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spitfire V C wing


beppe

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Re  spitfire C wing armament

 

 

I found a picture of  spitfire Vc JL 316, it looks as if she had only one gun and no stub for the second one.

Cpuld the wing be reverted to "B" configuration.

 

 

Cheers,

Joseph

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4 minutes ago, beppe said:

Cpuld the wing be reverted to "B" configuration.

 

no.  A wing change is possible, but unlikely.

 but the B vs C wing are very different.what could be done is removal of the the mounting stub, and the hole plated over.

 

see here

http://spitfiresite.com/2010/04/concise-guide-to-spitfire-wing-types.html

note they have a different UC geometry too

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No, there were too many internal differences (and some external).  It is an example from the (short on Spitfires) production run of the fitting without the second opening for armament.  This is much more common on Seafires.  It was a feature of the well-known civil Spitfire "G-AxJV"  (x because I don't recall the full registration.)

 

PS (Troy sneaked in):  At the height of the siege in Malta there were some exchange of wings in order to boost the number of serviceable aircraft, but I've not seen any listing of examples.  So theoretically it could have happened in Italy later too, but it seems less likely because the MUs would not be under the same pressures of time and need.

 

 

Edited by Graham Boak
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The lack of the outer stub on some Spit Vc means that some more care is needed to identify the subvariant if the code or the upper or lower wing surfaces are not visible. Best way to check is to look at the shape of the cannon barrel fairing: the Vb and Vc fairings were different, with the former showing an almost constant change in section from the leading edge and a good length of the barrel exposed while the latter has parallel sides for around half of the fairing length, followed by a change in section and a small part of the barrel exposed. Checking a couple of pictures will show what I mean much better than I can explain.

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1 hour ago, 304th BRAT said:

The removal of the stub for the second cannon was also a mod on some Spitfire 9's

 

 I knew that I should have said that Juliet Victor was (and in its current incarnation still is) a Mk.IX.  I'd just add that this was a mod on the production line not a change to existing aircraft in-service.  There were two different parts for the section of leading edge that included the exit for the cannon: one with two exits and one with only the one.  The intention was to standardise on the latter but plans were changed to accomodate the E wing armament of a 0.5 Browning inboard and a 20mm Hispano outboard, so only a small number of Mk.IXs were built with the single exit.  I must admit that I wasn't aware that any Mk.VC had been built with these, but maybe I just forgot.

 

Filing off the "chimney" from an existing wing in wartime - you'd have to have committed some heinous crime to be given that task.  I really don't see any point in bothering.  You'd be better employed polishing the beast.  However it isn't a particularly difficult task to swap such pieces is you really want to - I believe such has happened during the postwar life of 'JV in private hands.

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Sorry Graham, but I'm not so sure about that- the cannon port plate (don't know Supermarine's name for it) is under the leading edge skin on the 'c' wing, so changing it would be at least as major a job as filing off the unwanted chimney.  I don't know what the mod process was, but I don't fancy the job either!

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Fine by me Bob, that shows that changing it in service is even less likely.  

 

For some idea of how many spare wings there were likely to be around (so why bother changing a C to a B?) see the following thread from Flypast's Historic site.  Yes it is about Halifaxes but look at post 12, Spitfires at 156 MU.

https://forum.keypublishing.com/showthread.php?144886-So-They-Converted-A-Halifax-To-Carry-Spit-Fuselages

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Filing off the "chimney" from an existing wing in wartime - you'd have to have committed some heinous crime to be given that task.  I really don't see any point in bothering.  You'd be better employed polishing the beast.

Graham Boak

 

Sorry Graham, but I'm not so sure about that- the cannon port plate (don't know Supermarine's name for it) is under the leading edge skin on the 'c' wing, so changing it would be at least as major a job as filing off the unwanted chimney.  I don't know what the mod process was, but I don't fancy the job either!

Gingerbob

 

Fine by me Bob, that shows that changing it in service is even less likely. 

Graham Boak

 

 

 

Hi Graham and Bob,

Removing the outer cannon 'Chimney' was unlikely, and apparently a hell of a lot of work, but it was done.

