Building the exhaust systems for Snoopy's (OH-XEA) engine

Suomeksi

Alongside the covering of Snoopy’s fuselage frame, building the exhaust systems for the Continental A-65 engine to be installed in Snoopy has been continued. Snoopy’s original Continental A-65 engine and its exhaust system have not survived. However, for Snoopy we obtained a similar but damaged engine from the PIK-11 OH-YMD aircraft, which was involved in an accident. We are building new exhaust systems for the engine to match those originally designed and built for Snoopy by Esko and Ari Hietanen.

Photo: Esko Keskinen

Because the engine cylinders and cylinder heads extend outside the fuselage covering, the pair of cylinders on each side has its own simple exhaust system. Each consists of straight exhaust pipes leading from the cylinder exhaust ports to a silencer, the silencer itself, and a short tailpipe. In addition, on the right-hand side an intake-air preheating box is connected to the silencer. The early stages of building the exhaust systems were described in the Tuesday Club blog published on 30 January 2026.

Once the 40 mm diameter exhaust pipes had been attached by their flanges to the cylinder exhaust ports, welding the silencer tubes to their ends could begin. The ends of the pipes attached to the exhaust ports had been cut to match the curved surface of the silencer tubes. For welding, the silencer tubes were secured to the engine with straps so that they pressed tightly against the ends of the pipes attached to the exhaust ports. This positioned them well for welding.

Photo: Ari Aho

The silencer tubes were first tack-welded to the pipe ends at a few points using a MIG welder. This gave the exhaust system its initial structural integrity. Once the tack welds had been checked, the joints between the silencer tubes and the pipes attached to the exhaust ports were welded all the way around. The welds were initially smoothed with a rotary metal burr fitted to a drill and a grinding disc fitted to an angle grinder.

The ends of the silencer tubes were still open. They were closed by welding a round end plate, 100 mm in diameter, to each end. For this purpose, blanks for four end plates were cut from 1 mm sheet metal. A 40 mm opening was made in the centre of the plates to accommodate the tailpipes that would be welded into them.

The edges of the silencer-tube end-plate blanks were ground so that the plates fitted snugly inside the end rims of the silencer tubes. To prevent the end plates from slipping deeper into the tubes during welding, four screws were inserted through the side of each tube near its endto act as stops.

The end plates were tack-welded in turn at a few points to both ends of each silencer tube. Once the tack welds had been checked, the securing screws could be removed. Each end plate was then welded continuously around the rim of the silencer. The weld was ground smooth with an angle grinder. The same procedure was used to weld all four end plates into place.

Next, work began on the intake-air preheating box to be fitted to the side of the right-hand silencer. The box is 200 mm long, its width is slightly more than one third of the circumference of the silencer tube (about 160 mm), and it is 20 mm deep. Photographs of Snoopy again provided the model. 
To make the box, a piece of 1 mm sheet steel was cut to size for the cover. The cover plate was curved in a rolling machine to match the curved side of the silencer, allowing for the box’s 20 mm depth. Two strips of sheet steel were also cut, 20 mm wide and matching the length of the intake-air preheating box. These strips were welded to the long sides of the cover to form the sides of the box, and the welds were ground smooth. The intake-air preheating box, still open at both ends, could then be test-fitted to the side of the silencer.

To close the ends of the box, curved end pieces were cut from 1 mm sheet metal. The blanks were shaped to fit the ends of the box. Once again, the end plates were first tack-welded at a few points to each end of the intake-air preheating box and then welded fully into place.

The surface of the intake-air preheating box still needed both an inlet pipe for air entering the box and an outlet pipe carrying preheated air from the box to the carburettor. These 50 mm diameter pipes were welded to the intake-air preheating box in the positions shown in photographs of Snoopy.

The entire assembly could now be welded to the side of the right-hand exhaust system’s silencer tube. The silencer on the right side of the engine thus received an intake-air preheating box matching the original.

Photo: Esko Keskinen

The perforated tailpipes for the rear ends of the exhaust silencers were still missing. They were made from 45 mm diameter steel tubing. Two 100 mm lengths were cut from the tube, and three rows of 10 mm holes, matching the original exhaust pipe, were made in their sides. The holes were first drilled with a 5 mm bit and then enlarged to 10 mm with a conical bit mounted in a pillar drill. The completed perforated tailpipes were welded into the openings at the ends of the silencers so that, as in the original design, they pointed diagonally away from the fuselage. This prevents hot exhaust gases from damaging the fabric covering on the side of the aircraft’s nose.

Photographs of Snoopy also show 10 mm high reinforcing strips running along the engine-side centreline of each exhaust system’s silencer tube. These still had to be made. Blanks for the strips were cut from 1 mm sheet metal and welded into place. Once again, the welds were ground smooth. The exhaust systems on both sides were now structurally complete and ready to be fitted to the engine.

Photo: Juha Veijalainen

Although the exhaust-system welds had already been ground smooth as the components were built, they were given a final finishing when preparing for painting. This involved both grinding with various tools and applying filler to some of the welds, particularly where welding had left small cavities. These welds were filled using two-component Plastic Padding chemical metal. Once the filler had hardened, the seams were sanded with a grinding disc and finally with 1000-grit wet-and-dry abrasive paper.

The exhaust systems for Snoopy’s Continental A-65 engine are now ready for painting. Keeping with the original, they will be painted silver.

Photos: Lassi karivalo, unless otherwise mentioned

Translation to English: Erja Reinikainen