The cannon armed Mk I has always intrigued me, so when I discovered the story, I had to model one.
Soon after the Spitfire began production, the Air Ministry was keen on adding cannons to the Spitfire. The reason was simple: all the other nations were showing off their new fighters with cannons! Actually most only had mock ups of cannons, or larger caliber (12.7mm or .50 inch) machine guns. Most still had basic rifle caliber guns as did the Spitfire and Hurricane. Up until the Battle of Britain even Fighter Command was cool towards cannons, viewing the 8 x .303 inch guns sufficient to their needs.
The Air Ministry however continued to pursue the cannon. The 5th production Spitfire, K9791, was removed from production and used for mock ups; based on this L1007 was then modified to allow for 2 x 20mm cannon; all 8 guns being removed. This was as early as 1938; actual modfication and testing ensued into 1940, 30 aircraft being modified and fitted with the new armament. The modification could be viewed as simply new wings (to some degree that's initially all it was) with a switch for the cannon on the control column. The operational use required much more development to get the cannons to work properly and not jam.
The g forces during aerial combat flexed the wings of the Spitfire and while not an issue with the .303 guns, it turned out to be a major issue with the 20mm cannon. For starters, the cannon had to be rotated to ensure they would fit with minimal bulges above and below the wings. Then the problem of the drum remaining tight as it connected to the breech had to be solved, and finally what to do with the excess gasses and links/cartridges as it fired.
Ultimately these were solved into 1941 and to ensure reliability as a gun platform 4 of the .303 machine guns were re-installed for a 2 x 20mm plus 4 x .303in configuration. This became the "b" wing configuration, the "a" wing being the 8 x .303 inch Brownings. Due to the weight of the armament, the higher power of the Merlin 45 was preferred in the Mk V, so all Mk I and Mk II cannon armed fighters that remained in the inventory were upgraded to the Mk V standard, or reverted back to the "a" wing.
This particular subject is one of the first 30 conversions to the Mk I, which had only the 2 x 20mm cannon installed; the Brownings being removed due to weight. No 19 Squadron, RAF was converted to the cannon armed Mk I in the Summer of 1940, at the height of the Battle of Britain. Unfortunately, due to the regular jamming of the cannon they rarely got off more than a few rounds before having to retire from the fight due to an inability to fire their weapons! While they continued to score kills, they were very frustrated and at the time had many of the most experienced and higher scoring aces. They quickly reverted back to the Mk Ia but by the time they completed the transition to get back into the fight, the BoB was essentially over for the day fighter phase, the Germans having shifted their incursions to the night time.
Wing Commander George "Grumpy" Unwin, DSO, DFM & Bar, was a Flight Sergeant during the Battles of France and Britain, having shot down 14 enemy during his initial combat service. The subject of this build was his aircraft during September, 1940.
This is the AZModel limited run "Spitfire Mk Ib" kit. It is the same set of sprues as their Mk IIb, Vb and VI boxings, with the only difference being the instructions and decals. All only offer the externally armored canopy and unfortunately only offer the later Mk III (aka Mk V) round oil cooler. To properly model a Mk I or II from this kit an earlier Merlin III oil cooler (semi-circular) has to be sourced.
While technically a limited run kit, AZModel has done a great job of making their kits assemble like a main stream kit. Flash was non existent and all the parts fit perfectly. No slots or tabs are present for attaching parts, so care must be taken with alignment, but they do attach well. I had zero issues with construction.
I sourced the earlier Mk I oil cooler from an Airfix Mk I that I had converted to a Va. It fit perfectly into the location on the wing underside.
Painting was straight forward for this scheme:
- Dark Earth -- Vallejo Model Color 70-921 English Uniform;
- Dark Green -- Tamiya XF-81
- Sky -- Hataka A026
- Night -- Tamiya XF-69
The new paint I tried was Hataka's version of Sky. Not bad, it's a bit less intense than other paint makers' Sky and I like the color, however it doesn't brush well (likely I've not figured the right balance of thinner, retarder and flow improver). It airbrushed okay but I need to thin it a bit more which means I need to, you guessed it, find the right balance of thinner, retarder and flow improver.
I used the kit decals, but I have to say they turned out to be a bit translucent, and inconsistent. The small sheet of stencils where dark and went on perfectly and the carrier disappears under a coat of setting solution. However the markings, while the proper color, seemed "off" and upon closer inspection (ok, via my magnifiers) I could see the dots from the silk screen printing. I applied them anyway and some looked ok and of course at arm's length (my standard) they looked just fine. They also had a filmy residue that didn't seem to want to come off, but luckily when it dried it dried clear. Ultimately the decals did not silver, so it looks ok but do not meet the quality of the rest of this build. Ah well, done and dusted.
I enjoyed this build and during construction decided to buy a few more in the Vb boxings. Now they are hard to find but AZModel released a more modern set of sprues in their Admiral line and I hope to make one soon. They say they will also release these with the later internally armored windscreen, and then I can begin easily modeling the later Mk Vb subjects.
Thanks for looking...