Spitfire III Prototype, N3297, Spring/Summer 1940

Finished! This is the prototype Spitfire III, of which only this and another were ever made; the type being superseded by the Spitfire V.

The Subject

The Spitfire III was meant to be the ultimate Merlin engined Spitfire; a truly air superiority aircraft that would outperform anything expected from Germany for the foreseeable future. Well, at least until the next Spitfire was ready, the Spitfire IV which was to be powered by a Griffon engine. It was to be faster, higher flying, more maneuverable at all altitudes and support up-gunning to as many as 6 20mm cannons!

Refinements expected with the more powerful engine were drag reducing elements such as flush rivets throughout, retractible tail wheel, and a refined windscreen. A shorter span was recommended with changes to the ailerons to permit better roll control at lower altitudes as well as better speeds.

N3297 was taken from the production line and given Merlin XX to provide additional power. The Merlin XX was 4 inches longer than the Merlin III so a modified nose was required. Additionally, the added power meant a new radiator was required, and ultimately 3 different configurations were tested. A retractable tail wheel was devised and different configurations of windscreen were tried.

At least 3 different wing configurations were tested, all based on the standard Spitfire wing. The first was a short span wing; the tips were removed at rib 19 and a rounded cap installed. This required the ailerons to also be shorted. This configuration used the original 8x.303 inch gun wing.

The second wing used the same wing but reinstalled the standard length wingtips. This was in response to Fighter Command’s complaint that wing loading was already too high, so reducing the wing area made takeoffs and landings too dangerous. The third, and final wing configuration was the universal or “c” wing of 4x 20mm cannons or 2x cannons and 4x .303in guns. First tried on the Spitfire III this later became standard on the Mk Vc and early Mk IX, XII and XIVc.

A number of windscreen configurations were tried, but ultimately the standard used on the later Vb and subsequent marks chosen. Again first tested on the Mk III.

The new engine required better cooling; first the oil cooler. This became standard on the Mk V and XII even being retrofitted to some older Mk I and II still in service. A number of coolant radiators were tried, the first being a larger cooler that looked similar to the Speed Spitfire radiator. The second had a boundary control layer. Other configurations tested were more similar to the Mk XII and/or IX configurations.

Ultimately, the Spitfire III became, effectively, the prototype for all later marks. While N3297 did not get the newer Merlin 60 series, its sister W3237 did including the dual radiators that were eventually standard on the Mk VII/VIII/IX series. W3237 would look more like a Mk VIII than a Mk III during its entire career. N3297 was used until nearly the end of the war for testing purposes, ultimately being scrapped, as was W3237.

The Model

Obviously I chose to model N3297 as she appeared early in her career. If I’d chosen any other configuration she would have looked mainly like an early Mk VIII but with a shorter nose and 3 blade prop. That’s an idea for another subject…

As shown in an earlier post, I chopped the nose and added a plug and then clipped the wings inboard at rib 19. The oil cooler is from the Airfix Va kit, which is the basis for this conversion. The coolant radiator is scratch built. The canopy is from a Mk IX kit.

Since the Mk III was started in 1939 and first delivered before June 1940 to Fighter Command for some comparative testing…AND…the only photos I have (which are copies of all that remain) indicate very low contrast I chose the standard Dark Earth, Dark Green with Night/White undersides. When N3297 was reconfigured later in the year with a standard wing, I’m sure it was Sky underneath; Yellow with a yellow P in circle where not introduced until 1941 so I didn’t plan for these markings.

I originally started to brush paint but switched to my airbrush since I had already done too many experimental things. Other than national markings and serial number, no other markings were applied. Decals came from the donor kit plus 8 inch Night letters/numbers from an Xtradecal sheet.

Summary

Well, it certainly looks different on my shelf. I must admit I don’t like the lines of the Mk III and wonder if that had more influence on the reports from Fighter Command than wing loading? If it had better lines would that fault have been overlooked? Clipped wings later became standard (albeit not so short). The larger radiator looks awkward, and impairs the clean lines of the Spitfire even more. But all-in-all I like having this on my shelf. It’s an interesting conversation piece, and given the importance of the Mk III in later development, is an important step in the Spitfire’s story.

Thanks for looking…