PDA

View Full Version : Spitfire & Bf-109. Which one has more drag resistance?



Kuna15
12-26-2005, 06:27 AM
Following few topics on forums I have asked myself this question. I have regarded Bf-109 as one of the 'draggier' machines in game... unlike Spitfire.

Xiolablu3
12-26-2005, 06:40 AM
I would like to know the correct answer to this too, I have read in a few sources that the 109 was the 'draggier' model too, but these sources are by no means definitely reliable, all coming from British sources and not scientific, so cannot be relied upon.

Can anyone offer anything to this discussion please?

Badsight.
12-26-2005, 06:53 AM
Kuna have a favour to ask of you

check PM

Slickun
12-26-2005, 09:27 AM
A few months ago, a guy was on the forums that was, apparently, an aerial engineer.

This question came up. He said, and I'm no engineer, that drag coefficients could be figured, in a "ball park" way, by looking at a planes weight, drag, thrust, and then comparing that to the top speed. All at a given height, of course.

In other words, the P-51 is a big, heavy plane compared to the Spits with almost identical engines, yet the Mustang went faster. The reason, of course, is lower drag.

All this was brought up because of the 109K. All that HP, low, low weight, yet it was basically as fast as the P-51B, a rather less powerful and much heavier plane. Why so slow?

This guy worked it out, and we find the 109 was very, very draggy, or it would have been much faster. According to this guy, and I forget his name, forgive me, the 109 had a very high drag coefficient, akin to twin tailed bombers.

JG53Frankyboy
12-26-2005, 09:34 AM
Spitfire Mk.Vb and Bf109F-2 are mostly rated at he same max speed.
with the Merlin 45/46 engine more powerfull than the DB601N.

and these variants "should" have the cleanest "outfit" all variants - normal ones, not polished or special made like PR Spits ....

p1ngu666
12-26-2005, 10:03 AM
spit is abit dragier perhaps, but it is a bigger plane

its highspeed drag was very low tho http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

ImpStarDuece
12-26-2005, 02:16 PM
The Spitfire is a little draggier than the 109.

Its a little bigger and a little heavier, and its larger wing area produces more drag than the smaller wings on the 109. Hence the Bf 109 is usually around 5-15 mph faster on the same amount of power, with the exception being the quite draggy 109E.

Both aircraft got worse as the war went on, as various lumps and bumps were added to both planes. More armament, different canopies, different radiatiors, new engines ect, all added weight and disruptions to the airflow over the fuselage. The 109 did get a major aerodynamic clean up with the F model, and the Spitfire a smaller one with the Mk VIII.

British tests showed that reducing external drag could consideraly increase top speed. In 1943 RAF Boscombe Down took a calpped out storage Spitfire V and clocked it at 359 mph at full throttle height. They then repainted it, polished the leading edges, cut the cartridge ejector shoots flush, replaced the fish tail type ejectors with Mk IX type multi ejectors, removed the internal carburettor snow guard (never really used operationally), added a circular mirror instead of the old square on and added a whip type antenna instead of the mast type.

After each modification they did a speed test to see if there was an improvement. At the end of the tests, that clapped out Spitfire V was doing 387 mph at full throttle height. An impovement of around 28 mph over the speed when first tested, and of about 15 mph over a 'service standard' Spitfire Vb.

The lessons; be nice to your crew chief, he may just save your life. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Airmail109
12-26-2005, 02:28 PM
I find it hard to believe that this

http://www.rob.clubkawasaki.com/jas4719.jpg

Is less dragy than this

http://www.walneyairshow.co.uk/images/mk14-spit.jpg

Badsight.
12-26-2005, 02:47 PM
Spitfire had probably the fastest wings of any WW2 fighter , big wing area (comparativly) but were thinner than any other mono fighter of WW2

the thicker Bf-109 wings with the airflow disturbing slats & wheel humps being created lass drag ?

i mean one of the arguments about the turning ability of Bf-109 is their good lift load (for the wing area)

ImpStarDuece
12-26-2005, 02:51 PM
Put a Mk V in that line up Airmail, instead of a 1944 Mk XVI, and a regular 109F instead of a 109F trop. Dont forget to add the mirrors, antenna mast, .303 ports, exhaust stubs and non-retractable tail wheel for the Mk V.

Then add a Mk XIV with the Griffon up front and compare it to a G-14 or K-4.

Airmail109
12-26-2005, 02:53 PM
Oh and heres the MKXIV http://www.militaryairshows.net/legends03/img_7489.jpg

Thats the meaning of clean lines....

Abbuzze
12-26-2005, 03:27 PM
Originally posted by Aimail101:
Oh and heres the MKXIV [IMG]
Thats the meaning of clean lines....
... and lowered aerodynamical efficince.
Yes a nice photo, but take a closer look at the XIV.. monster radiators, bulges at the cowling cause of the bigger engine, bulges at the top of the wings for the 20mm cannons.
http://frenchaces.free.fr/photos/highdef/478.jpg
Also like the 109, with the exception of the Kurfürst no complete wheelcovers...

