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Graham Boak

Relationship between P-11g and P-24

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Ok, so the computer graphic is just plain wrong.  But so are the cross-sections showing the original narrow fairing, which presumably the cg is based upon.  The difference in fin height is interesting, but doesn't explain any length difference.  Excuse me for having doubt over the credibility of some of these numbers.

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From the same book - there are different production variants of P24, all lenght diffferncesa are due to differeng engine/cowling layouts

pzl24_kagero_011.jpg

 

Here are drawings of fuselage construction of P 24

pzl24_kagero_020.jpg

and here just main part of P11c - please note that cockpit ara is in monocock for P24 and it frame in case of P 11 (front is the same or almost the same)

pzl24_kagero_019.jpg

But this figure is all wrong:

pzl24_kagero_021.jpg

The windows were not exactli flat, however not like here, bound in middle!

Like that (still from the same book!)

pzl24_kagero_006.jpg

or even better here

pzl24_kagero_007.jpg

On the photo of windscreen you can see that frame is not stright, is is smoothly bound in a concave way.

Please go throught all this review

https://www.modellingnews.gr/el/νέα-μοντελισμού/pzl-p24a-g-andrzej-glass-tassos-katsikas-3d-monograph-no66-κagero?fbclid=IwAR0pNuExxMPV9ur5IzeE9cMiIi9bL2Wi41XeUlMNuSx5bP0yxlnCEWIx3f8

This newer Kagero monography has bilingual text! So you have it in English. I hope you can read it despite not perfect quality of photos

Regards

J-W

 

 

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Posted (edited)

Gents,

Let me explain where the "45cm insert problem" lies. Book mentioned above is excellent and is also the best source about P.24 ever written. Without doubt Mr. Glass (author) is one of most important experts on the history of Polish aviation. Of course information included there is correct according to all current historical knowledge but - and - of course it does not mean it can't contain errors, especially in drawings.

Problem lays in your understanding of author words. To correctly understand this book, you have to know the genealogy of both projects: P.11 and P.24 (covered in the book btw). Both projects are based on P.7 fighter.
The information on fuselage extension by 45 cm refers to P.7 fuselage and not to P.11c.

Let's leave the wings and focus on the fuselages: the main culprit of the misconception I'm writing about is the too literal and sometimes overzealous interpretation of the book content.

Let's start with basic information: 'P.24 is an evolution of P.7'.
This is only the information corroborating the idea that the project was developed in parallel with P.11 (as better, export version).
This should be understood literally: P11 was created from P.7, and P.24 was also created from P.7 with both development projects following parallel paths. And remember, P.11 was first and P.24 used it's features already developed.

That is to say:
a) both P.11 and P.24 originate from the same line, namely: P.7.
b) they were developed in parallel and follow the same ideas: improved visibility for the pilot (5cm seat elevation), and stronger and heavier engine (45 cm extension of fuselage) in comparison with P.7.

It is necessary to follow the history of P11c first, and understand/observe what changes have been introduced on P11c in relation to P.7.
Fuselage has been extended, and the pilot seat has been raised.
Sounds familiar?

 

Please note that the P.24 had three prototypes, and trace them all, with emphasis on the one that has become a production model.

- The first P24/I was created from the one of P.7 (produced at the time) and it was necessary to change the geometry in the same way it has been done in the P.11c - lengthen the fuselage (45cm), give a higher pilot seat (5cm). The vertical stabilizer was also used as in P.11a.
Most people remember this entry and tend to think that this 45 cm applies to all P.24. This is a cardinal error, as this description refers only to the first and second (see below) prototype.
- The second one, P24/II, had a fuselage based on the one from P.7, similarly to the first one, but due to numerous changes (i.a. wings I am omitting here) it was named 'Super P.24'.

- In the autumn of 1935 the P.24 a third prototype was created.
At that time the factory was no longer producing P.7, but it was producing P.11c and this is why fuselage of P.11a/c* was used for the construction of the third prototype - which became the production model for P.24.

