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FM/DM threads Everything about FM/DM in CoD

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  #1  
Old 09-29-2012, 10:22 AM
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Varrattu Varrattu is offline
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@ Kurfürst

Thank you.

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  #2  
Old 09-29-2012, 11:32 AM
Holtzauge Holtzauge is offline
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There are a number of issues with the outlyer 109E 500 km/h sea level top speed:

First of all the Baubeschribung 500/570 Km/h speed curve does not map any known engine power/alt curve: These either have the characteristic bulge associated with the hydralic clutch or the notch type with two speed superchargers where as the curve showing 500 Km/h at SL and 570 Km/h at altitude in the Baubeschribung has a straight line between these points. So which DB601 in a series Me109E had this power/altitude characteristic? None that I have seen published.In addition the date of the the Baubeschribung is stated as "circa 1939"and reference made to the Yugoslavian manual. So this looks more like some early marketing material supporting Messerschmitts export activities which also predictably for marketing material includes a caveat of plus minus 5% which would then place the more realistic speed performance of around 475 Km/h within the guaranteed range.So to conclude, the data supporting 500 Km/h SL speed either references prototype data or refers to some early marketing material. In addition, it looks like estimate for the "guaranteed" engine data coming close to 500 Km/h for the V15 prototype is for 1,35 not 1,3 ata.

Moving then to some more realistic speed estimates based on what could be expected of a series type aircraft at 1.3 ata: Note that the C++ simulation data for the high and low altitude speed of the +6.25 and +12 boost Spitfire is quite consistent with historic data. Using the same principles for calculating the Me109E low level speed the result also yields around 570 Km/ at altitide but at low level the result is around 475 Km/h not 500 Km/h. These curves were calculated using the actual historic series type engine data and consequently show the effects of the hydraulic clutch, something missing from the 500/570 Km/h chart. I'm sure the usual suspects will question the validity of the C++ simulations but as an answer to that we have the Me109E figures posted by HoHun on the All About Warfare forum (www.allaboutwarfare.com) and as can be seen the calculations agree remarkably well. In addition one can conclude that both calculations agree quite well with the actual measured top speed posted earlier by Al Schlageter.

Finaly, it's interesting to note the type of evidence evaluation practiced by some in this forum: There was a mountain of evidence supporting 100 octane that was dismissed as inconclusive and now we are expected to swallow a molehill of evidence for 500 Km/h sea level top speed when most data, calculated and test measurements point to something around 475 Km/h.

Talk about double standards....
Attached Images
File Type: jpg Me109 and Spit 1 speed alt chart PA1.JPG (177.4 KB, 16 views)
File Type: jpg Me_109_speed_comparison_Hohun_big.JPG (215.4 KB, 16 views)

Last edited by Holtzauge; 09-29-2012 at 11:40 AM.
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  #3  
Old 09-29-2012, 11:46 AM
Kurfürst Kurfürst is offline
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Quote:
Originally Posted by Holtzauge View Post
There are a number of issues with the outlyer 109E 500 km/h sea level top speed:

First of all the Baubeschribung 500/570 Km/h speed curve does not map any known engine power/alt curve: These either have the characteristic bulge associated with the hydralic clutch or the notch type with two speed superchargers where as the curve showing 500 Km/h at SL and 570 Km/h at altitude in the Baubeschribung has a straight line between these points.
The Baubeschribung curves are obviously simplified, drawing a straight line between low level and FTH performance. Again, nothing uncommon in that, Rechlin did the same thing for a tested G-1 chart:



Quote:
So which DB601 in a series Me109E had this power/altitude characteristic? None that I have seen published.
All, in fact:



Quote:
In addition, it looks like estimate for the "guaranteed" engine data coming close to 500 Km/h for the V15 prototype is for 1,35 not 1,3 ata.
Unsurprising, since both the V15a flight tests results and guaranteed specs in the Baubeschreibung are for 1.35ata.

The sillyness lies in that some people want to compare these 1.35 ata results to 1.3ata, uncorrected figures, and the fact that uncorrected results achieved with the less powerful DB 601A-1 at 1.3ata / 990 PS are irrelevant when modelling our 1.35 ata / 1045 PS Bf 109E equipped with the DB 601Aa.

The rest of your post is irrelevant.

BTW it's worth comparing the V15a (WNr. 1774) results with the speed results with a Swiss export Bf 109E-3a. The reports show remarkable similarity in the top speed achived at altitude with the original VDM propellor of J-347 (572 vs. 564 km/h at rated altitude), especially when taking into account that J-347 already saw considerably use. However the low level speeds diverge greatly (498 vs 464 km/h at 0m altitutude). Note that the low-level performance of V15a with the Höhenlader (high altitude supercharger speed, or 'F.S gear' in British terms) shows good agreement with J-347 at both high- and low altitudes.

