In Dire need of adhesive advice

[goonstopher]

I have come to a stand still. I am so scared to pic the wrong adhesives and sealers for my sonotube subs because the end caps were custom and cost a lot of money.

I will list what i need to seal and the challenges and finally some things i considered.

1. Top end cap to 8" port
Challenge A. - The port overlaps a hole in the top of the endcap but the port is not perfect so it does not meet the endcap flush in all places IE there might be some gaps.
Challenge b. - The port is metal and the endcaps have a high gloss automotive cleat gloss paint job on them.

My thoughts were use liquid nails mirror adhesive then seal the inside with spray foam - I am a bit scared of the mirror advesive because of possible VOC content and the fact that is says allow one week before sealing in when used on mirrors. Would Expoxy be safer? Also I have never seen anyone use spray foam as a sealant and wondered why?

2.Bottom and top end caps to the sonotunes
Challenge A. - The custom end caps are maybe under a quarter inch small or less but luckily the outside lip more than covers the difference

The challenge is that once I center it the sides of the endcaps that were meant to attach to the sides of the tube will have small gaps that I could use ahdesive on BUT the primary or initial hold will have to be applied the the underside of the outside lip.

Is there an adhesive I could use that would safely fill this small gap rather than relying on this cumbersome 2 step solution?

3. Sonotube being used as a port (8") to the metal port

Again there is not a perfect fit so while there is one small point of true contact the rest has slight gaps to be filled, it also has to be strong enough for metal and being used in a vibrating port (although 15hz tune wont vibrate that often ha)

[ThomasW]

Hot glue will be fine attaching the port to the flare

Epoxy is probably too brittle to glue in the end-caps, IMO there needs to be a bit of flexibility in the adhesive given the characteristics of the tube. Epoxy would work for attaching the port flare but you'd need to be extremely careful not to get any on the finished pieces since only solvent will remove it.

Since you have finished end-caps, and finish material applied to the outside of the tube the adhesive options are limited.

I'd insert the port end-cap and run a bead of Liquid-Nails on inside of the enclosure where the wood meets the tube. Insert the driver end-cap and repeat the process. If you don't want to have VOCs you'd need to use a siliconized acrylic latex caulk as the 'glue'

Unless the goal is to decrease the internal volume of the enclosure, I don't understand what function spray foam would serve in any subwoofer.

[goonstopher]

Thanks - i have looked at many liquid nails options.

So far I see the heavy duty low VOC as being the most versative but the project one says it can fill gaps up to 3/8" unfortunately it does not seem great for metal or painted surfaces. Someone suggested polyurethane construction adhesive but that term is so broad that it means nothing to me. The spray foam was to fill in any gaps, I am scared of usuing silicone caulk because of the acetic acid release.

[collo]

I recently used hot-melt glue to install some 6 inch PVC ports.

There is a problem. The glue becomes firm very quickly. By the time you have put the glue right around the perimeter of the joint, you may find that you can't fully seat the port in the baffle. At this stage, you probably can't get it back out again either.

I found a better solution is silicone. You can get "neutral-cure" silicone that is recommended for sealing metal roofs, which doesn't emit acetic acid.

For mounting the endcaps to the sonotube, go with Thomas' recommendation.

[kingpin]

polyurethane construction adhesive is commonly known as PL Premium. This is the one youwant to use as it has some flexibility to it and is also a gap filler. Understand though that these are gap fillers but they will have air pockets inside if you do not use enough.

I would run some rope caulk on the lip for your air seal and then use the pl premium as your glue and gap filler. After the PL dries use your router or a chisel to remove the excess and than lay a good bead of acrylic caulking for finishing.

Make sure you let the PL dry for 24 hours before sealing it with the caulking though so it has time to let the gasses escape.

You could also use silicone as your finish as it comes in different colours also.

You can use the PL on the port also but I would recommend anywhere there is a gloss finish to lightly sand that area where the adhesive will be present for a better bond.

Mike

P.S. I went through at least 5-8 tubes of the stuff for all mu builds. WEAR GLOVES!!!

[ThomasW]

I can't imagine a properly made end cap having 3/8" gaps.

Polyurethane caulk/adhesive is available a home center stores, it has a high VOC component, but basically sticks anything to anything

As Collo suggested there is Silicone II it has no acetic acid component. Standard silicone works fine if you just give it a couple days to off-gas.

[kingpin]

Just curious...but from my days of training and going to seminars with companies like G.E. silicone is not really a glue. A sealer yes, an actual adhesive no. There is a marine silicone made by most companies(I prefer) the 3M product that can be used as a glue as well.

My .02. LOL

Mike

[ThomasW]

Just curious...but from my days of training and going to seminars with companies like G.E. silicone is not really a glue.

Trust me if you put a bead of silicone around the frame of a driver and put it in the hole, you'll find out it's impossible to remove without the total destruction of the frame. So I'll call it a glue....

[kingpin]

Trust me if you put a bead of silicone around the frame of a driver and put it in the hole, you'll find out it's impossible to remove without the total destruction of the frame. So I'll call it a glue....

LOL!
I trust you Thomas.

I'm just thinking if the op has that much of a gap he may need something quite a bit better than silicone. But, as the saying goes there is more than one way to skin a cat!

hmm...now I'm hungry.

[Dennis H]

If the sonosub is ported, it's getting air from the outside and you don't need to worry about VOCs getting trapped in the tube. I'd use polyurethane caulk/adhesive (in a tube, applied with a caulking gun) for everything. It sticks better than any other flexible glue I've used.

[goonstopher]

Yes I got the PL premium and a non-acetic acid silicone for the air seal.

I figure I will used the silicone on the inside of everything after the pl premium is dry.

[Dennis H]

PL premium will seal out air as well or better than silicone.