I know the arguments for and against plywood have been done to death
This is a query on plywood construction.
Is there or has there ever been another method of making plywood ; other than the standard grain crossing at right angles??
I was watching a program on the space suits used by US astronauts and the weave of the fabric was mentioned as contributing to the strength vs weight issue.
The space suit fabric was woven with dual warps at an angle to each other of 45 Degrees and the weft crossed them ( I think that is how it was described)
So here is the idea I have had and I was wondering IF it has been tried.
Instead of laying up the plys at right angles to each other it may be beneficial to lay alternate layers at 45degrees, so that each "LAYER" of the finished ply would be 7 layers thick or more
So like this
First layer 0
second layer 45
third layer 135
4th layer 90
5th layer 45
6th layer 135
7th layer 0
What are peoples thoughts possible? prohibitively expensive?
you know the reasonable measured thought experiment sort of thing
This is a query on plywood construction.
Is there or has there ever been another method of making plywood ; other than the standard grain crossing at right angles??
I was watching a program on the space suits used by US astronauts and the weave of the fabric was mentioned as contributing to the strength vs weight issue.
The space suit fabric was woven with dual warps at an angle to each other of 45 Degrees and the weft crossed them ( I think that is how it was described)
So here is the idea I have had and I was wondering IF it has been tried.
Instead of laying up the plys at right angles to each other it may be beneficial to lay alternate layers at 45degrees, so that each "LAYER" of the finished ply would be 7 layers thick or more
So like this
First layer 0
second layer 45
third layer 135
4th layer 90
5th layer 45
6th layer 135
7th layer 0
What are peoples thoughts possible? prohibitively expensive?
you know the reasonable measured thought experiment sort of thing
An interesting idea. How about cutting your panels at 45 degrees to the sheet, and adding full length vertical braces to the panels?
Andy I live in Australia our marine ply uses the normal lay-up alternate layers at 90 Degrees
I thought that the whole idea of plywood was that the grain orientation was anything BUT random
Hi Allen, that would mean an extra stage in the woodworking process, my thought was would the orientation I suggest have benefits ??
I thought that the whole idea of plywood was that the grain orientation was anything BUT random
Hi Allen, that would mean an extra stage in the woodworking process, my thought was would the orientation I suggest have benefits ??
If you want to test whether 45* or random orientation, you could easily lay up multiple layers of say 3mm 3 ply how you want them.
You might call it differently in Oz. Here marine ply is the stuff that the police use to board up broken windows and it is anything but regular. It looks like the wood eating monster has sneezed at the wood press.
3/4" MDF is certainly VERY RANDOM and good for cabinet buidling.
Sandwiching boards together is not really practical unless you have access to some means of applying consistent pressure ove the glued area during the drying process.
OK I know the stuff OSB Oriented strand board
Horrible stuff
Nope marine grade ply uses totally void free wood and a very water resistant glue and is over here usually made from hoop pine
Horrible stuff
Nope marine grade ply uses totally void free wood and a very water resistant glue and is over here usually made from hoop pine
I agree, I wouldn't use it for cabinet building unless it was sandwiched (on the outside anyway) with something more presentable. They do make it 1" thick though, I used it during the build of my house extension.
The orientation of the strands in the astronaut suits is likely set to optimize the strength characteristics of the material with the need for flexibility in the garment. Most things constructed of plywood are intended to be rigid so the requirements are not consistent.
I would cite cross-ply tyres as a potential demonstration. Radials were adopted due to their supple sidewalls. Cross-plys were just too stiff.
The other version of plywood is made of blocks of wood glued up to form a solid panel and that is then covered by veneer. It is primarily used for furniture and has a higher grade of veneer.
I have made my own plywood. This was done in a press we built here to create curved loudspeaker cabinets. Ended up using wood grade epoxy glue as the others we tried did not give the working time or adhesion needed. Used compressed air to drive the press closed around 6000 pounds of pressure as they were small floor monitor boxes.
I used fir veneer made for custom laminators, a bit hard to find. Better plywood is made of birch veneer. I use Norwegian birch as it is the best. I even have some in marine grade. (When I found the importer had it in stock I bought it all!) There is also Russian birch which is decent plywood better the the local Fir stuff. Then there is Chinese birch made from Russian trees and used to be sold at Home Depot. It is the worst of any birch plywood. Of course don't confuse any of those with Birch veneer Fir core plywood. That is what most non-specialty suppliers sell.
The reason why plywood does not do 45 degree cross laminations is that would result in greater waste and not add any useful strength.
I have made my own plywood. This was done in a press we built here to create curved loudspeaker cabinets. Ended up using wood grade epoxy glue as the others we tried did not give the working time or adhesion needed. Used compressed air to drive the press closed around 6000 pounds of pressure as they were small floor monitor boxes.
I used fir veneer made for custom laminators, a bit hard to find. Better plywood is made of birch veneer. I use Norwegian birch as it is the best. I even have some in marine grade. (When I found the importer had it in stock I bought it all!) There is also Russian birch which is decent plywood better the the local Fir stuff. Then there is Chinese birch made from Russian trees and used to be sold at Home Depot. It is the worst of any birch plywood. Of course don't confuse any of those with Birch veneer Fir core plywood. That is what most non-specialty suppliers sell.
The reason why plywood does not do 45 degree cross laminations is that would result in greater waste and not add any useful strength.
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45 deg layers add shear strength. Plywood isn't often subjected to loads in this fashion that would be a problem for orthogonal plies.
Strength is the least of worries for a cabinet. Though you might have a point if it's shear stiffness - but it's simply a matter of load orientation. Does a cabinet experience shear?
I would wonder how large of a speaker you'd be building to need such extremes of rigidity to warrant trying to sqweak every ounce of strength from ply... The --average-- loudspeaker doesn't have huge surfaces or endure the strains plywood is designed for (being the floor for instance).
If I craved such strength I'd do this:
Ply together 4 sheets of G10 at 90 degree increments.
Wood is my milleiu but even if you were to go nuts and make sappelle or maple ply, well, for super-strength you can't beat Dupont's arsenal...
I'm pretty sure the resulting speaker would be bullet proof.
If I craved such strength I'd do this:
Ply together 4 sheets of G10 at 90 degree increments.
Wood is my milleiu but even if you were to go nuts and make sappelle or maple ply, well, for super-strength you can't beat Dupont's arsenal...
I'm pretty sure the resulting speaker would be bullet proof.
I don't think my statement was worded well. Shear strength isn't a concern for enclosures. Strength is really only a concern for handling. 45 plies aren't going to affect stiffness appreciably. Thus no need to worry about it.
I fear you folks are worrying too much. Part of what I do for a living is repair and rebuild old PA speakers, 95% of which are normal 3/4" birch ply. Before you can do any real damage to the box, the drivers inside will be totally trashed - cracked baskets, shifted magnets, sheared mounting bolts, etc. Even butt jointed plain MDF is likely to stand up better to shock loading than the contents. Strength is not an issue. 😉
Yes but there is something alluring to building things with absurd strength. You could park a challenger tank on the last deck I built, and my pine side table is strong enough to serve as gallows for an iron elephant.
The late Don Pearson (Grateful Dead, Jefferson Starship. Hot Tuna etc) used to hit the box with a mallet. A dead thud was passing any resonance was not.
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