Albin 27 sound insulation----new thoughts

[REO]

I have removed the engine from my Albin 27 and am prepping the engine compartment. Sound insulation is high on my priority list. I had previously been focusing on the bottom of the engine compartment covers and the bulkhead directly in front of the engine, but improved access to the area on either side of the engine has changed my focus.
There are several unobstructed paths for sound to get from the engine compartment to the pilothouse. A previous owner installed four large speakers in the pilothouse wall. By removing the speakers I have discovered that there is a clear path behind the wall directly to the engine area on both sides of the pilothouse. Hoses and wires run through the areas, so it will not be easy to install a solid floor section. On the port side the storage compartment near the cabin entry has an opening in the top of the cabinet behind the wall that leads indirectly to the engine. The pilothouse walls are quite thin, so it seems like a lot of the engine noise was actually coming from that area.
I am considering building walls in the engine compartment on both sides of the engine, but air access for engine running and compartment cooling is through 4 vents high in the hull on both sides. My most current scheme is to build a wall on the starboard side with a sound baffle for air circulation above the holding tank. There is no room for a sound baffle on the port side, so I am thinking that an insulated wall where I can fit it in will help, and covering and insulating the openings from the top will help. I am considering making small sand bags to fit in the openings that I can access from the speaker holes. I also plan to build insulated boxes behind the speakers
Has anyone found a good way of sound insulating these area.
Materials are another conundrum. The sound insulation panels from Soundown seem to be the best, but quite pricey when you add in shipping. I found the MLV at Home Depot, but it was about the same price. I have looked at automotive products, but they aren't really designed for this purpose. I am close to biting the bullet and ordering from Soundown. Any thought will be appreciated.

[Mainer]

Read your note with interest as my A27 Isuzu engine is very noisy.

When I was researching sound deadening products the leading vendor was Soundown, in no small part because their product had a significant lead portion. Apparently they have eliminated lead (likely a risk aversion) and their sound deadening is no longer considered as effective. My pilothouse/cabin is unusually noisy because it has a hard windowed teak backside with two teak doors.

Because my engine is so large and the shaft alignment requires it's top to be so close to the underside of the hatches I have virtually no room to install any sound deadening material without having it rest on the engine in several places, sooo...

My solution was to cover the pilothouse flooring with 2 layers of 1/4" rubber blanket, plus a layer of household carpet pad, and topped with indoor/outdoor carpet. This has made a substantial improvement, however it is a pain to roll up this combo to open the engine hatches.

My observation through all of this is that by far the largest source of noise is the cabin floor, and I believe trying to soundproof other areas (like the pilothouse wall) would not yield much noise reduction in the pilot house.

Best wishes in your efforts to reduce engine noise.

Dick

[Ambler27FC]

There are some part numbers for sound deadening material at the end of this thread:
viewtopic.php?f=28&t=11885&p=81052&hilit=Repower#p81052

I don’t think it is quite as good as the Sundown because it doesn’t have a layer of rubber (two materials absorb more frequencies than one) but it is cheaper so you can use it liberally. I doubled the thickness on the engine hatches where i could. If you could improve the under-deck insulation, that may be a winning move.

I though about adding sound blankets on either side of the engine (in front of the tanks- and leaving space for air flow) but haven’t found a good way yet. Sound bounces off hard surfaces so best to trap it in the engine compartment. Those panels you’ll see on the auditorium walls can make a difference.

I have carpet, which helps. Played with adding a mat over the hatch, which made a measurable difference but wasn’t with the effort for me - I check the engine regularly.

I think these boats are reasonably quiet, but on a long drive I’ll pull the noise cancelling headset! No price on comfort.

[REO]

Mass is the what blocks sound. That's why mass loaded vinyl is so important in the best sound isolating material made today. But, the good stuff is sure costly. My engine hatches weigh a ton. That must count as mass?? Some sound absorbing foam, or rubber blanket and carpet pad should help reduce sound bouncing around, in effect echoing. I think I may have room on the underside of the hatches for some sound absorbing foam. Limited headroom limits what I can do above. I am betting that even a 1/4" of foam on the underside of the hatches would help reduce sound bouncing around in the engine compartment. I also agree that rolling stuff up to get at the engine will be a pain, so I am trying to avoid that.

