New plexiglass windows for the Snoopy's cockpit

Suomeksi

The experimental aircraft Snoopy (OH-XEA), under restoration in the Tuesday Club, has plexiglass windows on the doors of the left- and right-hand sides of the cockpit. They have been preserved, but turned dim, yellow, and scratched. Therefore, they will be replaced. The original ones are of polycarbonate plexiglass, to be used also in the new ones.

Photo by Esko Keskinen.

We decided to test assembling the original dim glasses in place, to find out how they were fastened, thinking about buying and assembling new plexiglasses. For attaching the glasses, there are threaded brackets in the fuselage frame of the cockpit, into which the plexiglasses are fastened with screws.

When the original plexiglasses were fitted in place it was noticed that the holes for attachment screws no longer matched everywhere with the holes in the brackets of the fuselage framework. The plexiglasses had somewhat changed their form and shrunk over time. Thus, in many places, new holes had to be drilled or existing holes had to be enlarged to match the plexiglass holes with those in the brackets of the fuselage framework.

When attaching the plexiglasses with screws into the brackets had started, it was observed that the threads in the brackets no more worked in all of them. Therefore, into all of the bracket holes for the plexiglass on the sides of the cockpit and the doors, new threads were made with a tap for 4 mm screws. These screws were purchased and then the old plexiglasses could be mounted into place. Now, the test-fitted old plexiglasses were detached, and marks matching with their attachment brackets were made onto them with a felt-tip pen, for drilling holes into the new plexiglasses. 

New plexiglasses were bought from an Etra shop, where they were cut ready into the shape of the old ones. The old plexiglasses had the thickness of a good millimeter only, and were thus rather flimsy. Therefore, we decided to buy a little bit stronger material and ended up with the thickness of 2 mm. The sawed edges of the new plexiglasses were ground smooth.

Holes were made into the new plexiglasses for attachment screws, according to the original ones. The old plexiglass was placed on top of the new one, and the spots for holes were marked with felt tip pen onto the new one. With a column drill, 4 mm holes were drilled. When screwing the plexiglasses in place was started, it was noticed that the 4 mm holes were slightly tight, and the plexiglass could not be pressed smoothly against the fuselage framework. The holes were widened, and thereafter the plexiglasses of the cockpit door and the left-hand side wall could well be pressed against the fuselage framework. The new plexiglass windows had been assembled. For the time being, the protective films on the plexiglass surfaces will be left in place.

The cockpit windscreen has also been plexiglass, but is has not been preserved. Thus, it must be made. It is a single pane, the same sheet of plexiglass in the front as well as the parts bent to the sides. The bent plexiglass has been attached to its brackets in the fuselage framework through the screw holes by its edge.

To make a new windscreen, we plan to proceed by first making a cardboard model of it. Accordingly, we will get a sheet of plexiglass that will be bent in shape for attachment. It will also be made of 2 mm polycarbonate, bent into the angular shape of the Snoopy’s windscreen by heating.

A large sheet of cardboard was cut and started to be formed into the place of the windscreen, cutting it smaller piece by piece, until it corresponded with the shape and size of the original windscreen visible in photos of the Snoopy. It was checked that the edges of the cardboard will settle in line with the windscreen attachment brackets of the fuselage. There are still adjustments to be made until, based on the spread-out cardboard template, a sheet of polycarbonate plexiglass of its shape will be purchased and bent into its final shape.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation to English by Hannu Mononen.