wmaxt
Staff Sergeant
lesofprimus said:
I agree 100%.
wmaxt
Fw-190 Dora-9 vs P-51D Mustang
- Thread starter Soren
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I agree 100%.
wmaxt
syscom3
Pacific Historian
The P38 also had some thrust from its exhaust.
Im also curious, are these figures with a painted surface? Ive read somewhere that by skipping the paint on your aircraft, you can gain a few mph.
Im also curious, are these figures with a painted surface? Ive read somewhere that by skipping the paint on your aircraft, you can gain a few mph.
pbfoot
1st Lieutenant
the paints weight alone will cause lost of speed airliners that are painted usually have less useful cargo capacity I once heard that a 747 has over a ton of paint on it these numbers of top speeds are always in a/c that are highly waxed (xtra duty from personal experience) and access panels would probably be sealed and streamlined after all the numbers have alot to due whether the manufacturer gets a contract
wmaxt
Staff Sergeant
syscom3 said:
Thats true at least to the extent of weight and paint finish. I read recently that it was estimated that the paint on a C-18 (twin Beech?) added up to about 91 horsepower penalty.
The numbers for the P-51, P-38, P-47 can be assumed to be without paint as they hit the lines in mid 44 or later. The F4U-4 and 109 had painted surfaces.
wmaxt
- Thread starter
- #165
Well said Les.
Lunatic the reason modern fighters use a laminar flow airfoil design is purely because it allows them to go faster, thats it. If modern jet fighters were using conventional airfoils their speed would be decreased considerably, and going supersonic would be more difficult. However low speed maneuverability would be alot better with the conventional airfoil.
One thing that is worth knowing about laminar flow wings is that they stall earlier and more violently in turns than conventional type wings. This is why modern day fighters use automatic slats and flaps, to prevent these early stalls in banking maneuvers. And this is also why laminar flow wings weren't particularly efficient on WWII fighters, because of the low speeds the a/c were flying at, speeds where a conventional type wing will provide much better maneuverability.
However there are two good points about the Laminar flow wing which WW2 fighters could benefit from, and that was an increased speed when flying straight and a better acceleration in dives. Both things which are good to have if your only going to rely on B&Z tactics.
Lunatic said:
Lunatic the reason modern fighters use a laminar flow airfoil design is purely because it allows them to go faster, thats it. If modern jet fighters were using conventional airfoils their speed would be decreased considerably, and going supersonic would be more difficult. However low speed maneuverability would be alot better with the conventional airfoil.
One thing that is worth knowing about laminar flow wings is that they stall earlier and more violently in turns than conventional type wings. This is why modern day fighters use automatic slats and flaps, to prevent these early stalls in banking maneuvers. And this is also why laminar flow wings weren't particularly efficient on WWII fighters, because of the low speeds the a/c were flying at, speeds where a conventional type wing will provide much better maneuverability.
However there are two good points about the Laminar flow wing which WW2 fighters could benefit from, and that was an increased speed when flying straight and a better acceleration in dives. Both things which are good to have if your only going to rely on B&Z tactics.
FLYBOYJ
"THE GREAT GAZOO"
plan_D said:
Yep - like other aircraft late in the war...
It also eliminated another process during assembly.
Jabberwocky
Staff Sergeant
Painting an aircraft makes quite a large difference in speed. Not only from its weight, but also from its drag. British testing of the Mustang I showed that when standard British camoflage and markings were painted on speeds dropped by around 8 mph.
The matte black paint originally used on Mosquito night fighters was abandoned because it had significantly more drag than the RAF standard semi gloss finish. Apparently the speed loss was on the order of some 22 mph.
Speed trials on an underperforming Spitfire Mk V (EN946) showed that rubbing down, repainting and polishing just the wing leading edge increased speed by ~6 mph. With some other fairly simple modifications, they later got the same Spitfire Mk V up to 385 1/2 mph, or about 15 mph faster than a standard Mk V.