It´s like many people allready said, 109 and Spitfire were very similar in over all drag, the Spitfire with the better coefficient, and the 109 with the smaller surface.
Beside, coefficient of the 109F2 was 0.023

Airmail109
12-26-2005, 03:31 PM
And those lines are still cleaner than the 109 Gs Abbuze

Xiolablu3
12-26-2005, 03:33 PM
I suppose its all relative, retractable tail wheels on some spits and some 109s mean less drag than on ones without.

The 'bumps' for the 13mm guns on the G6 models will add drag.

The bubble canopy apparantly adds drag doesnt it>? Later Spits had this.

Therefore ots very hard to answer this question and would depend on exact models.

The 109F would probably be the least draggy of the 109s and maybe the Spitfire Mk8 would be the least draggy of the Spits?

Not exactly scientific I know. http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

Abbuzze
12-26-2005, 03:40 PM
Originally posted by Aimail101:
And those lines are still cleaner than the 109 Gs Abbuze

If you feel better if the spitfire have nicer lines, it doesn´t change anything about the drag.

Low_Flyer_MkII
12-26-2005, 03:46 PM
http://virtualskies.arc.nasa.gov/aeronautics/tutorial/calculating.html

Hristo_
12-26-2005, 04:24 PM
in general:

Spit - more area, but lower coefficient
109 - less area, but higher coefficient

Can it be any simpler ? http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Abbuzze
12-26-2005, 04:31 PM
Originally posted by Hristo_:
in general:

Spit - more area, but lower coefficient
109 - less area, but higher coefficient

Can it be any simpler ? http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

No! http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Hristo_
12-26-2005, 04:32 PM
http://www.military.cz/british/air/war/fighter/spitfire/spit_bank1.jpg

Not without lumps and bumps. Huge radiators as well.

jugent
12-26-2005, 04:40 PM
If you try to follow a spit in a 109 in a dive that turns into a steep climb, the 109 seems to have a brakeshute.
The Me-109 kept the worldrecord of speed.

I dont think that all theese things from real life is possible to simulate in this arcade-game.
Its up to the programming team to give the plane the characteristics they want.

If the german engineers was so bad that they made a small airframe with big drag, they would never have hade the competense to build the V1, V2 and the first operational jetfighter.

The german engineers was very skilled, and got the best wind-tunnel during WWII. They where building a bigger one when the war ended, and the French dismanteled it and brought it to france.

The figures from the german wind-thunnel was used by the russian and swedish airforces when they build the arrow-winged aircraft mig-15 and the SAAB J29 which held many world records.

So I am sceptical to that the german engineers who where so skilled othevise, should build a small aircraft with great drag.

p1ngu666
12-26-2005, 05:25 PM
well, i bet the v1 makers where really proud, that there v1 was faster than the RAF.

then a tempest cruises up to one in level flight and shoots it down in a display of insolent suporitey http://forums.ubi.com/images/smilies/59.gif

v2 was much faster ofcourse, shame more died making it than by its use against london and other places.

if i was abit of air, id much rather have a spitfire slide past me than a 109 http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

rather have a ju88s slide past too, smooth canopies for the non ouchy win http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif

neural_dream
12-26-2005, 05:28 PM
I'm confused about who's draggier. So, I'll believe ISD.

I used to think that the BF109 was much draggier and (lighter and) that was why it could decelerate (and accelerate) so quickly.

Just a guess: Doesn't the BF109 have a significant advantage by having its nose at the center of the geometrical plane that meets the air, comparing to the spitfire which has the nose higher? [Sorry for poor vocabulary].

Kuna15
12-26-2005, 05:32 PM
Hey @ ND although I'm not some expert on this issue (otherwise I wouldn't have asked this) but I think that fast acceleration doesn't improve with more drag. On the contrary.
With less drag aircraft should accelerate faster and decellerate slower. That is of course afaik.

In concrete case, Bf-109 accelerates fast because of powerfull machine fitted.

neural_dream
12-26-2005, 05:34 PM
I meant since lighter accelerates faster and since draggier decelerates again faster. Bad use of parentheses http://forums.ubi.com/images/smilies/35.gif.

Kuna15
12-26-2005, 05:36 PM
Originally posted by neural_dream:
I meant since lighter accelerates faster and since draggier decelerates again faster. Bad use of parentheses http://forums.ubi.com/images/smilies/35.gif.

Like I said I'm not an expert so you got me confused there for a moment http://forums.ubi.com/groupee_common/emoticons/icon_redface.gif. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Viper2005_
12-26-2005, 05:37 PM
What is it with everybody around here and radiator size?

