Restoration of the Blenheim navigator?s seat

Suomeksi

We received the Blenheim V-series or “short-nosed” Blenheim’s navigator and pilot seats for restoration at the Tuesday Club.

Both the seat’s steel tubes were badly rusted, but neither seat had suffered significant damages. The navigator’s seat, or rather stool, was significantly more straightforward to restore because of its simple structure and smaller size. It would greatly help restoring the pilot’s seat, if the seat pan could be separated from the seat frame. The aim of the seat restoration is to clean the rust from the surfaces of the supportive tubes and smaller parts, grinding the aluminium surfaces and finally painting them.

We began the restoration with the navigator’s stool. The padding was detached first and the seatbelt as well. The seatbelt was partly torn and needed to see a cobbler.  The seat cover of leather has worn out and lost its colour. It needs to be conserved. We will not do it.

We examined the round shaped seat plate, bent at the edges, for shades of paint found on the surface. Light green colour was visible, under which darker green could be seen. Thus the surface of the seat plate had lastly been painted with light greenish grey paint and under it there was an older darker green paint.

Paint residue could also be found from the surface of the steel tube stem of the seat. This process was helped when the rusty stems of the seat were treated with Industrial ECO Complex Blue-solution. The solution revealed a green shade of paint on the surfaces of the tubes. In addition, some old pigment or paint chaff was scraped from the surfaces of the rusted tubes of the stem. Some of it was placed under a 600 times magnifying microscope. It turned out that there were three different layers of paint on the tubes of the stem. The lowest was brown, then grey and greenish grey on the surface, in other words the same shade that was found on the surface of the seat plate. In consequence we decided to paint the seat with the similar shade of light greenish grey paint.

To start the restoration proper, we detached the aluminium seat plate from the stem. It was fastened to the stem both with bolts and rivets. The bolts were loosened first. After that the rivets attaching a bracket to the edge of the seat in the upper part of the stem were drilled out, after which the seat plate came off the stem.

Then we started to remove the rust from the stem steel tubes. The rust was removed from the tube surfaces, so that a layer of surface paint became visible. The tubes need not be ground to gleaming metal, because we use Isotrol lacquer and paint for the painting. The Isotrol will stop the rusting from spreading, even though rust would have stayed in the rust crevices of the steel tubes.

Rust was ground off first with a coarse sanding paper, wiping the dust off at times. We then moved to finer sanding papers, feeling at the same time with fingers whether the surface of the tube was clean and smooth enough. After the coarse surfaces had become smooth and the old paint became visible, the sanding of the steel tubes was complete.

We moved on to deal with the seat plate. It was an easier task. The aluminium surfaces of the seat plate were lightly sanded with fine sanding paper. We didn’t indulge in any grinding off of the old paint. The main thing was that loose paint was removed from the seat surface and the aluminium surface became smooth.

After both the steel tube stem and the aluminium seat plate had been ground, they were lacquered with clear Isotrol, which leaves a protecting film on the metal surface. For the surface paint it was necessary to define the shade of the seat colour. We ended up with the grey green Temalac ML 90 BS 283 shade for the seat. With this formula the seat’s Isotrol oil paint was shaded.

Two Comprehensive school students, doing their work experience learning period at the Finnish Aviation Museum, painted the stem and seat plate of the navigator’s seat. Well, at first the quality of the work left something to be desired. However, with careful guidance a good result was achieved. That’s just the purpose of this kind of work experience period, isn’t it?

After the painting it was time to reassemble the seat. The glass bead blasted original assembly bolts were fitted, and the seat stem was riveted to the edge of the seat plate. The rivets were finally painted grey green, to avoid eye sore. We had a cobbler repair the seat belt. The restoration of the navigator seat in the Blenheim bomber was ready.

Photos: Lassi Karivalo

Translation to English: Matti Liuskallio