Aluminum hull sound-proofing

General boating discussion
steve-r
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Aluminum hull sound-proofing

#1

Post by steve-r »

Curious minds want to know :-)
The hypotheses is: Aluminum hulls, while lighter, stronger, etc , can be noisier than that other stuff....hull pounding in a chop... wave slap at anchor, engine vibration, etc.
Some mfg'rs spray foam, and we have the separate spray or not to spray polyurethane vs polystyrene discussion.
Some mfg'rs lay in soundproofing panels....I think Ironwood references this approach on their site. ( what do they use btw? )
I can appreciate thinner gauge hull material may be more susceptible to flexing and noise.. ( eg riveted cartoppers)
If you assume a 1/4" hull, properly built with longitudinals and cross ribs, and a welded alum floor ( not vinyl covered wood), and 3/16" sides, and no floatation regulations apply, then:
a) is soundproofing required? preferred?
b) what are the alternatives? (do you still spray foam? )
b) and what is the right way to do it? ( i realize this can have multiple perspectives .. for a mfg'r, keeping material and construction cost low, or as an operator, quietest ride, future mtce cost )

all views are of interest !!
Steve Ronson
18' Kellahan CC
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Re: Aluminum hull sound-proofing

#2

Post by steve-r »

lotsa views, no opinions? how about some input from the builders on here?
Steve Ronson
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goatram
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Re: Aluminum hull sound-proofing

#3

Post by goatram »

Steve I know what oil canning is and I have road in a Smokercraft 20' with the .160" thick hull and it sounded bad. My Northriver 21' is a lot quieter by far .250" bottom. It has no flotation and came with plywood floors. It does make some noise though it is something that I can live with. Your question is kinda vague.

Are you asking the question as a user or as a builder? Foam as you stated has the corrosion issues. Cut the weight of the boat by using less alloy in the right areas and you increase the capacity, decrease the complexity of the build, and save money. You require a quiet boat a plastic one might be the right fit for you. Ease of maintenance and good looks are important then get a alloy one. my two cents are free. I hope I helped, otherwise disregard. :soap: :banghead:
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steve-r
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Re: Aluminum hull sound-proofing

#4

Post by steve-r »

nope, not a builder. didnt mean to be vague. just thinking about the sound-proofing decision if i were to have another alloy built without foam, and wondering how its done.
my Kellahan is 3/16 bottom and 1/8 sides, has 4 longitudinal stringers, not too many cross ribs, is completely foamed under the wood floor, which most definitely muffles some sound, but still bangs the chop loud & hard. Mostly because its so light , and the flat chine, it bounces across the top of waves and doesn't cut thru them so much.
(maybe i'm biased...i'll live with the noisy ride before i'll invest in plastic, and wear my AAB.com shirt with pride!!! )

"sounds" like one vote says a .250 bottom , unfoamed , doesn't need soundproofing. any others?
Steve Ronson
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Re: Aluminum hull sound-proofing

#5

Post by Bob5292 »

Personally I don't see much need for sound insulation on a small boat. There are lots of spray-on materials like Silent Running and Mascoat Delta-T. I haven't really heard any first hand positive experiences about these products but at the boat show, a thick coating of Silent Running SR1000 did dull the sound on a piece of metal he had on display. At the same boat show, a very reputable builder said that they have tried all the coatings and they don't do much. I think it would at least take the "Tinnyness" out of the boat. I was tempted to do the underside of my decks but it didn't seem worth the hassle.

It really comes down to cost. If you want to spend the bucks you can make an alloy boat as quiet as any glass boat. A 72 x 54" piece of 2 inch SoundDown"foam" is about $200 and near $400 for that same size with the moisture barrier. A 5 gallon bucket of SR1000 is about $700. The rubber like sound barrier similar to what Ironwood had on the hull of his boat weighs 2lbs per sq ft and is about $200-$300 for a 4'x8' sheet depending on the type. I happen to like the perforated aluminum headliners with sound absorbing foam behind them. Supposedly the sound travels through the perforations and is then trapped in the foam. I was in a 6x8' pilot house that had the perforated headliner, acoustic panels on the walls, with a thick rubberized floor covering and you could carry on a conversation and it was almost eerie because there was zero echo. The only reason I have been soundproofing my boat, is so I don't have to get up to pee every 5 minutes from the sound of water lapping at the hull and rain dripping onto the walk arounds and cuddy.