The Spitfire's radiators were designed with the Meredith Effect in mind, and therefore produced very little nett drag "on design". In fact they may have produced nett thrust.

The Mustang had an even better radiator installation...



This report is of not inconsiderable interest. The late Lee Atwood of NAA appears to hold the view that the Mustang's speed advantage over the Spitfire was almost entirely brought about by its superior radiator installation.

http://www.airandspacemagazine.com/ASM/Mag/Supp/JJ99/Mustang.html

However, it is worth pointing out that in normal operation, especially at high speed, the Spitfire's radiators were almost always closed, and that the need for a boundary layer diverter under the wing was less than it would have been with an under fuselage installation.

Consideration was given to the adoption of a P-51 type radiator installation for the Spitfire, but the disruption such a change would have caused to production was considered excessive.

In addition the P-51 had a laminar flow wing and a higher wing loading, which probably put it into its laminar flow bucket at full power in FS gear (especially likely with the V-1650-3 engine due to the higher FTH) - as such a direct comparison of top speed between the Spitfire IX and the Mustang in level flight isn't quite fair.

Perhaps the best solution to this subsection of the debate would be to carry out some calculations; but it's Christmas and I can't be bothered to go digging for the correct books.

Maybe later I'll have a go...



As for drag, you need to specify what kind of drag you're talking about. Zero lift drag or L/D max or what...

Whilst you're at it you need to specify your Mach number of choice, as drag is very sensitive to Mach number.

The Spitfire was an exceptional performer with regard to performance at high Mach number due to its thin wings.

Overall I'd just like to add that the truth is rarely pure and never simple...

Abbuzze
12-26-2005, 05:51 PM
Originally posted by neural_dream:
I meant since lighter accelerates faster and since draggier decelerates again faster. Bad use of parentheses http://forums.ubi.com/images/smilies/35.gif.

The 109 decelerates faster in turns, not because of the drag, but because of the smaller wings, they need more AoA so drag in turns is increasing more.

For the meredith effect of the Spitfire radiators, never heard of this before. Any source for this?

TooCooL34
12-26-2005, 05:57 PM
In-game acceleration test thou it won't tell everything

Alt: Sealevel
Radiator : Closed

Bf-109G6/AS
250 to 400 : 13 sec
400 to 450 : 8 sec
450 to 500 : 13 sec
500 to 550 : 26 sec

Spitfire MkIXe
250 to 400 : 17 sec
400 to 450 : 11 sec
450 to 500 : 25 sec
500 to 550 : virtually takes forever

Now insist 1C programmers attached dragchute for 109. http://forums.ubi.com/images/smilies/59.gif

Viper2005_
12-26-2005, 06:28 PM
What matters is speed/(bhp/tonne)

The G6/AS has an awful lot of horses dragging it through the sky thanks to MW50.

The Spitfire IXe in game is actually an LFIX in that it is fitted with a Merlin 66. At 5750' it gives a little over 1700 bhp. At sea level it only puts out rather less power due to the increased power consumption of the (throttled) supercharger. 1500-1600 bhp would be a reasonable estimate.

What I don't know is the weight of the Spitfire IXe in game.

I'll leave you to plug in numbers for the Bf-109G6/AS...

neural_dream
12-26-2005, 07:00 PM
Originally posted by Abbuzze:
The 109 decelerates faster in turns, not because of the drag, but because of the smaller wings, they need more AoA so drag in turns is increasing more.
Thanks, that explains it, assuming that the BF109 is less draggy.

ImpStarDuece
12-26-2005, 07:03 PM
All ingame Spitfire Mk. IXs have a Merlin 66, not just the Mk IXe. Peak horsepower is 1720 hp, at 8,500 feet. Power at sea-level is 1580 hp at +18 lbs (and about 1975 hp with +25lbs boost), and 1505 hp at 21,000 feet. The LF designation can be applied to all of them, because of the engine, regardless of other features.

The only exception to this is the HF Mk. IXe, which has a Merlin 70, a very similar engine, with slightly different reduction and blower ratios. It produces 1,710 hp at 11,000 feet.

We really do need a 1942 F Mk IXc, with a Merlin 61 at +15lbs, and/or a early 1943 F Mk IXc, with the more powerful Merlin 63/63a at +18 lbs, but the same blower ratios as the Merlin 61.

Climb and acceleration were slower, as were speeds below 22,000 feet. The F Mk. IX with Merlin 61/63 engines were designed to be most competitive above 25,000 feet. The LF Mk. IX were designed to be most competitive between about 8,000 and 25,000 feet.

