F7F (P-65) Tigercat

[jcf]

What was basically an enlarged jet-engined F7F was looked at for the role eventually filled by the Douglas F3D.

[tomo pauk]

Many thanks

[sandiego89]

Nice 

reeled one in....

[KJ_Lesnick]

tomo pauk

Yep - the graph states the velocity in mph and rate of climb in fpm.

Okay, that makes more sense

The intakes on the F7F indeed served as you stated

Honestly jet-engines are so much easier to grasp LOL

Going with a liquid cooled engine obviously necessitates the cooler for gylcol/water mixture

Correct

If the engine is intercooled then another cooler is needed, at least for Anglo-American engines.

Actually, the F4U used the same intake to feed the oil-cooler and intercooler right?  Would that work in some arrangement here by doing one of the following

• Add a scoop under the engine like the F4U-4
  
• Enlarging the oil-cooler either in width, depth, or some combo of both
  
• Repositioning the intakes
  

I'm not sure which intake was the cooler and which was the intake.

The engine powers need to be compared without the ram effect. The R-2800-22W have had 1850 HP at 14000 ft, 1600 HP at 16000 ft, that would make maybe 1400 Hp at 20000 ft, and 1100-1200 HP at 25000 ft. Ram effect (most pronounced at high speed) will add some 5000 ft to the listed altitudes in these cases (both P&W and P. Merlin).

I thought the figures on the speed/horsepower chart were based on ram being present (after all, the P-51's HP keeps going up a bit)

The V-1650-7 was available maybe 10 months earlier than the R-2800-22W, that is also a major point of difference historically, another bonus being maybe 20% increase in range/radius.

When was the R-2800-18W and 22W available?

As for the alternatives you mentioned - all will work fine in an what-if.

Of course, and I of course explained why they weren't feasible.  I never gave the weight of the V-3420 much thought but I figure the engine was pretty close to the CG

The predilection for turbochargers was shared between the US Army and VVS

I didn't know the Russians did much work on turbochargers, was the turbocharger work sidetracked due to Stalin's purges?

the LW and RN were firmly in single stage engines camp

If I recall some Seafires had twin-stage superchargers...

RAF and USN indeed jumped at the chance to have 2-stage engines once available. All said is for the time between mid-1930s to mid war.

That looks right...


joncarrfarrelly

The Curtiss Hawk 75R had an auxiliary mechanical supercharger, not a turbo-supercharger.

Whoops!

What was basically an enlarged jet-engined F7F was looked at for the role eventually filled by the Douglas F3D.

It seems by that point you'd be better off just procuring a new plane, I don't know what the mach limits of the F7F's wings were...

[rickshaw]

Nice 

reeled one in....

Seems to be using good bait, wonder what it is? 

[KJ_Lesnick]

Are you accusing one of us of trolling?

Because last I checked we had a decent discussion going over here...

[tomo pauk]

Actually, the F4U used the same intake to feed the oil-cooler and intercooler right?  Would that work in some arrangement here by doing one of the following

• Add a scoop under the engine like the F4U-4
  
• Enlarging the oil-cooler either in width, depth, or some combo of both
  
• Repositioning the intakes
  

I'm not sure which intake was the cooler and which was the intake.

Each intake in the F4U-1 provided the air for 3 'things':
- oil coolers
- intercoolers
- engine itself

The F4U-4 indeed added the under-engine scoop that fed the engine (hence leaving the wing intakes' air just for oil coolers and itercoolers) , the -5U have had 2 'cheek' intakes, one per each of the 'Sidewinder' compressors that provided the compressed air to the engine-stage compressor.

I thought the figures on the speed/horsepower chart were based on ram being present (after all, the P-51's HP keeps going up a bit)

The reason why the engine power of the P-51D keeps going up is the presence of two stage compressor. BTW, the military power of the P-51D was 1370 HP at 21400 ft, WER was 1500 HP at 19300 ft, no ram - there is no way that either R-2800-22W or -34W will come close in power vs. drag here. On 150 grade fuel, WER was 1800 HP at 12000 ft.

When was the R-2800-18W and 22W available?

The 1st F4U-4 (ie. with -18W, the 2-stage 'C' series R-2800 as it was the single stage -22W) was delivered by December 1944. Don't know yet about the F7F. The 1st P-51D was delivered by January 1944.

I didn't know the Russians did much work on turbochargers, was the turbocharger work sidetracked due to Stalin's purges?

Purges have had next to no development on that. Soviets probably came to the same conclusions as the USAC once the ww2 started in 1939 - they set for non-turbo engines for the reson they could have those in numbers. Once the air war in the East turned into mostly low altitude campaign, the emphasis onn turbo was even more sidetracked.

If I recall some Seafires had twin-stage superchargers...

Not by mid war...

[wuzak]

If I recall some Seafires had twin-stage superchargers...

Not by mid war...

Not at all during the war!

