Spitfire MK Ib

[dfqweofekwpeweiop4]

I was looking at the KP Spitfire Mk Ib and Mk IIb in my stash and no surprise, they are the same kit but with a different prop/spinner and Coffman starter bulge on the Mk IIb. My question is not relating to that but to the wing and one of the marking options. One of the options is for George Unwin's aircraft of no 19 sqd in August 1940. I read that the Mk Ib was initially armed only with a pair of 20mm cannons. So my question is that, did the early batch retain the .303 mg gun positions and associated panels etc despite not having the actual guns in the wings? It's not critical as I fancy doing one of the other options as well but it will help me decide which one to do.

 

thanks

Mike

[Jure Miljevic]

Hello, Mike

I have been asking myself exactly the same question for the last few months as I am quite fond of building a model of Unwin's Ib. The only photo of these early Spitfires Ib I found is the prototype of the version L1007. The photo shows machine gun openings blanked with metal ovals and there is no openings visible below wings. This, however, was a standard Mk.I (not marked as Ia until first Ib arrived) and I am inclining towards possibility that Ib (pre-)series dispensed with machine guns and ammo boxes panels altogether and that wings outboard of cannons had panels similar to those of later PR versions. Unfortunately, I have no proof for this assumption and would be very happy if some other member can support this. Cheers

Jure

[The wooksta V2.0]

More likely the ejection chutes were patched and doped over, much like on some of the PR aircraft.

[Greenshirt]

I recently completed this kit as Unwin's Spitfire. According to StH it was called "cannon armed Spitfire" as Mk Ib was not yet a designation. And later the b wing configuration included the .303s which this one did not. 

 

Take care of the underwing bulge configuration; it's different than the standard b wing, using a smaller bulge available on the sprues. The instructions are a bit vague. You also need to fill the vent next to the wheel well as that was a later b wing fix. 

 

Full build summary here. 

 

NB: just realized I didn't address the bulge in my blog. 

[Jure Miljevic]

Hi, The Wooksta!

I respectfully disagree with you. Reinstalling machine guns, ammo boxes and removing patches from wing leading edges and ejection chutes was well within squadron armourers' abilities and would at worst take few man-hours per aircraft. Yet No 19 Sqn. dispensed with cannon-armed Spitfires on 3rd September and had not been issued with Spitfires Ib (at least some, if not all of them were the same aircraft that served with the unit during the summer) until late November. I imagine two months long factory level modification must have included more than just a basic maintenance. Cheers

Jure

[Graham Boak]

The early cannon-armed Spitfire Mk.Is had new-build dedicated cannon-only wings, which would not make installing machine guns as easy a matter as they would be reinstalling into a wing from which the mgs simply been omitted.  Replacement wings were built: it is not stated anywhere I've seen whether the early wings were scrapped (or at least reduced to useful parts) or rebuilt as standard b wings.  It would take some time to design, tool and produce the appropriate modifications, whether new or rework.

[gingerbob]

Oh dear, looks like I need to revisit my files...

[dfqweofekwpeweiop4]

11 hours ago, Greenshirt said:

I recently completed this kit as Unwin's Spitfire. According to StH it was called "cannon armed Spitfire" as Mk Ib was not yet a designation. And later the b wing configuration included the .303s which this one did not. 

 

Take care of the underwing bulge configuration; it's different than the standard b wing, using a smaller bulge available on the sprues. The instructions are a bit vague. You also need to fill the vent next to the wheel well as that was a later b wing fix. 

 

Full build summary here. 

 

NB: just realized I didn't address the bulge in my blog. 

 

I think you built the old AZ kit not the one I'm talking about. KP did an all new tool Mk Ib/IIb and Vb in 2015/16, which is what I have, there are no Mk VI bits on it and you get both types of oil cooler with the kit. Plus the moulding is much sharper and cleaner, in fact, pretty much like a mainstream kit but without the locating holes, usually found on mainstream kits.

 

2 hours ago, Graham Boak said:

The early cannon-armed Spitfire Mk.Is had new-build dedicated cannon-only wings, which would not make installing machine guns as easy a matter as they would be reinstalling into a wing from which the mgs simply been omitted.  Replacement wings were built: it is not stated anywhere I've seen whether the early wings were scrapped (or at least reduced to useful parts) or rebuilt as standard b wings.  It would take some time to design, tool and produce the appropriate modifications, whether new or rework.

 

That's what I was suspecting would be the case but hoped my suspicions were wrong. However, I quite like the other markings in the kit, so it's not a problem.

 

thanks

Mike

[dfqweofekwpeweiop4]

Ok, so on to the next questions.