Hristo_
12-27-2005, 12:48 AM
from: http://www.virtualpilots.fi/feature/articles/109myths/

Me 109 fuselage and drag

- The G-6 sure had its bumps, but the rest is certainly not true. 109 used Meredith effect and used at least up to the F model boundary layer bypass in the radiators. The 109 K-4, and to some extent the 109 G-10 as well, were considerably cleaned up aerodynamically compared to earlier 109 G's, especially the 109 G-6. The 109 K-4 reintroduced the retractable tail wheel and had among other features completely covered wheel wells (like the P-51).
- The efficiency of the 109 airframe was proven very early in 1937, when a Emil airframe was prepared and a DB-601 engine was tuned to deliver 1700PS. This machine reached 611km/h at sealevel, world record. Except for a very careful surface finish, all difference to the serial 109E were a different spinner, no weapons, and a modified hood. This plane was not the 209, also called 109R, which reached later a much higher speed. Even 8 years later this speed was barely reached with such a power.
- The aerodynamic efficienc of the 109 was based on several reasons. The three most important were:

* Small overall surface, especially wingarea. To compensate for the high wingloading during takeoff and landing, very efficient slats and flaps system was installed. The usually turbulent flow in the tail section lead to a very low overall surface area in this area.
* Inverted V-engine, giving the airframe an larger angle to the usually low mounted wing. This reduced interferenz drag and THIS was also the reason why the pilot head space was rather small. Nevertheless it was one reason why the 109 had a surpisingly high diving speed (only fools believe those spit dive tests with Mach numbers up to 0.9 btw.) what saved also their lives quite often.
* Centered propellor position, thrust line going right through the COG, also allowing for better view forward down

- Meredith effect was nothing of unusual to be used in WW2 fighter radiators. Spitfire, Yakolevs AND Bf 109 enjoyed this effect. In fact the Bf 109F`s radiators were designed to take maximum advantage of it. To quote the relevant part from the Wright Field evaluation of Bf 109 F:
"Each flap is divided in two sections : the outer section is a modified split arrangement serving the additional purpose of controlling the airflow through the internally mounted wing radiators. At the front edge of the radiator is a hinged plate, linked with the trailing edge flaps to open with them. This plate picks up the boundary layer on the underside of the wing, and discharges it on the trailing edge. This form of boundary layer control causes smoother flow through the radiator, thereby reducing the area for proper cooling".
- In other words : the same principle as on the Mustang. Take notice that also the oil cooler on the 109 worked the same way and it dissipated one third of the engine heat, practicaly acting like an extra engine cooler. Very clever design there.
- After the re-design that occurred with the Friedrich, the Me 109 fully employed the Meredith effect. It's radiator had boundary layer separation with separate discharge, a continously adjustable intake and a continously adjustable outlet that was automatically regulated to create thrust. That's the same degree of sophistication as found on the Mustang. The thermodynamic effect of the engine cooling was well-known in the 1920s and 1930s and in fact had been first pointed out by Hugo Junkers in 1915 when he acquired a patent for the "Düsenkühler" ('jet radiator'). Thermodynamics probably were the most advanced science in the late 19th/early 20th century due to their tremendous economical value in a society that based its wealth primarily on steam engines. The "Meredith" effect probably was painfully obvious to Junkers, who included it right in the first aircraft he ever built.
"The Messerscmitt fusalge is remarkably clear and bulletlike. The engine is compactly mounted in the nose and enclosed by easily removeable cowling. Proturbulances that mar the clean lines are cut to the minimum by partially submerging the coolant radiators in the wing."
- Wright Field evaluation of Bf 109 F

- From what I understand the Bf109F and later models used a "boundary layer bypass duct which significantly improved pressure recovery at the radiator face."
- Lednicer, Aeronautical Journal June/July 1995

Abbuzze
12-27-2005, 04:14 AM
Originally posted by Viper2005_:
What matters is speed/(bhp/tonne)

The G6/AS has an awful lot of horses dragging it through the sky thanks to MW50.

The Spitfire IXe in game is actually an LFIX in that it is fitted with a Merlin 66. At 5750' it gives a little over 1700 bhp. At sea level it only puts out rather less power due to the increased power consumption of the (throttled) supercharger. 1500-1600 bhp would be a reasonable estimate.

What I don't know is the weight of the Spitfire IXe in game.

I'll leave you to plug in numbers for the Bf-109G6/AS...

Ok here it comes, first a Spitfire, all values from this homepage:
http://www.spitfireperformance.com/spit9.html

SpitIX - 18lb/sq - BHP@SL 1575 - 330/336mph - 530-540 km/h

109 G6 - 1,42atü - PS @SL 1475 - 324 mph - 521 km/h

Don´t forget that 1BHP is 1.0139 PS so the DB605A is delivering 1455 BHP
So with 120bhp difference. (7.5pct more power) the IX is 6-12mph (9-19km/h)faster than a bulgy G6.

