New 109's

[Noir]

on the P51 vs 109 topic, you guys were talking about the P51B drag with the racks, but a P51D pic was  posted...(quite obvious with the 3 guns on the wing).

If I remember well the P51D had redesigned zero drag racks while the B model had what was available at the time, so I think you can't compare using that picture. Plus as someone said, you can't compare aerodynamics just by the looks, else we won't need drag tests. (can't remember the actual name)

[Kurfürst]

See Rule #4

[Kurfürst]

Originally posted by Angus
Well, racks or no racks, the P51 is very fast for its weight and HP's.
Similar power to what - the 109G-6?

They don't have similiar power, though the Mustang's power varied between the variants, even lower powered ones had at least +200HP advantage. Ie. the P-51D had 1690 HP at SL, the 109G-6 had 1455 HP.

The 109G-2's drag was equalalent to a 0.369 m2 flat plate, for example. G-6 was somewhat higher, I could give it but the doc is not with me.

From what I have seen, the P-51D and 109K had very similiar total drag, reaching very similiar powers on similiar powers, at least near ground level.

[Kurfürst]

Originally posted by LRRP22
Don't you think that maybe most bomb racks looked the same for a reason?  Don't you think they would look more like gondolas, if the gondola shape was more efficient?.

They did't care, as noted. You are basically arguing that a box shaped bombrack is more aerodynamic than a nicely curved and smoothened gondola. Silly in itself, it's like box-shaped cars are more aerodynamic than teardrop shaped ones.

The built-in rack of the 109, Schloss 503 already mentioned, which was capable of carrying 1100 lbs bombload or a droptank, had a nice curved surface and no protusions, like gondolas. And it came with only -4kph speed loss.

A nice fairing can do wonders, btw. The 300lit droptank when mounted came with something like 40-50kph speedloss. However, with a small fairing placed between the DT and the Schloss 503 rack, it was reduced to 1/3 of that...

Aerodynamics is all about shape, not about frontal area.

[LRRP22]

Originally posted by Kurfürst
They did't care, as noted. You are basically arguing that a box shaped bombrack is more aerodynamic than a nicely curved and smoothened gondola. Silly in itself, it's like box-shaped cars are more aerodynamic than teardrop shaped ones.

The built-in rack of the 109, Schloss 503 already mentioned, which was capable of carrying 1100 lbs bombload or a droptank, had a nice curved surface and no protusions, like gondolas. And it came with only -4kph speed loss.

A nice fairing can do wonders, btw. The 300lit droptank when mounted came with something like 40-50kph speedloss. However, with a small fairing placed between the DT and the Schloss 503 rack, it was reduced to 1/3 of that...

Aerodynamics is all about shape, not about frontal area.

They didn't care?  A patently ridiculous claim.  

The Mustangs wing racks were "box shaped"?  Another ridiculous claim.

And gondolas did have protursions- a nice, long cannon barrel and a proturding ejection port.  

Tell us again how the 109K's nose was cleaner than the Mustangs...


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[MiloMorai]

No protrusions Kurfy?

As can be seen in the photo the rack certainly did have protrusions.
http://cipres.cec.uchile.cl/~bebustos/jpg/me109g6s.jpg

[Angus]

From Kurfurst:
"From what I have seen, the P-51D and 109K had very similiar total drag, reaching very similiar powers on similiar powers, at least near ground level."
The 109K peaked at some 2000 hp right, and had lots of power at S.L.
So, the P51D peaks with 1690 hp.
Or do you refer to the less boosted 109K????

[LRRP22]

See Rule #4

[LRRP22]

Originally posted by Noir
on the P51 vs 109 topic, you guys were talking about the P51B drag with the racks, but a P51D pic was  posted...(quite obvious with the 3 guns on the wing).

If I remember well the P51D had redesigned zero drag racks while the B model had what was available at the time, so I think you can't compare using that picture. Plus as someone said, you can't compare aerodynamics just by the looks, else we won't need drag tests. (can't remember the actual name)

 

That's true.  I would expect the D's racks to incur slightly less drag penalty than the B/C's.  How much, I don't know.  None of the testing establishments differentiated between the two.  Both the USAAF and RAF attributed a 12 mph loss to both types at max speed.


