Here is the drawing that Joe was referring to:
Between the posts the unsupported timber will sag or deflect. Over the center post the timber will crown.
This causes this "exaggerated" wave shape effect in the timber.
At the point where the sag or deflection changes to a crown is called the point of "inflection".
This point is where the timber is neither sagging nor crowning. It has the least amount of both forces.
This, I am told, is where the joint should be made. If I understand all this correctly.
Here is the graph to prove this:
I personally don't recommend putting a scarf over a post because of this graph, but each situation is different, and they all have to be figured out, and built based on this.
Jim Rogers