 

The alternative markings are for no 92 sqd, Dec 1940, which is the standard Dark Green/Earth over Sky camouflage except with one of the wing's underside is Black. First thing is that I've read that the batch of aircraft (being a later batch) was built with 2 cannons and 4 mg's, just like the B wing we're all familiar with, so first question, was this pretty much a standard B wing found on the IIb and Vb? As stated the kit is a Mk Vb with bits for the IIb and Ib on the sprues.

 

Assuming you can build the 92 sqd Mk Ib oob without filling panels and modifying etc, there are other issues I'm thinking of. The first is that the ailerons are modelled as metal ailerons (told you it's really a Mk Vb kit!), which I thought were introduced on the Mk V, so would the later batch of Mk Ib and the IIb's have had fabric covered ailerons or metal ones? Next up is to do with the wheel well colours. I know that Spitfires could have the wheel wells painted the underside colour, aluminium or interior green. I usually go for the underside colour to keep things easy (and more fun for me) but when they painted the wing undersides Black and White, what colour did they use then? I have other Spitfires I'm thinking of doing with Black + White wing undersides as well. Would I be correct in assuming the Mk Ib had the de Havilland prop/spinner and the Mk IIb the Rotol unit?

 

thanks

Mike

[Greenshirt]

My notes from StH show only 30 of the cannon only wing sets being made, during Summer 1940 and deployed during BoB. By December most (likely all) were recalled and modified to b configuration standard. The aircraft may or may not have been modified, as some serials seem to have reverted to a configuration, while others were upgraded to Va and/or Vb standard. I suspect this is because they cycled into the modification process anyway, and airframes were used as they were queued. 

 

Yes, it was the AZ, my apologies. I don't have the later KP except in the Vb boxing. 

[Graham Boak]

I believe that after the initial batch of cannon-only wings there was only one standard of b wing, as far as the armament was concerned.  The wheel wells will not have been repainted when the underside of the wings were.

 

The Mk.I will usually have had the DH prop, the Mk.II the Rotol, but exceptions existed.

[gingerbob]

I'm digging into the files now, but haven't yet found some of the specific comments I am remembering.  So here's an interim take on this:

 

30 "cannon" Mk.Is were ordered, not counting one or two "Trial Installations" prior.  These were adapted to carry 2 20mm as the only armament, but that is not to say that the structure was altered [except, obviously, where the cannon went].  Mounts and plumbing for the outer .303 positions were left out.  When asked about the prospects, Supermarine indicated that the last couple of this batch of 30 could be delivered with the 4 .303s additional to the Hispanos.  [Edit: as it turns out, 7 were equipped with the mixed armament at time of delivery, and the rest were modified to that standard.  Though now that I think about it, with a few lost on ops, I wonder if ALL 30 were actually brought to this standard?]

 

Some "mixed" armament examples went to 19 Squadron (from 11 Aug- see comment from ORB in later post) but in early September the cannon Mk.Is were withdrawn and sent to an OTU [at least some were], due to the unreliability of the armament at that time.  A few had already been lost, and a few more damaged in the ensuing months, but (and again, going on memory) most were re-fitted with the .303s- the need to install deleted plumbing, etc made it more complicated than "tear off the dope patches and put some guns in there!"

 

Meanwhile tinkering continued to try to get the cannon to function, HOWEVER the plan for future production was upright-mounted Hispano with belt feed, not more of the drum-fed variety.  At some point an order for an additional 100 sets of "B wings" (my term for simplicity) was placed, but it was kept on hold for a while.  Thus, there was NO other manufacture of cannon wings until the decision was made to go for the Merlin 45 in the "Mk.I airframe", at which time the 100 wing order was applied toward that (with, initially, a projected delivery rate of 20 per month).

 

The available "cannon Is" became the first to receive Merlin 45s (aside from Trial Installation), and therefore became the first Mk.Vs.  It does appear that some went to 92 Squadron while still Mk.Is, but this is a bit confusing from what records I have available.  I surmise that they were to try out the improved installation (and they WERE deemed more acceptably reliable, though problems persisted for some time) and/or to help 92 prepare for the "Vb" that they were really intended to be equipped with.

 

Incidentally, virtually all of the photos I've seen of Mk.IIbs have DH props, not Rotols, despite the usual association that Graham mentioned.

 

bob

Edited February 18, 2017 by gingerbob

[gingerbob]

This is worth a careful reading:

 

 

possibly larger version: http://s620.photobucket.com/user/gingerbob/media/PICT0018_zpsaagwwx1k.jpg.html

[dfqweofekwpeweiop4]

What about the metal ailerons on the kit?

