Razorbacks versus Bubbletops

[216th_Jordan 1291]

Seeing that we get two earlier versions of the P-51 and the P-47 with a lot of hype for them.

What makes Razorbacks so desired? Visibility is obviously worse, but I seem to remember from Il-2 1946 that at least P-51B/C and P-51D had some performance differences in favor of the B/C versions - but I can't find the respective charts again. Does anyone have that? What else is there?

Edited November 29, 2019 by 216th_Jordan

[LuseKofte 3760]

Razorbacks give me a excuse for being a lousy spotter. 
personally I can not explain my affection for the P 47. And Razorbacks in special. They jus look meaner and cooler.
But I know Razorbacks had advantages over the bubbletops. I never seem to remember what. They where however favored for some sort of missions

Edited November 29, 2019 by No.322_LuseKofte

[RedKestrel 3663]

I like the razorback just because its kind of a different look. Its mostly the aesthetic, it has the early war look.

It did have a little more stability, a little higher top speed, possibly slightly better in the turn(?). So there will likely be some small performance advantages.

[spitfirejoe 218]

the clear advantage of a Razorback compared to a Bubbletop is that the Pilot is more secure against bullets coming from his 6.

Edited November 29, 2019 by spitfirejoe

[Alexmarine 227]

Because Stupid Sexy P-51B with Malcom Hood 😍

[Voidhunger 776]

Spoiler

 

 

Edited November 29, 2019 by Voidhunger

[=BES=Senor_Jefe 146]

There's a small aerodynamic advantage, however around the time bubbles became prevalent, the engines got stronger, often negating the advantage.  The "protection" I'd argue is negligible, since the only real difference is a thin sheet of aluminum.  The armor behind the headrest could still be present with the bubble while still holding the visibility advantage.

 

I think people are hyped because the difference in models is just different enough to be new, and it opens opportunities for more of those planes to play with the eastern front rigs while not being OP.  Just a thought 

[III/JG53Frankyboy 141]

32 minutes ago, spitfirejoe said:

the clear advantage of a Razorback compared to a Bubbletop is that the Pilot is more secure against bullets coming from his 6.

why should it be so?

The armour was behind the pilot, if Razorback or Bubbletop.

[Legioneod 2027]

Razorbacks just look beautiful. There were aerodynamic advantages as well like yaw stability in the P-47 and less drag due to having no bubbletop iirc.

 

Just look at this thing.

 

[=LG=Mad_Mikhael 200]

I love both, P-51 and P-47, but I'm worried about poor visibility in razorbacks versions. I hope we will get Malcolm Hood.

EDIT: Oh, yes, I should add "Malcolm Hood as modification".

Edited November 29, 2019 by =LG=Mad_Mikhael

[Legioneod 2027]

5 minutes ago, =LG=Mad_Mikhael said:

I love both, P-51 and P-47, but I'm worried about poor visibility in razorbacks versions. I hope we will get Malcolm Hood.

As long as it's an option and not standard I'm all for it.

[Gambit21 5621]

1 hour ago, Legioneod said:

 

 

 

 

This was Whisner's ship.

Princess Elizabeth was coming to visit the squadron at Bodney, so the C.O. made him change the name of his aircraft...he wasn't happy about it.

 

[DD_Fenrir 88]

For me it's entirely superficial regards the Mustang; despite the better combat effectiveness of the 'D' I just find the 'B'/'C' a prettier looking aeroplane. Love 'em!

[BornToBattle 285]

4 hours ago, No.322_LuseKofte said:

Razorbacks give me a excuse for being a lousy spotter.

😂

[Luftschiff 383]

Unlike the bubble tops they're aesthetically pleasing.

[Dramborleg 16]

If I recall correctly, bubble tops have a little more drag than a razorback variant  If everything else remained the same a bubbletop variant may be a little slower.  I think the 51B is slightly faster than earlier 51D's until other improvements were made.  Also, there is a loss of stability in yaw with a bubbletop since you lose some fuselage area.  Later model P-51D's and P-47's like the M have fillets added to the vertical stab to gain back some stability.  I know Aces High isn't considered sim-enough by some here, but I remember some guys preferred the 51B there when furballing.