The official speed and range for a Mk XI PR Spitfire was suppose to be around 420 mph and around 2,300 miles with a 170 gallon overload tank. However, ground crews and even pilots would regularly strip, fill, wax and polish all the aircraft leading edges, which reportedly gave another 10-15 mph speed and add up to 200 miles range over the by the book numbers. When speed is your only defence, you do everything you can to maximise the advantage.
The matte black paint originally used on Mosquito night fighters was abandoned because it had significantly more drag than the RAF standard semi gloss finish. Apparently the speed loss was on the order of some 22 mph.
Speed trials on an underperforming Spitfire Mk V (EN946) showed that rubbing down, repainting and polishing just the wing leading edge increased speed by ~6 mph. With some other fairly simple modifications, they later got the same Spitfire Mk V up to 385 1/2 mph, or about 15 mph faster than a standard Mk V.
The official speed and range for a Mk XI PR Spitfire was suppose to be around 420 mph and around 2,300 miles with a 170 gallon overload tank. However, ground crews and even pilots would regularly strip, fill, wax and polish all the aircraft leading edges, which reportedly gave another 10-15 mph speed and add up to 200 miles range over the by the book numbers. When speed is your only defence, you do everything you can to maximise the advantage.
KraziKanuK
Banned
- 792
- Jan 26, 2005
Have heard that German paint was finer a 'grain' when applied than Allied paint, and thus smoother. True/false?
- Thread starter
- #170
Something that might be of interest: http://www.anycities.com/user/j22/j22/aero.htm
alejandro_
Airman 1st Class
- 281
- Jul 4, 2005
An interesting note:
- Cooling drag: 16%
- Fuselaje: 30%
- Wings: 31%
- Various: 4%
- Horizontal tail: 6%
- Interference drag: 9%
- Induced drag: 1%
- Vertical tail: 9%
What are the usual values for these parameters? I had come accross some information in a book but it was on jet aircraft. Somebody mentioned the cooling drag being up to 50% of the total drag...
Regards.
- Cooling drag: 16%
- Fuselaje: 30%
- Wings: 31%
- Various: 4%
- Horizontal tail: 6%
- Interference drag: 9%
- Induced drag: 1%
- Vertical tail: 9%
What are the usual values for these parameters? I had come accross some information in a book but it was on jet aircraft. Somebody mentioned the cooling drag being up to 50% of the total drag...
Regards.
FLYBOYJ
"THE GREAT GAZOO"
Very cool info!
- Thread starter
- #173
wmaxt
Staff Sergeant
alejandro_ said:
Interesting, it would be great if we had the same info for the rest of the planes.
Here are a few overall drag coefficents (C/D) and Lift over Drag (L/D) numbers to compare (by NACA/NASA
Plane -- C/D -- L/D
B-17G - .0302 - 12.7
B-24J - .0406 - 12.9
B-29A - .0241 - 16.8
B-26F - .0314 - 12.0
P-51D - .0163 - 14.6 the article above puts the C/D of the P-51D at .019957 which fits better with its relative performance.
P-38L - .0268 - 13.5
F6F-3 - .0211 - 12.2
PBY-5A .0309 - 7.73
wmaxt
wmaxt said:
But the problem is you are referencing info based upon old released data. For instance, top seed on the F4U-4 was not 4446 mph, it was 464 mph TAS at ~20,700 feet! That number is right out of the F4U-4 pilot handbook. For most US planes, immeadiately following WWII, the top speed figures given reflect Military Power, not WEP.
