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Bracing: expansion foam [message #34072] Mon, 22 October 2001 12:00 Go to next message
Harald is currently offline  Harald
Messages: 8
Registered: May 2009
Esquire
Hello Wayne,

Of course, I carefully read your message Bracing with regard to bracing the long panels with expansion foam; now I'd like to know how you do this exactly. Filling in the foam seems to be a 'dangerous' job, because you don't see what really happens inside the cabinet.

I would leave the cabinet open at the back and fill 3/4 of the cavities with the foam to preload the horn slopes, side panels, top and bottom panels.

After that I would assemble the back panel and drill the holes to fill the remaining 1/4 of the cavities. To my mind this reduces the risk of cracking the cabinet.

What do you think of this? Thanks for your assistance.

Harald

Re: Bracing: expansion foam [message #34075 is a reply to message #34072] Mon, 22 October 2001 18:01 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18784
Registered: January 2001
Illuminati (33rd Degree)
When filling an unused chamber with expansion foam, one must be careful to avoid overfilling. The foam expands and can easily crack or even burst a panel. You can build up the chambers while they are open and can ensure that the foam is acting as expected during its curing process. Or you can drill holes and inject the foam into them, plugging the holes when you're done. The open method has the advantage of allowing you easy access, so you know when you're close to being done. The filler hole method is "blind", but you don't have to mount a panel over foam that has already started to set up.
Re: Bracing: expansion foam [message #34086 is a reply to message #34075] Thu, 25 October 2001 03:00 Go to previous messageGo to next message
Harald is currently offline  Harald
Messages: 8
Registered: May 2009
Esquire
Hi Wayne,

Another question: The cabinets are glued, that's sure, but do you also screw them? Recently, my carpenter told me that it's absolutely sufficient to glue the panels.

I'm not sure if that's true, particularly with regards to large cabinets such as folded bass horns.

Thanks again.

Harald


Re: Bracing: expansion foam [message #34087 is a reply to message #34086] Thu, 25 October 2001 03:57 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18784
Registered: January 2001
Illuminati (33rd Degree)
I agree with your carpenter. My experience has been that a properly glued joint is stronger than the wood itself, in most cases. So it is not important to use screws, even on large cabinets. My cabinetmakers have stated this, and I've seen evidence that tends to confirm it. Cabinets that are damaged by strong impact often have broken panels, but glued joints remain intact.

Having said that, my cabinetmakers still use screws in some places within complex cabinets. They are used as clamps to provide hold-down strength while the glue is drying. They actually could be removed after the glue dries, but there really is no need. So they're left in place.

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