[Legioneod 2027]

5 minutes ago, Aeglos said:

If I recall correctly, bubble tops have a little more drag than a razorback variant  If everything else remained the same a bubbletop variant may be a little slower.  I think the 51B is slightly faster than earlier 51D's until other improvements were made.  Also, there is a loss of stability in yaw with a bubbletop since you lose some fuselage area.  Later model P-51D's and P-47's like the M have fillets added to the vertical stab to gain back some stability.  I know Aces High isn't considered sim-enough by some here, but I remember some guys preferred the 51B there when furballing.

I can't remember exactly but I think it was Gabreski who said he preferred the Razorback over the bubbletop P-47 due to better stability.

I'm interested to see how this is represented in-game and how different the two feel while flying.

[ZachariasX 2658]

6 hours ago, Legioneod said:

I can't remember exactly but I think it was Gabreski who said he preferred the Razorback over the bubbletop P-47 due to better stability.

I'm interested to see how this is represented in-game and how different the two feel while flying.

Not really stability as such. Rudder forces became too light and one could easily skid the aircraft at non permissive yaw angles. Adding the fillet increased rudder forces again to „safer“ levels.

 

10 hours ago, Legioneod said:

Just look at this thing.

Princess Elisabeth had a „D“ wing?

Edited November 30, 2019 by ZachariasX

[EAF19_Marsh 799]

1 hour ago, ZachariasX said:

Not really stability as such. Rudder forces became too light and one could easily skid the aircraft at non permissive yaw angles. Adding the fillet increased rudder forces again to „safer“ levels.

 

Possibly some slight benefit from the higher back in terms of lateral stability as essentially you are getting more of a ‘keel’, hence the implementation of fin fillets.

 

IIRC, there is an improvement in the drag with the higher backs as you avoid the slight turbulence which tends to come from the air-flow aft of a bubble canopy; there is a smoother flow. One reason why designers often revert to a higher, more blended design aft of the cockpit until the next conflict reminds everyone why visibility is important.

[ZachariasX 2658]

Just now, EAF19_Marsh said:

Possibly some slight benefit from the higher back in terms of lateral stability as essentially you are getting more of a ‘keel’, hence the implementation of fin fillets.

Actually, I'm not even sure if this is desired. I always thought so before flying the Spit, a plane that I thought had a tiny rudder for such power. Making these aircraft stable means they become a rather inert especially at higher speeds, where control forces require all your strenght anyway. The fin size just makes it harder to yaw. The amount of control you have over yaw is defined by the moving part. You will not be more precise in handling the aircraft with a larger fixed section of the stabylo at all. The extreme case is in with the Fokker Dr.I (for instance), where you have no fixed tail fin at all. This just means you have to hold your direction with your feet constantly for the benefit of making it way more invting to yaw the plane. But if you hold it on course it will fly as straight as if it had a large fixed tail fin.

[Sobilak 1]

http://www.wwiiaircraftperformance.org/mustang/mustangtest.html

There is a lot of differences about P-51 razorback vs bubbletop.  Go down the page to see some tables.

[Bremspropeller 2434]

2 hours ago, ZachariasX said:

Princess Elisabeth had a „D“ wing?

 

That's not a D-wing (and not an X-wing either!)

 

The B had had a smaller kink at the wing-fuselage fairing. Depending in the image you're looking at, earlier versions may or may not have had that kink, too.

The D had a larger kink anyway.

https://www.mustangsmustangs.com/p-51/variants/p51b

 

Edited November 30, 2019 by Bremspropeller

[JtD 2459]

Most performance differences are down to different engine and armament, not fuselage shape. The earlier P-51 B and C models mostly came with the 1650-3, the later D typically with the 1650-7 engine. The -3 was tuned for better high altitude performance, the -7 more for low altitude (Merlin 63 and 66 equivalents). You'd also get P-51B's with -7 engines, in which case the performance differences to the D were really small. The B held a small edge, owing to the somewhat lower weight because of less guns.

[danielprates 580]

15 hours ago, spitfirejoe said:

the clear advantage of a Razorback compared to a Bubbletop is that the Pilot is more secure against bullets coming from his 6.

 

I think bullets will simply waltz through everything except armour. So glass, pexiglas, metal, it's all the same. Only an armour sheet can make a difference.

 

Come to think of it, if the "razor" part in the razorback also functions as a structural element, it may fail if a lucky bullet goes through something critical. So if anything it should be worse!

 

.... although, iirc that space behind the pilot's head is where some bulky equipments were installed, radios I think, so that perhaps counts as an extra layer of protection.