 

I believe that in the UK, "Spitfire Mod 955" covered the "flushing off No.2 cannon projection". I have no info as to whether this work was ever officially done in the UK or not, but it appears that a few MK.IX A/C were modified, when and where I know not. (e.g. MH324, Mk. IX of No. 451 Sqn).

 

However, the mod found its way to Australia where it was incorporated in the RAAF's "Spitfire Order No.3", " Flushing off of No.2 cannon projection and fitment of single cannon blister", of late 1943. This purpose of the modification was to reduce aerodynamic drag. These mods were done on a small number of Spitfire VCs.  There is a well known, in-flight, shot of A58-175, (JG796), UP-Z, of No. 79 Squadron, after it had received the mod. (This shot has often been misidentified as a Mk VB).

 

The RAAF quickly came to the same conclusion that you have, i.e. it was a waste of time and resources. In March 1944, the RAAF Technical Section stated, "It has been found that the first part of the modification absorbs more man hours than anticipated and unduly delays erection of aircraft. The finished result is, in appearance, no better than the original streamlined cannon projection covering, and could safely be assumed not to warrant introduction for the labour involved in fitment".

 

The next month, a revised Spitfire Order No.3 was issued. This called only "for the replacement of the double cannon blister panels with the single cannon blister panel of reduced aerodynamic drag in order to improve maximum performance of the aircraft". The mod was only to be done to aircraft that had not received Air Ministry Modification No.782 before delivery to Australia. The new gun doors were manufactured in Australia. Units erecting Spitfire VIII A/C were advised not to remove the No. 2 cannon projections, and the section relating to the single cannon blister did not apply as all MK. VIII A/C were already so fitted.

 

As to the savings that might be gained by modifying the aircraft, the RAAF issued the following estimates.

  • 7 mph gain with multi ejector exhausts in lieu of fish tail triple ejector exhausts.
  • 3 mph gain with new type streamline mirror.
  • 5-6 mph gain with mirror removed, or mounted internally.
  • 2-4 mph gain with removal of outer cannon projection and fitment of single cannon cannon blister panels.
  • 8 mph by smoothing leading edge of wing by stopping, rubbing down, re-painting, and polishing.
  • 3 mph by polishing  and waxing rest of the aircraft.

So, as graham and Bob concluded, the removal of the outer cannon projection was an utter waste of time and resources. However, there was an Air Min Spitfire Mod covering the work, and someone, not clued up on aerodynamics, may have thought that it was worth the effort, particularly if he could order someone else to have it done to his A/C.

 

Peter

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Thanks Peter, especially for the table of benefits.  I was employed for some years doing, amongst other things, just that kind of excrescence drag analysis.  I was amused at the prime reference and guide being a postwar US book written by an ex-Messerschmitt man, with many of the diagrams showing Bf109s.  However, the air is the same for us all.

 

Whilst agreeing with the general level of the values, I would not expect any one of them to be actually noticed by a combat pilot under most conditions, and certainly not expect them to add up.  That would give some 30 mph benefit, which really would be noticed and sufficient to prioritise a fleet-wide programme of updates.   Now if I was responsible for a Mk.V squadron tasked with chasing hit and run Fw190s, then I'd start banging desks to get them all....

 

I also remain amused when reading about  testing such mods by back to back flights.  The results were adjusted back to standard conditions, but even so I think that nowadays most of these small differences would be lost in natural variation of the aircraft, engine and conditions.

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Thanks Peter, that gives me a little more information than I'd had before, and nicely correlates with my understanding of the situation.

 

The IXs that I've noticed with the mod- and I hasten to say that it has not been a very energetic search- are quite tight in the MA/MH serial range (if I remember those prefixes right), which makes me think that Castle Brom might have introduced the mod in production for a short time.  It is also possible, though, that for a short time it was performed after production, perhaps while at a Maintenance Unit.  (And now I realize I didn't check for a trend of MU, which I can do.)  While I've found documentation of the idea, I have not found documentation of its implementation.  (Except to add that the mod was suspended because there was another idea afoot to put .5s in, which of course ended up as the 'e' wing, and needed the second hole.)