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[Kurfürst]

See Rule #4

[Kurfürst]

Originally posted by Angus
From Kurfurst:
"From what I have seen, the P-51D and 109K had very similiar total drag, reaching very similiar powers on similiar powers, at least near ground level."
The 109K peaked at some 2000 hp right, and had lots of power at S.L.
So, the P51D peaks with 1690 hp.
Or do you refer to the less boosted 109K????

Be careful Angus with that 2000 HP. Lrrp2 always accuses me of 'cheating' when I am lazy and write HP instead of PS. There were about 1% difference between the two, but still...

Now what I had in mind is the +25 lbs (1960 BHP at SL) Mustang D with wingracks (379 mph at SL), and what 'Leistungen 8-109 K4' noted as SL speed of the 2000 PS (about the same power if we note PS/HP difference), 377 mph. You see it's very similar, though w/o the bombracks the Mustang would be faster. OTOH, the Mustang was tested w/o paint either, that's quite a bit of drag and weight - if you recall those stripped Ju86 intercepting modded Spits - so on equal footing, no paint/no bombrack, it's the same again.

With 1690 HP, and the usual wingracks, the Mustang IV was credited with 354 mph top SL speed, but there's hardly any comparably powered 109s...
the uglier G-14s were good for 568kph/352 mph at 1800 PS, whereas the low-boosted 109K would do 370mph with 1850 PS.

BTW if you are interested in that Mustang IV tests, I can happily send over the original, though I think it's also found on MW's site :

2.   Condition of aircraft relevant to tests.

      2.1  General. Photographs of the aircraft are attached to the present part of the report.

      The following were the chief external features:-

      Six .5" machine guns in the wings, ports and ejection chutes sealed with fabric.
      Camera gun port in port wing, sealed with fabric.
      Multi ejector exhaust manifolds with shroud-plates.
      Air intake in nose with internal ice-guard.
      Aerial mast without external aerials.
      Bead sight in front of windscreen.
      Air filter intake in lower left cowling.
      Faired bomb racks under the wings.

      The aircraft was not painted. The under surface of the wings back to the main spar and the whole of the top surface had been coated with a smooth composition, the joints being filled and the remainder being bare metal. The fuselage was left with the bare metal except for a matt anti-glare finish on the top engine cowling. All other parts of the aircraft were also bare metal, except the elevator and rudder which were fabric-covered and doped.

      In order to obtain adequate cooling, level speeds were done with the radiator duct flap set to a gap of 8½ inches, as coolant temperatures were excessively high with the normal setting of 7¼" gap.

          2.3  Loading. The tests were made at a take-off weight of 9480 lb. with the C. of G. at 100.2 ins. aft of the reference axis. This corresponded to a typical loading with no fuel in the auxiliary fuselage tank and no external tanks or bombs.

http://www.spitfireperformance.com/mustang/tk589.html

[Kurfürst]

BTW it's interesting to compare the P-51D TK 589 flight data (with wingracks) with the 'official

Let's recall that TK 589 did 354mph at SL at 67", and removing the wing racks would give an extra 12mph :

North American Aviation, Inc.
Inglewood, California
Report No. NA-46-130
2-6-46
Performance Calculations for Model P-51D Airplane
(N.A.A. Model No. NA-122)

      These calculations were prepared in connection with a comparison of the P-51D and P-51H airplane. Considerable effort was expended to achieve agreement between flight tests and calculated results, and the data as presented represent good agreement with most of the flight test results.

Calculated Altitude Performance
Fighter condition - No external load
67" HG M.P. - 3000 R.P.M.
9,611 LB
Maximum Speed

Standard Altitude Feet True Airspeed - M.P.H.  
Sea Level 368  


368 - 12 = 356...

TK 589 did 354mph....

[MiloMorai]

See Rule #4

[Kurfürst]

See Rule #4, #5

[LRRP22]

Whatever, Isegrim.  Rant all you want.  The fact is you're comparing a well-used Mustang IV hand-me-down to a theoretical 109K-4.
 

If the K-4 numbers are actually test data- then post them.  Period.


Mustang III sqns at +25 boost during summer of 44: 129, 306, 315, 316.  New evidence seems to indicate they never stopped using it.  That's all I'll say for now.

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