World War II low drag 1

[spitfirevi]

It's a bit late now, but what would result from stripping a prop fighter to engine, stub wings and pipe tail? Without a fuselage, the tail flaps could be minimal, and less weight may allow for skids instead of wheels,and so reducing weight. Did they have the tech. in 1940's to make engine bearings with enough cover to act as sealed bearings for 1 hour? That would allow for removing oil-sump, with possibly oil-petrol fuel for piston lube. Air cooling on a minimal engine block may remove glycol cooling. Impossible?
spitfirevi.

 

[MikeHalloran]

In a piston engine, the lube oil is the primary coolant for the pistons, and to a lesser extent for the cylinders and heads.

AFAIK, they don't have the technology _now_ to make plain bearings run without lube under major load for an hour, and if they did, so what? WWII missions ran much longer than that.

Both ideas have been addressed in research programs by the US Army, which would love to have generators powered by adiabatic engines that require neither coolant nor lube oil. They haven't quite reached the surplus market yet, or actual production, so they may have eluded your notice.

If you can find a good detailed cutaway of a WWII fighter, I think you'll discover that there wasn't a lot of empty space inside, what with the guns, and the bullets, and the fuel, and some fairly bulky avionics.







Mike Halloran
Pembroke Pines, FL, USA

 

[spitfirevi]

Thanks Mike. I found a comment on the fuselage:"The cockpit itself is between frame 8 and 11 ... On the first Spitfires, .. From frame 11 and aft frame 12 to 20 form an open structure where cables for the control surfaces and electrical wiring run." That allows for reducing the fuselage there. I was thinking of local defence where a fighter op. could be of 1 hour. Possibly a bearing could be packed in a short-life casing with oil, to replace the sump. The middle-level area of the block could have heat-radiating fins. The whole engine could even be replaced each combat, if the advantage gained meant that the plane survived and claimed enemy losses.
spitfirevi

 

[MikeHalloran]

The structure is open. That does not imply that the space is empty. Okay, let's assume that it could be empty, and you could reduce the volume of the airframe with a pipe boom. Would it reduce the weight? Maybe not, because the boom needs a heavy wall to carry moments. The tailplanes cannot be seriously reduced in area, hence weight, because a fighter has to be aerobatic. So all you gain is a new flutter problem.

The throwaway strategy presumes you have the capacity to produce an engine per sortie, and the logistics to deliver them to point of installation. Of course, entire airplanes have been designed and produced for one time use.

I think most fighter engines of WWII were dry-sump. Wet sump would be lighter. As you say, no-sump would be lighter still, but even if it worked, would dramatically increase maintenance requirements.

You can put all the fins you like on the block. They radiate to each other, which is useless, and to the engine cowling, which has minimum surface area to reduce drag. The benefit doesn't offset the weight penalty. Better to put the fins in some airflow and remote from the block, e.g. in an oil cooler.




Mike Halloran
Pembroke Pines, FL, USA

 

[rb1957]

the main aerodynamic purpose of the fuselage is to be a fairing for the pilot and the engine; so replacing the fuselage with a boom would probably hurt.

and what are these "tail flaps" you mention ... would that be a reference to the empennage (the horizontal and vertial tail surfaces) ... to only thing maintaining the stability of the plane ? ... probably not something you'd want to get rid of.

admittedly removing the radiators would improve the performance of the plane, slightly, but is the plane now a throw-away, 1 mission plane ... wouldn't this dramatically increase the manufacturing requirements in support of the fleet ?

 

[spitfirevi]

Would reduced weight cause less moments about the tail-pipe?
Would that pipe need less empennage than a fuselage with lateral pressure? Could that pipe be formed by 2 or 3 parallel small pipes? I was presuming that the engine might be replaced after reconditioning... I think I'm losing the game...
spitfirevi

 

[GregLocock]

What /exactly/ are you trying to achieve?



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Greg Locock

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[IRstuff]

Your OP assumes incorrect stuff. The weight of the wheels is not in the wheels themselves, but in the structural strengthening and actuators to lower/raise the wheels.

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[spitfirevi]

Greg,
I am just interested in optimising what they had available. Was it possible to re-think the concept of lumbering, slow battle-wagons? The idea of a minimal "pilot-on-engine" appeals to me. If it had a low-set cockpit canopy(with low side windows), and no oil-sump beneath the engine, the rear fairing would not be so crucial in drag. Would the lack of fuselage allow sharper turns?
Yes, the whole wheel assembly is what I meant when suggesting replacing them with skids - if the plane's weight could be reduced enough. A short dog-fight would not need a full fuel-load. But I think reality is against the idea of a hot-rod super-plane.
spitfirevi

 

[thruthefence]

If I'm not mistaken , during wwII there were proposals for "swarms" of cheap, basic fighters, fabricated from "non-strategic" materials, manned by minimally trained pilots.I don't know if any were actually constructed or demonstrated.

 

[rb1957]

"slow" and "lumbering" are not two adjectives i'd apply to most WW2 fighters.

the most successfull plane made from non-strategic materials would have to be the dH mosquito.

i think most pilots would object to being strapped to an engine and sent into a dogfight. those that have a death wish would probably object to having no frontal view (for take-off if for nothing else).

i think that the highest performance WW2 fighters were right up against other design constraints (aileron reversal (due to local shocks) and gloc to name a couple).

The drag of a short (unfaired) body is higher than the drag of a faired body.

You could have a tail-less plane, a la Me163.

 

[zifos]

I wouldn't call the spitfire slow and lumbering. Maybe slow compared to modern fighters (F-18, F-22).

