Sound absorbing panels
I need to replace all the sound absorbing panels inside the engine box of my 411.

There are so many kinds that I feel confused and I would positively like "the best" on the market whatever the price per square meter is. The needed material is not much, keeping the noise to the minimum level possible is very important, it is an operation that needs to be repeated very seldom and, last but not least, an S&S Swan deserves always the best!

I would appreciate very much all advices you may give.

Daniel, 411/004

Dear Daniel, I think the best ones in term of quality have the lead film inside (as far as I can understand the lead does not "absorb" the noise but is a great barrier), but of course this stuff is really heavy, so when you have to access the engine you must hoist a considerable weight. Why don't you think to install this kind of panels on the bulkheads and less heavier on the engine removable box...?

Yes, I agree, a Sparkman & Stephens designed Swan deserves just the best!

Looking forward what the experts have to say.

Fair winds!

Matteo (38/067 Only You)

Dear Daniel,
five years ago we replaced the engine room sound insulation of Infant (38/014). We used a heavy type of panel on both the bulkhead and removable engine box surfaces. The panel type (PU-VANA 30) is presented on this site: http://www.meluton.fi/frontpage.shtml. We have been satisfied, the noise is quite low and the material seems to be durable.
Smooth seas!
Jyrki

Dear Daniel,
I recently had to rplace the original sound insulation material as part of the MCA "coding", as the original was not fireproof. I used:

http://www.marinemegastore.com/cid/PQORXQAE3XLOE9CQWGF5A09X3555CBM0/category-Insulation-and-Soundproofing-ENGIMP004.htm

Foil faced with 25mm of black class O non-flammable acoustic foam, 5kg/m2 polymeric barrier and 7mm black class O non-flammable acoustic foam. Which fully meets the RCD (recreational craft directive). 4 sheets per box.

Sheet dimensions: 1000 x 600x 30mm.

This Boak Foil Faced Acoustic Insulation is a great Insulation & Soundproofing product. Manufactured by EC Smith & Sons, who also make other types of products such as boat switch panel, marine fuses circut breaker, Terminals for boats, sinks and taps, water food grade hose.We are sure you will be pleased with the Boak Foil Faced Acoustic Insulation with prices from £140.34 .

I glued this on with spray adhesive, but also used quite a number of screws and washers. I was pleased with the result, the engine noise is definitely lower than before

regards Cosmo Little ( Trinket, 41/31)

Dear Daniele and contributors

The two sound insulation products presented here are rather similar, and represent typical materials used for these purposes
They consist of 4 layers, each with a specific function:
- Surface layer, to be oil tight and tough
- Absorbtion layer of foam, absorbing the echo
- Heavy sound barrier, dampening the noise
- Distance layer, preventing barrier layer contact with the surrounding box

In addition to using such a material inside the engine box it is important that the box is tight without leaks where noise can escape. This is challenging because the propeller shaft and air ducts require openings. For best results noise traps are required for them.

On bigger yachts it is common to install perforated aluminium plate as protection over the sound insulation.

It will also reduce the noise level if the engine seatings are made heavier, for example by filling them with a mixture of polyester and sand.
Best regards
Lars

Daniel,

We also replaced the original noise insulation with EC Smith type panels.  (Interestingly the original stuff passed the MCA surveyors “match” test).  It made a noticeable difference and is well worth the time and effort.

With noise insulation, devil is in the detail.  So worth taking your time over the joints etc.   But as Lars says you will always get some leakage from the air hoses and where the stern tube exits the compartment.  You will also get some structural born noise. Other than making the seats heavier  as it will help to dampen out the vibrations, there is little you can do as its inherint in the structural layout and detailing of the boat.

 If you have space, a big difference will be noted by insulating the underside of the floorboards above the prop shaft. 

Wrt fitting, worth spending a little extra and getting the panels with the self  adhesive backing.  A lot less messy than pots of Evo stick.

All the best

Adrian

Daniel, I can support that also insulating the tri-angular floorboard in the aft makes a big difference. Do you have a hard coupling between the shaft and the engine or do you have semi flelible coupling with rubber which I am told also greatly reduces the noise levels?

John B

Dear all,
thanks to all your kind replies I think I finally found the right article: it is a 30mm thick sandwich made of two polyurethane layers enclosing an EPDM sheet and protected by an aluminized fibreglass quilt (apparently very nice looking!). The EPDM sheet substitutes the lead sheet but it is not much lighter. The total weight is approximately 3 kg/sqm.
I am still in doubt whether to fix it with screws and the proper washers or rely on its self-adhesive coat; I may end doing both...
It is pretty expensive but as, I wrote before, it seems worth.
Besides, I will surely follow the advice to put some absorbing panels under the floor of the aft cabin but I am afraid I do not see an easy way to improve the engine seating.

I have found a strange thing unmounting the old panels: instead of finding the ubiquitous "411/004" engraved on the wood I found the reference to another newer hull (presently I don´t remember but something higher than 411/010). It is the first time I find such an inconsistency and I am surprised because the box itself does not seem to be able to exit or enter in one piece easily from the boat!

Daniel, 411/004

Daniel, FYI on mine ,no 010 I need to remove the steps obviously, then I take off the handle on the engine box and it lifts out in one piece. But it is a tight fit.    

Daniel, FYI on mine ,no 010 I need to remove the steps obviously, then I take off the handle on the engine box and it lifts out in one piece. But it is a tight fit.    

John,
thank you for the indication, I will try the same procedure you suggest.
The idea of doing the job inside the boat did not appeal to me at all!

Daniel, 411/004

Following John´s advice, yesterday I happily succeeded in lifting the engine box out of the boat.
Now I am also trying to find the best solution for renewing the step plates as discussed in another thread.
The hull number written inside the box is indeed 008 which, according to this site, corresponds to a 411 called "Wanted". I wonder if Wanted has a box with written 004...
That number was well hidden behind the sound absorbing panels, no wonder that at Nautor´s they were not able to keep track of the totally identical boxes after installing the panels. :-)
This mixing of numbers probably makes our boats more interesting and valuable, like a rare stamp with a microscopical typing error! :-)

Daniel, 411/004