Author Topic: Brewster vs. P-38 Zoom test  (Read 8077 times)

Offline BnZs

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Re: Brewster vs. P-38 Zoom test
« Reply #45 on: July 16, 2010, 02:41:30 PM »
Yes, I understand the Brewster is a tiny plane with a relatively small drag footprint compared to many bigger monsters, but isn't the critical factor the amount of power vrs. weight AND drag?



Gents... I am the PERK THE BREWSTER! guy.  That said, a component you are all missing is the cd.  Look it up, you may be amazed, I know I was.  Drag and gravity are what slows a plane down in the vert.  The Brewster is ridiculously slippery.  How they got the airframe that slick, I don't know.  I am a combat engineer, not an aero guy.   

The Brewster does so well because people get into its fight, not staying in the fight of the ride they are in.  This is a tough one to fathom, Wmaker got me to swallow my pride on that several times since the plane was introduced.  Has to do with folks just not taking the time to look at the numbers.  HP has nothing to do with this discussion.  Hell you want to prove that one, do the test with the climb master, a K4.  It has a 1000 hp advantage to the Brewster.  Yet, CO E, the Brewster has a much lower cd and therefore offsets part of the HP difference.  Yes it will not out zoom the K4, but it will remain in gun range until the K4 stalls.  So.....

1.  Stay above a Brewster.
2.  Don't give up E to turn into one, he will reverse and you will die.
3.  Work on your aim and shoot them piecemeal.......
4.  PERK Wmaker. 



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Offline Stoney

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Re: Brewster vs. P-38 Zoom test
« Reply #46 on: July 16, 2010, 02:52:20 PM »
The Brewster is ridiculously slippery...HP has nothing to do with this discussion...

Wrong and wrong.  According to Dean, the Brewster had the highest Cdo of any U.S. production fighter built during the war.  Vertical performance is all about weight and thrust.  Thrust is a function of power available, so horsepower has everything to do with this discussion.
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Offline Karnak

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Re: Brewster vs. P-38 Zoom test
« Reply #47 on: July 16, 2010, 02:52:54 PM »
BnZs,

I think your expectations of size of the difference in the test results is the problem here, not the actual results.
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Offline Ack-Ack

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Re: Brewster vs. P-38 Zoom test
« Reply #48 on: July 16, 2010, 02:55:14 PM »
Since when did zeros and brewsters get WEP? :huh :confused:

That has nothing to do with this discussion and nowhere in this thread has anyone mentioned the Brewster or the Zeke having WEP.


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Offline THRASH99

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Re: Brewster vs. P-38 Zoom test
« Reply #49 on: July 16, 2010, 03:37:50 PM »
That has nothing to do with this discussion and nowhere in this thread has anyone mentioned the Brewster or the Zeke having WEP.


ack-ack
Uhhh...did you see the chart at the very beginning? It has Brewster and A6m5 wep, since when did they have WEP? :headscratch:

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Offline dtango

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Re: Brewster vs. P-38 Zoom test
« Reply #50 on: July 16, 2010, 03:56:38 PM »
Uhhh...did you see the chart at the very beginning? It has Brewster and A6m5 wep, since when did they have WEP? :headscratch:

That's just an artifact of the AH chart comparer thingy.
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Offline dtango

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Re: Brewster vs. P-38 Zoom test
« Reply #51 on: July 16, 2010, 03:58:03 PM »
Yeah, I'm a little dismayed by your post to Tango, I don't deserve this.

“Derserve’s got nothing to do with it.” (William Munny, Unforgiven)
I’m kidding with this statement BnZs ;).  I’ve always liked Clint Eastwood muttering that phrase.  (I was actually also trying to make fun of myself by suggesting I “learnt” my “gazinta ciphering” from Jethro but all of my attempt at humor obviously went over like a bunch of lead balloons!)

Please allow me to be serious for a bit.   I’m very sorry you felt I was treating you like an idiot.  Please accept my apologies.  

I’d like to rant philosophically for a minute.  The following applies for any FM dispute.  Your specific dispute is an example.  Put yourself in my shoes for a moment.  

A)   You’re still making the same assumptions that I’ve said you can’t make.  I’ve explained why you can’t in a variety of ways and in different BBS threads.  From my point of view you are ignoring what I (and others) have said over and over again.