[ZachariasX 2658]

1 hour ago, Bremspropeller said:

The B had had a smaller kink at the wing-fuselage fairing.

It looked rather kinky for a small kink. So I wasn't sure.

[Bremspropeller 2434]

[Sobilak 1]

1 hour ago, JtD said:

Most performance differences are down to different engine and armament, not fuselage shape. The earlier P-51 B and C models mostly came with the 1650-3, the later D typically with the 1650-7 engine. The -3 was tuned for better high altitude performance, the -7 more for low altitude (Merlin 63 and 66 equivalents). You'd also get P-51B's with -7 engines, in which case the performance differences to the D were really small. The B held a small edge, owing to the somewhat lower weight because of less guns.

But first series of the P-51D don't has dorsal fin, and has poor stability. Dorsal fin changed it, but P-51D has less stability by B/C version because fuselage gave it more.

B/C was lighter because 4 machine guns and different wings.  

Edited November 30, 2019 by Sobilak

[=362nd_FS=RoflSeal 598]

6 hours ago, ZachariasX said:

Not really stability as such. Rudder forces became too light and one could easily skid the aircraft at non permissive yaw angles. Adding the fillet increased rudder forces again to „safer“ levels.

 

Princess Elisabeth had a „D“ wing?

nah, P-51D's wing root extension is far more obvious

[Talon_ 1777]

19 hours ago, Senor_Jefe-6 said:

There's a small aerodynamic advantage, however around the time bubbles became prevalent, the engines got stronger, often negating the advantage.  The "protection" I'd argue is negligible, since the only real difference is a thin sheet of aluminum.  The armor behind the headrest could still be present with the bubble while still holding the visibility advantage.

 

Both the high-back versions of the P-51 and P-47 are slightly faster at the same boost.

[Legioneod 2027]

1 hour ago, Talon_ said:

 

Both the high-back versions of the P-51 and P-47 are slightly faster at the same boost.

This is true for the most part but it also depends on the prop used and the weight of the airframe.

 

I've done some test in-game comparing the P-47 razorback numbers to the D-28 and I think there is an error in how fast the D-28 is. Seems the D-28 is too slow when using lower boot settings of 56" or lower. Needs more testing but it seems in-game the lower boost you have the more dragy the aircraft is compared to RL. This also could be due to the AO Smith prop used but idk.

 

If we do end up getting the D-22 (hope so), it will be faster than all the bubbletops except for the D-25 and D-27 when using similar boost settings.

[Livai 323]

12 hours ago, 216th_Jordan said:

What makes Razorbacks so desired?

 

This -> 

[Voyager 197]

As I recall, didn't the P-51D also have a thicker wing than the B version?

 

I seem to recall something about the 'B' needing the guns mounted at an angle that caused a bend in the ammo feed, which caused problems with the guns jamming after high G manuvers, and that the P-51D used a thicker wing to allow the guns to be mounted vertically. 

[=362nd_FS=RoflSeal 598]

2 hours ago, Voyager said:

As I recall, didn't the P-51D also have a thicker wing than the B version?

 

I seem to recall something about the 'B' needing the guns mounted at an angle that caused a bend in the ammo feed, which caused problems with the guns jamming after high G manuvers, and that the P-51D used a thicker wing to allow the guns to be mounted vertically. 

Wing thickness was the same, the reason B had angled 50 cals was a left over from the A-36 Apache for the dive brakes..

[Cavalier 26]

7 hours ago, Legioneod said:

This is true for the most part but it also depends on the prop used and the weight of the airframe.

 

I've done some test in-game comparing the P-47 razorback numbers to the D-28 and I think there is an error in how fast the D-28 is. Seems the D-28 is too slow when using lower boot settings of 56" or lower. Needs more testing but it seems in-game the lower boost you have the more dragy the aircraft is compared to RL. This also could be due to the AO Smith prop used but idk.

 

If we do end up getting the D-22 (hope so), it will be faster than all the bubbletops except for the D-25 and D-27 when using similar boost settings.

When you do these tests do you have the supercharger fully engaged (throttle to the wall and boost-lever to 56")? Not having the supercharger engaged by not putting the throttle forward before boost may be causing your lack of horsepower... Although, I'm not even sure whether or not this effect is modeled in-game.

