Author Topic: FM2 as Brewster sub (discussion)  (Read 4773 times)

Offline Krusty

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FM2 as Brewster sub (discussion)
« on: July 02, 2008, 01:58:26 PM »
I find the urge to bring up this debate again.

This is NOT a slight on the folks running Rangoon, but I noticed the FM-2 is being used to sub for the Brewster (again...).

Even the early version of the Brewster Buffalo, the A1, without all of the weight gain of the A3 And the heavily upgraded armor on the B-339E versions, still weighed 5040 lbs loaded. It had a short stubby wingspan of 35' and a wing area of about 209 square feet. It had a single-row 950 hp engine. It had 1x .30cal and 1x .50cal in the cowling and 1x .50cal in each wing.

The F4F-3 and -4 had 38' wingspans, wing area around 260 square feet (more lift), a double rowed 1,200 hp engine. They weighed (not sure on this, just quoting wiki -- but this does NOT seem right) 7000 lbs for the F4F-3 and 7950 for the -4. The -3 had 4x .50cals and the -4 had 2 more optional outboard of those (bringing the total to 6x .50cal).

Performance:

The weight of the F4F is higher than the F2A, but the wing is considerably larger, producing much more lift, and the wing loading is almost dead even (24 lbs per square foot for the Brewster, 26 lbs per square foot for the F4F-3). That brings us to the horsepower and other areas. The wing loading is one indicator of turn performance, but that means nothing if you don't have the horses to pull you around a turn.

The F4F4 has 250hp more than the F2a. Even the Finnish Brewsters that folks like to talk about only had 1000hp engines. This means a LOT of extra power. Much improved climb rate and the ability to haul the nose around in a turn. Granted the F4F has more weight and inertia, but the spit9 has less weight than the spit8, but the spit8's extra power means it actually tuns better. The airframe is almost identical, but the greater horsepower gives it an edge. (See Gonzo's charts)

So the F4F4 has much higher horsepower. This also means climb and acceleration will be different. The brewster would have less climb rate (smaller wing, less horsepower to pull upward), perhaps turn worse than the Grumman design, and then there's the other thing.

Speed.

The Buffalo's top speed was 311mph at 18000 feet.

The F4F is 320mph at about the same alt, however the F4F has 2 additional supercharger peaks on its speed chart. I believe the Buffalo's engine is a predecessor to the FM-2s, which has only 1 supercharger peak. Supposing this is engine-specific (I don't know) the Buffalo might have 1 or might have no other power peaks.

That means that while the F4F has just over 280mph on the deck, the Brewster would be closer to 250 (or less).

That's not even counting the FM-2.

The FM-2 has the same wingspan wing area and armament as the F4F-3, weighs 7400 lbs according to AH's homepage, but it's got one major consideration that the F4F-3 doesn't have.

It has a 1,350 hp engine.

That's right. Stock F2A1 (before all the weight, the nimble version) has only 950 hp. The later versions had more hp, but performed even worse because all the weight gain nullified it. The Finnish version was re-engined and still only had 1000hp. Where the Brewster's deck speed may be around 250, the FM-2 easily breaks 300mph with its WEP rating on the deck. That's a helluva performance difference. Climb rate also jumps almost 1000fpm over the F4F3 with "just" 150 extra horsepower. Acceleration is significantly improved over the similar-framed F4F3, and the climb, speed, acceleration all translate into a performance package that would only beg the question: Why is this even remotely being used for the Buffalo stand-in?

So, as much as the F4F is better than the Brewster, the FM-2 is better than the F4F.

That's not just a bad match-up for a Brewster stand-in, it's just wrong!

Might as well use a Ju-88 to stand in for a He-70!

In the past when I've brought this very large performance discrepency up, the main defense is that the FM-2 has 4 50cal guns, which is close to what the Brewster had.

Well the P-51D has weapons "close to" the P-40E, but you wouldn't sub one for the other, would you?? Weapons are not the ONLY reason to use a stand-in. Performance makes up a far better match.

F4F4 is far better than the FM-2 [EDIT: as a Brewster stand-in], performance wise, but it's still not a very good match, outperforming the Brewster in most areas. It's the horsepower.

Just looking at weapons alone, if the F4F4 had to be used, it could be. That is to say in a scenario there is much better discipline than in the AvA or the MA or what-have-you. You can set a rule and it will be enforced down the line by squadron leaders.

We flew an entire FSO in P-39Ds, and we were forbidden to use the 37mm (20mm only) and we did so. There were no major violations, mass-rule-breakings, or any anarchy of that sort. The same will hold true for the scenarios. On the other hand, IF a rogue pilot takes the extra pair of guns they will be considerably heavier, and any turn and climb and acceleration performance will be worse off than without them. If a shot lands, it will have a greater impact, but will the shot land in the first place? Or will said pilot have handicapped himself into being shot down?