B)   You’re also asking me to spend my time and my effort to produce the “details and tedious figures” of why you can’t categorically assume what you’ve assumed.  I’ve already told you why, but from my angle you’re not listening.  What would lead me to believe that you would respond any differently if I provide the details to the why?
 
C)   Why is it that I have to provide all the intricate details and not you?  The argument isn’t between you and me.  The truth is that the argument is between you and Sir Isaac Newton.  I’ve already given you the basis for you to go have your fight conceptually and in details with Sir Isaac.
  
So how am I supposed to interpret your actions & how should I respond?  From one vantage point the above are classic signs that you’ve already formed an opinion and have closed your mind.  If I respond by providing more details then I open up myself to the risk of you wanting to further debate the details to prove that you are right instead which drags on and on.  There’s a high probability that all the effort I put in explaining will be a complete waste of time to me.

What incentive do I have to subject myself to the probability of some tortuous & exasperating debate where the debate really should be between the person with the FM dispute and Newton?  I already know the outcome of that.  Newton always wins.  But some people will argue until the cows come home to try and prove otherwise because they’ve already closed their minds.  To be clear, I’m not saying you’ve closed your mind but from your responses it’s hard to know.

So that’s my philosophical dilemma.  I’ve already given you the basis for testing & analyzing your assumptions.  If you aren’t willing to go examine that yourself, why on earth would it make sense for me to spend even more time and effort on my part in explanation?  I could be doing plenty of other enjoyable and useful things.
 
« Last Edit: July 16, 2010, 04:04:17 PM by dtango »
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Offline dtango

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Re: Brewster vs. P-38 Zoom test
« Reply #52 on: July 16, 2010, 03:58:44 PM »
Moving from the philosophical to the conceptual aero…because I actually do think you sincerely are trying to understand let me try stating the key concepts one more time.  Forget everything about B-239’s.  Forget A6M’s.  Forget your flight test results.  Push them out of your mind for a moment.  We need to first deal with the conceptual basis of your premise which is best steady rate of climb charts and best top level speed charts are good indicators of zoom climb performance.

You’re trying to extrapolate key variables from two narrow parts of the flight envelope (best ROC & top level speed) and then categorically apply them to a much broader range of an airplane’s flight envelope.  You just simply can’t do that because all the key variables are all changing with respect to velocity, altitude, & configuration (weight).  Of course complicating matters even more, velocity & altitude are dependent on the variables that they are changing.   All the things you’ve said about the key variables at best ROC & top level speed are mostly true, BUT they are only true for that specific flight condition.  2ndly you are also trying to take these variables independently to arrive at a conclusion which of course will mislead you.

The only way I know of estimating zoom performance is evaluating the variables across the range of the flight envelope and not just looking at best ROC & best level speed.  There are two ways you might approach this:

Evaluate the specific excess power (Ps) of the aircraft with respect to changing velocity, changing altitude, and a specific weight
Ps = (T – D) * V / W

The aircraft that has the highest time average Ps over the zoom climb will zoom “better”.  Let me emphasize, thrust & drag vary with changing velocity and altitude.  2ndly velocity itself varies with changing thrust, drag, & altitude.  All of this is effected by weight which of course changes as fuel and ammo are expended.  The best ROC & speed charts are for narrow band of the flight envelope (specific velocity, specific drag, specific thrust, specific altitude) and a fixed config (specific weight).  Zoom climbs will occur at a larger portion of the flight envelope and could be at altogether different weights too compared to the charts.

You could also approach it evaluating this:
F = ma = T -  D - W*sine(climb_angle) – for simplicity if you’re interested in a 90 degree zoom that resolves to
F = ma = T - D - W

You can rearrange that equation and use that as your basis to solve for acceleration, velocity, distance etc.  REMEMBER THOUGH – all of it varies and the only way to estimate zoom is calculate and factor what the variables are especially outside of the narrow band of best ROC and speed.

So there it is.  Do you want to deal with the details or are you still asking me to do so?  I very much prefer that you do it yourself.  You’ll learn a lot in the process.