 

thanks

Mike

[gingerbob]

Metal ailerons were not even tried (and found to be the solution) until November '40.  In early '41 there was a retro-fit programme going, with the usual frustrations about the pace.  Priority would have gone (in theory) to the Mk.V (retro and, for a time, meeting production?) and I really don't know how widespread metal ailerons were on any Mk.I/IIs.  Certainly the cannon Mk.Is would not have had them.  [Note: I try to avoid referring to "Mk.Ib" because the Mk.I was specifically left out when that suffix was decreed- by then they'd either become Mk.Vs or been written off/unairworthy.  I'm not going to hold it against anyone else, just a personal quirk.]

[dfqweofekwpeweiop4]

I'm just referring to it as a Mk Ib to differentiate it from the others and because it's easier than saying 'the Mk I with cannons' all the time. So, for an accurate Mk Ib, the metal ailerons are most likely incorrect for the aircraft in 1940? The Mk IIb might be Ok, as the earliest option is for an aircraft in June/July 1941, just before the Dark Green/Ocean Grey camouflage became the standard camouflage.

 

This is a bit of an issue as the ailerons are moulded on double thickness to the upper wing and are not separate parts, so cutting them off and putting new ones on is not something I was really wanting to do. I suppose I could just make it into a Mk Vb, seeing as that's what the kit really is and I've got plenty of aftermarket decals.

 

thanks

Mike

[gingerbob]

I don't work in 72nd normally, but my impression from past discussion is that it wouldn't be hard to "convert" the ailerons in place.  I guess it depends on your level of craftsmanship (mine highly in doubt!) and/or your degree of fastidiousness.  What I've got in mind is (perhaps) sanding smooth, a coat of paint where you want "rib tapes", then a coat of paint over all.  [EDIT: Within the last few weeks I saw a discussion about fabric-covered Spitfire ailerons, and what the tapes looked like, etc, but I don't remember where- perhaps here on BM, or FlyPast, or LargeScalePlanes, or...]

 

No worries about "Ib", just wanted to explain why I kept saying "cannon I".  And I'd be very confident that the ailerons were fabric-covered until they became Vs, at the very least.  Note also that they did not immediately receive the larger oil cooler when converted to V.

 

As for IIb ailerons, I'm hoping somebody will pop by that has made a study of that- I'm afraid I haven't found enough information to have confidence.  I wouldn't be surprised if the answer was "some"!

 

EDIT: I just re-discovered this fairly short prior thread, which has a list of, umm, "Spitfire Mark Is that have had Hispano 20mm cannon fitted to modified wings", and some other interesting (to me, anyway) discussion.

Edited February 14, 2017 by gingerbob

[gingerbob]

While killing a little time I dug up my pages of 19 Squadron's ORB, and I'll quote a few bits:

 

7/7/40 Duxford - Constant speed airscrews being fitted to all the machine-gun Spitfires in turn.  All the cannon Spitfires have them already on arrival. 

 

11/8/40 - New Spitfire equipped with 2 cannon and 4 Browning guns delivered today.  Is slightly overweight but in the general opinion is a step in the right direction.  Possibly another step in the right direction would be the re-equipping with the old eight-gun machines.  [This must have been X4231.]

 

(note: I didn't see any mention of Unwin in the ORB on quick read-through, though I don't think I copied the pages that list the details of each flight.)

 

4/9/40 (Fowlmere) - First day with 8-gun machines, and what wrecks.  At least the guns will fire.

 

Sadly, S/Ldr Pinkham was shot down and killed the next day, in P9422 (a regular Mk.I)

 

(I'll be back.)

Edited February 18, 2017 by gingerbob

[Jure Miljevic]

Hello, Bob

Thank you for information and the link you posted. I must admit I am still far from understanding situation regarding early cannon-armed Spitfires but at least now I am, as one of this forum's members wrote once, confused on higher level.

Another interesting question (for me at least): was in 1940 and early 1941 a constant speed unit associated with Rotol propeller and its somewhat blunt spinner only? If that was not the case than originally delivered cannon-armed Spitfires came with Rotols and than, while being converted to Ib and Vb standard, at least some of them (like R6908 and R6923) apparently received old fine and coarse pitch only De Havillands. Cheers

Jure

Edited February 16, 2017 by Jure Miljevic
incorrectly stated year 1940 changed to 1941

[Graham Boak]

There was a rapid campaign in June 1940 to change all variable pitch (fine/coarse only) DH props to a constant speed version.  This had been planned in 1939 but DH were quibbling over pay so it didn't go ahead.  By the time the cannons appeared, all front-line DH props would have been constant speed.  There is no external difference between the spinners for the cs and vp DH props.

[gingerbob]

"confused on higher level" - yes, that's right!

