From Bubble To Razorback

[george]

Normally we think as an aircraft design advanced, such as the Stang and T-Bolt, the razorback was upgraded to a bubble canopy. But in the case of the F-84, the early models were bubbles, but by the F it was a razorback. Are there other examples of this design philosophy, or is this the sole bubble to razor?

[shrike]

The MiG 21 evolved from a bubble in the early variants to a 'razorback' in the later interceptor versions. Arguably the spines on the A-4 and F-16 might count.
The I-16 went from closed cockpit to open, but that's not quite the same thing

[shrike]

I think the addition of a dorsal spine in contemporary jet combat aircraft might be from the need to increase interior volume rather than an aerodynamic requirement. I think that's the case with the F-16 and A-4 Skyhawk. My recollection is that the A-4 used it's "hump" for electronics on an otherwise very compact airframe. The F-16 added conformal fuel tanks and internal ECM and the dorsal spine contributed towards that. Maybe the F-84 dorsal spine was developed for similar reasons but may also have been added to increase directional stability. The F-84 was pre-area rule and may have suffered from some kind of high speed instability during it's development.

The P-47 and P-51 both went to bubble canopies solely for visibility. Both of them suffered aerodynamic penalties for doing so. The P-51 required a strake, and taller rudder and fin in later models

[sandiego89]

Good topic, beside the others mentioned, I can not think of many as drastic as the F-84.

Perhaps the TBM3W Avenger, never quite a bubble to start, but the airborne early warning version with the big radar on the belly, had the he all glass greenhouse aft the pilot faired over.

some honorable mentions that lost visibility as they matured:

A-1 Skraider- started as a single seat bubble, but some other versions had a four seat+ cockpit.

Mitsubishi F-1. Minimal change, adopted from the twin seat T-2. Rear canopy, and the intermediate side windows, of the F-2 were replaced with solid metal. Must have compromised over the should visibilty a bit.

Supermarine Attacker. Started with a bubble, but later versions had a more heavily framed canopy and a more metal toward the rear of the canopy teardrop.

XB-52. First one had tandem seating. Switched to side by side.

F-35B. Rear of the canopy more abrupt, less visibilty than the A and C versions, to allow for the lift fan behind the cockpit.

U-2 some later veriosn had a more pronounced canopy covering over the rear top- to reduce heat/sun in the cockpit.

[Chris Brame]

C-74 - went from double bubble to conventional.

[JohnB]

Any ex-F-84F guys out there?

What's in the spine...electronics, fuel?
Or was it done for aerodynamic reasons?
Per the discussion of A-4s and F-16 spines, recall that the F-105s modified in the "T Stick II" program had a lager spine for electronics.

[shrike]

Any ex-F-84F guys out there?

What's in the spine...electronics, fuel?
Or was it done for aerodynamic reasons?
Per the discussion of A-4s and F-16 spines, recall that the F-105s modified in the "T Stick II" program had a lager spine for electronics.

Ammunition storage for the wing root guns.