 

I confess I've assumed that Mk.Vs were done in service, and therefore "randomly", and haven't paid much attention to them.  My casual impression is that most such aircraft are to be found in the Med, but that's where most Vs were by then anyway. 

 

I'll fire up the Spitfire-o-Matic and report back on the IXs...

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I'm back.  Yes, MA/MH, and with the addition of the one Peter mentioned, I'm up to only 9 IXs that I've gathered that are missing the second stub.  Allowing for the gaps in individual records, these were all built (completed) from very late June through July '43 (at which time CB was just getting rolling on IXs and easing out Vcs).  There's no obvious trend of MU, BUT 5 of the 9 went from MU to 405 ARF/Heston Aircraft in August, and a couple more have holes before issue to a squadron.  Heston strikes me as the kind of place that might do that sort of work...

 

And I remembered to look up the mod.  Not 955, that's for a whip aerial.  Mod 820: To Remove the Outboard Cannon Front Mounting Casting.  Applicable to V, IX, XII [though was any XII so modified?]  First discussed in Dec '42 (by Local Technical Committee), and again in (if I read it right) spring '43.  Corresponding Seafire Mod 131 was listed as class 4B, the Spit mod class 3B, though there's another code that I can't make out first.

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18 hours ago, Graham Boak said:

Thanks Peter, especially for the table of benefits.  I was employed for some years doing, amongst other things, just that kind of excrescence drag analysis.  I was amused at the prime reference and guide being a postwar US book written by an ex-Messerschmitt man, with many of the diagrams showing Bf109s.  However, the air is the same for us all.

 

Whilst agreeing with the general level of the values, I would not expect any one of them to be actually noticed by a combat pilot under most conditions, and certainly not expect them to add up.  That would give some 30 mph benefit, which really would be noticed and sufficient to prioritise a fleet-wide programme of updates.   Now if I was responsible for a Mk.V squadron tasked with chasing hit and run Fw190s, then I'd start banging desks to get them all....

 

I also remain amused when reading about  testing such mods by back to back flights.  The results were adjusted back to standard conditions, but even so I think that nowadays most of these small differences would be lost in natural variation of the aircraft, engine and conditions.

Hi Graham,

 

I had a bit of a chuckle reading about your references. It was amazing how often a search for data turned up pre-war references. And in aerodynamics, Hoerner's Fluid Dynamics Drag, (and Lift), were primary sources, as were the Royal Aero Soc Data Sheets.

 

I believe those estimates the RAAF quoted came from Supermarine, but that is all they were, estimates. I don't believe any wind tunnel testing was done and, as you indicated, the results from flight tests involving such small changes are questionable. There were many myths and opinions floating around at that time. These resulted in the RAAF also, on two separate occasions, wasting a fair amount of time trying to replace the tropical filter on the MK.VC with something resembling the 'temperate cowling', but that's another story.

 

Peter

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16 hours ago, gingerbob said:

I'm back.  Yes, MA/MH, and with the addition of the one Peter mentioned, I'm up to only 9 IXs that I've gathered that are missing the second stub.  Allowing for the gaps in individual records, these were all built (completed) from very late June through July '43 (at which time CB was just getting rolling on IXs and easing out Vcs).  There's no obvious trend of MU, BUT 5 of the 9 went from MU to 405 ARF/Heston Aircraft in August, and a couple more have holes before issue to a squadron.  Heston strikes me as the kind of place that might do that sort of work...

).right) spring '43.  Corresponding Seafire Mod 131 was listed as class 4B, the Spit mod class 3B, though there's another code that I can't make out first.

 

Bob,

I'm in agreement with you that the modded Mk.IXs appear to have come from very early CB production. The jury is still out on where the mod was done, but I tend to favour the idea that it was done by CB. Don't know why I quoted that mod. It's what I had in my notes, but when I check I see you are perfectly correct, (as always 😊 )

Peter

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