Sound insulation

Dear Friends,

Although it is not a specific S&S Swan issue, I am very interested in ways of improving sound insulation from engine noise.

On our Swan 47 we have a 100 bhp Yanmar that makes quite a lot of noise. Of course we have tried to insulate the noise as best we could with the knowledge we have, but the sound is still too much. The wooden boxes around the engine doesn't leave us with much space for insulation. The floor boards in the aft compartment are already fitted with heavy plates.

I am very interested in possible solutions for this problem.

kind regards,

Jan

YULUNGA 47/11

Dear Jan,

on our 411 we did what I described in this thread. It did help and made the noise bearable, in the cabin and the cockpit, but it is still loud and a pain. One thing that made quite a difference was repairs to the drive train. We renovated our MaxProp propellor, changed the shaft seal amd bearing, realigned shaft and engine. This took away quite a bit of vibration noise.

Next time we change the waterlock/muffler I will look for a solution that reduces noise from that side. Most of the noise we hear in the cockpit is vibration in the hull. This can be dealt with by using a decoupling solution between engine and shaft, as described in multiple places in this forum, but is not easy to put in place. 

There is at least one classic Swan that has an electrical engine ...

Kind regards,

Christian IF 411/028

Thank you Christian.

Our engine noise outside in the cockpit is not that bad.

It is inside in the saloon where we cook and in the aft cabin, where we are supposed to sleep during passages where most of the noise is.

In our swan it is from the engine itself and not the drive-train.

thanks again!

Dear Jan,

There is an excellent, almost scientific, article in the German magazine Palstek, issue 5/2011, about how to reduce diesel engine noise on a sailboat. If you are interested, I can send you a scan. 

The article says that significant noise reduction of the engine can be achieved by: 

- covering the cylinder head cover with heavy noise reduction material. Sailboat engine often have very simple covers, whereas those of cars are double-walled for noise reduction.

- isolating the air intake of the engine. Normal and elaborate in car engines, often non-existant in boat diesel engines (like our Nanni). Noise from inside of the engine leaves through the air intake.

- the biggest effect can be achieved by isolating the exhaust sytem end-to end. Vetus sells exhaust water collectors that reduce noise. 

These measures reduce noise at the source. I plan to do something about the exhaust at some point.

There is then sound insulation. Given the little space in the wooden engine box, I could just put material 10mm thick there on our boat, but that helped, since the  material had been completely ripped out when the engine had been replaced under previous ownership. I also put much thicker material inside the engine compartment, but given the limited accessibility this was a major pain, and should have been done with the engine removed. It is important that there are no gaps in the insulation. Even small gaps can annihilate a large insulation effort. I am sure I still have such gaps; I closed some using non-inflammable construction foam. I have also put sound insulation under the floorboards in the aft cabin. Since this is where the engine gets its air, it is not a good idea to close the space under the floorboards completely. 

With all this done, and when closing the door and the four port lights of the aft cabing, we have acceptable noise in the cockpit, and one can sleep in the salon during passage with engine rpms below 1800. I am sure more can be done, and it would be interesting what further measures have been implemented by Swan owners. 

Kind regards,

Christian IF 411/028

Thank you Christian,

I would be very interested in the Palstek article.

can you please dm it to j.kooistra@wxs.nl?

thank you,

Jan, YULUNGA 47/11