Replacing engine insulation really worthwhile?

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eddystone

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One of the projects on my "possible" list is to replace the original foam engine box insulation which is getting near 30 years old. The VP 2002 isn't the quietest engine around and I can see the fire retardant benefit of the new foil backed sandwich material, but will it really make that much difference? Based on a comparative test in PBO a while back, it should cost me around £400, which is a lot when I'm also planning on a new main this year
 
I put a new engine in my boat and added a lot of super dooper insulation thinking it would be great. I like to think the noise level is better, but its barely noticeable. I think you need to do much more to improve sound levels drastically.

So I'd spend the money on a new jib as well as your new main sail! It'll be much more enjoyable to look at and your your boat will sail better for it. You might find that you are sailing more and using your engine less. A better result all round!

You could buy a set of ear defenders for the crew! It would also have the beneficial effect of keeping their ears warm!
 
Sound deadening is complex and it depends on where the problem lies. It is a bit like heat insulation in a house, useless if you leave the door open. Basically you are talking about vibrations through the air or through the structure which then transmits to the air. If the vibrations are outside the audible range then job done. I suppose the factors are:

1)vibrations integral to the engine: not a lot you can do other than tune the engine and look at air intake and exhaust.
2)vibrations transmitted to air in engine bay: sound deadening material covering main frequencies. Completely seal engine bay.
3)vibrations transmitted to structure: isolate engine from structure. Rubber mounts, shaft seals etc.

If you tackle only one area then the relative importance of the others increases.
 
pmagowan said:
Sound deadening is complex and it depends on where the problem lies. It is a bit like heat insulation in a house, useless if you leave the door open. Basically you are talking about vibrations through the air or through the structure which then transmits to the air. If the vibrations are outside the audible range then job done. I suppose the factors are:

1)vibrations integral to the engine: not a lot you can do other than tune the engine and look at air intake and exhaust.
2)vibrations transmitted to air in engine bay: sound deadening material covering main frequencies. Completely seal engine bay.
3)vibrations transmitted to structure: isolate engine from structure. Rubber mounts, shaft seals etc.

If you tackle only one area then the relative importance of the others increases.
Click to expand...

Point 2) has the important caveat of completely (acoustically) sealing the engine bay. This is not practical on many boats; for example, on mine the engine bay communicates with the bilge! Sound travels easily round corners, so if there's an air path from where the noise originates to where you can hear it, the sound will travel along it. The foam insulation on mine has the important job of cutting down sympathetic vibrations in the panels surrounding the engine (a loose screw on one of them magnifies the noise enormously!), but I doubt it does much to cut down air-borne noise from the engine.
 
I just did mine and its a massive difference. The top/lid was GRP , probably about 5mm thick and with the thick silver faced acoustic sheets. I binned the GRP and made a 60mm thick ply box lined with the acoustic foam. I reckon its half the noise. I think the critical bit is overlapping every joint to stop sound escaping. Also put foam under any bits of exhaust touching the hull and around mufflers and watertraps.
Edit- Maybe another contribution was lining the walls and ceiling in the wheelhouse with foam backed vinyl (its a motorsailor)
 
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The best stuff is the lead sandwich type. and I've used Noisekiller's many times.

However with my new engine being mechanically quieter than the 4108 it replaced, I found induction noise from the air intake to be a significant source of noise. So my solution was to remotely fit an airfilter box from a Ford Ranger under the cockpit, thereby reducing and removing the noise from the engine compartment.

I did some measurements with a decibel meter last year to prove I was not deluding myself because the noise level is below the level where it is intrusive - its no more disturbing than the engine noise in most cars or vans. Its also barely increases with revs.
Here is the link to the thread and my results. I never cease to be impressed with the overall low noise and excellent refinement from the new engine and my sound reducing steps.

http://www.ybw.com/forums/showthrea...ith-a-Marine-Power-Chinese-46bhp-diesel/page4
 
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You can do what I did.I used 2mm lead sheet and Vetus white soundproofing on top of it. The difference is amazing and I'm sure you'll pay a lot less than for similar effect lead sandwich stuff.
 
Just a point worthy of note.

My understanding is that the "lead" sheets aren't really lead these days, but bitumen.
Either way it's still very dense and slightly flexible and therefore absorbs low frequency noise well.
You can buy sound / vibration deadening pads for cars which are the same material and work equally well, easier to obtain and probably cheaper (just a hunch, I haven't checked).
 
single said:
I just did mine and its a massive difference. The top/lid was GRP , probably about 5mm thick and with the thick silver faced acoustic sheets. I binned the GRP and made a 60mm thick ply box lined with the acoustic foam. I reckon its half the noise. I think the critical bit is overlapping every joint to stop sound escaping. Also put foam under any bits of exhaust touching the hull and around mufflers and watertraps.
Edit- Maybe another contribution was lining the walls and ceiling in the wheelhouse with foam backed vinyl (its a motorsailor)
Click to expand...

What thickness ply did you use? I am about to do the same with my engine.
 
