Best (And Stupid Simple) Soundproofing Mod?

[swatski]

I've been newly inspired, lately, by @gmtech16450yz and other' postings on some novel ways to soundproof the boat. I myself have done many expensive and labor intense soundproofing mods... While I would say that several have proven reasonably successful - such as the RAAMat install etc. https://jetboaters.net/threads/another-soundproofing-thread-the-raamat-experience.11872/ - this new idea (here) is just crazy simple and yields crazy good results.

Of course - this most recent attempt started as something completely different, lol. I came across it initially when I was messing with my custom WakeMakers ballast install - I was fitting various bags in various spaces inside the hull and, in the process, noticed that some of those bags appear to attenuate engine noise...


Well, after some more experimentation - I can tell that stuffing "long" 350lbs ballast bags (inflated to the max with air) placed inside the back of the rear storage compartments (alongside engine bay bulkheads) cut the engine noise better than anything else I have tried, so far!!!


Crazy simple, too - basically, I'm using two older style bags that I no longer have other use for. Those are stuffed in the back of the storage compartments (pretty much dead space anyway) and inflated to fill in the space.

I will make some supporting modifications with foam sheets and and polyurethane, but even the crudest attempt yields astonishingly good results (relatively speaking of course).

Here are some (very bad pics) of the bags (those are inflated to the max, but sit inside larger outer cases).
Strbd:


And port:



I'll update during the week with some sound clips.

But - the difference is amazing. Such as simple mod...! I would say there is easily a factor of 2-3 drop in sound level during cruising. Unbelievable.


(I don't know to what extent the other soundproofing mods in my boat contribute to this latest success, but I would think it would work well on its own)


EDIT: Those air-filled bags would be used for regular cruising etc. only, and then deflated and removed for storage when rigging the ballast for surfing, of course.

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[zipper]

Very cool, "two birds one stone". Soundproofing and floatation all in one. In case of a "sub-move" or swamping.

 

[Mainah]

This gives me an idea. I have check valves on the top ouput of the bags what if I installed inline ball valves there and air inlets with check valves where I currently have plugs. I think the impeller pumps would hold at least 1 psi of air pressure. So could use one set of bags for both air or water. I could even rig up solenoid valves on my bulit in inflator to have the inflation plumbed and just press a button to fill with air.

 

[swatski]

This gives me an idea. I have check valves on the top ouput of the bags what if I installed inline ball valves there and air inlets with check valves where I currently have plugs. I think the impeller pumps would hold at least 1 psi of air pressure. So could use one set of bags for both air or water. I could even rig up solenoid valves on my bulit in inflator to have the inflation plumbed and just press a button to fill with air.

Yes, that would work, but not for long - as the impellers in reversibles get burned up quickly when running dry. Which is unfortunate, and also just about the only drawback of those reversible pumps as compared to aerator-type.

EDIT: I'm a moron! Can't read, apparently. See below vvvv.

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[Mainah]

Yes, that would work, but not for long - as the impellers in reversibles get burned up quickly when running dry. Which is unfortunate, and also just about the only drawback of those reversible pumps as compared to aerator-type.

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Not using the impeller pumps to pump air. They would evacuate the water and get shut off as normal acting as a seal to not let the air escape when I fill the bags with my now built in inflator from a different port on the bag.

 

[swatski]

Not using the impeller pumps to pump air. They would evacuate the water and get shut off as normal acting as a seal to not let the air escape when I fill the bags with my now built in inflator from a different port on the bag.

Of course! When you're right, you're right, lol. I edited my post...

I think that is the way to go, actually.

What I'm going to do next is stuffing of the hull cap and all the other gaps in the bulkheads, also filling all the spaces under the swim platform and the hull cap and along the gunnel spaces towards and inside the bow, just like @gmtech16450yz did, using a combination of foam scraps and expandable polyurethane.

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[SamCF]

I agree that random objects filling space is the best soundproofing. I keep my rear starboard compartment completely full of life vest, and rear port compartment holds the "Super Mable". Last trip out I removed most of the life vests to make room for a bucket of tools. I noticed it was louder then, but I didn't make the connection until I read this post.

I think the same would work in the fuel and ski compartments. I was looking around for a cheap closed cell foam and came across an above ground pool liner pad. 1/8" closed cell foam in 60'-100' rolls. I'm going to stuff the voids under the swim platform and in the fuel compartment with this: https://www.amazon.com/dp/B003TQMBLI/?coliid=IPY71MI54EKA6&colid=ALPHDI8HZYYL&psc=1&ref_=lv_ov_lig_dp_it

 

[Betik]

@swatski are you planing to use your boat as library ?

 

[swatski]

@swatski are you planing to use your boat as library ?

No. But I'm already hearing impaired. I'm told.