I don't think having an engine that last only 1 hour would be usefull. Even if you rebuild it after each flight. You then have 3 guys flying planes and 30 guys rebuilding/replacing engines just to keep up. More usefull to have 20 planes in the air and 10 guys doing maintenance/repair? I think so.

rb1957: I'm not sure what is considered a "tail-less" plane but I would considered the ME163 to have a tail. Although it is a short tail with no horizontal stabilizers. Does have a verticle stabilizer. The Horton HO 229, the Northrop YB-49, and the B-2 bomber are airplanes I would consider tail-less.

 

[spitfirevi]

Would an angled forward view through side-windows allow safe take-off and landing? Landing the less-heavy plane without heavy fuel-load, would be at slower speed . If the plane had more speed and acrobatics in dogfights, then its purpose in downing enemy bombers and fighters and surviving, would be realised. That would cut losses in pilots and planes and factories bombed, and so paying for the cost of re-fitting engines.
spitfirevi

 

[IRstuff]

Skids sticking out of the fuselage is certainly not going to make the plane aerodynamic.

This wholw concept has NEVER been proven to be effective. Pilots are the most expensive part of a plane; they are DEFINITELY not throwaway items.

While there have been demonstrations that swarms of cheap fighters can overwhelm a single high-performance fighter in a single dogfight, no country can afford to hemorrhage both planes and pilots on a continual basis.

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[btrueblood]

Spitfire,

The reason for the cowlings, fuselage, etc. on WWII fighters is to reduce the drag caused by the necessary bits of equipment (engine, pilot, tail structure, etc.). Very little "unnecessary" bits can be found on those planes. Very few aircraft designers add weight/structure without a really good reason for doing so.

Pre-WW1 airplanes had open truss tail booms. They were slow, and designers quickly found that by covering the trusses in fabric they could get quite a bit more speed.

Pre-WW1 planes also had un-cowled engines. NACA did a study that showed that cylinder head cooling could be improved, and drag reduced, by putting a streamlined cowl over the engine (google "NACA cowling").

Pre-WW1 planes had fixed-skid landing gear. Lots of pilots dug big furrows in the ground with the nose of the planes, and so the extra weight of rolling wheels was deemed a good idea (planes that don't crash on every landing can be re-used instead of recycled). Fixed wheels cause more drag than skids, so "spats" (streamlined fairings) were added, to gain a bit less drag and bit more speed. But the really fast planes were the ones where the wheels could be retracted. Even today, fixed-gear general aviation planes are much slower than retractable-gear versions, even when you compare equal powerplants.

Finally, air-cooled engines are just too bulky, especially if turbo/super-charged. The engine can be made more compact (and thus lighter per unit hp), and the frontal area can be greatly reduced by piping a liquid coolant thru the engine, to somewhere near the back of the fuselage (where all that "empty space" is), and dumping the waste heat there (this is how the P51 did it, and the clever design of the belly scoop makes the radiator produce a fair bit of ramjet thrust, which compensates for the drag of the inlet protrusion. This was probably one of the lowest-drag cooling systems in use in WWII, although the FW190 and TA152 had pretty neat setups as well).

Your OP seems to be taking a snide tone against WWII aircraft designers, although you may not have intended it. The reality is that an awful lot of brainpower, R&D, sweat, and creativity went into the designs of those planes, backed up by thousands of hours of wind-tunnel and flight tests. That the people involved were not dummies should be taken as a "given". If you need any further proof, just plot the top speed of aircraft on a timeline, and look at the huge jump that occurs near 1945, and shortly thereafter.

 

[spitfirevi]

IRstuff,
With the idea of raising speed, the skids would of course be retractable. I wrote of the purpose to survive, not losing pilots or planes.
btrueblood,
I wrote of air-cooling the middle-level of the block, as the top and bottom would need fairing. As Hitler's VWs are air-cooled, is it possible for 1 hour? The designers were compelled to follow bureaucratic orders, as pilots also had to follow ridiculous rules in the early days of combat. I am raising the unorthodox idea of bad engineering for brief tactical superiority. Would skids which extended beyond the nose avoid tipping on landing?
spitfirevi

 

[IRstuff]

In order to get the low friction on the ground, the skids would have to quite large and will be quite heavy.

Seems to me that you've assumed a certain paradigm of your own that has never been borne out in any combat, e.g., a 1 hr time limit for flight, that puts the time of station at less than 10 minutes. I don't see any practical reason for this. Unless you have close to parity, waiting for an opponent to that close to your bases is suicidal, as is limiting the amount of time on station. Also, combat fighting has never been about pure speed. That only works against fixed surface targets. Combat has almost always been about maneuverability coupled with adequate speed. That's why even a supersonic fighter like the F-22 still carries an M61A2 20-mm cannon. Moreover, having such little flight time means that you cannot do combat patrols or fighter escorts of bombers and cargo planes.

The crux of any systems engineering design is NOT optimization of individual components or scenarios, it's about the WHOLE system. Therefore, systems are always compromises to ensure that competing requirements are fulfilled to some degree.

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[spitfirevi]

The idea was for specific local defence only. Would it take 50 mins. to climb and return from contact? How would shock-absorbers go on alum-alloy skids at low-speed, with alum wheels? I'm getting desperate here..
spitfirevi

 

[IRstuff]

The point is such a concept has inherent flaws. You can't keep such a force on alert 24/7; they'd wear themselves out. Without early warning, they'd be useless. Sitting on the ground, they'd be sitting ducks for high-altitude bombing.

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[GregLocock]

In a counter-factual like this, what premise are you changing? Does it not strike you as odd that the 'best' fighters from each country had very similar performance?




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Greg Locock

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