I'm just saying we have the discipline to follow orders if they say "ONLY use the 4-gun package!" We've proven this before in several FSOs (non-specific to the F4F, I mean in regards to weapons options).

So, for the purpose of debate, there are better options than the FM-2 for the Brewster.

In fact, some pilots are so used to flying the FM-2 and shouting for the Brewster, they will probably be sorely disappointed if we ever get it in-game, because it doesn't perform at all like they were used to.


It's like flying a spit16 pretending it's a spit5, and then when the spit5 arrives it flies more like a spit1, and you wonder why you're not getting the same performance as the spit16 (hehe, that kind of a rambling example, ignore it if you don't understand)
« Last Edit: July 02, 2008, 02:11:17 PM by Krusty »

Offline angelsandair

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Re: FM2 as Brewster sub (discussion)
« Reply #1 on: July 02, 2008, 09:23:18 PM »
P-39D sub?  :confused:
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Re: FM2 as Brewster sub (discussion)
« Reply #2 on: July 03, 2008, 12:29:25 AM »
Actually, the FM-2 isn't being used as a stand in for the F2A.  The whole story is a bit convoluted.

If AH had every plane made, here's the allied plane set (I think) DoK was after for the original design of this scenario on the allied side:  Hurri I, Spit I, P-40B, P-40E, Beaufighter, F2A, and F4F-3.  The Beaufighter, F2A, and F4F-3 are not available, and the substitutes became, respectively, the A-20, the SBD, and the FM-2 -- and this is how the scenario was run the first time through.

The reason for the FM-2 as an F4F-3 (instead of the 4-gun F4F-4) is explained in the rules.  In terms of a match for performance, I don't know if the A-20 is the best substitute for the Beaufighter, but the best fit for the F2A is actually the 4-gun F4F-4.  This is based on looking at speed vs. altitude and climb vs. altitude charts out of America's Hundred Thousand, by Dean.  In those metrics, the F2A and 4-gun F4F-4 are very similar in speed vs. altitude, although the F2A interestingly has better climb vs. altitude.

However, if we were to match best realism of plane sets, there would be several other differences and consequences, and the reason for the given plane set is also described in detail in the rules.

Offline Krusty

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Re: FM2 as Brewster sub (discussion)
« Reply #3 on: July 03, 2008, 09:09:56 AM »
I'm not picking on Rangoon, mind you. I'm looking forward to it.

It just reminded me of the whole FM-2 as Brewster issue, and I thought I'd bring it up again.

Ever since I recall flying in the AvA the first time many many years ago (called CT back then), the FM-2 has been used as the Brewster. It's just not a good fit!


However, as a side note: The F4F-3 isn't at all like the FM-2. Again you're using only the weapons to match the plane, when in fact the F4F-4 is the F4F-3 with extra outboard guns.

Going back to my parallel, the P-50B and the F4F-3 also both have 4x50cals, you wouldn't sub them for each other, would you? Matching JUST for the weapons is a bad idea. FM-2 is clearly superior to the F4F-4 (even if the F4F has only 4 guns and is lighter)


P.S. Angel, the P-39 is one of the fastest planes of this time frame, has a major firepower advantage over the Brester (ESPECIALLY with the 37mm cannon) and while perhaps not as nimble, is 75-100mph faster than the Brewster on the deck, almost. I'd guess that makes it not a very good substitute. The P-39D is faster on the deck than the Brewster's top speed at 18k.
« Last Edit: July 03, 2008, 09:12:21 AM by Krusty »

Offline Widewing

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Re: FM2 as Brewster sub (discussion)
« Reply #4 on: July 03, 2008, 01:22:23 PM »
I'm not picking on Rangoon, mind you. I'm looking forward to it.

It just reminded me of the whole FM-2 as Brewster issue, and I thought I'd bring it up again.

Ever since I recall flying in the AvA the first time many many years ago (called CT back then), the FM-2 has been used as the Brewster. It's just not a good fit!


However, as a side note: The F4F-3 isn't at all like the FM-2. Again you're using only the weapons to match the plane, when in fact the F4F-4 is the F4F-3 with extra outboard guns.

Going back to my parallel, the P-50B and the F4F-3 also both have 4x50cals, you wouldn't sub them for each other, would you? Matching JUST for the weapons is a bad idea. FM-2 is clearly superior to the F4F-4 (even if the F4F has only 4 guns and is lighter)


P.S. Angel, the P-39 is one of the fastest planes of this time frame, has a major firepower advantage over the Brester (ESPECIALLY with the 37mm cannon) and while perhaps not as nimble, is 75-100mph faster than the Brewster on the deck, almost. I'd guess that makes it not a very good substitute. The P-39D is faster on the deck than the Brewster's top speed at 18k.

