Off-hand, does anybody know...?

[Hauksbee 103]

In WW2, the RAF eliminated the white ring from the rondels on wings, and added a yellow ring on the fuselage rondel. What's with that?

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[hood 2]

In the Pacific area I was led to believe it was because the red central area could be mistaken for the Japanese Rising Sun emblem, but if it was also changed in the European Theatre that does not seem to apply does it?

[+The Trooper 104]

From: http://cocardes.monde.online.fr/v2html/en/pays/royaume_uni.html

 

 

Roundel, three concentric stripes, red white blue, thick yellow border.

Type A1 roundel, with broad yellow border, introduced in 1938. The yellow border was necessary to improve the contrast, when used on the camouflaged aircraft, for a better and quicker identification. The british aircraft, previously painted aluminium, received then a dark tactical camouflage patterns when tensions rose in Europe (Spanish war, Munich crisis). First, it was used on the side of the fuselage and over the wings, then only on the sides, being replaced by the B type roundel over the wings. The under surfaces kept the A type roundel. It is associated to a fin flash with 3 equally wide stripes, identical to the current one.

 

[hood 2]

Sorry , my post was all awry.In the Pacific Theatre it was the red central patch that was removed because of its supposed resemblance to the Japanese Rising Sun emblem.

[33LIMA 972]

It's just one of several variations, trying to find the right balance between camouflage and visibility, from different aspects. Your pic is the 1939-40 era. Just before the war, the standard was Type B roundels (red and blue) on fuselage and upper wings:

 

 

The red/blue roundels would have been better for camouflage on the ground, from the air. The higher-vis fuselage roundels would have improved air-to-air recognition, without unduly compromising camouflage while on the ground. The 'Battle of Barking Creek' would have emphasised the desirability of that (a couple of Hurris were shot down by Spits, when a radar masking problem led to friendly aircraft being reported as incoming bogies).

 

At that time and up till about mid-1940, there were no roundels under the wings - for recognition from the ground, RAF fighters 1939-40 swapped 1938-era overall aluminium undersurfaces for half black, half white (or aluminium), with some variations.

 

 

About the time the upper surfaces were changed from dark green/dark earth to dark green/ocean grey in 1941 IIRC, roundel styles changed again, with thinner white and yellow rings, and for head-on recognition, yellow outer leading edges on wings.

[JimAttrill 24]

When I first worked on Harriers in 1969 they had shiny polyeurathane paint and roundels with the white ring.  Trying to stand on a wet wing with RAF issue rubber-soled shoes was quite dangerous given the extreme anhedral of the wing.  They discovered that the white rings were easily visible from 20 000ft and painted out the white.   Later the shiny paint was replaced by matt paint.   This was before the more modern low-vis markings came into use.