 

I'm not sure that I am answering the question you're meaning to ask, but after the 2-blade fixed-pitch prop, standard for the Spitfire Mk.I was the De Havilland metal prop, which, as you say, initially had a two-position operation.

 

The Rotol was intended to be constant speed from the beginning (I assume) and was planned for the Mk.II (which began to come out of the factory in June/July '40).  In the winter of '39/40 a limited batch of Mk.Is was fitted with Rotols in order to try out the advantages of constant-speed.  These are mostly associated with 54 Squadron, and they were unequivocally in favor, especially in "competition" with the 109Es that they met over France.  I don't believe that any other Mk.Is were equipped with Rotols, aside from TIs and perhaps some PR examples.

 

A "rush job" to convert Mk.Is to constant-speed operation was done starting in June (?) '40.  This essentially involved the addition of a prop governor, which the Merlin III had an accessory drive for already.  It would have also required the addition or modification of some controls.  Presumably Spitfires began to be delivered from the factory so-equipped at about the same time, and I assume that the cannon ones were an early example of this.

 

EDIT: Graham snuck in while I was thinking.  Graham, I hadn't remembered (or perhaps known) that there was already a plan to convert to constant-speed in '39.  Interesting.

Edited February 16, 2017 by gingerbob

[Jure Miljevic]

Hello, Graham and Bob

Thanks to both of you, what I was asking about was if installation of propeller governor caused external alternations of DH propellers and spinners and had trouble properly formulating a question. Bob, you mentioned a drive for constant speed propellers, already fitted to Merlin III: Was a governor mechanically driven? Cheers

Jure

[gingerbob]

Yes, the "propeller constant-speed governor" is (typically) driven by a gear on the engine.  It has flyweights that open or restrict oil passages, and the cockpit control essentially "tensions the spring" to set the desired rpm.  The engine will have a "pad" where the governor bolts on and meshes with a gear inside.  If there's no governor fitted, there's just a metal plate bolted on instead- the gear still spins, it just doesn't have anything to drive.  (There may also be a port for an oil line to connect to the governor, unless that is plumbed internally.)

 

So, as a hypothetical (not necessarily technical) example, if the pilot gives more throttle, the engine begins to increase rpm, but the flyweights "fly out more" because of this, open the oil passages a little, which allows more oil (under some pressure) to flow to the prop hub, putting pressure on the piston which forces the blades to rotate to a slightly more course angle, which takes more of a bite and consequently absorbs the increased engine power at (essentially) the original rpm.

 

(Curtiss Electric props, found on some US types, also had a speed (rpm)-sensing governor, but prop pitch was changed by electric motors instead of hydraulic pressure.)

 

Thus, I think the ORB isn't technically accurate when it says "Constant speed airscrews being fitted..."  I don't recall any mention of having to change props for this modification, just add the accessories.

 

Edited February 16, 2017 by gingerbob

[Graham Boak]

I don't recall where I read about the dispute over funding, but given the known benefit of constant speed propellers it would have been more astonishing if DH hadn't been working on the matter.  Certainly since it became known that the Air Ministry were pushing/funding the creation of Rotol (from Bristol and Rolls Royce).  The classic tale of an independent action by an RAF engineering officer in June 1940 leading to a rapid, almost overnight, campaign of re-equipment, as told in The Narrow Margin and elsewhere, just doesn't ring true.  As an ex-engineer, I didn't see how DH could design, tool up for, produce hundreds-off of the bits and assemble/qualify a force of fitters within a few days.  It makes much more sense that they had already placed the parts in production and were sitting ready for the go-ahead, with bits on the shelf ready to go.  Which doesn't mean that it wasn't a major effort to get the job done in the time.

 

There is a story out af DH concerning work being done ahead of contract, and whether they'd ever be paid for it.  To which the (internal) response was that if the job didn't get done, then they wouldn't be around to get paid.  This is usually linked to the early Mosquito times but I think it fits the cs prop story better.  Typical of the times, perhaps.

 

There's an excellent view of the fittings under a Merlin III in the Haynes book of the Hurricane.  The vacuum pump (to replace the venturi) on the starboard side, the CS unit on the port.  Which explains why the Hurricane had a narrower nose with bulges to accommodate these later developments.  I've not seen explained why the Spitfire had a wider nose from the start, to fit the Rotol which was initially given to the Hurricane in preference.  The latter however was probably a later decision after the designs were flying and had been compared in practice.

[Jure Miljevic]

Hello, Bob and Graham

Again, my question should be better formulated, still you provided answers. I have only ever learned about hydraulically or electrically driven propeller governors and I wondered what kind of purely mechanical transmission gear would be needed to accomplish this. I did not realise you meant mechanically driven hydraulic pump. Well, live and learn. Cheers

Jure