Given there is zero chance of acoustically sealing the engine bay, which is completely open to the area under the cockpit sole, sounds like not worth the bother until the existing foam disintegrates. Alraedy have a new jib thanks.
 
I spent around £300 on trying to reduce my engine noise from around 95db to 83ish db.would I bother again? No. I think if you are serious about this you need to encase the engine in a box not forgetting underneath and just having a pipe vent through to the air filter, then you might have a over heating problem in hot climes.
 
eddystone said:
One of the projects on my "possible" list is to replace the original foam engine box insulation which is getting near 30 years old. The VP 2002 isn't the quietest engine around and I can see the fire retardant benefit of the new foil backed sandwich material, but will it really make that much difference? Based on a comparative test in PBO a while back, it should cost me around £400, which is a lot when I'm also planning on a new main this year
Click to expand...

What boat is it?
 
I did Ariam's engine bay last winter with about £500 worth of Noisekiller's genuine lead (not bitumen) insulation. The previous insulation was almost non-existent, just a thin layer of ratty foam on some (but not all) of the surfaces and the noise in the cabin was intrusive to say the least. Even with a raised voice you couldn't talk to someone at the galley from the helm, you'd have to shout to get them to stick their head up into the cockpit. Now it's just a background noise; nicer without, but motoring for hours if necessary is a reasonable proposition rather than an endurance run.

The insulation has a sticky backing, but this is really just to help hold it in place during installation. You'll need lots of stainless screws and penny washers to secure it properly. Get plenty of 4" foil tape (some eBay sellers have good deals) - you'll need way more than you expect but applied over all the joints and odd shapes it helps give a really smart result.

An added bonus beyond the noise reduction is that Ariam's engine bay now looks really smart :encouragement:. Apparently when my parents take the boat to Maxi Owners rallies, my Dad keeps making everyone look at it :D

Pete
 
prv said:
I did Ariam's engine bay last winter with about £500 worth of Noisekiller's genuine lead (not bitumen)
Pete
Click to expand...
+1 for Noisekiller's lead/foam sandwich. I also used penny washers although if you do try to remove it, the adhesive remains attached and the foam comes away from it.
Its also easy to bend and stays put, unlike the mineral loaded springy sandwich type.
 
pmagowan said:
Sound deadening is complex and it depends on where the problem lies. It is a bit like heat insulation in a house, useless if you leave the door open. Basically you are talking about vibrations through the air or through the structure which then transmits to the air. If the vibrations are outside the audible range then job done. I suppose the factors are:

1)vibrations integral to the engine: not a lot you can do other than tune the engine and look at air intake and exhaust.
2)vibrations transmitted to air in engine bay: sound deadening material covering main frequencies. Completely seal engine bay.
3)vibrations transmitted to structure: isolate engine from structure. Rubber mounts, shaft seals etc.

If you tackle only one area then the relative importance of the others increases.
Click to expand...

I respectfully disagree. Type 2 air vibration will be deadened by any non-hard surface that does not vibrate. Generally softer the better. Look at the underside of the bonnet of your car. That mat of fibrous material is for sound deadening.
The foil,if any, helps somewhat also. I am not saying it is as good as purpose designed sound deadening material but it is surprisingly good & relatively inexpensive.

Type 1 noise can be helped greatly by a proper air silencer/filter available at local motorbike or auto performance shops. Just make sure it is large enough to pass the required air- ie: get one that is made for a similar or larger displacement engine.
A 4" dia. air intake hose wrapped in insulation & led from the engine to the lazarette or somewhere aft of the crew is good.

There are other vehicles besides boats that use relatively inexpensive engine sound deadening techniques quite effectively. As long as the material is not affected by dampness & is fireproof,they are worth a try,especially if cost is a factor.

Cheers / Len :)
 
Len Ingalls said:
I respectfully disagree. Type 2 air vibration will be deadened by any non-hard surface that does not vibrate. Generally softer the better. Look at the underside of the bonnet of your car. That mat of fibrous material is for sound deadening.
The foil,if any, helps somewhat also. I am not saying it is as good as purpose designed sound deadening material but it is surprisingly good & relatively inexpensive.

Type 1 noise can be helped greatly by a proper air silencer/filter available at local motorbike or auto performance shops. Just make sure it is large enough to pass the required air- ie: get one that is made for a similar or larger displacement engine.
A 4" dia. air intake hose wrapped in insulation & led from the engine to the lazarette or somewhere aft of the crew is good.

There are other vehicles besides boats that use relatively inexpensive engine sound deadening techniques quite effectively. As long as the material is not affected by dampness & is fireproof,they are worth a try,especially if cost is a factor.

Cheers / Len :)
Click to expand...
A paper bag will hold water but I prefer a bucket! :)

Almost any barrier will assist in noise reduction but sound deadening materials will be superior and the cost is mostly in the fitting. I would buy the correct stuff which will perform far better than a thermal insulation and then concentrate on fitting it really well. If you really can't afford it I would start putting my loose change in a jar and live with the noise until you can. I wouldn't put the effort into a half assed job.
 
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