A couple of points, if I may...

The differences between the F4F-3 and F4F-4 were considered profound by those who flew both. Added in the F4F-4 were the two additional guns w/ammo. However, the entire wing structure was different. The F4F-4 added folding wings (F4F-3 wings were fixed). These changes added substantial weight. This weight reduced the MIL power climb rate from 3.7 minutes to 10k (F4F-3) to 5.3 minutes to 10k (F4F-4) and substantially reduced the Wildcat's agility. Never a fast rolling fighter, the added outboard weight reduced the initial roll rate even further. The FM-2 brought Wildcat performance back up to that of the F4F-3, while allowing for more fighters on a flight deck and lower maintenance R-1820 powerplant.

Performance differences between the export Brewster and the F4F-4 were not significant. The F4F-3 and the RAF Brewster were both armed with four .50 cal MGs. Thus, the F4F-4 with the 4 gun option would be a good replacement.

Brewsters could reach 285 mph at sea level. The USN F2A-2 could manage about 322 mph at 16,500 feet.

By the way, the P-40B has two .50 cal and four .30 cal MGs.

My regards,

Widewing

My regards,

Widewing

YGBSM. Retired Member of Aces High Trainer Corps, Past President of the DFC, retired from flying as Tredlite.

Offline Krusty

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Re: FM2 as Brewster sub (discussion)
« Reply #5 on: July 03, 2008, 01:30:46 PM »
I think I suggested the P-40b (or some other early in-line) and the main objection (from CT residents at the time, long ago) was that it wasn't a radial craft.

 :huh <-- my reaction at the time

Only problem is the P-40B is noticably faster than the F4F4 above 2k.


P.S. The Brewster and the F4F had similar airframes. They did measurements and found that the squat appearance of the Brewster was an illusion. If anything it had a larger frontal area, and yet with several hundred horsepower less it's going to out-run the F4F on the deck?

I don't know if I buy those numbers you quote from AHT. From past discussions (regarding P-39s, maybe? Long time ago) some of the data is estimated, not actually tested.
« Last Edit: July 03, 2008, 01:34:55 PM by Krusty »

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Re: FM2 as Brewster sub (discussion)
« Reply #6 on: July 03, 2008, 01:58:06 PM »
Yep, from the data in America's Hundred Thousand, above about 9k, the speed vs. alt of the F4F-3 and the FM-2 are the same (with the FM-2 being faster below that).  The F4F-3 and the FM-2 have seeming almost the same climb vs. altitude.  The F4F-4 has closer speed vs. alt to the F4F-3 below 9k than the FM-2, but less close  above 9k.  The F4F-4 has much different climb vs. alt than the F4F-3 -- there the FM-2 is a very much better choice.

So, it depends.  You want to match speed below 9k at the expense of the climb being way, way off and the speed above 9k being off?  Then use the F4F-4 as the F4F-3.  If you want to exactly match speed above 9k and nearly exactly match climb performance at all altitudes at the expense of speed below 9k being off?  Then use the FM-2 as the F4F-3.  Using the FM-2 also has the added advantage of no one mistakenly taking 6 guns rather than 4.

As for the F2A, I was very surprised to see that it is pretty close in speed and climb to the F4F-4.   Given little things I've read here and there about the F2A, I had assumed it would be a dog compared to the F4F.  It's not.  In fact, I wonder if it has the same climb and speed performance yet better turning ability.

Offline Krusty

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Re: FM2 as Brewster sub (discussion)
« Reply #7 on: July 03, 2008, 03:12:11 PM »
Yep, from the data in America's Hundred Thousand, above about 9k, the speed vs. alt of the F4F-3 and the FM-2 are the same (with the FM-2 being faster below that).  The F4F-3 and the FM-2 have seeming almost the same climb vs. altitude.

I recall there was quite a hub-bub with AH's FM-2, in that it had WEP, then it was removed, then Bodhi supplied some obscure documents that did in fact prove the FM-2 had WEP.

Without WEP the FM-2 is very much like the F4F4.

I don't think the AHT is using WEP in that comparison, or perhaps it's an early FM-2 without WEP. Or maybe it's a FM-1 or some other mistake.

The FM-2 makes a lot more horsepower than the F4F, weighs very close, and has the same wings/drag/airframe.