A few things got me poking around looking for sources of noise other than the hatches.
I found and old AOG post where an owner had taken decibel readings and found that a lot of noise was coming from the storage compartments on the sides of the pilothouse. Since my engine is now removed, I can not replicate those readings, but I believe them. I was shocked to see the large open space leading directly to the engine compartment when I removed the wall speakers. My pilothouse walls are about 1/4" solid fiberglass, so there's not much mass to block sound that gets up there. Also, when I crawled in and looked at the bottom of the floor on either side of the hatches I found no sound isolation material.

I spent a lot of time looking at options yesterday. Here is my latest thinking.
I think the hatches and floor have enough mass, so I am going to try to get some sound absorbing material stuck, or stuffed to the bottom of these surfaces. Some less expensive acoustic foam may be good enough in this area.
I feel the same way about the forward bulkhead. From the hole for the toilet hose I can see that the bulkhead is at least 2" thick with heavy fiberglass on both sides. That should count for some mass, and I don't really care if some sound gets into the forward cabin underway. Acoustic foam with an aluminum facing should work there. Treatment on this wall is also cosmetic, so the foil surface will look good and clean easily. Seems to me that I don't really need the expensive MLV stuff.
I'm going to build removable walls on both sides of the engine compartment covered with soundown MLV and foam sheets. The walls will not be airtight, but hopefully they will baffle sound coming up in the floor and pilothouse walls. The walls have to be removable, since there is equipment behind them.
Since I can get into the walls through the speaker holes, I'm thinking about some way to attach sand bags to block the large holes where the filler hoses and wires run. I'll eventually build boxes to enclose the speakers. Soundown on the inside of the storage compartment doors could also be good.
I looked at the materials at McMaster Carr and it looks like they only sell to businesses. Can an individual purchase from them?
Any thoughts on my plans are much appreciated.

[nebulatech]

I was pretty sure McMaster Carr sold to individuals, but about a year ago, a friend told me they were overpriced. I've since found that to be true, at least for fasteners and metal, so I search online for other sellers with a priority for the ones that don't charge tax or shipping. In my region, the sales tax is 9.5%. If McMaster Carr is your best option, I just visited their website and created an account. On the shipping, business name is optional. I didn't see any field asking for a TIN, so perhaps you're good to go? You might have to select "credit card" instead of "invoice."

I keep thinking spray foam is a good idea, but last night I looked it up and it turns out spray foam doesn't add much sound insulation. Just wanted to share that. If mass is key, I would think denser foam, like a camping ground pad, would be a good material. Then again, the acoustic foam tiles look to be open cell and not so dense. I'm theorizing that if the sound insulation is in the engine compartment, it should be open cell, less dense, to interrupt the air vibration, but if it is outside the engine compartment, density would be more advantageous. On this subject, I'm no expert, so I'm just spitballing FWIW.

Regarding your speakers, the backing boxes are a great idea. Not only will they block engine sound, they will help channel the music output for your speakers, especially if you add ports.

[Ambler27FC]

Most sound absorbing material are porous like open-cell foam or felt. I believe the idea is that the sound waves enter the material and bounce off multiple surfaces, losing energy with each bounce. Dense material can block, but hard surfaces block by reflection and would leave the noise in the engine compartment to find another escape path.

McMaster does do personal CC orders. It is a good place to start and see what is out there - they are the Amazon of industrial supply. You might not buy metal there, but many prices are competitive. I'm a design engineer, and when you are ordering allot of stuff sometimes the convenience of one-stop shopping costs less.

[REO]

Had a nice chat with a Soundown rep yesterday. The whole story is that mass blocks sound and a softer more porous material reduces the tendency for the sound to bounce back. Both are often needed. I am going to use the half inch Soundown composite ( MLV with foam on both sides) on the forward bulkhead. I'm going to try to attach some MLV to the underside of the floor on the starboard side of the engine hatches. The rest will have to wait until the new engine is in. I am concerned about access and airflow. Maybe things will be clearer with the engine in place.

