Is plywood stronger than solid wood?


Stobes21
 Share

Recommended Posts

Dumb question perhaps, but I'm thinking about building a canvas covered gun case to transport my break action shotgun to and from the range. Something like this, which looks way classier in my mind than a plastic case.

So anyway, the basic box needs to be strong and durable but as light as possible. Appearance doesn't matter since it'll be covered. I was thinking 3/8 or 1/2" Baltic birch ply would be the ideal material since it is strong, stable, and lightweight. But I was wondering if a lightweight solid wood like poplar would be stronger planed down to an equivalent thickness. Thoughts?

post-16916-0-04936800-1423778728_thumb.j

Link to comment
Share on other sites

Generally speaking as plywood is made of multiple plys with grain running at right angles to adjacent plys it will be much stronger than a similar thickness solid wood which can split along the grain.

Fibreglass and carbon fibre layups are done in a similar way and produce super strong lightweight structures.

There are always exceptions and somebody may know of a super strong wood.

I would make the case from 1/4" to 5/16" thick materials.

Link to comment
Share on other sites

Solid wood is stronger along the grain than plywood but plywood is more uniform.  A solid wood shelf will sag less than a plywood shelf.

 

Think torsion box though.  Two layers of 3mm BB with a 1/4" web between them will be almost as strong as 12mm BB but significantly lighter.  Put the grain direction of the two skins at 90 degrees to each other since 3mm BB is really bendy across the grain and that will help balance out any twist in the plywood.

Link to comment
Share on other sites

If you follow krtwood's suggestion, and make a torsion panel design, you could use 1/4" solid wood strips for the interior bracing and edges. That would give you 1/2" thick edges to work with, and box joints would be super strong.

I think I may steal your idea, there are a couple of long guns in my closet that deserve a nicer case....

Link to comment
Share on other sites

Solid wood is stronger along the grain than plywood but plywood is more uniform.  A solid wood shelf will sag less than a plywood shelf.

 

Think torsion box though.  Two layers of 3mm BB with a 1/4" web between them will be almost as strong as 12mm BB but significantly lighter.  Put the grain direction of the two skins at 90 degrees to each other since 3mm BB is really bendy across the grain and that will help balance out any twist in the plywood.

Strictly speaking this depends on how one is loading it.  It would be almost as strong in torsion loads, much weaker in tension and compression, and vastly weaker in shear.

 

Of course torsion loading is the most common way wood fails so for most uses this is true.

 

Quick primer on kinds of forces.

 

https://www.teachengineering.org/view_lesson.php?url=collection/wpi_/lessons/wpi_forces/wpi_lesson_1.xml

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share