[KJ_Lesnick]

tomo pauk

Each intake in the F4U-1 provided the air for 3 'things':
- oil coolers
- intercoolers
- engine itself

I didn't actually know that, though I suppose it makes sense as I didn't see intakes anywhere else.

As for the F7F: Which intake is the oil-cooler?

The F4U-4 indeed added the under-engine scoop that fed the engine (hence leaving the wing intakes' air just for oil coolers and itercoolers)

I assume it meant more air could be used for oil cooling and intercooling?

The reason why the engine power of the P-51D keeps going up is the presence of two stage compressor.

Did the RR Merlin bypass one of the stages?

BTW, the military power of the P-51D was 1370 HP at 21400 ft, WER was 1500 HP at 19300 ft, no ram

I'm not sure what octane was used in the test data that I have, and at some point they boosted to 75"

there is no way that either R-2800-22W or -34W will come close in power vs. drag here.

I'll give you that, but the power is useful at lower-speeds...

The 1st F4U-4 (ie. with -18W, the 2-stage 'C' series R-2800 as it was the single stage -22W) was delivered by December 1944.

I understand the dates, but I'm curious if I understand the rest: The -18W was a twin-stage version of the -22W?

Purges have had next to no development on that. Soviets probably came to the same conclusions as the USAC once the ww2 started in 1939 - they set for non-turbo engines for the reson they could have those in numbers.

So turbos were harder to mass produce?

Not by mid war...

So that came later...

[tomo pauk]

The inboard intake was for the oil cooler. The exit of the air was through a flap at upper wing surface, can be seen here: https://upload.wikimedia.org/wikipedia/commons/2/28/F7F_Tigercat_N747MX_La_Patrona_2014_Reno_Air_Races_Silver_photo_D_Ramey_Logan.jpg

I assume it meant more air could be used for oil cooling and intercooling?

Indeed.

Did the RR Merlin bypass one of the stages?

No.

I'm not sure what octane was used in the test data that I have, and at some point they boosted to 75"

On 130 grade fuel - up to 67 in Hg  for both V-1650-3 and -7 (1500 HP at 19300 ft for the -7). Above that manifold pressure the 150 grade fuel must be used.

I'll give you that, but the power is useful at lower-speeds...

It's always useful

I understand the dates, but I'm curious if I understand the rest: The -18W was a twin-stage version of the -22W?

Both -18W and -22W, plus -34W and -57 (that was supported by turbo) were the 'members' of the 'C' series R-2800 engines. Don't think that we can talk about the -18W being a version of the -22.
The post-war 'E' series featured, for example, -30W (1-stage) and -32 (but still with water injection, 2-stage but with 3 impellers).

So turbos were harder to mass produce?

Harder than what? As for the turbos themselves, it depends what country we're talking about. The USA produced them in tens of thousands - they have had enough of money and industrial capacity to do so. Soviets were not in that position, especially once the Germans invaded. The 3 main types of Soviet engines (Mikulin, Klimov, 14 cyl Shvetsov) were produced in maybe 4-5 factories (Mikulin in just one?), comparing with R-2800, R-2600, V-1710 and V-1650 being produced in 10-12 factories.

[KJ_Lesnick]

tomo pauk

The inboard intake was for the oil cooler. The exit of the air was through a flap at upper wing surface, can be seen here: https://upload.wikimedia.org/wikipedia/commons/2/28/F7F_Tigercat_N747MX_La_Patrona_2014_Reno_Air_Races_Silver_photo_D_Ramey_Logan.jpg

Now that's a beautiful picture: Because the oil-cooler goes straight through in the way it does I would assume it would be unsuitable for being used as an intercooler?  Would the outboard intake suffice?

Indeed.

Makes sense

No.

Well if the RPM is tied to a gear ratio it's RPM would be dependent on whatever the engines was correct?

On 130 grade fuel - up to 67 in Hg  for both V-1650-3 and -7 (1500 HP at 19300 ft for the -7). Above that manifold pressure the 150 grade fuel must be used.

Understood

It's always useful

Yup, though at high altitude it makes little difference evidently

Both -18W and -22W, plus -34W and -57 (that was supported by turbo) were the 'members' of the 'C' series R-2800 engines.

Okay, so they were all part of the same line

Harder than what? As for the turbos themselves, it depends what country we're talking about.

So it's a matter of industrial capacity?

[tomo pauk]

Yes - if the industry cannot churn them (or anything) during a major war, then it does not matter what have the engineers come out with.

Because the oil-cooler goes straight through in the way it does I would assume it would be unsuitable for being used as an intercooler?  Would the outboard intake suffice?

Hmm - actualy, the oil cooler 'tunnel' might suffice for the needs of intercooler for the V-12 of the era. The air intake will go either under (Merlin) or above engine (V-1710), leaving the outboard intake for the intercooler; obviously, the air need to exit somewhere, too, so that will need to have it. The cooler(s) for the engine can go into the 'beard', under the engine itself.

Well if the RPM is tied to a gear ratio it's RPM would be dependent on whatever the engines was correct?

Yes.

