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Why was there so little NMF in the RAF?


Doc72

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Hello everybody!

Just another question I would like to discuss with you: Why were so few RAF aircraft finished in Natural Metal?

When camouflage became unfashionable in the 1950s and 1960s, many air forces left their aircraft unpainted. Certainly, there was also a lot of "silver" in the RAF, but in most cases this was High Speed Silver. Obviously, natural "metal" Mosquitos or Vampires would have been difficult. Nevertheless, even the Hunter T.7 (strangely single-seat Hunters were almost always camouflaged, even though contemporary French or US fighters were not), Meteors, Canberras etc were rarely seen "naked", but almost always painted silver. The only British aircraft, I can think of, that was NMF for a great part of its career is the Lightning.

What was the reason for this? Fear of corrosion due to the British weather or more corrosion-prone aluminium alloys used?

Edited by Doc72
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The use of overall high speed silver as a camouflage scheme has its roots in the camouflage conference of October 1945 where a number of options were evaluated. The use of natural metal aircrafts had been considered during the war, with Churchill himself mentioning this in 1944. It was agreed that at that stage there was no real need for camouflage on air superiority types but it was however decided that the manufacturing methods used in Britain required a certain amount of filling on the surfaces, something that did not go well with an unpainted finish. When the matter was discussed again after the war, it was agreed to leave day fighters in an overall silver scheme. During the conference it was also agreed that the camouflage policy would have been reviewed in 5 years time.

The review occurred starting in late 1949 and by Summer 1950 it was completed. Day fighters had been divided in long and short range types, with both supposed to be camouflaged (in different schemes). Later however Fighter Command run trials with a number of schemes and the overall silver scheme resulted the less visible, so it was retained in service for short range day fighters. During these tests one of the aircrafts involved was a USAF F-84G in natural metal finish and this was found to reflect light too much and too easily visible.

Move forward another couple of years and the decision came to camouflage all fighters, retaining silver for the undersides of Fighter Command aircrafts.

Bombers on the other hand received the silver scheme in the early '50s after a short use of the light slate grey/medium sea grey/PRU blue scheme. Canberras were the first to be so painted, followed by the Valiant and then the other V bombers (that used this scheme for quite a short time).

Overall the silver scheme was considered a good compromise between the advantages of having no paint (that saves time during production and maintenance) and the requirements of lower visibility (the silver scheme was the best of the ones tested from this point of view)

I don't have documents on the Lightning camouflage therefore I can't comment much on the reason why initially this type was left in NMF. I suspect that it may have something to do with the bad behaviour (real or perceived) of paints of the day at high speed, where kinetic heating can quickly damage certain paints.

Interestingly the USAF, that had pretty much all their types in NM during the '50s, coated some aircrafts in service in the UK with grey or silver paint and later all USAF types received a coat of aluminum lacquer. The war in Vietnam spelled the end of NM or silver painted schemes

Edited by Giorgio N
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The USAF F105 was finished in a silver lacquer rather than NM as well for corrosion prevention

The F-105s were originally in natural metal, they were repainted in silver lacquer as part of project Look Alike starting in 1962. All the F-105Bs and the Ds serving in Europe had been found to suffer from corrosion and the coat of paint helped reduce the problem. Similar corrosion problems occurred to the F-101 of 81st TFW

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The Lightning had the bright tail and spine paint removed from bare metal finish in order to easily check for fine cracks. Following the analysis of the Comet disasters, fears of metal fatigue in aircraft skins was more common at this time - whether this was influenced by a number of tail failures (Lightning, Victor) is not recorded but these may have been behind some of the worries. One particular alloy chosen for British aircraft in the early 50s had unfortunately a low fatigue life and a lot of individual aircraft built at this time had a short service life. The Valiant was the most well-publicised type to suffer from this, but there were a lot of early Hunters (and Swifts?) with what appears now to be a very short active life. The development of better alloys, stricter fatigue monitoring and better inspection devices reduced the need for visual checking of bare metal, permitting the needs of camouflage and corrosion protection to dominate.

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The F-105s were originally in natural metal, they were repainted in silver lacquer as part of project Look Alike starting in 1962. All the F-105Bs and the Ds serving in Europe had been found to suffer from corrosion and the coat of paint helped reduce the problem. Similar corrosion problems occurred to the F-101 of 81st TFW

Correct Giorgio

I was just trying to be briefer which is rare in a lawyer! Always enjoy your posts by the way

John

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Sorry John, didn't mean to sound pedantic but I in the end I did :D

As I'm being pedantic, may be worth adding that of course not all USAF aircrafts ended up in silver, ADC painted their aircrafts in overall grey.

Regarding the US Navy brief venture in natural metal schemes, the aircrafts finished in this scheme actually had a coat of clear lacquer to protect against corrosion. This was however not enough and the experiments ended soon. The same service however used a good number of aircrafts in natural metal for second line duties from land bases.

As we're speaking of NM finishes that were not really in natural metal, Soviet aircrafts also had a coat of clear lacqer over the metal

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The use of overall high speed silver as a camouflage scheme has its roots in the camouflage conference of October 1945 where a number of options were evaluated.

