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Poplar ply - any good?
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infrasound View Drop Down
Old Croc
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Joined: 13 May 2011
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Points: 2262 		Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 17 February 2021 at 6:13pm
Thanks for the link snowflake! Just what I'm after.


Stiffness is determined by the bracing primarily, thickness second.

With proper bracing, "just" 9mm of poplar ply can exceed the stiffness of 24mm birch plywood in cabinet.

Add a CF/GF skin to that and you're fixing that wear resistanceParty


Nb. 'Proper bracing' involves multiple rounds in FEM analysis & isn't a walk in the park. With guessing the bracing, you can go surprisingly far though.





Edited by infrasound - 17 February 2021 at 6:16pm
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VECTORDJ View Drop Down
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Points: 489 		Post Options Post Options   Thanks (0) Thanks(0)   Quote VECTORDJ Quote  Post ReplyReply Direct Link To This Post Posted: 17 February 2021 at 9:05pm
Why send all the time and work to make custom speaker cabs and use cheapie ply??? The best I have found is "Finland" 3/4" 4 x 8 foot 100 % birch exterior...........Like a Rock....
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Points: 3061 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 17 February 2021 at 9:19pm
Originally posted by VECTORDJ VECTORDJ wrote:

Why send all the time and work to make custom speaker cabs and use cheapie ply??? The best I have found is "Finland" 3/4" 4 x 8 foot 100 % birch exterior...........Like a Rock....


the good poplar isn't cheap - if anything it's more expensive than birch.
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VECTORDJ View Drop Down
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Points: 489 		Post Options Post Options   Thanks (0) Thanks(0)   Quote VECTORDJ Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2021 at 8:02pm
I am basing My choice of Finland 4 x 8 sheets as to what is stocked in Maine USA. The Poplar cored ply here has very thin Birch outer layers and is not water proof. Sort of soft too.  Go Finland. Like a Rock.
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Originally posted by infrasound infrasound wrote:


Stiffness is determined by the bracing primarily, thickness second.

With proper bracing, "just" 9mm of poplar ply can exceed the stiffness of 24mm birch plywood in cabinet.


How exactly did you reach that conclusion?
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snowflake View Drop Down
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Points: 3061 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 05 March 2021 at 12:16pm
Originally posted by stevie stevie wrote:

Originally posted by infrasound infrasound wrote:


Stiffness is determined by the bracing primarily, thickness second.

With proper bracing, "just" 9mm of poplar ply can exceed the stiffness of 24mm birch plywood in cabinet.


How exactly did you reach that conclusion?

deflection of a panel is proportional to the width^3 and inversely proportional to the thickness^3.
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infrasound View Drop Down
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Points: 2262 		Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 05 March 2021 at 1:48pm
Originally posted by stevie stevie wrote:

Originally posted by infrasound infrasound wrote:


Stiffness is determined by the bracing primarily, thickness second.

With proper bracing, "just" 9mm of poplar ply can exceed the stiffness of 24mm birch plywood in cabinet.


How exactly did you reach that conclusion?
]

FEA and some physical validation Smile
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Points: 425 		Post Options Post Options   Thanks (0) Thanks(0)   Quote stevie Quote  Post ReplyReply Direct Link To This Post Posted: 05 March 2021 at 2:27pm
And did all this FEA and physical validation result in a commercial product?
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infrasound View Drop Down
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Nope, only for personal toys

IMO it would be hard to commercialise, specifically due to the cost, assembly complexity, tolerance, wear and definitely overall strength.

I'm happy to manage these personally, but wouldn't scale well upwards from there
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