Add a lot of extra horsepower and you're getting better climb rate and top speed.

http://www.gonzoville.com/ahcharts/index.php?p1=f4f4&p2=fm2

You'll note, though, that even without WEP the FM-2 still out-climbs the F4F4 by a noticable margin. HTC based this off actual tests somewhere (while they may be mum on which ones, we know they are particular about their sources).

Offline Widewing

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Re: FM2 as Brewster sub (discussion)
« Reply #8 on: July 03, 2008, 03:54:58 PM »
I recall there was quite a hub-bub with AH's FM-2, in that it had WEP, then it was removed, then Bodhi supplied some obscure documents that did in fact prove the FM-2 had WEP.

Without WEP the FM-2 is very much like the F4F4.

I don't think the AHT is using WEP in that comparison, or perhaps it's an early FM-2 without WEP. Or maybe it's a FM-1 or some other mistake.

The FM-2 makes a lot more horsepower than the F4F, weighs very close, and has the same wings/drag/airframe.

Add a lot of extra horsepower and you're getting better climb rate and top speed.

http://www.gonzoville.com/ahcharts/index.php?p1=f4f4&p2=fm2

You'll note, though, that even without WEP the FM-2 still out-climbs the F4F4 by a noticable margin. HTC based this off actual tests somewhere (while they may be mum on which ones, we know they are particular about their sources).

Data on the FM-2's powerplant isn't obscure. The R-1820-56W is rated for 1,360 hp at 52" MAP @ sea level. That is where the AH2 modeling goes awry. In the game, WEP doesn't show an increase in MAP at Combat Power until about 4,000 feet, exactly backwards of what the chart below shows.



Climbing ability of the FM-2 was excellent, as shown in the graph below. Note that its rate of climb in MILITARY power is 3,600 fpm at sea level.



Our FM-2 is modeled with the engine mentioned above, the R-1820-56W. The W indicates water injection. Only later run FM-2s had water injection. Earlier aircraft fitted with the -56A and -56B did not. They were limited to 1,300 hp. Some tests of FM-2s with the -56W engine show as much as 1,475 hp at sea level in low blower. This produced a sea level speed of 312.5 mph.



My regards,

Widewing
My regards,

Widewing

YGBSM. Retired Member of Aces High Trainer Corps, Past President of the DFC, retired from flying as Tredlite.

Offline Krusty

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Re: FM2 as Brewster sub (discussion)
« Reply #9 on: July 03, 2008, 08:07:15 PM »
Very interesting, WW.

"The R-1820-56W is rated for 1,360 hp at 52" MAP @ sea level. That is where the AH2 modeling goes awry. In the game, WEP doesn't show an increase in MAP at Combat Power until about 4,000 feet"

I wonder if that's some sort of oversight on HTCs part, rather than a deliberate under-modeling.

If you notice on HTC's own chart, they have a similar speed spike with WEP, which would imply the power is there... somewhere(?)

http://www.hitechcreations.com/ahhelp/models/charts/fm2spd.gif

but I see what you mean about the missing climb increase, as well.

http://www.hitechcreations.com/ahhelp/models/charts/fm2clmb.gif

It's interesting to note that even without the 1450 hp power (which looks like you have to bypass the regulator to reach -- maybe why HTC didn't use that setting, since they like standard settings), the FM-2 at sea level is still as fast as the Brewster at its peak alt  :)


P.S. Thanks for the charts!

Offline angelsandair

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Re: FM2 as Brewster sub (discussion)
« Reply #10 on: July 04, 2008, 08:34:21 AM »


P.S. Angel, the P-39 is one of the fastest planes of this time frame, has a major firepower advantage over the Brester (ESPECIALLY with the 37mm cannon) and while perhaps not as nimble, is 75-100mph faster than the Brewster on the deck, almost. I'd guess that makes it not a very good substitute. The P-39D is faster on the deck than the Brewster's top speed at 18k.

20mm option? I'm deadlier w/ that than the 37mm... :D

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Here lie these men on this sun scoured atoll,
The wind for their watcher, the wave for their shroud,
Where palm and pandanus shall whisper forever,
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Offline valdals

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Re: FM2 as Brewster sub (discussion)
« Reply #11 on: July 21, 2008, 11:58:15 AM »
why replace the beaufighter with the A20? Use the boston III. for the buffalo id use the SBD or the f4f-4.  and why not add the D3A ?

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Re: FM2 as Brewster sub (discussion)
« Reply #12 on: July 21, 2008, 02:53:15 PM »
why replace the beaufighter with the A20? Use the boston III. for the buffalo id use the SBD or the f4f-4.  and why not add the D3A ?

The A-20 is a better fit for the Beaufighter, especially considering the armament of the Beaufighter.

The other questions are answered in the rules writeup and the given references.