Bob
steve-r
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Re: Aluminum hull sound-proofing

#6

Post by steve-r »

Bob, interesting...the cost & weight tradeoff are important factors to consider, more than i expected.
i didn't appreciate how expensive soundproofing materials are. wow!
interesting thought to sound treat the cabin/cuddy instead of the hull.
rain, wave lap, and a few age related issues ...thats all i need is another reason to pee in the night... lol
thanks for the informed reply!
Steve Ronson
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Jay Perrotta
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Re: Aluminum hull sound-proofing

#7

Post by Jay Perrotta »

Steve,

As you point out we are discussing polyurethane foam in another thread but the substance speaks directly to your question.

When in an open, plate-built alloy boat I don't find the need for sound-proofing very high. The wind noise, engine noise etc makes the hulls sounds pretty unnoticeable. At rest the wave slap is more noticeable than GRP but nothing annoying or troublesome. The only place I would see a problem would be in something like a flats boat where the noise might scare fish.

On the other hand if you have an enclosed alloy boat where you are going down below - especially underway, the noise of an uninsulated alloy hull is significant and bothersome. In our Rock Salt 34' the boat is uninsulated but open. Underway and on a drift there is no "problem" with noise from the hull..

It does have a stand-up head in the console and when you go in there underway it is quite noisy. Doesn't really matter if you are going to the bathroom for 3 minutes but were it an enclosure meant to take a nap or prepare a meal it would have to be insulated I would say.

Since polyurethane foam is the only substance that meets USCG flotation requirements and does a great job at sound mitigation it makes sense to use the stuff for sound deadening and get some added flotation.

Just my 2 cents...
Jay Perrotta
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Re: Aluminum hull sound-proofing

#8

Post by Chaps »

If you look closely at the pic in my sig you can see that the inner hull sides on my LaConner have vertical stiffening ribs and the Edwing doesn't. The LaConner is very quiet (for an alloy boat) running through chop, the Edwing is pretty noisy. Both boats are well ribbed and stiffened below decks, both are all 1/4" hulls & sides. I think large expanses of unsupported aluminum (even 1/4") is a primary source of deafening noise.
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steve-r
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Re: Aluminum hull sound-proofing

#9

Post by steve-r »

Jay, I'm thinking more walkaround pilothouse style than open.
I guess the only time it would really matter is if you're actually trying to sleep. underway just deal with it and know that if you want the pounding to back off , slow down.
in addition to the hull foam, is there any additional soundproofing in the Pacific 26SCS sleeper cabin area?
wave-lapping at rest will likely be at the bow, will a cuddy be an echo chamber?
sound absorbing panels in the cabin area referenced earlier would help, at some cost.

i'd bet i hear my boat less when underway if i had more deadrise (ie. 18 deg instead of 12 ).

Chaps, your comparison says its back to design and construction...build it right (not that your Edwing is built wrong, but the LaConner looks heavy duty ) and that can go a ways towards eliminating the "tinny" symptom. i' saw an older alloy recently that looked like the sides were 1/8" and had a wavey pattern in them amidship, like they've been flexed in and out a few times ... thats gotta be noisy.
i need some seatrials. the local marina has an Ironwood, a Broadwater, a North river, a Silverstreak, and a Hewescraft, but i dont know the owners.. the marina wont give me contact info, maybe i'll just leave a complimentary note about what a great looking boat they have, tell them I'm keen to hear what they think of their toys, and hope they call me, then segue the chat into a possible ride...and hear it firsthand.

really appreciate all the experience on this site! thx!
Steve Ronson
18' Kellahan CC
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Re: Aluminum hull sound-proofing

#10

Post by pjay9 »

Speaking of noise my Raider has a swish swoosh singing sound under way that isn't always there and really have not figured when it really happens. It seems to be when it moves up and down thru chop or a little bit of porpoising. When I look at the hull the lifting streaks are skip welded the whole length...so I conclude that the water is squirting thru the crack and filling the void, sort of like blowing air between your fingers with a piece of paper in between...you get that squeaky sound.
My solution...ignore it! This topic is interesting and I saw a demo of the paint on stuff on a hunk of metal and it seemed to work, but the cost was not worth it. On my old Charter boat the engine room had not sound barrier, so i went to the Boeing surplus store and found some aircraft barrier...cost effective and durable. It was a roll of vinyl that was heavy and impregnated with lead and other stuff. used to line the interior of cabins. It blocked the sound. I even covered the intakes and left it like a flap, so it could move freely as air for the engine increased the opening got bigger yet blocked the path of the sound somewhat...it worked! Capt PJ
2009 Raider 185 Pro Fisherman, 2005 90Yamaha, 2012 Yamaha9.9HT, 2008 EzLoader roller, 2004 Dodge TCD dually, 2005/2015 Lance1161
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