I have a heavy gate (shown below) mounted to a concrete pillar using a 2x8 board and a piano hinge. The board cupped and finally split, so I must replace it.
The mounting board has a piano hinge along one edge. It bolts to the pillar with three bolts positioned 3-1/2 inches from the hinge edge (not quite along its center line).
As you can see in the picture, there is a metal post that takes the weight of the gate most of the time (when it is fully closed or fully open). The post is raised to move the gate.
When the post is raised, all of the weight and quite a lot of torsion is put on the mounting board, tending to want to tear the board apart.
Without the post holding the weight, I expect the weight of the gate will put shear force on the mounting board when the gate is closed and tension force when the gate is open. That force will be (nominally) parallel to the grain of that board.
I'm surprised it lasted as long as it has, about 25 years. But my local planning office pointed out that wood that I might buy today is generally not as strong as what was available 25 years ago. (I guess growers optimize their products around changing objectives, which makes sense).
All of this makes me think I should choose a replacement board carefully. For instance, I have read that Douglas Fur is stronger than Redwood, but wouldn't have the same resistance to moisture and bugs. (This is in Southern California, so moisture should not be as big an issue as it might be in other areas.) I understand that treated lumber is typically not very dense, so I would expect it to be a poor choice for strength. What I understand may also be entirely wrong.
I don't know how much the gate weighs, but the frame is made of steal tubing. I can't change that right now, so I have to go with just replacing the mounting board.
What commonly available woods would be most suitable for this application (in the 2x8 dimensioned size)? My biggest concern is the shear and tension forces, followed by resistance of the environment.
I'm considering laminating a couple pieces of 3/4"marine plywood (7 layers each) together to replace the mounting board. I think I can weatherproof that and it might give me the tear resistance I want. I don't know if there is any other disadvantage to this, but would be interested to know if anyone would agree or disagree.