The engine compartment is rather more crowded then I’d first envisaged, the plan had the nose section non-tapered, very similar to an SE5a, whereas it is tapered in plan, side and front elevations. The standard silencer just wouldn’t fit so I decided to just use a flexy pipe, about 6" long, attached to the scale outlet. Having talked to other Laser owners we thought that this would give sufficient silencing.
The bent pipe is for the crankcase breather, saves having an extra hole in the under pan and blasts the oily mess away from the fuselage.
This system worked well, up to a point!
Laser engines normally sound very realistic and although it wasn’t excessively noisy, to me it sounded a lot more like a single cylinder.
Without any expansion chamber the exhaust is hotter, I’m sure we’ve all suffered from “frozen finger” when operating spray cans for a prolonged time, as gasses expand they lose heat. The hot exhaust mixed with the breather output may explain the paint problems as it is directed onto the undercarriage.
I’ve now made a remote silencer from brass sheet.
I’ve only test run, not flown, the engine with this, it’s certainly a lot quieter, I think more so than with the standard silencer, I just hope that it cools the exhaust sufficiently and that the engine noise is back to it’s original realistic self!
The throttle linkage caused some headaches, with the carburettor angled it wasn’t an easy job until I thought of the idea of making the linkage run back into the fuselage first. The Bowden cable loops around the fuel tank and then back into the engine compartment, a bit messy but it works.
The bolt through the firewall is one of a pair, the other one in a similar place on the other side of the fuselage, which carry the current for the remote glow. They also help secure the firewall as they go through brackets bolted to ply fuselage doublers (see photo on page 1).