Dive Bombing: USN vs USAAF/USAF

[KJ_Lesnick]

I could redraw if you wish...

[wuzak]

You mean something like the F6F, where the lower cowling intake supplies air to teh engine, the oil cooler and the intercooler?

http://aviadejavu.ru/Images6/MM/MM-97/0200-03-2-11.jpg

I believe 110 is the oil cooler. In Green and Swanborough, An Illustrated Anatomy of the World's Fighters, 110 is marked as "oil cooler duct".

[KJ_Lesnick]

You mean something like the F6F, where the lower cowling intake supplies air to teh engine, the oil cooler and the intercooler?

Could that work?

[wuzak]

You mean something like the F6F, where the lower cowling intake supplies air to teh engine, the oil cooler and the intercooler?

Could that work?

It did work.

[KJ_Lesnick]

It did work.

Well, I was wondering if it would work with the level of efficiency that the upper and lower layout worked with?

[wuzak]

It did work.

Well, I was wondering if it would work with the level of efficiency that the upper and lower layout worked with?

Possibly.

[KJ_Lesnick]

Wuzak

Possibly.

That would have been an interesting as a prospect wouldn't you say?  It looks like it would improve over the nose visibility which is always good.

As for the other structures, I'm curious what your thoughts are

• Canopy: Looks rather clunky.  I'm curious if a bubble canopy would be better?
  
• Tailfin: The dorsal root looks odd (no sweep at the base), is there any reason for this?
  

[wuzak]

Wuzak

Possibly.

That would have been an interesting as a prospect wouldn't you say?  It looks like it would improve over the nose visibility which is always good.

I would say that the XA-41's air intake was above the cowl because of the engine's down draft carburettor.

The F6F and the F4U had, essentially, the same engine.

The F4U had a down draft carburettor too, but it was fed from the auxiliary stage supercharger, via intercoolers (XA-41 single stage, no intercooler).

The F4U seemed to benefit more from ram than the F6F, so maybe it wasn't all that great.

• Canopy: Looks rather clunky.  I'm curious if a bubble canopy would be better?
  

Not a clue.

As for the other structures, I'm curious what your thoughts are

• Tailfin: The dorsal root looks odd (no sweep at the base), is there any reason for this?
  

Also, not a clue.

I am not an aerodynamicist, and even then the appearance of the tail fin is not necessarily a guide to its performance. I would need a detailed evaluation, as the design team would have done, to assess the merits of the fin shape.

[KJ_Lesnick]

Wuzak

The F6F and the F4U had, essentially, the same engine.

Both were downdraft correct?

XA-41 single stage, no intercooler

Would an twin-stage, twin-speed with intercooler be useful?

The F4U seemed to benefit more from ram than the F6F, so maybe it wasn't all that great.

The F4U's intakes were in the wings...

Also, not a clue.

I am not an aerodynamicist, and even then the appearance of the tail fin is not necessarily a guide to its performance. I would need a detailed evaluation, as the design team would have done, to assess the merits of the fin shape.

True enough point: Still there are some rules of thumb.  I'll do some looking into this

[wuzak]

Wuzak

The F6F and the F4U had, essentially, the same engine.

Both were downdraft correct?

No, that was the difference.

The F4U-1 (R-2800-8) had a downdraft carby, the F6F (R-2800-10) had an updraft carby.

XA-41 single stage, no intercooler

Would an twin-stage, twin-speed with intercooler be useful?

Probably not for a low altitude attack aircraft. It will just add weight, and the extra performance will be where the aircraft does not operate.

The F4U seemed to benefit more from ram than the F6F, so maybe it wasn't all that great.

The F4U's intakes were in the wings...

Yes, except for the F4U-5.

[KJ_Lesnick]

Wuzak

No, that was the difference.

The F4U-1 (R-2800-8) had a downdraft carby, the F6F (R-2800-10) had an updraft carby.

But in either case the F4U-1's airflow would have basically turned through 180 degrees to make the engine, and probably even more as it would have had to go aft, then turn around and head up on top and forward.

Probably not for a low altitude attack aircraft. It will just add weight, and the extra performance will be where the aircraft does not operate.

Yes but I was under the impression that during the cruise inward to target could include a variety of altitudes.  I do remember hearing something to the effect of the SBD's often cruising in for dive-bombing runs from 14,000 to 20,000 feet then diving on down.  I figure if you could get the critical altitude up to around 25,000 to 28,500 feet, you'd be able to reduce drag during that portion of flight and fly farther.