Also, in your figures for the P-51 power where is the radiator thrust? Yes, it does not overcome the drag of the plane, but it does cancel out 90-100% of the cooling system induced drag, which does not occure for any of the other fighters you've listed (actually the F4U-4 cooling system does generate some thrust, but much less than that of the P-51).
wmaxt said:
I took the numbers given from various sources, and the fact that, at any speed over ~180 mph IAS the P-51 cooling system cancels out at least 90% of the cooling system induced drag. Cooling systems accounted for between 10 and 20% of the drag on WWII prop fighters, I used 12% which I am confident is low for the P-51 since it was a slick design, and extrapolated the numbers from there - somewhere there is a figure for how much equivalent HP the radiator thrust system is making at a given speed (I'll try to find it when I have time - IIRC it's 340 hp @ ~ 400 mph at 20 or 25K). The key point is that drag increases with the square of the velocity, and so does the radiator generated thrust. So at higher speeds the effective power provided by the system becomes quite large.[/quote]
wmaxt said:
And just how much thrust do you think was being generated by the prop? Cruising at 400 mph, 150 lbs of thrust is probably more than 10% of the prop thrust. Another thing is the fact that as the reaches increasingly higher speeds the prop thrust becomes limited because the tips cannot exceeding mach, thus prop efficiency is dropping off, where the radiator thrust is not effected by such concerns. As for the cooling system effectiveness, sheer size of the radiator core (which is why I believe my figures are low - on the P-51 the cooling system was huge so the drag was probably closer to 20%, not 10%) ensures exceptional cooling which was one reason the P-51 didn't benefit much from water injection.
As for every plane today having such a system... they would if they used conventional engines and flew at high speeds. However, any modern plane that is going to stustain these kinds of speeds is going to be using a jet or a turbo-jet engine. It's a solution to a problem that is no longer really relevant. At the speeds of modern civilian piston powered prop's the expense of routing the cooling system in a manner similar to that of the P-51 is not justified for the meager gains achieved at the speeds these planes fly.
wmaxt said:
Some of both. Personally, I think the laminar flow wing was more about providing room for fuel than anything else. Having the maximum thickness at the center rather than 25% back from the front of the wing makes for a lot larger tanks. Some advantage when cruising was achieved vs. a conventional wing of the same thickness, but there were conventional wings that were thinner, provided the same lift, and induced less drag - they just had no room for fuel. So I'd say the radiator thrust system not the laminar flow wings was the bigger contributer to its speed.
=S=
Lunatic
Jabberwocky
Staff Sergeant
Lunatic:
My October 1944 and April 1945 charts for F4U-4 both have 446 mph as max speed for military power and 452 mph as max speed for War Emergency Power at 70" HG and 20, 300 and 20,800 feet respectively.
Configuration was clean and T/O weight was ~12,500 lbs
This is the first time I have run into the 464 mph figure. Are you sure it isn't just a typographic error?
My October 1944 and April 1945 charts for F4U-4 both have 446 mph as max speed for military power and 452 mph as max speed for War Emergency Power at 70" HG and 20, 300 and 20,800 feet respectively.
Configuration was clean and T/O weight was ~12,500 lbs
This is the first time I have run into the 464 mph figure. Are you sure it isn't just a typographic error?
Jabberwocky said:
Check for yourself...
http://www.history.navy.mil/branches/hist-ac/
Notice the "clean configuration" figures in the notes and convert KNOTS to mph.
=S=
Lunatic
Jabberwocky
Staff Sergeant
Lunatic said:
Thanks for the link. Great stuff.
My Broadband is going to be worked overtime tonight! 
Looking at the F4U-4 link, I think it possible that one of us has made a mistake in our calculations.
Max speed is given as 393 knots @ 20,500 feet.
1 knot = 1.1508 miles
393 kph = 452.25 mph
So, by my calculation, the max speed of the F4u-4 is 452 mph.
Also, check the knots to mph conversion chart on the side of the 1.6mb F4u-4. 393 knots is pretty much bang on 452 mph.
syscom3 said:
Yeap but that does not mean that the aircraft can not handle the 9Gs.
syscom3
Pacific Historian
If the pilot is unconscience, then it doesnt matter if the plane can handle 9 gee's or 20 gee's. Its going to be shotdown.
