Sunday, 22 August 2010

Golden Claude & Updates

The release of Special Hobby's 1/32nd A5M has rekindled interest in the "golden" finish of this iconic type. One of the best representations I have ever seen is Tom Cleaver's superb model, featured at the Modelling Madness website. To my mind it captures perfectly the anodised "Bento-box" appearance remembered by some eyewitnesses. My thanks to Tom Cleaver and Modelling Madness for kindly giving permission to show and link to it here.

Whether this finish was the result of a clear varnish applied over the natural metal or of using anodised aluminium in construction (or both) remains unconfirmed. In the USA the National Bureau of Standards had begun an investigation into the corrosion of light metal alloys used in aircraft as early as 1925 and this included various coated and uncoated surfaces, as well as the application of paints. During the 1930's the subject was explored in the UK and Germany with particular interest in aluminium pigmented paint coatings. A 1938 National Bureau of Standards report by Willard Mutchler (NACA No.633) concluded that the use of surface treated alloys together with aluminium-pigmented paint offered adequate protection in maritime conditions, provided the materials were not subject to frequent immersion.

In the UK around the same time Cellon had produced a grey primer paint with zinc oxide and yellow oxide combination additives which was found to be more effective than alumium-pigmented paints in resisting maritime corrosion. This grey paint was subsequently marketed as "Cerrux Grey". In Germany similar developments in coating protection were being explored with the introduction of corrosion-resistant grey paints in place of earlier alumium-pigmented paints. Germany had sold several aircraft types to Japan in the late 1930's and it is inconceivable that these protective coating developments had not been communicated within the proprietory or technical literature accompanying these exports.

Anodising had first been used on an industrial scale in 1923 to protect Duralumin seaplane parts from corrosion. This early chromic acid process was called the Bengough-Stuart process and was documented in British defence specification DEF STAN 03-24/3. Oxalic acid anodizing was first patented in Japan in 1923 so the process was known to the Japanese. It may have been considered an appropriate means of protecting aircraft in maritime environments where full immersion was not expected (as with carrier based aircraft). It is not unreasonable to expect that there may have been a certain amount of experimentation in developing corrosion-resistant finishes and coatings once this all-metal type entered service, so where we expect a single finish there may have been several throughout the service life of the type, including ultimately painting with the "special grey paint for light metals". 

The aspect of anodising that may be of interest in respect of Claude is that it can produce yellowish integral colours without dyes. Shades of colour can be in a range which includes pale yellow, gold, deep bronze, brown, grey, and black. Some advanced variations can produce a white coating with 80% reflectivity. The shade of colour produced is sensitive to variations in the metallurgy of the underlying alloy and cannot be reproduced consistently. Therefore where one looks in vain for signs of a transparent coating in photographs of the natural metal finish A5M this does not necessarily mean that the aircraft in question was not "yellowish" (or "gold") in appearance. Some modellers may agonise over interpreting or choosing a finish but my advice would be not to sweat it and if you prefer a straightforward natural metal then go for it.

Japanese Aircraft Interiors by Robert C Mikesh

I was astonished to read some particularly dismissive comments about this important work of reference at a well-known modelling forum. In addition to citing a lack of information on actual interior colours, one poster stated that he had "read it through and then sold it". Is it a novel?  I cannot imagine trying to retrieve the copious amounts of information in the book without having it to hand. It is a work of reference and in my view indispensable. The main issue with using it is in the various colour standards cited and the occasional inconsistency in matching them.

Another poster commented that as a reference it was "dated". Really? Does this mean that the precise photospectrometric colour measurements from actual aircraft recorded in the book have been superceded? Hmm. Perhaps a blurring of the difference between knowledge and opinion. I encountered this once myself, where Mr Mikesh's measured values (colour values measured from the actual extant paint surface with photospectrometric equipment) were disputed in favour of the appearance of colour photographs and the memory of a museum visit.

Well to get back to Mr Mikesh's "lack of information" here are some facts. The book covers 18 Army types and 28 Navy types, of which precise colour information is given for 11 (61%) and 19 (68%) types respectively. The grand total is precise colour information for 30 (65%) types out of 46. On the shelf within reach, permanent and in the absence of anything else, pretty useful I should say.

RS Models E15K "Norm"

From correspondent Jeff Groves I received these useful comments about the kit .

"I recently finished the Xotic-72 Norm kit, and had issues getting it to sit right on the beaching gear.  If you look at the few pictures of the actual aircraft available, the main wheels of the dolly sit right under the leading edge at the wing.  Despite adding weight to the main float (and even the propeller spinner!), there is just too much plastic aft of the wheels and the plane sits on it's tail.  My solution was to add an extension to the after part of the dolly to place some support aft, as some IJN dollies had this "double ended" configuration.

As seen in the screen shots, RS have provided a dolly which is designed to sit too far aft.  The rear support rests aft of the step on the main float on the model, it was actually just forward of the step.  Correcting this is not simply a matter of scooting the model back - the support heights are different, plus the model will sit on it's tail when the dolly is properly positioned.  The dolly alignment markings on the box art match the prototypes, but the dolly provided will not match these.  Without some change, the finished model will have the glaring error of the dolly markings on the float not lining up with the dolly.

Models should decide on an acceptable correction before beginning this build."

Thank you for this!

Computer Woes

Please bear with me. I have been experiencing some pretty horrendous problems recently which make connection difficult and unpredictable. Normal service will, I hope, be resumed soon!

Image Credits: Special Hobby A5M2b by Tom Cleaver via Modelling Madness, with permissions.