P.24 mid (under-wing) section was used as in the previous prototypes and external dimensions were the same as in P11c - both models were already extended in comparison to P.7.
In other words, there was no need to extend or raise the fuselage of P.11c, because it contained the same geometric changes as P.24, introduced in the parallel path of development. Of course, for P.24, the internal structure was changed to withstand greater forces, the engine bed was welded from pipes, and so on. And this plane, called Super P.24 bis, (with further modifications) became a model for serial machines.

Differences in length between all P.11c/f and the versions of P.24 result from the engines and their housings and propellers used, and not from the extension of the fuselage.
Please remember this checking models, books and writing anywhere about this 45cm...

 

*edits: to make it more clear I removed duplicates and changed term/name from P.11c to P.11a/c* in one place - which I mean that P11a mid part fuselage construction system was used together with P11c geometry and tail.
Difference between P11a and P11c fuselage construction generally lays in the cockpit part as P11a used semi-skinned construction and P11c used frame with removable paneling. Also, tail section was different between versions P11a and P11c.

 

Edited by HKR

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Thank you JWM and HKR, great info and explanation.

 

Regarding the Kagero books, is the Aviation Monograph special edition No.7 just a hardcover version of Monograph 66? If not, which one is better?

 

Cheers,

 

Vedran

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They are both softbacks. No. 7 was published in 2004 and came with a decal sheet. Later additions did not have the decal sheet. I think it would be difficult to find now. No 66 is an updated version with more information and illustrations, published in spring of this year.

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I'm sorry I don't have time to read carefully all posts in this thread but I clearly see that there is some confusion here.

For sure P.11c and P.24 fuselages were different, both externally and in internal construction. P.24, like P.7a and P.11a had longer semi-monocoque (stressed skin) section, spreading from the tail to the (approximately) control panel/windscreen area.  This can be clearly observed both on the photos and drawings (not on these Kagero book renders, which are wrong!). PZL P.7a, P.11a and P.24 have many horizontal lines of rivets on the fuselage sides under the cockpit and two diagonal lines of rivets in that area. These are rivets typical for stressed skin construction.

Opposite, PZL P.11c has stressed-skin fuselage section shorter, from the tail to the headrest area. This can be observed both on the fuselage sides (no lines of rivets under the cockpit) and on the internal structure (obvious frames inside the cockpit).

PZL P.11c internal framing attached to the semi-stressed section in four points:

spacer.png

 

PZL P.24 fuselage: longer stressed-skin section (also seen from inside, with seat attached - no heavy frames!!!), 45cm long additional framing (between undercarriage leg and stressed-skin section), "normal" framing with undercarriage legs attached (same as in P.7a and P.11a):
spacer.png

 

As you see - while it is not wrong to say that final version of P.24 was developed from P.11, it was for sure not developed from P.11c, but from P.11a (different fuselage!!!)

 

AZUR have cheated with its P.11c - took P.24 fuselage and changed only the wide "hump" behind the canopy with the narrower one but left the P.24 internal and external structure of the cockpit area and the front fuselage. It is wrong. Also the AZUR wingroots are wrong for the P.11c.

 

Speaking about Kobuz, again, I don't think the fuselage cames from the P.24 (especially in the prototype, which had serial number 8.129 of the production P.11c).

 

Machine guns synchroniser for three-bladed propeller - I have no doubts it existed in Britain for Gladiators, but was it available in Far-Eastern Poland landing ground in September 1939 when the unarmed Kobuz prototype was armed? Maybe yes (maybe it was installed already in factory, before the war), but maybe not?

Edited by GrzeM

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4 hours ago, GrzeM said:

As you see - while it is not wrong to say that final version of P.24 was developed from P.11, it was for sure not developed from P.11c, but from P.11a (different fuselage!!!)

