Bubble canopies?

[vinnye]

I wonder why some fighter designs went from Razorback designs (Spitfire, P51 and P47) and some did not (F6F and F4U)?
The benefits seemed to be better all round visibility and possibly better aerodynamics?
So why did the two best fighters in the Pacific not follow suit?

 

[wuzak]

The F2G version of the F4U was to have a bubble canopy.

I'm guessing that production won over potential improvements, including bubble canopies.

 

[vinnye]

I was wondering if that may have been a reason?
They were both excellent fighters already and were getting the jod done as is - so maybe left that way?

 

[MikeGazdik]

In reading some Grumman testing articles, I believe with Corky Meyer, they were dealing with problems of directional stability problems when testing bubble-canopies. With the U.S. Navy having a very conservative record, I think it may be they did not want to risk making a change for that reason, and interrupting supply as stated. The U.S. Navy would control the procurement of both the F5f and F4U.

 

[CobberKane]

In effect, the Hellcat did get its bubble canopy - and a lot more besides. They called it the Bearcat. Bear in mind too that blown canopies can frequently be less aerodynamic than canopies that are faired into the fuselage, because they create a zone of low pressure in the space where the raised fuselage used to be. This can also cause directional instability. The Malcom hood P 51 was held by many pilots to be faster than the P51D, and the later model required the addition od a raised fin forward of the tail to restore stability. The trade off was massively improved visibility - vital for a fighter pilot.

 

[davebender]

Too late to help the USN. However French pilots flying CAS missions in Indochina probably appreciated the F8F.

 

[vinnye]

OK - I get the fact that the change to a bubble canopy changed the aerodynamics and affected stability. I am sure this happened with the Spitfire, P51 and P47 as well, and solutions were found to overcome this. The improved visibility was a benefit worth making the changes for. Unless you need quantity at all costs - which seemed to be the US Navy's primary concern.
It now seems worth asking why the LW did not copy this idea. I have seen a P51 pilot get into a Me109 and could not believe how poor the visibility was!

 

[drgondog]

In effect, the Hellcat did get its bubble canopy - and a lot more besides. They called it the Bearcat. Bear in mind too that blown canopies can frequently be less aerodynamic than canopies that are faired into the fuselage, because they create a zone of low pressure in the space where the raised fuselage used to be. This can also cause directional instability. The Malcom hood P 51 was held by many pilots to be faster than the P51D, and the later model required the addition od a raised fin forward of the tail to restore stability. The trade off was massively improved visibility - vital for a fighter pilot.

Cobber - The Malcom Hood P-51B-1 with high altitude Merlin 1650-3 was faster for equal load out than any of the P-51D's. The dorsal fin mod was applied to Both the P-51B and D. The yaw stability issue had nothing to do with either the canopy or the razorback (although it was thought so). It was only when the P-51H with 13" extended fuselage and re-designed vert Stab that yaw issues were resolved..

As to the adverse pressure gradient on the windscreen the P-51D was superior with greater slope. See the Lednicer report I posted in the P-51 performance Thread.

http://www.ww2aircraft.net/forum/flight-test-data/p-51-performance-thread-12670.html post #4

 

[tyrodtom]

You really can't say the Luftwaffe needed to copy the bubble canopy, the Fw190 was flying in action with a bubble canopy before any allied fighters , I believe. But they never redesigned the Me109 for a bubble. The Me209 and Me309 both had bubble canopies, didn't they ?

 

[zoomar]

I think the pure bubble canopy is one of those innovations that were really just cosmetic, and did little if anything to improve the planes that had them. Kind of like fins on 1950's cars. Since they were uniquely western (US and UK) and thus continued into the postwar jet age thay are also associated with modernity. I've read that many USAAF and RAF pilots preferred Mustangs with Malcom hoods to P-51Ds, while the A6M was lauded for its visibility from the many framed glasshouse canopy it had. No Soviet, Japanese, or German wartime fighter had true bubbles (all-round vision framed canopies such as those most Japanese planes had and which were on late war Yaks and Las as well as the Me-262 are not the same as bubble canopies), and only the prototype Fw-190 sported what we might consider a true bubble.

 

[tyrodtom]

Making the bubble canopy was why most were slow to adopt it, not because they didn't care about fashion.

Getting a relately distortion free bubble wasn't easy, it took a lot of experimenting with materials and techniques to get it right. We take for granted all the things made with plastics today, in the early 40's, big, clear, bubble canopies, that you had good wision through and the sun didn't turn opaque in a few months, were new technology that not everybody had perfected.

When you speak of the Zero canopy, you need to know that all the flat panes in it were glass, not safety glass, not tempered glass, just common glass.

 

[wuzak]

You really can't say the Luftwaffe needed to copy the bubble canopy, the Fw190 was flying in action with a bubble canopy before any allied fighters , I believe.

Westland Whirlwind

 

[tyrodtom]

Westland Whirlwind

You're right, the Whirlwind prototype did fly before the first Fw190, but close enough in time so that I would doubt Tank copied the Whirlwind's canopy.

 

[yulzari]

Makes the Miles M20 canopy all the more impressive.

