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November 2006 Meeting Report

Aircraft Conservation by Chris Knapp


The subject of the November meeting was of especial interest to the more aeronautically inclined members as it was on the subject of “Aircraft Restoration”, expertly given by Chris Knapp, Conservation Manager at the Duxford Imperial War Museum .

Chris initially discussed the present day philosophy behind conservation, being, essentially, the concept of preserving an object for as long as possible with the minimum of intervention. This entails giving priority to reuse original components whenever possible. If this is not possible then identical replacements need to be sourced, although these may be anywhere in the world. Only when alternative components are not available is consideration made to making a replacement, using, whenever possible, the original materials. Failing that, other materials will need to be employed which may call upon considerable improvisation to match the original appearance. An example was given of making replacement knobs, previously Bakelite with an entirely different plastic material using cocoa to match the characteristic brown colour. Sometimes luck intervenes such as when a Perspex cockpit cowl was discovered being used as a tomato cloche for decades which proved to be the same type required for one of the planes being painstakingly restored.

There are nine principal agents for decay, these being:

Direct, wrongly applied physical force which includes overcleaning
Articles being lost through simple theft, vandalism or just poor management
Fire – either accidentical or arson
Water from flooding or spillage
Pests such as insects, vermin, mould and microbes
Contaminants from pollutants, dust, acid rain and dirty hands
Light
Temperature. This should be carefully controlled to avoid fluctuations. High temperatures can accelerate corrosion while low temperatures may well cause embrittlement

Humidity. Chris pointed out that the humidity control in the most eastern exhibition hanger was very poor but hopefully considerably improved in the newly restored and enlarged hanger

When carrying out a restoration project the issues which need to be considered are those which result in the final object looking as near as possible to the original while in everyday use, not when it has just come from the factory. Of prime importance in these present times is the question “Is it safe”. As an example Chris cited the banning of highly toxic chromate based paint primers with a much less toxic alternative.

The talk was illustrated by the conservation projects of two WW2 aircraft from the opposite extremes of size.

One of the smallest of the aircraft at Duxford is the Focke Achgellis Fa 330A. This was a small helicopter type of craft used for sea observation from U boats. Basically it was launched from a U boat so that the pilot could see what lay beyond the visible horizon from the conning tower. If, as sometimes happened, an enemy boat appeared the U boat had to dive quickly, leaving the poor pilot to a fairly certain death. A crated and unused machine was obtained by Duxford but the paint work had to be completely restored and the warped wooden frame carefully straitened out over a period of several weeks.

At the opposite extreme was the B52 bomber which had been exposed to the Cambridgeshire weather for 13 years before being extensively restored. This was a very important project which had to be carried out in time for an important exhibition. The total area which had to be re- painted was around 8000 square feet, much of the surface being badly corroded. It was a mammoth task, but with the valued help of hundreds of hard working volunteers the job was done on time. The restored plane is now proudly sited in the American Museum at Duxford.

Understandably, Chris finished his fascinating talk by pointing out that this museum was well worth a visit, especially since it is on our doorsteps

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