[nebulatech]

I'd love to see pics when you get it in place

[REO]

The engine should arrive in about a month. Then a few weeks to get things in-I hope. I'll start a new posting in the A27 area under sound isolation pictures.

[SkipRocks]

I'm a strong believer in Soundown, but it took two tries and a lot of costly Soundown for me to get it right in my '85 A27 sport cruiser, but we think it was worth it. The original engine had been replaced with the 130 HP Volvo Penta TAMD31 when I purchased the boat and it was a screamer in both the cabin and wheelhouse. In the cabin I put Soundown in the hanging locker on both the floor & back wall (and installed shelving), and the aft bulkhead of the head before glassing the entire head in to waterproof and add a shower (yet to do). In the engine compartment I put Sundown on bulkhead between the front of the engine compartment and the cabin, full width of the hull - I rewired & replumbed the boat at the same so everything was addressed w no existing holes. I also removed the water tank from the port side - the holding tank on the starboard side was already gone - and I put Soundown on the hull from the platform to the underside of the deck before replacing the water tank and holding tank. I put Soundown on the top (underside of the deck) - including both hatch covers. I put Sundown on the aft bulkhead (back of the engine on each side). WOT on the engine is 3900, never even come close to that, but we do generally run at 2800-3000. The noise level went from really loud, to bearable. Then I built a removable bulkhead between the two saddle tanks and the reduction gear, and then enclosed the rear as well and put Soundown on all of it (4 hand screws give me "fairly" easy access to the reduction gear). After enclosing around the reduction gear as well the sound level in the wheel house now approaches quite pleasant. The advice that I was given that I'll pass on... You have to enclose & insulate EVERYTHING. I can't remember if the Soundown I used was 1 1/2" or 2" thick, but it's the heavy 2lb/ft density and includes a lead barrier. It came shipped in a roll 48" wide and 12' long.

[REO]

Thank you for some really valuable input.
Holey mackerel! I wasn't planning on that much, and I was expecting more. Sounds like you did it right and then some. The best advantage I have is the new Beta 50. It should be quieter in the first place. I'm going to look very closely at what you did before I make a final decision on how much Soundown to order. One concern I have is airflow for combustion and cooling in the engine compartment. I have been planning a baffled air vent to get air from the hull vents to the engine compartment. If I build walls that are airtight on both sides I'm concerned that not enough fresh air will get in. Does your engine compartment seem hotter than before the Soundownization?
For the immediate future I am getting the stringers modified to install the new engine. Everything takes about 10 time as long as I think it will.

[REO]

SkipRocks
I forgot to comment on the shower conversion. I am also working on our shower. We cut off the existing cabinet and eliminated the tiny sink to get more room. The only part of the project that is completed is the drain. It was more work than I anticipated. First, the drain is just a hole in the floor. The edges of the hole were not sealed, so the wood between the fiberglass floor and underside rotted. I had to cut back to good wood and re-glass. Then there was the hose fitting. The original shower dumped into the bilge, a guarantee of stinky bilge water. There is barely room for a hose connection. I glassed the hose connection fitting into the floor when I rebuilt the floor. Getting the hose connected requires skinny arms and strong fingers. I ran the drain hose to a shower sump above the bilge pump in the forward bilge. The shower drains overboard through a new above water bilge pump through hull.
How did you waterproof your walls?

[SkipRocks]

Sundown: When I said I enclosed EVERYTHING with Soundown I meant almost everything. The fresh air intakes on each side remain open as originally intended. I never had a temp on the engine compartment itself pre & post Soundown, but I can say that the engine runs at the same temp (engine is cooled by sea water of course).

Shower: We did the same - I removed the itty bitty sink/cabinet in the head (it's only one step to the galley sink anyway). I waterproofed the walls by first sanding them down and then laying fiberglass on everything. For the aft bulkhead I installed the Soundown, then Coosa board (sp?) and then fiberglassed it. Have yet to install the shower, but it's ready. To keep peace in the family I also pulled the old head and replaced it with a significantly pricier electric toilet w a macerator. FYI I also had the same rotten wood around the drain in the head floor that required a similar repair.