[wuzak]

I can't find a really good picture of it, but teh B-17's intercooler was fed by one of the leading edge ducts, and the air left by pone of the slots on teh wing

http://s568.photobucket.com/user/bgorin/media/B17IntercoolerIPC.png.html

http://www.air-and-space.com/20050510%20Santa%20Maria/DSC_0433%20B-17G%20N93012%20Nine-O-Nine%20left%20wing%20l.jpg

[tomo pauk]

KJ asked about the Mach limit of the F7F. I have some dive limit numbers, should give us the ballpark.
In the manual for the F7F-1, the limit of indicated air speed at 30000 ft was 300 kts (345 mph), thus soundly beating the P-38 redlined at 290 mph at same altitude. 290 mph IAS at 30000 ft works as 440 mph true air speed. Interestingly enough, the wing profile of the F7F was just a tad thinner than of the P-38 - NACA 23015 vs. 23016 (values for the root).
The P-51, one of the best divers due to the laminar flow wing, was redlined at 340 mph IAS (P-51B) at 30000 ft, and 325 mph (P-51D). The P-47N was at 318 mph IAS at 30 kft.

[KJ_Lesnick]

tomo pauk

Hmm - actualy, the oil cooler 'tunnel' might suffice for the needs of intercooler for the V-12 of the era.

Except the R-2800 isn't a V-12... I'm not interested in the V-1650/V-1710 idea as you'd have less power at low altitude (plus keeping the radial is better from the standpoint of damage resistance).

The cooler(s) for the engine can go into the 'beard', under the engine itself.

Or in this case like the F4U-4's layout...

Yes.

Then why would the horsepower keep going up?  On at least some charts: Power stays around a certain amount; then falls off.  The only thing I can think of would be

• Failure to factor in a normal increase in HP as speed goes up
  
• Ram compression
  
• The factoring of exhaust into the HP: At 350 mph 1 hp = 1 lbf
  

KJ asked about the Mach limit of the F7F. I have some dive limit numbers, should give us the ballpark.
In the manual for the F7F-1, the limit of indicated air speed at 30000 ft was 300 kts (345 mph), thus soundly beating the P-38 redlined at 290 mph at same altitude. 290 mph IAS at 30000 ft works as 440 mph true air speed.

Hmmm, I'm not getting the same numbers here

I have a mach/airspeed chart readily available and here's what I got for the chart

........TAS @ Mach 1..........IAS @ Mach 1...........Altitude

• 661.5 kt/761.2 mph...661.5 kt/761.2 mph...0'
  
• 650.0 kt/748.0 mph...650.0 kt/706.0 mph...5000'
  
• 638.3 kt/734.6 mph...566.3 kt/651.7 mph...10000'
  
• 626.5 kt/721.0 mph...520.1 kt/598.6 mph...15000'
  
• 614.3 kt/707.0 mph...475.2 kt/546.9 mph...20000'
  
• 602.0 kt/692.8 mph...431.8 kt/496.8 mph...25000'
  
• 589.4 kt/678.3 mph...389.7 kt/448.4 mph...30000'
  
• 576.5 kt/576.5 mph...350.0 kt/402.8 mph...35000'
  

.
Based on these figures

• 290 mph indicated at 30,000 feet comes out to 438.7 mph true, or Mach 0.65 for the P-38
  
• 318 mph indicated at 30,000 feet comes out to 481 mph true, or Mach 0.71 for the P-47N
  
• 340 mph indicated at 30,000 feet comes out to 514.3 mph true, or Mach 0.76 for the P-51B
  
• 325 mph indicated at 30,000 feet comes out to 491.6 mph true, or Mach 0.72 for the P-51D
  
• 345 mph indicated at 30,000 feet comes out to 521.9 mph true, or Mach 0.77 for the F7F-1
  

Some of these numbers seem suspect as the speed where mach effects start to kick in on the P-38 is generally listed at 0.67-0.68 with the airplane out of control by 0.74; the listed mach number at which the P-47 usually seems to encounter Mach effects are around 0.67 though it seems to retain a degree of maneuverability to 0.72, and I'm uncertain at what speed control is lost.  

I'm not sure when the P-51 started encountering mach effects, though I remember hearing that it the aircraft's maximum safe diving speed was 0.84, though I'd almost swear I heard 0.85 mentioned once; the Spitfire's maximum safe diving speed was Mach 0.85, though speeds ranging from 0.891 to 0.94 were achieved

Interestingly enough, the wing profile of the F7F was just a tad thinner than of the P-38 - NACA 23015 vs. 23016 (values for the root).

At the penalty of sounding stupid: Is that the P-38 or F7F figures you're listing?


wuzak

I can't find a really good picture of it, but teh B-17's intercooler was fed by one of the leading edge ducts, and the air left by pone of the slots on teh wing

http://s568.photobucket.com/user/bgorin/media/B17IntercoolerIPC.png.html

Both have a similar offset, so I suppose one could theoretically use the oil-cooler as an intercooler