hi
i was looking around for material to build a curved enclosure for altec/gpa 416 and found this bendable cement board that looked interesting.
i have some experience in kerf cutting wood and also built curves with wood slats but was hoping that this material would be easier and faster to build curved cabinet walls with.
just wondering if anybody has tried it or if there are good arguments not to use it. a 3'x6' board 1/2" thick weighs 54 lbs. costs $19 at menards.
some more details about he boards:
PermaBase Flex® is a bendable cement board that can be used to wrap beams, columns, arches or anywhere an evenly curved surface is required. It's easy to install and can save the installer time and money. PermaBase Flex can be installed inside or outside and finished with tile, veneer or natural stone, thin brick or stucco.
Impact resistant with excellent overall compressive strength characteristics.
Impact resistant with excellent overall compressive strength characteristics.
Bends immediately, easily and evenly without water saturation or kerf cuts. Creates uniform curved surfaces.
Easy to cut and install with screws. Easy installation, reduces skilled labor costs.
Can be used in both interior and exterior applications.
Dimensionally stable.
30-Year Limited Warranty on PermaBase Interior Applications. 15-Year Limited Warranty on PermaBase Exterior Applications.
Dimensions: 1/2" x 3' x 6'
Shipping Dimensions: 72.0 x 36.0 x 0.5
Shipping Weight: 54.5 lbs
i was looking around for material to build a curved enclosure for altec/gpa 416 and found this bendable cement board that looked interesting.
i have some experience in kerf cutting wood and also built curves with wood slats but was hoping that this material would be easier and faster to build curved cabinet walls with.
just wondering if anybody has tried it or if there are good arguments not to use it. a 3'x6' board 1/2" thick weighs 54 lbs. costs $19 at menards.
some more details about he boards:
PermaBase Flex® is a bendable cement board that can be used to wrap beams, columns, arches or anywhere an evenly curved surface is required. It's easy to install and can save the installer time and money. PermaBase Flex can be installed inside or outside and finished with tile, veneer or natural stone, thin brick or stucco.
Impact resistant with excellent overall compressive strength characteristics.
Impact resistant with excellent overall compressive strength characteristics.
Bends immediately, easily and evenly without water saturation or kerf cuts. Creates uniform curved surfaces.
Easy to cut and install with screws. Easy installation, reduces skilled labor costs.
Can be used in both interior and exterior applications.
Dimensionally stable.
30-Year Limited Warranty on PermaBase Interior Applications. 15-Year Limited Warranty on PermaBase Exterior Applications.
Dimensions: 1/2" x 3' x 6'
Shipping Dimensions: 72.0 x 36.0 x 0.5
Shipping Weight: 54.5 lbs
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So it sounds like it has high mass but not the stiffness of cement which will mean it should be better damped as well compared to normal cement. Sounds interesting but I would still want a stiff outside layer as well if for nothing else than structural integrity.
Give this a read: A Whitepaper: The Audibility Of Cabinet Panel Resonances. Maybe it will give you some ideas.......
Give this a read: A Whitepaper: The Audibility Of Cabinet Panel Resonances. Maybe it will give you some ideas.......
Read through the pdf. Convex shapes require the rough side to face outward so would require another layer of something to finish. Requires bracing support of 8" or less so it sounds like a backer board and face surface treatment would be in order.
Same is required of sand.
Same is required of sand.
hum4god,
I think this might be a very good material for making a mid bass horn, by using maybe 3 layers bent to the horn profile and using epoxy glue between each layer.
I think this might be a very good material for making a mid bass horn, by using maybe 3 layers bent to the horn profile and using epoxy glue between each layer.
Three layers = a forklift I don't own
I wonder what the binders are? To me that would be critical. The radius min is 6", would be nice if closer to 4". Wonder if heat would aid bending a bit tighter, hmmm what was that I was just reading
Ply/bitumen/butyl/flex/felt
Greebster,
I guess if you are going to make one side of the horn using 3 full sheets then yes, it would be VERY heavy, however a 1/2 sheet would give a 3' x 3' and about 27 lbs. per layer.
That would not be too bad and make a nice sized mid bass horn with low end cutoff around 80hz. to 100hz. Making the curved side panels is the hard part and the top and bottom pieces could be made of 2 layers of 3/4" baltic birch plywood to cut down the weight.
However, I would not want to move this horn frequently unless the is part of an exercise workout program !!!!
I guess if you are going to make one side of the horn using 3 full sheets then yes, it would be VERY heavy, however a 1/2 sheet would give a 3' x 3' and about 27 lbs. per layer.
That would not be too bad and make a nice sized mid bass horn with low end cutoff around 80hz. to 100hz. Making the curved side panels is the hard part and the top and bottom pieces could be made of 2 layers of 3/4" baltic birch plywood to cut down the weight.
However, I would not want to move this horn frequently unless the is part of an exercise workout program !!!!
Well, don't forget that everything that comes from a commercial outfit is going to involve at least a small measure of marketing and hyperbole. But yea, I thought it looks like a pretty good strategy and something that is diy possible with similar materials. I don't have access to a workshop anymore, so I've been trying to figure out how to build something similar using fiberglass on the outside, then a layer of rubber followed by a layer of cement. I think I'll want to put a light coat of resin on the inside of the cement too and then follow that with decreasing densities of insulation. I figure I can get curved surfaces with this strategy as well.
The stuff you're looking at seems to me as if it's almost combining layers 2 and 3 from that article together into one. So both high mass and high damping - but not the stiffness, so no really high Q layer. Might be worth trying though.
The stuff you're looking at seems to me as if it's almost combining layers 2 and 3 from that article together into one. So both high mass and high damping - but not the stiffness, so no really high Q layer. Might be worth trying though.
jReave,
You could also use several layers of bendable plywood " wiggle board " to make the curved sides of a mid bass horn which is what I did. However, you must use a furniture grade epoxy and not wood glue as it "creeps" and would be much less rigid. Where I live, it comes in 8' x 4' x 3/8" thick sheet and weighs much less than cement board.
You could also use several layers of bendable plywood " wiggle board " to make the curved sides of a mid bass horn which is what I did. However, you must use a furniture grade epoxy and not wood glue as it "creeps" and would be much less rigid. Where I live, it comes in 8' x 4' x 3/8" thick sheet and weighs much less than cement board.
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