Now for more powerfull versions:
http://www.spitfireperformance.com/spit14v109.html
SpitXIV - 18lb/sq - BHP@SL 1850 - 358mph - 576km/h
SpitXIV - 21lb/sq - BHP@SL 2050 - 367mph - 590km/h


109 K4 - 1,8 atü - PS @SL 1850 - 365mph - 587km/h

So 1850PS are 1825BHP. A K4 with less power is 7mph(12km/h)faster, and to match the speed
of the K4 the XIV need 225BHP(!) more.

You can judge the results by yourselfe.. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

ImpStarDuece
12-27-2005, 05:21 AM
Originally posted by Abbuzze:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Viper2005_:
What matters is speed/(bhp/tonne)

The G6/AS has an awful lot of horses dragging it through the sky thanks to MW50.

The Spitfire IXe in game is actually an LFIX in that it is fitted with a Merlin 66. At 5750' it gives a little over 1700 bhp. At sea level it only puts out rather less power due to the increased power consumption of the (throttled) supercharger. 1500-1600 bhp would be a reasonable estimate.

What I don't know is the weight of the Spitfire IXe in game.

I'll leave you to plug in numbers for the Bf-109G6/AS...

Ok here it comes, first a Spitfire, all values from this homepage:
http://www.spitfireperformance.com/spit9.html

SpitIX - 18lb/sq - BHP@SL 1575 - 330/336mph - 530-540 km/h

109 G6 - 1,42atü - PS @SL 1475 - 324 mph - 521 km/h

Don´t forget that 1BHP is 1.0139 PS so the DB605A is delivering 1455 BHP
So with 120bhp difference. (7.5pct more power) the IX is 6-12mph (9-19km/h)faster than a bulgy G6.

Now for more powerfull versions:
http://www.spitfireperformance.com/spit14v109.html
SpitXIV - 18lb/sq - BHP@SL 1850 - 358mph - 576km/h
SpitXIV - 21lb/sq - BHP@SL 2050 - 367mph - 590km/h


109 K4 - 1,8 atü - PS @SL 1850 - 365mph - 587km/h

So 1850PS are 1825BHP. A K4 with less power is 7mph(12km/h)faster, and to match the speed
of the K4 the XIV need 225BHP(!) more.

You can judge the results by yourselfe.. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

The Spitfire was generally slower than the 109 at low alts, but faster at high altitudes. IN the medium alt bands (8-25,000 feet) they swap back and forth like a double helix, depending on model.

Also, if you clip the wing tips on a LF Spitfire V/IX, you add 5 mph to the sea-level speed. So a LF IX/XVI with clipped wings should do about ~340 mph at sea level (~547 kph), or ~25 kph faster than a 109G6.

Part of the problem with Spitfires is the HUGE amount of airframe, wing, engine, armament and other modifications that went on in the war.

On a side note, I have been running some speed trials with the LF MK V and LF Mk V (CW) Spitfires. They are currently about 20-25 kph short of their tested top speeds at ~6,000 feet. A normal wing LF Mk V should do 350 mph (565 kph) at 5,900 feet, while I can only get it up to 545 kph. A clipped wing LF Mk V should do about 575 kph, while I can *just* push it to 550.

I'd appreciate it if some more talented individuals could give it a try, and see what speeds they hit.

Kuna15
12-27-2005, 05:40 AM
@ ISD, robban75 is the man for this sort of things as he was already done numerous such tests. Acceleration, top speed S/L or best alt etc.
I remember that he was pointed out that for some results one must wait for quite a while 'till the aircraft reaches its max. speed. But it seems that gap of ~25kp/h will be hard to fill...

ImpStarDuece
12-27-2005, 05:57 AM
Just another interesting point.

A Spitfire V, with normal wings, could do ~460 kph at sea-level. The same basic airframe, with a cropped supercharger and an increase in rated engine power, could do ~525 kph. or over 530 kph with clipped wing-tips. Horsepower at sea-level was about 1480 hp.

So on about 100 less hp, the LF Mk V was almost as fast as a LF Mk IX at sea-level. It goes to show that despite power increases, weight is always an important component in drag calculations.

TooCooL34
12-27-2005, 06:07 AM
If it's just about max speed ( not acceleration or deceleration), why don't you refer to neural_dream's a/c guide?
It's quite accurate so you don't need to do it all by yourself.

Abbuzze
12-27-2005, 06:18 AM
Originally posted by ImpStarDuece:

So on about 100 less hp, the LF Mk V was almost as fast as a LF Mk IX at sea-level. It goes to show that despite power increases, weight is always an important component in drag calculations.

Absolutly correct, thats also the cause for the fact that at low level the 109 is faster, and at high altitude the Spitfire is faster.
Higher wingload mean higher AoA in greater altitude, thats increasing drag and slow down the 109 there, while at low alt it makes it faster.

Xiolablu3
12-27-2005, 07:38 AM
Interesting stuff which I never knew, thanks.

Also 109G6A/S is much faster than the Spitfire 9 in game which I never realised, from experience I thought they were around the same speed.