Tango
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Offline Wmaker

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Re: Brewster vs. P-38 Zoom test
« Reply #53 on: July 16, 2010, 04:55:00 PM »
Someone's gonna hit his head hard into integral calculus. ;)

 ...or not. :frown:
« Last Edit: July 16, 2010, 06:52:07 PM by Wmaker »
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Offline uptown

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Re: Brewster vs. P-38 Zoom test
« Reply #54 on: July 16, 2010, 05:45:12 PM »
I love Tango to death, but I ain't got a clue what the hell he just said.  :confused:  Altough I did understand this part....
That's just an artifact of the AH chart comparer thingy.
  :lol
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Offline dtango

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Re: Brewster vs. P-38 Zoom test
« Reply #55 on: July 16, 2010, 08:36:52 PM »
I love Tango to death, but I ain't got a clue what the hell he just said.  :confused:  Altough I did understand this part....  :lol

Uptown- try reading the part you don't understand after a few beers :D.  Does wonders for me!

Tango
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Offline Chalenge

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Re: Brewster vs. P-38 Zoom test
« Reply #56 on: July 18, 2010, 11:37:07 PM »
You don't think 800-900lbs does anything to the maneuverability of an aircraft? I don't have my AHT at hand as I'm out of town but IIRC G105-Cyclone didn't produce 1200hp. The take off power that I seem to remember is 1100hp. So based on that Buffalo Mk.I would be roughly 800lbs heavier while having only 100hp more. No a very good trade off and totally irrelevant variant when estimating the performance of the B239 we have in AH. Someone with AHT can double check my figures.

Most of what you posted I snipped out because you (as several others) assume wrongly about the airplane I mentioned. I believe if you check you will find that the aircraft mentioned in the "anecdotal" article was in fact one delivered to the West Indies and not to the RAF. That would mean 1200 hp and not the 1100 you mentioned (which is incorrect either way... the RAF models were 1000 hp). I would like to know where you get your weight figures from.

dtango... as I said (and obviously you didnt read) I have heard online that the 239 was introduced into the game and then "performance boosted" because it didnt meet someones expectations (a single individual). Again I repeat my assertion that if that is in fact the case the airplane is a fiction and should be removed.

However... as I already said (also) I have greater faith in Hitech than that. I do not believe it to be the case.

Sometimes I think you guys get so wrapped up in your online "nametags" you lose your grip on reality. In five minutes I will have forgotten about all of you. Carry on.
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Offline grizz441

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Re: Brewster vs. P-38 Zoom test
« Reply #57 on: July 18, 2010, 11:40:50 PM »
you lose your grip on reality.

Irony at its finest.

Offline Chalenge

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Re: Brewster vs. P-38 Zoom test
« Reply #58 on: July 19, 2010, 12:03:28 AM »
Irony at its finest.

Ha! I mentioned you to someone this weekend (I dont know why). I said "I know a clown just like you online." I cant remember his name either.  :devil
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Offline Wmaker

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Re: Brewster vs. P-38 Zoom test
« Reply #59 on: July 19, 2010, 02:48:01 AM »
Most of what you posted I snipped out because you (as several others) assume wrongly about the airplane I mentioned. I believe if you check you will find that the aircraft mentioned in the "anecdotal" article was in fact one delivered to the West Indies and not to the RAF. That would mean 1200 hp and not the 1100 you mentioned (which is incorrect either way... the RAF models were 1000 hp). I would like to know where you get your weight figures from.

Like I said I'm out of town and can't check my copy of America's Hundred Thousand where I get my weight figures from. All the B339s were several hundred pounds heavier than the B239. Exactly how much depends on the different sub variants and the configuration of individual airframes. Anyone with a copy of AHT could check the exact weights. I'm just wondering why RAF pilot would be flying a Dutch Brewster? If you are so certain of it I'm sure you can provide a source which confirms it? All I've ever heard from this particular mock dogfight is that it was a RAF Buffalo Mk.I. It is true that the Dutch Buffalos were better machines than the RAF planes from the Belgian order. Anyway, it doesn't matter either way which B339 it was as all of them are still different airplanes when it comes to weight/power compared to the B239.


dtango... as I said (and obviously you didnt read) I have heard online that the 239 was introduced into the game and then "performance boosted" because it didnt meet someones expectations (a single individual). Again I repeat my assertion that if that is in fact the case the airplane is a fiction and should be removed.

However... as I already said (also) I have greater faith in Hitech than that. I do not believe it to be the case.

If you don't believe that Hitech/HTC would do such a thing (I wouldn't either) then why keep repeating it?? I already posted a link to the thread which discusses the flight model changes of the B239. Everything you hear isn't necessarily true. Here's the link once again: http://bbs.hitechcreations.com/smf/index.php/topic,270213.0.html
« Last Edit: July 19, 2010, 03:00:40 AM by Wmaker »
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