 

[drgondog]

I think the pure bubble canopy is one of those innovations that were really just cosmetic, and did little if anything to improve the planes that had them.

That would be wrong - the difference in rear visibilty was HUGE and important for tear drop (Bubble) canopies. The difference in the Malcolm hood versus birdcage canopy was important in the 5 O'Clock to 7O'clock visibility to such fighters as the Spit and P-51B.

Kind of like fins on 1950's cars. Since they were uniquely western (US and UK) and thus continued into the postwar jet age thay are also associated with modernity. I've read that many USAAF and RAF pilots preferred Mustangs with Malcom hoods to P-51Ds, while the A6M was lauded for its visibility from the many framed glasshouse canopy it had.

The Zero did not have a 'turtleback' like the Spit and P-51 so the only difference was 'rib's versus 'clear' with respect to P-51D

No Soviet, Japanese, or German wartime fighter had true bubbles (all-round vision framed canopies such as those most Japanese planes had and which were on late war Yaks and Las as well as the Me-262 are not the same as bubble canopies), and only the prototype Fw-190 sported what we might consider a true bubble.

There is a reason most top air combat fighters (F-22, F-15, F-16, MiG 35, etc) have Full 360 vision Bubble canopies...

 

[CobberKane]

I think the pure bubble canopy is one of those innovations that were really just cosmetic, and did little if anything to improve the planes that had them. Kind of like fins on 1950's cars. Since they were uniquely western (US and UK) and thus continued into the postwar jet age thay are also associated with modernity. I've read that many USAAF and RAF pilots preferred Mustangs with Malcom hoods to P-51Ds, while the A6M was lauded for its visibility from the many framed glasshouse canopy it had. No Soviet, Japanese, or German wartime fighter had true bubbles (all-round vision framed canopies such as those most Japanese planes had and which were on late war Yaks and Las as well as the Me-262 are not the same as bubble canopies), and only the prototype Fw-190 sported what we might consider a true bubble.

Sorry zoomar, but this initial statement is plain nonsense. The designers did not go to all the hassle of developing blow canopy maunfacturing and then have to tackle the handling issues they caused just for the purpose of making their plane pretty - they did it becase bubble canopies provided significantly improved vision, particularly in the vital rearward quadrant. The many positive comments of pilots who flew such aircraft as the P 51 and P 47 after this modification indicate how important it was. I agree though that there seems to be a bit of confusion about the difference between a bubble canopy, as fitted to the P51D, and a raised framed canopy as fitted to the Zero. A bubble canopy consists of a large rear section of self-supporting blown perspex that secures against a much smaller framed foward section that usually incorporated a plate of armoured glass. A raised framed canopy is simply domed framework fitted with glass panels. it would provide better all round vision than a faired framed canopy, but nowhere near as good as a bubble canopy.

 

[GregP]

There is a strong misconseption that switiching to a bubble canopy caused instability in the P-51D / K. Not so .... really.

There were a NUMBER of culprits:

1. Changing from the Allison to the Merlin resulted in considerably more area forward of the CG when they fitted the larger, 4-bladed propeller.
2. They ALSO put in the fuselage tank, and THAT moved the CG backward while simultaneously having more blade area forward of the CG. They were looking for solutions to that when they went to the P-51D and the bubble canopy. The dorsal fin extension helped cure the problem in the P-51D and it was retrofitted not only to many P-51D and K models that were originally shipped without it, but also to many P-51B and C models that also were originally shipped without the doral fin extension.

The main cuplrits were the new prop for the Merlin and teh fuselage tank; the bubble canopy was minor in comparision to the first two.

Here is a drawing of a famous P-51B WITH the dorsal fine xtension: http://information2share.files.wordpress.com/2011/06/north-american-p51-b-mustang.jpg

 

[CobberKane]

There is a strong misconseption that switiching to a bubble canopy caused instability in the P-51D / K. Not so .... really.

There were a NUMBER of culprits:

1. Changing from the Allison to the Merlin resulted in considerably more area forward of the CG when they fitted the larger, 4-bladed propeller.
2. They ALSO put in the fuselage tank, and THAT moved the CG backward while simultaneously having more blade area forward of the CG. They were looking for solutions to that when they went to the P-51D and the bubble canopy. The dorsal fin extension helped cure the problem in the P-51D and it was retrofitted not only to many P-51D and K models that were originally shipped without it, but also to many P-51B and C models that also were originally shipped without the doral fin extension.

The main cuplrits were the new prop for the Merlin and teh fuselage tank; the bubble canopy was minor in comparision to the first two.

Here is a drawing of a famous P-51B WITH the dorsal fine xtension: http://information2share.files.wordpress.com/2011/06/north-american-p51-b-mustang.jpg

How about the fin on the P47N?

 

[GrauGeist]

I hate to say this, but the Fw190 did not have a true bubble canopy and neither did the Me262...both had the trailing portion of the canopy faired into the fuselage where the P-51, Typhoon and P-47D (etc.) did not. These were bubble canopies.

 

[gumbyk]

What I understand is that it was the reduction in vertical area aft of the C of G that caused stability issues, hence the fillet on the fin. It wasn't the bubble canopy (or whatever you want to call it)per se, but the other changes in the airframe as a result.