I know the 109G6A/S is really a 1944 plane and not a G6 at all/mishmash of certain 109s, but still interesting as these planes are often against each other on the better servers and make for a great balanced fight.


Thanks for posting guys. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

249th_Harrier
12-27-2005, 07:56 AM
I think (can't remember source) that the primary design concept for the bf109 was low drag. The bf109 had the smallest frontal area, wing area, and surface area of any modern WWII fighter other than yak3. All of these factors should reduce drag. It was one of the first designs using a low-drag aluminum skin.

I wonder if the original poster really meant which is more aerodynamically clean (lower drag coefficient). Some drag is due to creation of turbulence, some due to skin effect, some due to pressure differential, etc. Critical mach matters too. So I don't think there is a single coefficient,more like a complex formula with multiple coefficients.

In general spit is regarded as aerodynamically cleaner, but single number cannot show the difference.

JuHa-
12-27-2005, 10:27 AM
Also 109G6A/S is much faster than the Spitfire 9 in game which I never realised, from experience I thought they were around the same speed.

Can agree when 110%+WEP is used, but they're quite equal when we're talking about max. cruising
speed. (no overheating)

And Spit likes being high more than Me109 ingame.

p1ngu666
12-27-2005, 11:48 AM
yeah, 109s got a big power increase from teh alchol http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif

ElAurens
12-27-2005, 12:05 PM
I get a big increase from teh alcohol too, but my head hurts in the morning.

http://forums.ubi.com/images/smilies/35.gif


An interesting thread gents.

Remember that the coeefficient of drag in not the same thing as total drag. Can be confusing.

Carry on.

neural_dream
12-27-2005, 12:06 PM
So, as I asked a little earlier,

Doesn't the BF109 have a significant advantage by having its nose at the center of the geometrical plane that meets the air, comparing to the spitfire which has the nose higher? [Sorry for poor vocabulary].
Can anyone with aeronautical engineering knowledge answer that?

p1ngu666
12-27-2005, 12:51 PM
think the prop is actully in a similer position, theres a gearbox that shifts where the prop shaft goes

JuHa-
12-27-2005, 01:30 PM
Doesn't the BF109 have a significant advantage by having its nose at the center of the geometrical plane that meets the air, comparing to the spitfire which has the nose higher? [Sorry for poor vocabulary].

Hmm. If the center of the prop would be on the same axis as the center of mass, that would
beneficial. Otherwise there would be additional effect of torque that would try to raise or
lower the nose. (prop pulling the mass from a high point of contact f. ex) This should be
countered with lift, which usually adds to the overall drag in most conditions. I guess there would be a point of balance somewhere, but not
all over the envelope.

Center of the geometrical plane... I guess you're thinking of the "aerodynamic cone" that
is created by the foremost part of the flying object? (sorry for inappropiate term) As a guess
I'd say that as long as rest of the fuselage fits inside that cone, it doesn't really matter?

Hristo_
12-27-2005, 02:18 PM
Makes sense.

Similar case with wing guns vs hub cannon, although much more pronounced in case of the prop.

HellToupee
12-27-2005, 05:27 PM
hows that spit with the db engine compare then :P

alert_1
12-28-2005, 01:42 AM
hows that spit with the db engine compare then :P
..nad Me109G with Merlin (HA1112)?

alert_1
12-28-2005, 01:46 AM
http://www.wcam.mb.ca/AC/HISPANO.html
http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Abbuzze
12-28-2005, 12:00 PM
http://www.unrealaircraft.com/hybrid/spitfire.php

Xiolablu3
12-28-2005, 03:26 PM
Excellent read, thanks Abbuze http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Great pic on the page of the actual plane

http://www.unrealaircraft.com/hybrid/pages/dbspit_1.php

249th_Harrier
12-28-2005, 06:43 PM
Originally posted by Abbuzze:
http://www.unrealaircraft.com/hybrid/spitfire.php

This article is very interesting. There seems to be an extra factor that I hadn't considered before: lift. The Spit airframe has more wing area, which gives it more lift. Therefore it doesn't need the long takeoff roll the 109 does. At low alt, the Spit airframe is slower since the drag is higher (note: total drag, not "drag coefficient"). As altitude increases, the Spit airframe becomes more competitive, and finally surpasses the 109. How? I am guessing the 109 must be flying with a nose-up attitude (positive AoA) to maintain altitude since the wings don't supply enough lift when the air is thinner and the engine supplies less power. Can anyone confirm this?

