Why was the F4u faster than the F6f?

[gwshaw]

Originally posted by stantond
Thanks Greg, that's what I though.  

But, where is the ram air taken in for the F4U-1 models?  They have no chin scoop like the -4.  I don't think the oil coolers in the wing roots would work very well for carburettor air.  Would part of the engine cooling air be used?  If that is the case I see no reason why the F6F or P47 could not have done the same.  


Regards,

Malta

There are splitters in the wing inlets; oil cooling, carb air and intercoolers. The F4U-4 and -5 moved the carb inlets to the chin and cheeks IIRC. I have diagrams of them all, but in storage somewhere until november or so.

Greg Shaw

[joeblogs]

This is the second time I've seen you take swipes at engine experts based on little more than a hand waive (the first was Wilkinson).

White's new book is based on heaps of P&W internal reports. His data on engine models in the earleir books were generally drwan from primary, not secondary materials.

Now if you want to talk about his description of planes, that's another thing. But when it comes to engines, this guy is one of the best.

Originally posted by pasoleati
White´s second book is much better than his first one but not on par with Whitney´s effort. One of White´s problems is his use of sources. E.g. his descriptions of individual aircraft type development is often taken from very dubious sources like Squadron/Signal in actions. Another problem is that he gives the power rating, but the tables don´t have any boost info.

[joeblogs]

F4u

What was the PN number on the fuel for the rating?

-Blogs

Originally posted by F4UDOA
JoeB/GWShaw,

I haven't been on the boards in a while so this conversation is refreshing.

Here is my source. It is the 15 October 1945 POH for the F4U-1D. It is revised with updates until 1 December 1952 and it is very thorough with a full performance diagrams. It shows the R2800B block producing 2300HP at sealevel at 57.5"MAP, 2100HP at 58.5"MAP at 14500FT and 1925HP at 19,000FT all at WEP.

Both lower ratings are at 2700RPM and the High blower is at 2550RPM.

Also there is a column for with RAM and NO RAM that shows no difference for HP rating only in critical altitude.

I would show you the scan but my PC has been down for months and all my scans are trapped in a lifeless hunk of junk. If I can retrieve the doc I will post it ASAP.

[F4UDOA]

JoeB,

100/130

I promise I will post this when I can.

[pasoleati]

Originally posted by joeblogs
This is the second time I've seen you take swipes at engine experts based on little more than a hand waive (the first was Wilkinson).

White's new book is based on heaps of P&W internal reports. His data on engine models in the earleir books were generally drwan from primary, not secondary materials.

Now if you want to talk about his description of planes, that's another thing. But when it comes to engines, this guy is one of the best.

Wilkinson is pure unadulterated ****, nothing more.

As for White, do check the section giving basic info on each engine model and tell me if you can find e.g. the well known R-2800-57 WER of 2800 hp. It is mentioned in another part of the book, but no WER data is found in the model data section.

True, White privileged access to P&W archives. He told of this long before the book was published.

Whitney´s major problem is that his knowledge of non-American engines (except the Merlin) is not on par with the knowledge on US engines. This makes many of his comparisons quite dubious.

And he also tends to look everything through Bushian lenses. Trust me, I know this.

[HoHun]

Hi Joe,

>We are all familiar with the other arguments that explain the disparity in Vmax between these two planes. White's explanation suggests the disparity should be greater at lower altitudes. That should be pretty easy to check, but I am afraid I can't do it right now.

Well, I guess I'm in direct opposition ot White then :-) In my opinion, the disparity should be decreased at lower altitudes because the F6F has the benefit of not being hindered by ram.

There's an engine power chart for the BMW801D showing both rammed and static power that illustrates just that point.

The external air intakes for the Fw 190A that were designed to reap the benefit of ram effect also worked in the way I described: They improved high-altitude performance while deteriorating low-altitude performance.

Regards,

Henning (HoHun)

[HoHun]

Hi Joe,

>I added a note to your thread on turbosupercharging on the P47.

Ah, thanks, I'll have to check that one out! :-)

Regards,

Henning (HoHun)

[gripen]

Hm... Depending on MAP, the engine stage of the R-2800s used in the F4U and F6F had very low FTH. If we assume high MAP, the difference between the FTH of the engine stage and the optimal height to activate lower gear of the auxilary stage is several hunred meters. At this altitude range the plane which utilize RAM has an advantage. The first FTH is a bit higher and the optimal altitude to activate the auxilary stage is higher as well.