Edited December 1, 2019 by Cavalier

[Legioneod 2027]

4 hours ago, Cavalier said:

When you do these tests do you have the supercharger fully engaged (throttle to the wall and boost-lever to 56")? Not having the supercharger engaged by not putting the throttle forward before boost may be causing your lack of horsepower... Although, I'm not even sure whether or not this effect is modeled in-game.

Throttle full forward. I've done it both ways i think but either way the D-28 is still slower than what it should be at lower power settings. Like I said, this could be due to the A.O. Smith prop on the D-28 in-game instead of the Curtis Paddle Blade that it mostly used irl.

Edited December 1, 2019 by Legioneod

[PainGod85 374]

21 hours ago, Talon_ said:

 

Both the high-back versions of the P-51 and P-47 are slightly faster at the same boost.

 

This assertion does not hold up to closer scrutiny.

 

 

Spoiler

The P-51B-5 running 67" achieved 371 mph at sea level with the -3 engine clean, without racks.

Spoiler

 

Another B-5, -7 engine,  during testing with 150 grade fuel achieved the following speeds at SL:

67" - 360 mph
72" - 375 mph

75" - 383 mph

 

The documents available do not say whether bomb racks were installed.

 

Spoiler

 

The same P-51B-15 (-7 engine)  with and without racks, again SL:

 

67" - 364 mph w/

75" - 380 mph w/

75" - 388 mph w/o

 

Spoiler

 

Another B-15, again with the -7 engine, without wing racks:

 

67" - 376.5 mph

 

Spoiler

 

Three P-51B-15s over several runs, speed averages. -7 engine, no mention whether racks were installed:

 

67" - 356 mph

75" - 374 mph

 

Spoiler

 

P-51D with racks, -7 engine:

 

67" - 375 mph

 

Spoiler

 

Another D with a -7 engine, no specific mention whether racks were used for the speed tests, though they were installed on the plane at least for some tests:

 

67" - 368 mph

 

 

 

 

Overall, there are more tests of the B, with several outliers in performance towards both the upper and lower end of the scale. In the end, it averages out in light of measuring tolerances etc.

I'm too lazy to draw up sources for the P-47, but I expect numbers to run along the same line as with the Mustang.

[LuseKofte 3760]

The Malcolm hood did make aerodynamical problems for the P 51

[migmadmarine 337]

On 11/29/2019 at 6:11 PM, Gambit21 said:

 

 

This was Whisner's ship.

Princess Elizabeth was coming to visit the squadron at Bodney, so the C.O. made him change the name of his aircraft...he wasn't happy about it.

 

Was it named specifically after her, or a different Elizabeth?

[=362nd_FS=RoflSeal 598]

The tactical characteristics chart shows very little difference between the bubble and razorback P-51s, though what is to note is the P-51D had new bomb racks that reduced speed by only 4mph instead of 12mph.

The P-47s on the other hand show a much bigger difference in performance between bubble and razorback.

Edited December 1, 2019 by =362nd_FS=RoflSeal

[chuter 147]

Just for historical perspective, back in the day the only aircraft ever referred to as "Razorback" was the P-47 due to its rather "sharp" spine.  (I know, I grew up using "razorback" for any/all high-back fighters myself ...)

 

As for "keel area" and its effect on stability its actually not a thing in these particular examples.  When bubble canopies were added to the P-51 and P-47 there was an introduction of turbulence behind the canopy that took away some of the effectiveness of the fin.  The Mustang had already lost some directional stability with the B when the Merlin was installed due to the four blade propeller replacing the less destabilizing three blade* but the bubble canopy's turbulence pushed the previously not toooo bad directional instability over the line and a directional fix was fast tracked.  The reason for the fin leading edge extension (LEX) equipped D's having less rudder authority than the straight finned version was the LEX mod included switching the rudder trim/servo tab to trim/anti-servo tab resulting in a given input force providing less rudder travel. 

 

Maybe the biggest advantage for the bubble canopy Mustang pilot was a better view over the nose for deflection shooting due to the higher seating position.  There were a few pilots who preferred the B/C's overall handling to the D's** but in early '45 were ordered out due to it being expected that almost anything without a bubble canopy was German (Eagleston was in a B when shot down by P-47s).

 

*The Brits were trying to fix the B's reduced stability problem from the get-go while the USAAF figured the pilot with his rudder pedals could fix it.  Later on, after the D's fin LEX's were developed they were adapted to the B and C models as well though their need for it was less.

 

**For instance, quicker roll response due to less wing weight but ... not modeled.