Abbuzze
12-29-2005, 03:01 AM
Originally posted by 249th_Harrier:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Abbuzze:
http://www.unrealaircraft.com/hybrid/spitfire.php

This article is very interesting. There seems to be an extra factor that I hadn't considered before: lift. The Spit airframe has more wing area, which gives it more lift. Therefore it doesn't need the long takeoff roll the 109 does. At low alt, the Spit airframe is slower since the drag is higher (note: total drag, not "drag coefficient"). As altitude increases, the Spit airframe becomes more competitive, and finally surpasses the 109. How? I am guessing the 109 must be flying with a nose-up attitude (positive AoA) to maintain altitude since the wings don't supply enough lift when the air is thinner and the engine supplies less power. Can anyone confirm this? </div></BLOCKQUOTE>

A very good description!

Beside anyone knows how long the Spitfire needed to take off?
The figures for a F2 are 250m for leaving ground and further 250m to reach 20m altitude.

ImpStarDuece
12-29-2005, 04:00 AM
Spitfire II manual gives a figure of 150 yards and less than nine seconds to take off.

Abbuzze
12-29-2005, 05:17 AM
Found some figures for the Spit V at
http://www.spitfireperformance.com/spitv.html


e) The take-off run in zero wind and standard conditions is 330 yards, and the distance to clear a 50 foot screen is 530 yards.

Numbers for the F2 are
262 yards for take off, and distance to clear 65 foot is 546 yard.

I have to admit, I´m surprised...

darkhorizon11
12-29-2005, 11:21 AM
This is like comparing apples vs. oranges because:
a. theres two different types of drag, parasite which is a result of the aerodynamic shape of the aircraft cutting through the air, and induced with is drag created as a result of lift production

b. theres like umpteen different versions of each aircraft that are all different, ie Spit Mk.I vs. bf-109D-2 or bf-109k-4 vs. Spit Mk.XIV


But my two cents:
Parasite drag increased over the years on the Spitfire with larger radiators larger nose and propeller as well as the larger cannons that were placed on it. The bf-109 on the other hand decreased its drag when they put in the DB inline engine and rounded in the wingtips in the F variants. So I'd say the bf 109 surpassed the Spit in the parasite drag category as the war progressed and new variants were built.

Induced drag, like I said is drag created as a direct result to the production of lift. It is caused by the wingtip vortices mostly. The Spit and its wing remained supreme in this category, although the 109 also improved throughout the course of the war.

JuHa-
12-29-2005, 12:11 PM
http://encyclopedia.thefreedictionary.com/induced%20drag

Likely I'm stating nothing new with the link, but may be of interest for understanding drag a little
better.

A nice analysis of the coolers and overall aerodynamics can be found from here:
http://us.share.geocities.com/hlangebro/J22/EAAjanuary1999.pdf

HellToupee
12-29-2005, 04:05 PM
Originally posted by Abbuzze:
Found some figures for the Spit V at
http://www.spitfireperformance.com/spitv.html
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
e) The take-off run in zero wind and standard conditions is 330 yards, and the distance to clear a 50 foot screen is 530 yards.

Numbers for the F2 are
262 yards for take off, and distance to clear 65 foot is 546 yard.

I have to admit, I´m surprised... </div></BLOCKQUOTE>

might be explained by the fact spitfire does not use flaps for take off.

jurinko
12-29-2005, 05:29 PM
Anyway, Spitfire in FB can do any maneuver with negligible speed loss (maybe even speed gain http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif) while Bf after pulling the stick has a feeling like it is ploughing the hard soil with the rear wheel.

Xiolablu3
12-29-2005, 09:01 PM
Originally posted by jurinko:
Anyway, Spitfire in FB can do any maneuver with negligible speed loss (maybe even speed gain http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif) while Bf after pulling the stick has a feeling like it is ploughing the hard soil with the rear wheel.

And the discussion was all going so well... http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif

You are talking about high speed manouvres, which the 109 did not do well, it was a good slow speed dogfighter tho, as Mark Hanna says, but not as good as the Spitfire.

Read this : http://www.bf109.com/flying.html

Quote from that page - Mark Hanna who has flown both planes, Spitfire and 109 :-

(About the 109) It will definitely out-maneuver a P-51 in this type of flight, the roll rate and slow speed characteristics being much better. The Spitfire on the other hand is more of a problem for the '109 and I feel it is a superior close in fighter.

p1ngu666
12-29-2005, 09:30 PM
maybe oleg should just take the he111 fm, double the weight, cut the range to 15km, half the power, fourfold the drag, and stick it on the spitfire.

just aslong as it can do 300kph, any slower and then its just annoying. then we get a realistic spitfire http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif

Abbuzze
12-30-2005, 02:29 AM
Originally posted by HellToupee:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Abbuzze:
Found some figures for the Spit V at
http://www.spitfireperformance.com/spitv.html
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
e) The take-off run in zero wind and standard conditions is 330 yards, and the distance to clear a 50 foot screen is 530 yards.

Numbers for the F2 are
262 yards for take off, and distance to clear 65 foot is 546 yard.