Anyway, the speed curves in the F4UDOA's pdfs seem to support this, there is a difference between the activate height of the auxilary stage of the F4U and F6F (roughly a bit less than 1000m). Infact, some curves seem to  indicate that the sea level is "above" the first FTH for both planes ie the F4U has an advantage from sealevel until it reaches the optimal height to activate the auxilary stage.

gripen

[pasoleati]

Originally posted by pasoleati
Wilkinson is pure unadulterated ****, nothing more.

As for White, do check the section giving basic info on each engine model and tell me if you can find e.g. the well known R-2800-57 WER of 2800 hp. It is mentioned in another part of the book, but no WER data is found in the model data section.

True, White privileged access to P&W archives. He told of this long before the book was published.

Whitney´s major problem is that his knowledge of non-American engines (except the Merlin) is not on par with the knowledge on US engines. This makes many of his comparisons quite dubious.

And he also tends to look everything through Bushian lenses. Trust me, I know this.

One correction: That major problem paragraph refers to White, not Whitney. And the Bushian eyes refers also to White.

[gripen]

Well, while everyone has a right to have an opinion about White, it's quite clear that White is right in this case; the F4U had an advantage over the F6F at low altitude due to use of RAM air for engine stage charger (at high MAP). It also seems that there were also differences when using the auxilary stage; the F6F has a bit higher FTH than the F4U despite it's claimed to be a bit slower (according to this) ie it uses the RAM air more efficient.

gripen

[joeblogs]

See what I mean?

Wilkinson can be criticized because he only had access to the data in real time, and that meant poorer data for some countries. But that's not your tack.

White knows his US & UK engines and he really doesn't write about anything else.

Why don't you get his book and look up the -57 himself.

-Blogs

[joeblogs]

That would make sense when you have to throttle back to avoid over boosting. These things sound consistent to me.

If you had a continuously variable speed supercharger (as in the 109) you would not have that trade off.

-Blogs

Originally posted by HoHun
Hi Joe,

>We are all familiar with the other arguments that explain the disparity in Vmax between these two planes. White's explanation suggests the disparity should be greater at lower altitudes. That should be pretty easy to check, but I am afraid I can't do it right now.

Well, I guess I'm in direct opposition ot White then :-) In my opinion, the disparity should be decreased at lower altitudes because the F6F has the benefit of not being hindered by ram.

There's an engine power chart for the BMW801D showing both rammed and static power that illustrates just that point.

The external air intakes for the Fw 190A that were designed to reap the benefit of ram effect also worked in the way I described: They improved high-altitude performance while deteriorating low-altitude performance.

Regards,

Henning (HoHun)

[TequilaChaser]

hmm,
sometime ago, ( over 8 years or so), there was a report I read where Grumman and Vought did some after war experiments on the F6f-3/-5 and the F4U-1/-1D

at different alts both planes flew side by side full throttle and was with in a couple of KIAS/TAS of each other. no big significant differences from each other. In the report the main factor in why one plane ( the F4U) showed higher speeds etc was because of the location of the pitot tube.........when the pitot tube was located in nearly the same place on each aircraft, the speeds were near identical, but when placed in there orginal locations the F4U always showed superior speed over the Hellcat......

might be something, someone would want to research........maybe someone recalls this from long ago......( best I recall I found this article/report in the historical Grumman data back around 96/97 when I was a Hellcat F6f-3 fanatic )

If I find the photo copy of the report I will send to someone to post here.....but this is all from my memory so don't hold your breathe


TC

[pasoleati]

Originally posted by joeblogs
That would make sense when you have to throttle back to avoid over boosting. These things sound consistent to me.

If you had a continuously variable speed supercharger (as in the 109) you would not have that trade off.

-Blogs

In fact the DB 605 blower drive isn´t completely infinite. In the 605A at TO&WER setting the boost control thottle restricts the boost to 1.42 ata up to about 2100 m altitude. The drive has two oil pumps (two gear pumps in one casing), one of which supplies the clutch and another supplies all of its flow to cool the clutch up to that altitude. From 2100m to 5700 m (at WER) the latter pump feeds increasingly the clutch until at 5700 m both pumps supply all oil to the clutch.

Source: Finnish edition of the DB 605A-C manual.

[pasoleati]

Originally posted by joeblogs
See what I mean?

Wilkinson can be criticized because he only had access to the data in real time, and that meant poorer data for some countries. But that's not your tack.

White knows his US & UK engines and he really doesn't write about anything else.

Why don't you get his book and look up the -57 himself.

-Blogs

Maybe, but the Jane´s AWA of the same period has much more reliable data and e.g. the sections on the Jumo 211J and DB 605A are in perfect agreement with the respective engine manuals while Wilkinson is pure speculation.

And I do have White´s latter book.