Grzegorz,

It is generally accepted information P.24 used P11c fuselage rather than P11a which was an older solution with cockpit arrangement in lower position. However semi-skinned cockpit part system has been chosen for P24, it would be oversimplification to state whole P11a fuselage was taken. It is an mix of P11c fuselage geometry with cockpit arrangement (pilot seat in higher position) and it's (P11c) tail together with P11a cockpit skinning construction system.

Edited by HKR

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14 hours ago, GrzeM said:

PZL P.24 fuselage: longer stressed-skin section... 45cm long additional framing

 

Ah, perhaps this explains the confusion over "45 cm longer fuselage"- if the semi-monococque structure is 45 cm more of the fuselage?

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8 hours ago, gingerbob said:

 

Ah, perhaps this explains the confusion over "45 cm longer fuselage"- if the semi-monococque structure is 45 cm more of the fuselage?

It's quite complex thing and maybe in a hurry I was not precise enough: the additional 45cm is not semi-monocoque area, but traditional frame section inserted between the stressed-skin (semi monocoque) tail and classical frame of the front with undercarriage legs, wing strut roots and engine mount. It is visible on the photos above, but maybe not very clearly. I'll try to indicate with colours on the photo soon.

The stressed-skin fuselage section of P.24, P.11a and P.7a are more or less the same, excluding the fin and fairing behind the headrest/canopy.

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22 hours ago, HKR said:

Grzegorz,

It is generally accepted information P.24 used P11c fuselage rather than P11a which was an older solution with cockpit arrangement in lower position. However semi-skinned cockpit part system has been chosen for P24, it would be oversimplification to state whole P11a fuselage was taken. It is an mix of P11c fuselage geometry with cockpit arrangement (pilot seat in higher position) and it's (P11c) tail together with P11a cockpit skinning construction system.

Well, could you point to the source of that "generally accepted information"?

Most popular schemes (this one from Andrzej Glass and Co.classic PZL P.11 monography) show the other version:
spacer.png
I don't state that you are completely wrong, but what makes "P.11c fuselage" the "P.11c fuselage"? In the whole line of the PZL P. fighters the P.11c (and P.11f) was unique with only one feature: long frame (truss) construction in the area between headrest to the engine (as shown on the colour photo attached to my earlier post). The rest (P.6, P.7a, P.11a P.11b and all P.24) had the stressed-skin (semi monocoque) area from tail to the (approximately) control panel. So maybe outside look and geometry of the P.24 fuselage is really more similar to the P.11c, but really it is still the P.7a or P.11a fuselage lenghtened with 45cm truss insert between rear wingstruts and the control panel area - which makes it more similar to the P.11a fuselage in construction. I may be wrong, but I think that the P.11c engine was more lowered than the P.24 one.

Edited by GrzeM

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In which case it is wrong to state that the P-24 rear fuselage was longer than that of the P-11c, and Azur were quite correct.  I still believe that such an increase would be visible in photographs, but the comment about rivet patterns does cast some doubt.

 

Either way, there may well be no argument that the Kobuz prototype used a P-11c airframe, but that does leave some doubt about the status of any production version, and makes precious little difference to the modelling of either in 1/72 using existing models.  Given that the modeller requires a P-24 wing, and a fuselage with a full canopy and no guns, then the best one to use is that from a P-24.

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Comparison of the P.11c and P.24 fuselages:

 

P.24 (semi-monocoque are covered, classic frame/truss area uncovered). Cockpit area is semi-monocoque.The semi-monocoque part was almost identical in P.7a, P.11a and b, all P.24.

spacer.png

 

PZL P.11c in similar state (note that cockpit area is frame/truss construction, semi-monocoque starts behind pilot's seat).

spacer.png

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14 hours ago, GrzeM said:

Well, could you point to the source of that "generally accepted information"?

Most popular schemes (this one from Andrzej Glass and Co.classic PZL P.11 monography) show the other version:

Well, I'd say, to deny commonly accepted information, that you should prove it wrong?