I have to admit, I´m surprised... </div></BLOCKQUOTE>

might be explained by the fact spitfire does not use flaps for take off. </div></BLOCKQUOTE>

I think you are right, very easy explanation http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif
I looked at a G2 manual, 109 take off was with 20 deg flaps down, so in this configuration the 109 produces more lift than the spitfire. But with more drag I think.

Xiolablu3
12-30-2005, 08:56 AM
I apologise for falling down to his level with my previous post, if you guys could please ignore it. http://forums.ubi.com/images/smilies/51.gif

dugong
12-30-2005, 06:08 PM
"Drag Resistance" Seem like a double negative. More like which has less "drag" or less "resistance?" Not both?

Anyway, I would say the Spit has much less drag than the 109. The 109 seems very "boxy" but that could just be my perception. The Spit seems curved in all the right places.

Kurfurst__
01-01-2006, 07:24 AM
The Spitfire had a wing-related Cd0 of about 0.022 according to some RAE docs (I recall it from memory as I can't find them, however they relate to a prototype, but it was certainly very close to this, even if not precisly the thing).

The Bf 109 F-4 had a Cd0 of 0.023 according to Messerschmitt datasheets.

Both values of 0.022-23 re pretty much avarage for a WW2 fighter. The 109 plus is that it's not only rather clean, but also very small.

From these it's easy to arrive at equivalent drag flat plate areas by multiplying the coefficient with wing area. Thus we get around :

Spitfire IX = 5.325 sq.feet
Bf 109 F-4 = 3.98 sq. feet

A while ago there was a comparison, the flat area of the 109 was only slightly larger than the P-51's, but of course the laminar flow wings are a big plus for high-speed drag (apart from clean lines).

Of course that's comparing a relatively clean Bf 109 (though the aerodynamic properties are practically identical to the 109G-1, G-2, G-3, G-4, and perhaps worser than that of the 109K) with a mid-war Spitfire, but that's how things went, the Spitfire started with a very nice clean airframe, then they started adding bulged canopies, cannons, canonn bulges, and a 2nd radiator that kept getting bigger and bigger, cowling bulges for the Griffon... trouble is they never seriously tried to improving it. The very first 109s started pretty dirty, the Emil was quite a bit cleaner but could do with improvements. They received an almost perfect ine with the 109F and early Gustavs, but then of course the extra stuff needed for operations detoriated things, only to be cleaned up again with the 109K.

All in all, the 109 is much less draggi then the Spitfire which has ca 1/3 more drag. This is quite appearant when ones compares the powers required to reach a given speed, the 109 (except for the Emil) usually required 2-300 HP less to get the same speed. Of course such comparisons are not very reliable, since the overall thrust is varied with propeller effiency vs. altitude, and thrust from exhaust and radiator ducting.

Keep in mind that Cd0s are NOT units of aerodynamical 'cleaness', they are just coefficients relating to the wing area that was readily available, and helped designers toget some idea about the effect of equipment changes on the same design. Comparing different designs with it is rather pointless because of the many variations effecting it.

Kuna15
01-01-2006, 07:50 AM
Originally posted by dugong:
"Drag Resistance" Seem like a double negative. More like which has less "drag" or less "resistance?" Not both?

I'm not familar too much with this sort of things but here is some example I used to understand better
http://www2.sciencefairs.bc.ca/regions/gvrsf/2003public/m259e.html
More drag resistance = worse plane aerodynamics, low efficiency rate (travel less amount of space in given time).


Anyway, I would say the Spit has much less drag than the 109. The 109 seems very "boxy" but that could just be my perception. The Spit seems curved in all the right places.

Those were my initial thoughts too.

RocketDog
01-01-2006, 11:52 AM
Originally posted by Kurfurst__:
Keep in mind that Cd0s are NOT units of aerodynamical 'cleaness'

I think you're wrong about that.

As I understand it, the Cd0 really is a measure of how clean an airframe is whilst the Cd0 multiplied by wing area is a measure of the total drag.

Your claim the the Bf-109 was less draggy than the Spitfire (despite both having almost identical Cd0s) simply reflects the fact that the Spitfire had a bigger wing.

To see where you've gone wrong, consider that by your argument the very streamlined Concorde (low Cd0) is much more draggy than a Flying Flea (high Cd0). Whereas in fact, the Flea only has lower total drag because it has a tiny wing area compared to Concorde.

Don't mix up drag coefficients and total drag - they are quite different!

Cheers,

RocketDog.

JuHa-
01-02-2006, 10:39 AM
My understanding goes like this:

Cd0 - how much wing generates drag at 0 lift.
Doesn't take into account the airframe.

Cdi - induced drag, due to lift vector direction

People at NASA are defining total drag (related to wings) as: Cd = Cd0 + Cdi

I disagree that Cd0 is the efficient that takes the airframe into account, but I think the
CDswet is the right number for that.

CDswet - overall drag coefficient that includes all the surfaces (wings + airframe)