While I'm at it, what did the AD-1 use for supercharging?

Yes, except for the F4U-5.

It used a sidewheel supercharger -- what's that?

[wuzak]

The F4U-1 (R-2800-8) had a downdraft carby, the F6F (R-2800-10) had an updraft carby.

But in either case the F4U-1's airflow would have basically turned through 180 degrees to make the engine, and probably even more as it would have had to go aft, then turn around and head up on top and forward.[/quote]

I apologize. I think I have the carby directions mixed up. The F4U was an updraft, the F6F a downdraft. But I will have to confirm this.

This is the induction system for the F4U.



Note that the R-2800 used in both the F4U and F6F was two stage. The carburettor sat between the two stages and was fed via the intercooler(s).

It is a rather tortuous path, though.

Probably not for a low altitude attack aircraft. It will just add weight, and the extra performance will be where the aircraft does not operate.

Yes but I was under the impression that during the cruise inward to target could include a variety of altitudes.  I do remember hearing something to the effect of the SBD's often cruising in for dive-bombing runs from 14,000 to 20,000 feet then diving on down.  I figure if you could get the critical altitude up to around 25,000 to 28,500 feet, you'd be able to reduce drag during that portion of flight and fly farther.

Flying high is offset by having to climb to that altitude with all the ordnance aboard. Which will use wuite a lot of fuel.

While I'm at it, what did the AD-1 use for supercharging?

I'm sure we've been here before. The AD-1 used a single stage supercharger. I'm not certian as to whether it was a single or two speed drive.

Yes, except for the F4U-5.

It used a sidewheel supercharger -- what's that?

It's called a "sidewinder".

The R-2800-32W had two auxiliary stage superchargers feeding the single main supercharger. These two superchargers were handed and mounted with their axes perpendicular to the engine's, and were driven by a cross shaft. 

[KJ_Lesnick]

wuzak

I apologize. I think I have the carby directions mixed up. The F4U was an updraft, the F6F a downdraft. But I will have to confirm this.

Okay

This is the induction system for the F4U.

You aren't kidding when you say a torturous path

Note that the R-2800 used in both the F4U and F6F was two stage. The carburettor sat between the two stages and was fed via the intercooler(s).

Both used inter-cooling?  Then why was the P-51B/C/D able to cruise so much higher?

Flying high is offset by having to climb to that altitude with all the ordnance aboard.

A problem which affected the B-29's, and later on they'd cruise usually around 14,000 - 20,000 feet: I'd like to point out that it's fundamentally more efficient to cruise high; the issue is how much fuel is required to get up there, and that is affected by climb and acceleration-rates: This plane has a higher power loading than the B-29.



Which will use wuite a lot of fuel.[/quote]

While I'm at it, what did the AD-1 use for supercharging?

I'm sure we've been here before. The AD-1 used a single stage supercharger. I'm not certian as to whether it was a single or two speed drive.

Yes, except for the F4U-5.

It used a sidewheel supercharger -- what's that?

It's called a "sidewinder".

The R-2800-32W had two auxiliary stage superchargers feeding the single main supercharger. These two superchargers were handed and mounted with their axes perpendicular to the engine's, and were driven by a cross shaft. 


[/quote]

[wuzak]

Engines for the F4U:

XF4U-1: XR-2800-1 - updraft carburettor
F4U-1: R-2800-8/8W - updraft carburettor
F4U-2: R-2800-8 - updraft carburettor
F4U-3A: R-2800-16 - single stage engine coupled to Turbo Engineering turbocharger, downdraft carburettor
F4U-3B: R-2800-14 - single stage engine coupled to Turbo Engineering turbocharger, downdraft carburettor
F4U-4: R-2800-18W - downdraft carburettor, fluid coupling for auxiliary supercharger
F4U-5: R-2800-32W - updraft carburettor, the one with the side mounted auxiliary superchargers
F4U-6: R-2800-83W - single stage engine for ground attack variant, downdraft carburettor
F4U-7: R-2800-18W - F4U-4 for French Navy.

The F4U-4 had the supercharger intake under the nose. The R-2800-18W had a downdraft carby.




The F4U-5 had two intakes - one on either side of the lower nose.



The R-2800-32W had an updraft carby.

[Captain Canada]

Great pics. Thanks.