But, of course, take my hand: it is good to start with reading books. It is not strange than most books about P.24 were written the same author, Mr. Glass - so if you take one, you have the same information included in the other ones.
You can choose what to read:
Andrzej Glass - Militaria no. 2 - PZL P.24
Andrzej Glass - Kagero no. 3007 - PZL P.24 A-G (it is the same as Monograph no.66)
Andrzej Glass - ZP Grupa - Polskie Konstrukcje Lotnicze no.1 - Samoloty myśliwskie PZL P.11, PZL P.24
Andrzej Glass - Stratus - Polskie Konstrukcje Lotnicze vol. III
Taking the last one, for example on the page 61, you would read (it is polish text, so let me translate):
"Since the PZL Aircraft Factory, after relocating in 1935 from the Mokotów airport to the Okęcie airport, no longer manufactured PZL P.7a aircraft, but a seriously improved aircraft PZL P.11c, it was decided to modify PZL P.24 so parts from P.11c could be used in PZL P.24 production. In autumn 1935 the construction of a prototype PZL P.24/III was started, which was to become a model for the serial version. From P.11 adopted wings, with a slightly longer span than P.7, as well as the rear fuselage and the tail."
Finally, you can take one more position:
Przemysław Skulski - ACE Publication - Seria Pod lupą no.14 - PZL P.24
which contain exactly the same information.

 

Regarding to scheme you show, I am not sure what you want to say. It is showing what I wrote earlier above: both P11 and P24 were developed paralely from P.7 construction. It does not show impact of them to each other. In the books I listed you can easily find that impact marked.

14 hours ago, GrzeM said:

I don't state that you are completely wrong, but what makes "P.11c fuselage" the "P.11c fuselage"?

As I already mentioned, at the time P.24/III raised, there were no other fuselages produced than P11c. So you're asking why to call P11c fuselage being in production, as P11c? Because they named it P11c, ... or maybe there were no other than P11c, who knows. Or maybe due to fact the last produced P11a was finished on summer 1934, and over one year later, when P24/III was born, P11a fuselages could not be found?
I can't judge.

 

Edited by HKR

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10 hours ago, HKR said:

As I already mentioned, at the time P.24/III raised, there were no other fuselages produced than P11c. So you're asking why to call P11c fuselage being in production, as P11c? Because they named it P11c, ... or maybe there were no other than P11c, who knows. Or maybe due to fact the last produced P11a was finished on summer 1934, and over one year later, when P24/III was born, P11a fuselages could not be found?

I can't judge.

 

I think it is some misunderstanding here. I have proved, also with the clear photographs, that even the most advanced production P.24 examples featured different fuselage construction than P.11c.

P.6, P.7, P.7a, P.11a, P.11b and all P.24 variants had long stressed skin (or semi-monocoque) fuselage section spreading from the tail to the windscreen (and including the whole cockpit area). This feature was also used in Romanian more advanced IAR 80/81 fighter, which was produced in Romania basing on the P.24 fuselage. See the photo: stressed skin fuselage ends just below the windscreen:

spacer.png

 

Opposite, the P.11c (and P.11f) had the stressed skin section limited to the part between the headrest and the tail (as I showed on the big photo in earlier post). That's it.

 

Of course the PZL.P24 third prototype and all the production P.24 examples shared many features of the P.11c, but these planes had not "p.11c fuselages" or "P.11a fuselages" but their own, new, P.24 fuselages, in some aspects similar to the P.11c, but in main construction feature (stressed-skin vs. frame/truss) more similar to the earlier P.7a and P.11a. That's the fact, not an opinion.

Edited by GrzeM

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P.24 fuselage from the Romanian spare parts catalogue:

spacer.png

 

 

PZL P.11c fuselage from the factory manual (short stressed skin part "3", long frame/truss part "1" and "2"):

spacer.png

 

PZL P.7a fuselage (long stressed-skin part, like in P.24). Note diagonal formers in the cockpit area, same as in the P.24.

spacer.png

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21 hours ago, GrzeM said:

I think it is some misunderstanding here.

Indeed. I am talking about completely different problem, and not strictly about fuselage construction.

