S-Line Comfort Plus Package (C.P.P)

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Many Yachts, even nowadays in the range up to 80 feet, are noisy during transit and anchor condition. Over the years Silent Line assisted many Yacht Owner’s solving their annoying unnecessary noise | vibration problems.

Recently (2017) we assisted a Yacht Owner having problems sleeping at night having his stateroom forward of the engine room in which he had to deal with 53 dB(A) mainly emitted by the generator set. This is by far too high even on a Yacht in this size. We installed the S-Line (C.P.P) and ended up with 35 dB(A) emitted by both generator set running | AC operational and zero speed stabilizers.

Scope of Supply S-Line C.P.P:

High Volume generator set mounts:

The generator set is a serious sound source at anchor condition, not only air- borne noise but also structure- borne noise. How to solve this:

Engine Room Insulation Package:

Most of the engine rooms have limited insulation meaning foam and perforated plate. Foam is a nice and well-known product however the insulation value is zero (0).

This means it does not reduce noise from one room to the other room. Foam only absorbs the noise (reduce the noise inside the engine room) in case the foam is not covered with aluminium foil. This however is the case onboard many Yachts.

This means that absorption of the foam (covered with aluminium foil) also becomes zero (0).

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What should be used:

In average the noise level inside the engine room with the generator set running is approx. 75 dB(A), with the main diesel engines running we end up with approx.

105 dB(A). It is important to keep the noise inside the engine room as much as possible and for that reason the S-Line C.P.P engine room insulation package contains:

  • Closed RAL painted aluminium sandwich panels :
    click here for material datasheet
  • Sandwich Foam – Mass Layer – Foam layer :
    click here for material datasheet

The overall space required in order to install the S-Line C.P.P is 75 mm (void included) however if the space is available we prefer (by increasing the void) 100 mm space. The S-Line C.P.P must be installed at:

  • Forward engine room bulkhead
  • Overhead inside the engine room
  • Hull sides
  • Aft engine room bulkhead

Engine anti- vibration mounts:

In most cases, onboard Yachts up to 80 feet, the main diesel engine and gearbox are flanged. The drive train (in most cases) does not contain a flexible coupling and thrust bearing. In case of a Volvo Penta I.P.S system it is more easy but still proper soft anti- vibration mounts are recommended capable of absorbing the trust.
Pending on the type of engine, output in kW and rpm and the gearbox ratio we will select the best anti- vibration mounts suitable for your Yacht. Upon request (recommended) if the space is available we offer the below shown highly flexible coupling with trust block.


Silent Line, in close consultation with Volvo Penta, is proud and honored to make some modifications to the above shown system knowing:

Anti-vibration mounts:

Pending on the requirements the standard Volvo Penta mounts do work however in case the client requires additional comfort from vibration point these mounts are “too stiff”.

With approval of Volvo Penta, we are able to select softer anti vibration mounts which ensure more comfort especially at idle and maneuvering speed. This however must be done in combination with the below mentioned topics. Only changing the mounts will not give the ultimate solution.

Cardan shaft:

A cardan shaft is, standard, installed between the engine and the pod. The cardan shaft gives an excellent flexibility however as it is a steel-to-steel connection it is “poor” from vibration | structure borne noise isolation meaning:

We isolated the engine from the ship foundation by improving the mounts however with the cardan shaft the vibrations are transmitted from the engine into the POD still ending up at the ship structure.

With approval of Volvo Penta, we changed the cardan shaft and installed a different coupling which offers us flexibility and isolation using a rubber element within the flexible coupling.

Exhaust Bypass System:

Many years ago, onboard the Zeelander Z44 as shown below, we updated the standard Volvo Penta exhaust system by adding a bypass system.
The openings in the back, as shown above, are used for the bypass system which operates from idle up to maneuvering speed and then automatically closes. This avoids vibrations due to exhaust gases coming out of the tail of the pod at idle up to maneuvering speed.

Nowadays Volvo Penta supplies this as well as an option.

Exhaust hose:

The above shown (black) thick exhaust hose which runs from the engine unto the pod is “too stiff” in combination with the afore mentioned modifications. By changing the mounts, install the special flexible coupling and bypass system we have to update this hose as well. Instead of the rubber hose we are using a SS pipe with flexible bellows on the engine side and pod side which gives us the flexibility we are looking for.


The first project, in which we are not allowed to show any details, will be equipped with all above mentioned features as the client requested the latest technologies in the field of noise and vibration control. This project will be launched later this year, so stay tunes with us as we will give you the results after the sea trail.

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