes of the otherwise unloved Albacore (such as an enclosed cockpit and more powerful engine) might have provided something like that?
 
I don't know if you're quite being fair:
Hurricane has flaps while Gladiator does not - Hurricane stalls at 77mph u/c & flaps up; 63mph u/c & flaps down...

Lift is ^2 function of speed... so while 10 mph isn't large number, it represents >38% increase in lift at speeds in question.
A 38% increase in landing distance is the difference between landing on a small/slow Carrier and overshooting into the deck​

If I add another 10 mph to the Hurricane to land with flaps up (sort of splitting the difference between the clean and dirty numbers), the lift has increased >80% versus the weight/wing area difference with the Gladiator of ~75%.

And that matches my understanding of why biplanes clung around: they might have lost in top speed*, but they won when it came time to land/take off.
As you get slower, the effects of wing interference, etc become smaller, and the effects of weight greater.​
*When you only have FP propellers/limited power, so top speed of monoplane vs biplane are similar, landing performance takes on greater importance.​

There's a similar concern with fixed landing gear - when you're landing in someone's cow pasture/field, landing slow with rugged gear is more important than when you're landing on a concrete strip a couple miles long.

And there is still a significant amount of clean up which may be done on the SBC in addition to T ThomasP 's suggestions . (They will add a little weight which will hurt landing speed, but they will significantly reduce drag) <I would move to internal bombay..>
Attach the top wing to the fuselage with a single pylon, not 4 struts + wires or direct to the fuselage ala Gregor FDB-1​
Get rid of the wires on the wings (structural engineering/material <aluminium alloys> have progressed significantly since WWI)​
Change the wing end struts to a single pylon (aka Hs.123)​
 
don4331 said:
Hurricane has flaps while Gladiator does not
Click to expand...
Gladiator had flaps, both upper and lower wings. Not big but they were there.

They hung down about 90 degrees, they were more air brakes/drag producing rather than lift generators. But then the Hurricane's flaps were down around 80 degrees when landing.

Both planes used split flaps. Upper wing surface did not move.

They were mainly intended to steepen the approach angle/glide slope. Flaps got a lot better in just a few years.
 
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