Strength of Joints

I was doing a little test of the strength of different joints.

I planed some hard maple down to 3/4 and ripped it to 5" wide. I made 5 different styles of joints you might find. T&G, 1/2 Lap, 1 Dowel, 2 Dowels, and a Biscuit. I then cut a slot right at the joint on the bandsaw, so each glue area was exactly 3" wide, to make each test start as even as possible.

We then tested them in tension to see which ones held up best.

As we were bolting these grips into the machine, I joked "Watch this thing pick this piece of steel right off the ground" I was more worried about the grips being able to hold onto the piece than it lifting it off the ground

Sorry, crappy cell phone pics.

Well it turns out, my first test, a T&G, picked the steel right off the ground, all 1500 pounds of it, before breaking, have u ever heard 1500 pounds of solid steel fall right in front of you without warning? We then bolted it down and continued the tests.

I dont have my numbers in front of me, but the 1/2 lap was the stongest, with an average of around 2700 pounds. The T&G and 2 Dowels were around 2400, the one dowel was around 1600, and the biscuit was around 1200. Keep in mind this is a 2.25 square inch area that the two boards meet.

Just figured someone might be interested in this.

I would have liked to do a Kreg screw, maybe some dowels AND half laps, Im sure I could come up with a few more fun things to try.

EDIT: To give credit, this was tested in the Norwich University Civil Engineering Lab