Run along quietly now…
Uninsulated engine rooms radiate more noise and vibration than insulated ones – at least that’s the claim. So is it true, and just how easy is it to fit yourself?
Poppy is a 60ft widebeam built by Louis & Joshua in 2005; she has a 62hp five-cylinder Beta engine on flexible mounts. The Beta is cooled by a skin tank the length of the engine room.
Prior to fitting acoustic insulation the noise wasn’t particularly bad, but cruising long distances in Europe, it became a priority to reduce noise. I reckon the ideal diesel engine is cocooned, 30ft from the cockpit, driving a hydraulic motor beneath the steerer’s feet. Anything else is a compromise, so we set out to do the best we could with what we had.
Changing the engine location was not an option (obviously), so insulating it was the logical choice. There is a wide selection of noise reduction material available. Without being a professor of acoustics, it’s quick and easy to learn that two things need to happen to reduce noise. Some frequencies can be ‘reflected’ back into the engine room, while others respond better to being ‘mopped up’ into a spongy material.
To get the best performance across the range of frequencies radiated by the engine, gearbox and propeller, we opted for 50mm foam on a hard plastic backplate, with a shiny aluminium foil finish. The foil reflects, while the foam absorbs. The hard plastic base is coated with a contact adhesive. More about that later. We rejected thinner (and cheaper) materials – having found quite a few that were 30mm thick – on the assumption that the thicker it was, the better. blade, using a short sawing motion. As the insulation pieces are stuck on, significant pressure needs to be applied to the material. We used a selection of battens of differing lengths to push a piece of plywood that compressed the insulation all over. Failure to apply sufficient pressure results in the insulation falling off half an hour later, as we discovered to our cost early on.
Fitting the insulation to the aluminium engine room cover was simple and done in one piece. As soon as the material was stuck down, the cover was turned upside down on the pontoon we were moored to, and heavy weights were placed on top.
If a piece of insulation does fall off, don’t panic. It’s not ruined, but you can’t use the glue as-is. First, remove all traces of glue residue from the engine room using copious amounts of white spirit (or whatever solvent is recommended) and rags. Next, apply spray contact adhesive on both the