Below is a sequence drawing of the relationship of the dart to the spur of the atlatl during the throwing motion. Here, the launch is pictured from right to left.
At the start of the throw, the tip of the spur is inside the cup in the rear the dart. As the atlatl is pulled forward and levered upward, the spur rotates out of the cup in the rear of the dart and the dart is connected to the atlatl only because the atlatl is moving faster than the dart.
The rear of the dart actually slides across the top surface of the spur tip until that brisk, downward, wrist flick simultaneously, with great torque, pushes the dart away and the dart slides off the back of the spur.
This is why I have advised people making their first atlatl to:
- Think ball and socket as it relates to the tip of the spur and the cup of the dart. A sharp pointy spur is not a good thing. The tip of the spur should be dull and rounded. Small enough to fit inside the cup of the spur but blunt enough to easily rotate into and out of the cup without digging into the inside wall at the rear of the dart. When a sharp pointy spur tip digs into the wall of the dart, it can cause a misfire (hooking the shot) and split the dart open like a can opener.
- Trim excess wood beyond the end of the spur. The rear end of the dart needs to slide right off the end of the spur and not get slapped by any excess wood sticking out beyond the spur during that brisk downward wrist flick at the end of the throwing motion.
I would go so far as to advise that the top surface of the spur should be flat rather than rounded. If the spur is round, there is a possibility that the rear of the flexing dart may slide off one side or the other during the throwing motion. I actually have carved a groove in the top of my spurs to guide the rear of the dart straight off the back of the spur. This eliminates that one in ten misfire.
If you have any questions about atlatl or dart design, contact Ray Strischek.