This would suggest that J-347`s level speed results were achived with the Höhenlader in operation and agree well with the results of Bf 109E-1 / V15a WNr. 1774.

Also note that the Baubeschreibung agrees well with the V15a results, but the curves are bit more simplified (mean avarage results).

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Last edited by Kurfürst; 09-29-2012 at 12:29 PM.
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  #4  
Old 09-29-2012, 05:03 PM
TomcatViP TomcatViP is offline
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Quote:
Originally Posted by Kurfürst View Post


BTW it's worth comparing the V15a (WNr. 1774) results with the speed results with a Swiss export Bf 109E-3a. The reports show remarkable similarity in the top speed achived at altitude with the original VDM propellor of J-347 (572 vs. 564 km/h at rated altitude), especially when taking into account that J-347 already saw considerably use. However the low level speeds diverge greatly (498 vs 464 km/h at 0m altitutude). Note that the low-level performance of V15a with the Höhenlader (high altitude supercharger speed, or 'F.S gear' in British terms) shows good agreement with J-347 at both high- and low altitudes.
There was some diff btw the 109 exported in Switzerland and the original E. Notably in aerodynamics.
I don't think you can make a comparison without taking this fact into account.
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  #5  
Old 09-29-2012, 05:33 PM
Kurfürst Kurfürst is offline
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Quote:
Originally Posted by TomcatViP View Post
There was some diff btw the 109 exported in Switzerland and the original E. Notably in aerodynamics.
I don't think you can make a comparison without taking this fact into account.
What kind of difference do you have in mind?
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  #6  
Old 09-29-2012, 05:41 PM
TomcatViP TomcatViP is offline
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Quote:
Originally Posted by Kurfürst View Post
What kind of difference do you have in mind?
I hve in mind the guns (barrel for sure). I think the rad were different. But I need to check this. There is also a good article on the net (in French probably) if you browse around "bf109" and switzerland ("Suisse"). Will try to have a look.

EDIT:
Guns for sure and prop

Last edited by TomcatViP; 09-29-2012 at 05:53 PM.
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  #7  
Old 09-29-2012, 05:51 PM
Kurfürst Kurfürst is offline
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Quote:
Originally Posted by TomcatViP View Post
I hve in mind the gun barrel for sure. I think the rad were different. But I need to check this. There is also a good article on the net (in French probably) if you browse around "bf109" and switzerland ("Suisse"). Will try to have a look.
Yes I will check that, I had a good (IIRC German language) book about Swiss 109s, which helped me to ID J-347's WNr. and service record.

As for the gun barrels, I am not sure - one of the tests being waved about is explicitely about measuring the speed diff. between guns present/not present, and it's about 1 km/h.. I'd imagine different gun barrels amount to even less.

Rads look interesting though, this might account for something, but again, looking the Swiss test results, the difference is only about 8 kph at VDH, which from my experience, is an extremely good match for a serial production plane compared to the guaranteed specs!

Quote:
Originally Posted by Holtzauge View Post
Seeing you seem to be such an expert perhaps you would be so kind to point out what is wrong in my Me109E speed/alt chart and how it really should look like?
Well for one it probably has wrong data.. guessworked drag, guessworked wing effiencies, guessworked propeller effiency, manipulated until it fits one's agenda.

As Tagert said, garbage in... garbage out.

BTW, care to tell why you disappeared from allaboutwarafe forums? I am sure it's hell of a story.
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  #8  
Old 09-29-2012, 01:32 PM
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Holtzauge, that pretty much sums it up.
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  #9  
Old 09-29-2012, 04:55 PM
Holtzauge Holtzauge is offline
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Quote:
Originally Posted by Robo. View Post
Holtzauge, that pretty much sums it up.

Yes, I think the case for 500 Km/h SL speed for the Me109E is rather weak.

I don't fly CloD but used to fly IL2 some before, mostly Me109's and Fw190's so I'm not interested in porking them in any way.

What I do want is as realistic performance as possible in any sim which is not something you get if you like some people in this forum consistently take the inside envelope of any allied data and the outside envelope for the Me109 if you get my drift. None mentioned and none forgotten
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  #10  
Old 09-29-2012, 05:35 PM
Kurfürst Kurfürst is offline
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Quote:
Originally Posted by Holtzauge View Post
Yes, I think the case for 500 Km/h SL speed for the Me109E is rather weak.
Well of course, since we have your toy excel sheet against thoroughly documented test data!
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