Installing Soundown sound foam insulation

[osprey877]

I recently sound proofed my engine compartment with the above. It is a 1" foam sheet made up of 2 layers of foam separated by a dense rubber layer and faced with aluminum film. It is quite heavy.
My problem is that it won't stay stuck to the ceiling of the engine compartment, which is the bare fibreglass surface of the underside of my cockpit sole. I used the recommended 3M hi tack spray adhesive as well as some aluminum anchors that I glued to the underside of the cockpit sole with some construction glue in a tube. "No More Nails" I think. It stayed in place for a week or so while the boat was at the dock, but as soon as I was underway it started to fall down. Could be the heat or the vibration or both. The spray adhesive is still tacky enough to hold the foam in place temporarily, but not permanently.

Anybody have any experience with this product and any suggestions? It is basically attaching heavy closed cell soft foam to bare fibreglass. Thanks.

[DeValency]

I need to renew my own engine room insulation and the top insulation attachment with glue has always been an issue. My plan is to find at least four spots where a small diameter bolt can be installed and sealed with 5200 and hold the entire insulation panel with some 1”W flat long aluminum bars.

[nmuir]

I needed to add thin battens in my engine room ceiling to keep it in place. Glue alone was insufficient. Walls are ok with adhesive alone even a few years on.

[Bill O]

I used screws and large fender washers to hold ours in place.

Since you probably don't want to punch holes in you f/g, would attach wood w/a good adhesive behind the foam. Let the adhesive cure, then use screws to hold the foam in place. Use fender washers or battens to help distribute the load.

[Cheechako]

Your sole is likely a cored sandwich right? Just use big fender washers and screws after you glue it.

[osprey877]

Originally Posted by DeValency

I need to renew my own engine room insulation and the top insulation attachment with glue has always been an issue. My plan is to find at least four spots where a small diameter bolt can be installed and sealed with 5200 and hold the entire insulation panel with some 1”W flat long aluminum bars.

I had thought about something similar but was worried the through bolts and aluminum bar would transmit vibration to the hull, defeating the purpose of the soundproofing.

[osprey877]

Originally Posted by Cheechako

Your sole is likely a cored sandwich right? Just use big fender washers and screws after you glue it.

Good idea. I will check if cockpit sole is cored. However, As noted above, I would prefer to find a glue or adhesive that works as I think the mechanical fasteners may compromise the soundproofing effectiveness. The installation instructions seem to stress that there shouldn’t be any direct route for sound waves to be transmitted Out of the engine compartment. Or perhaps I’m being overly concerned?
I noticed online that there is two sided tape that is used to permanently attach acoustic tiles to wallboard etc. Anybody have any experience with this. Or with perhaps a tile or flooring adhesive?

[psk125]

We glued the aluminum anchors that came in the soundproofing kit with epoxy. They've held for about eight years now.

[Bill O]

Originally Posted by osprey877

Good idea. I will check if cockpit sole is cored. However, As noted above, I would prefer to find a glue or adhesive that works as I think the mechanical fasteners may compromise the soundproofing effectiveness. The installation instructions seem to stress that there shouldn’t be any direct route for sound waves to be transmitted Out of the engine compartment. Or perhaps I’m being overly concerned?

Yes, I believe you are over thinking it.

[Bullshooter]

Is there room to build a U-shaped piece of support, such as 3 pieces of wood, and install (in 2 separate places) upside down so the middle of the U is against the foam on the ceiling? Just trying to think of a way to avoid holes thru the F/G.