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Discussion Starter #1
I am working on my 520 liter, 26" 13 hz tube for a UXL 18 (driver is still a couple weeks out). I got lucky and found a 26" tube sitting in a local warehouse, which is usually a special order item. What I didn't realize until I bought it is that it is the "Finish Free" style-- with their "Duraglas" coating on the inside, which chips off like 3/64" thick chunks of plastic--with some of the cardboard backing. I have read about people peeling off the film coating from the inside of their tubes, but this seems to be something different.

I would like to leave it in place, if possible, because it is so thick and doesn't come off well. I can just cut the endcaps to account for the lining; I am wary of gluing them on, and was planning on bolting them onto the sonotube through a thin strip wrapped around the outside. (Unless the press-fit just comes out really, really secure.)

The 2nd issue with the lining is attaching egg-crate foam to the inside, which I understand to be a good idea. Obviously, the lining is made for things not to stick to it... maybe if I rough it up with a rasp or coarse sandpaper, I could get the foam to stick with spray-on glue? Anybody have advice or experience with this lining?

Thanks!
 

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Discussion Starter #3
Haven't bought the foam yet; I was thinking 1.5" or 2. So basically a foam tube of this thickness has enough rigidity to hold its own form... sounds good, then I will proceed with the lining.

I am also planning on a ring to brace the end of the port, although I don't think I see most people doing this. Not necessary? Seems useful though, as it will alsobe the flare, hold the polyfill in place up away from the driver, and provide some mid-tube resistance to crushing in case of accidents.
 

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The foam will hold itself in with a little tension. Trying to spray glue it would be a real pain because it sticks on contact. You can't slide it in.
 

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If you do end up wanting to glue the foam in I would try a couple spot tests with and without surface prep to see what you're dealing with. I think sanding or rasping would get you the surface you'd need.

I think the support brace is a great idea for the reasons you came up with. Look forward to seeing your build! :T
 

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I can just cut the endcaps to account for the lining; I am wary of gluing them on, and was planning on bolting them onto the sonotube through a thin strip wrapped around the outside. (Unless the press-fit just comes out really, really secure.)

However you mount the end caps they need to be completely air tight. Press-fit won't be enough, the caps need to be totally sealed.

 

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Discussion Starter #7
ok... what I'm thinking of is a flexible but fairly solid strip which would wrap completely around the tube and screw through the tube into the endcaps, sandwiching the cardboard... kind of like a beadlock. I haven't thought of the perfect material yet though; I think metal might resonate. Maybe nylon, but I don't know where to find that.

Gluing would be easier, but I'm concerned about needing to get into the tube again to adjust the port, stuffing, etc.
 

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A metal strip bolted to the end cap will not resonate. It will be constrained in all degrees of freedom. That would definitely be recommended over a nylon strip.

However, finding a strip thick enough to give you sufficient transfer of loads and still be pliable enough to bend may be a little difficult. I would recommend aluminum bar stock somewhere in the 1/8 to 1/4 inch thickness range, which you should be able to bend easily.
 

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I am working on my 520 liter, 26" 13 hz tube for a UXL 18 (driver is still a couple weeks out). I got lucky and found a 26" tube sitting in a local warehouse, which is usually a special order item. What I didn't realize until I bought it is that it is the "Finish Free" style-- with their "Duraglas" coating on the inside, which chips off like 3/64" thick chunks of plastic--with some of the cardboard backing. I have read about people peeling off the film coating from the inside of their tubes, but this seems to be something different.

I would like to leave it in place, if possible, because it is so thick and doesn't come off well. I can just cut the endcaps to account for the lining; I am wary of gluing them on, and was planning on bolting them onto the sonotube through a thin strip wrapped around the outside. (Unless the press-fit just comes out really, really secure.)

The 2nd issue with the lining is attaching egg-crate foam to the inside, which I understand to be a good idea. Obviously, the lining is made for things not to stick to it... maybe if I rough it up with a rasp or coarse sandpaper, I could get the foam to stick with spray-on glue? Anybody have advice or experience with this lining?

Thanks!
djbachelor,
Interesting project! Do you have a build thread - would love to follow along and see some photos :)
 

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Discussion Starter #13
Thanks for the tip on aluminum bar; I might be able to come up with something like that.

What do you guys think of egg crate Memory Foam for lining the inside? I can find a 2" california king mattress topper for about $40, which is a pretty cheap price and the only thing big enough to wrap all the way around the inside (84" circumference). I don't know if it's closed or open cell though, or what the acoustic properties are. 2" foam is not really going to be blocking any low frequency waves anyway, is it?
 

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Discussion Starter #15
Ok I found relatively cheap acoustic foam... is 2 1/2" too thick? I wanted to go with thicker because it is 80 inches wide and the inner circumference is about 82"; I figure the extra thickness will take up the slack when it's compressed into a circle and be enough to hold it against the side.
 
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