'High Speed Silver' was the colloquial description for a finishing scheme introduced in 1949 in response to complaints that "ordinary" Aluminium paint did not adhere well to high speed jets. The specification was DTD 772 which was for a high gloss finishing scheme and included paint colours other than just Aluminium (such as for national colours and serials), but where Aluminium was used the finish was referred to by that term - it was not a paint 'colour' per se. It consisted of a pigmented synthetic resin primer directly applied to the metal surface, a filler, then a finish coat which was suitable for application over both primer and filler and finally two polishes, a cutting compound and a liquid polish to create a very high gloss. Components finished in this scheme were marked DTD 772 over the relevant 'C' for cellulose or 'S' for synthetic as both types of paint were included in the scheme. It was one of the earliest combination paint and finishing schemes within specification.
The term 'High Speed Silver' is often misapplied, for example to post-war Spitfires and Tempests, and even more inappropriately to pre-war biplanes.
Nick
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I don't know why, probably corrosion related as mentioned above, but for me the application of High Speed Silver paint during etc 1950s and 60s is a blessing for us modellers interested in that era. I don't mind trying to achieve a good NMF, but Tamiya TS-17 Gloss Aluminium is a whole lot easier!

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As we're speaking of NM finishes that were not really in natural metal, Soviet aircrafts also had a coat of clear lacqer over the metal

Clear lacquer pigmented with silver paint..... seen peeling on this Su-15 I photographed in Kiev......

su-15_paint_02.jpg

Ken

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As the subject of RAF NM Lightnings has cropped up may I point out that these aircraft were some 20 to 45 percent painted Aluminium. Got some notes somewhere, I'll see if I can find them.

HTH

Dennis

PS - The skin of the Lightning itself formed an anti-corrosion layer - Alclad - ALuminium Clad Duralumin. The aluminium layer, only a few microns thick was known as a "Sacrificial Layer"

Edited by sloegin57
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'High Speed Silver' was the colloquial description for a finishing scheme introduced in 1949 in response to complaints that "ordinary" Aluminium paint did not adhere well to high speed jets. The specification was DTD 772 which was for a high gloss finishing scheme and included paint colours other than just Aluminium (such as for national colours and serials), but where Aluminium was used the finish was referred to by that term - it was not a paint 'colour' per se. It consisted of a pigmented synthetic resin primer directly applied to the metal surface, a filler, then a finish coat which was suitable for application over both primer and filler and finally two polishes, a cutting compound and a liquid polish to create a very high gloss. Components finished in this scheme were marked DTD 772 over the relevant 'C' for cellulose or 'S' for synthetic as both types of paint were included in the scheme. It was one of the earliest combination paint and finishing schemes within specification.
The term 'High Speed Silver' is often misapplied, for example to post-war Spitfires and Tempests, and even more inappropriately to pre-war biplanes.
Nick

Nick is absolutely correct, in fact the only reference that I have been able to find with reference to "High Speed Finish" was in this Docker Brothers advert in Flight for 2 December 1948 and I firmly believe that this is where the misconception springs from (it's in the small print) :-

K3dcpAb.png

Dennis

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Thanks everybody, especially Giorgio N. I have learned a lot.

The need for filler on British aircraft and concerns about the silver paint not able to withstand the speed and heat of the Lightning explains a lot. Early British jets like the Canberra indeed look very smooth with panel lines filled and sanded down (don't tell Airfix!).

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Were the Washington bombers used by the RAF in the 50s ever painted with lacquer? And as an aside, did the B-29A have fabric control surfaces, or was it all aluminium/Duraluminium?

Cheers,

Al

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Thanks everybody, especially Giorgio N. I have learned a lot.

The need for filler on British aircraft and concerns about the silver paint not able to withstand the speed and heat of the Lightning explains a lot. Early British jets like the Canberra indeed look very smooth with panel lines filled and sanded down (don't tell Airfix!).

Glad the info was of use ! Just to clarify though, I have no hard evidence on the Lightning, the decision to have the airframes mostly unpainted may have been due to some totally different reason, more so as Dennis mentioned that many panels were indeed painted. And also, Nick is of course right that the term High Speed Silver was only introduced at a certain point. I've been using it in a general but not fully correct way

Were the Washington bombers used by the RAF in the 50s ever painted with lacquer? And as an aside, did the B-29A have fabric control surfaces, or was it all aluminium/Duraluminium?

Cheers,

Al

Washington's retained the original USAF natural metal finish. A few even had gloss black undersurfaces from their Korean War days. I'm not sure if any was repainted silver at some point

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The ultimate in NMF is the highly polished finish so beloved of American warbirds. However, when it was used on the RAF Queen's Flight Andovers the amount of polishing the aircraft recieved resulted in reduced skin thickness and loss structural integrity as the rivet heads were removed by the polishing. Not exactly what you want with the Monarch on board. The shiny aluminium was therefore covered in a coat of paint which could just as equally be kept clean and shiny and was cheaper to replace when the polishing wore it away.

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When I was doing my trade training in the RAF, we were regularly reminded that the primary reason for painting an aircraft was to prevent corrosion and that camouflage was of secondary importance.

The Lightning might have been seen differently, as it was intended to be an interim type, which, once it became more permanent was rapidly given a decent coat of paint.

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When I was doing my trade training in the RAF, we were regularly reminded that the primary reason for painting an aircraft was to prevent corrosion and that camouflage was of secondary importance.

The Lightning might have been seen differently, as it was intended to be an interim type, which, once it became more permanent was rapidly given a decent coat of paint.

Exactly the same as I was taught in the late 50's early 60's. As long it looked roughly the same - good enough.

Dennis

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Washington's retained the original USAF natural metal finish. A few even had gloss black undersurfaces from their Korean War days. I'm not sure if any was repainted silver at some point

Were the Washingtons not an interim type on lease?

If so, then the US would have had a lot of say into what could and couldn't be done with them.

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I used to work at an establishment where bits and pieces were tested with explosives or vice versa, one of the pieces was shaped very much like a Lightning wing and much to my surprise it

had a wooden leading edge, can anyone confirm this?

Tony

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