Quote

I have proved, also with the clear photographs, that even the most advanced production P.24 examples featured different fuselage construction than P.11c.

Well, I took an impression the only you proved is fact you are not reading carefully.
I am talking about general length of both models P.11c and P.24 and "45cm extension" which does not apply to serial P.24 - basic fuselage except engine, was not longer than P11c. At this point all this explanation has no connection to the internal structure overall, and no connection to 45cm truss before cockpit.

My intention is to explain that change of the cockpit section structure has not affected the length, that's all.

There are no doubts about construction system used for the cockpit skinning in P.24. At this point I have no idea what do you want to say, or prove here.

You are just repeating me and stating you proved... the same already written:

On 07/10/2019 at 23:14, HKR said:

[...] fuselage of P.11a/c* was used for the construction of the third prototype - which became the production model for P.24. [...] which I mean that P11a mid part fuselage construction system was used together with P11c geometry and tail.

And yes, of course this means P.24 construction is specific only to this type, what I mention later:

On 12/10/2019 at 00:42, HKR said:

[...]However semi-skinned cockpit part system has been chosen for P24, it would be oversimplification to state whole P11a fuselage was taken. It is an mix of P11c fuselage geometry with cockpit arrangement (pilot seat in higher position) and it's (P11c) tail together with P11a cockpit skinning construction system.

 

Because I started to believe you tend  to think P.24 was build from the lego blocks and particular sections were taken from specific versions, I emphasize that above.

So let's say it again: of course P.24 fuselage was new and one of a kind. It used best solutions from the previous versions, i.e it was not pure 11c or 11a and a mix of them (as stated above in my previous post).

It still does not connect to the length.

Quote

Of course the PZL.P24 third prototype and all the production P.24 examples shared many features of the P.11c, but these planes had not "p.11c fuselages" or "P.11a fuselages" but their own, new, P.24 fuselages, in some aspects similar to the P.11c, but in main construction feature (stressed-skin vs. frame/truss) more similar to the earlier P.7a and P.11a. That's the fact, not an opinion.

Facts are not so simple as you describe, unfortunately. From this point of view, I'd say this above is an opinion, not a fact.

So, where is disconnection in opinion? Mainly where you state P.24 is closer to P7/11a and I state as all Polish historians, that it is closer to P11c.

 

I'll try to clear it up.

P11a used stressed skin in the cockpit section and in the fuselage section behind cockpit. It used specific-type tail, with specific horizontal and vertical stabilizers.

The support truss in P11a was used from the front of the cockpit to the main truss. For the purpose of discussion we can consider it as shorter section of the P11c truss. Of course chronologically it was designed first.

Cockpit arrangement in the cockpit section was used in a "low" position. It was standard construction inherited from P7 family.

 

P11c used truss in the cockpit section and stressed skin in the fuselage section behind cockpit. It also used specific-type tail, with specific horizontal and vertical stabilizers, different in comparison to P11a.

The truss in P11c extended from the cockpit forward, to the next (main) truss. In other words, we can consider it as an extended section of the P11a truss.

Cockpit arrangement in the cockpit section was used in a "high" position. It was new construction and yet another change in opposition to P11a.

Please remember it was not simple as it seems and definitely not just pilot seat installation 5cm higher. All arrangement has been changed as floor, control stick etc.

 

P24 used mix of the solutions: cockpit section with stressed skin as in P11a but with arrangement in high position as for P11c, before cockpit short truss connecting to the main one. Fuselage behind cockpit together with whole tail has been adopted from P11c, not from P11a. All this made it unique, however technically said, it used more from P11c than from previous prototypes (and P7/P11a).

 

At the end I'd only quote Mr. Glass:

"One can risk a claim that the serial P.24 took more from P.11c than the prototype P.24/II. From the prototype P.24/II took over mainly the front part of the fuselage, engine and cannon."

 

I really don't think there is any historical confusion about it, unless you don't read it carefully again.

Edited by HKR

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