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[Betik]

No. But I'm already hearing impaired. I'm told.
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is this feedback from a legitimate otologist ? or from the one who might be confusing "selective hearing/stubbornness" with "hearing impaired" ?

 

[swatski]

is this feedback from a legitimate otologist ? or from the one who might be confusing "selective hearing/stubbornness" with "hearing impaired" ?

Let's just say... it is starting to look like a consensus.
So I better preserve what I can.


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[Glen]

Fantastic input.

Being underway, with no noise, has always been my chief love for sailing!

 

[Scottie]

Can someone explain why this would make an improvement? I'm not versed in sound deadening, so I don't know why air in a bag would have a different effect than just the normal air that's in the compartment already. If its just about taking up space, then a foam block or really anything else would also work....??

 

[Mainah]

Can someone explain why this would make an improvement? I'm not versed in sound deadening, so I don't know why air in a bag would have a different effect than just the normal air that's in the compartment already. If its just about taking up space, then a foam block or really anything else would also work....??

Think of it like insulation in a house. First you need to seal gaps to impead direct tramission of the thermal energy. Then you add material that traps air to slow down the conductivity of the thermal energy. Sound works a bit differently but the principles are similar.

 

[swatski]

Can someone explain why this would make an improvement? I'm not versed in sound deadening, so I don't know why air in a bag would have a different effect than just the normal air that's in the compartment already. If its just about taking up space, then a foam block or really anything else would also work....??

I think it is because sound is propagated as a wave, that gets disrupted by barriers/compartments. Denser media will absorb more of those waves, but I also noticed many a highway/construction site sound barriers are... just air-filled big containers of sorts.

An open-cell foam is probably best - as a filler - and certainly better than air, but it is not practical in a boat as it will, inevitably, get wet and moldy.

I have done a LOT of mass-loaded dampening in the two yammies I owned and it's been disappointing overall, I believe it's because the mass ratios between sheet metal of a car body and those mass loaded vinyl etc. thingies are a lot more favorable as compared to fiberglass wall of a boat hull.

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[M@__]

Nice work. That’s a really good idea.

I can’t lie. I threw 8 strategically placed life jackets in the bilge area. Haven’t tested, but they float and won’t breakdown and clog the bilge.

I think I have some memory foam pillows someplace.

 

[ralphsmithiii]

I'm glad I found this thread! While I don't have any ballast bags and they appears to be pretty expensive ($200 or so per?), I do have a TON of this for a studio I have in my house:
https://www.amazon.com/Silverback-Sound-Dampening-Foam-Thick/dp/B00MAQNAPY

I'm wondering if I can show a bunch of it back in the corners similar to the ballast bags to help fill the space and dampen the sound. My only real concern is how wet they could possibly get since they are spongy-like material versus a ballast bag. Maybe its worth trying just to see how/if much improvement there is using it since its just sitting in my garage doing nothing.

 

[swatski]

I'm glad I found this thread! While I don't have any ballast bags and they appears to be pretty expensive ($200 or so per?), I do have a TON of this for a studio I have in my house:
https://www.amazon.com/Silverback-Sound-Dampening-Foam-Thick/dp/B00MAQNAPY

I'm wondering if I can show a bunch of it back in the corners similar to the ballast bags to help fill the space and dampen the sound. My only real concern is how wet they could possibly get since they are spongy-like material versus a ballast bag. Maybe its worth trying just to see how/if much improvement there is using it since its just sitting in my garage doing nothing.

Oh, those will get wet no doubt, sooner or later depending on climate and boating style/activities. But then you just remove/replace.

I was very surprised one time driving fast when someone opened one of the rear compartments - the amount of sound emanating from that space was huge! Seat down cuts it off, but filling the space does even better.

Now - not advising anyone to do that at any speed, but try to open or even crack open the engine hatch and rev up the engines. The noise is absolutely ridiculous. You will be installing a nice seal on that hatch in a hurry after that! Come to think of it, the hatch seal is the single most (cost/labor) effective mod for alleviating noise issues.
If I did not want to do anything else, I would do that seal, and stuff the rear storage compartments (bulkheads on the sides of the engine compartment) to the gills with anything that absorbs sound (and I mean anything, like old blankets will do, lol)
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[ralphsmithiii]

@swatski I haven't looked yet, but, is there a specific seal/material/method to sealing the engine hatch? Or do I just need to go to Lowes/Home Depot and pickup some 3m door seal tape to seal it?

 

[swatski]

@swatski I haven't looked yet, but, is there a specific seal/material/method to sealing the engine hatch? Or do I just need to go to Lowes/Home Depot and pickup some 3m door seal tape to seal it?

This is a good seal that works great and will not interfere with closing the hatch (and will not pop the hinges out) - in post #19
https://jetboaters.net/threads/another-soundproofing-thread-the-raamat-experience.11872/

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