Tremendous thanks to Bill Hays for generously providing a template for this design, and giving permission for the sale of this interpretation of it.
The Harpy is a unique and visually stunning slingshot design, typical of Bill's work and capable of exceptional accuracy. In our experience though, it is also somewhat hand-size specific. This provides quite the challenge for conventional manufacturing. Our 3D printing system offers infinitely variable sizing, so customers may order a slingshot fit to their hand.
In order to test the suitability of a 3D printed Harpy, loops connected to a load cell were attached to the band mounting points on a fork. A mechanical winch was attached at the far end, and force increased until failure occurred. The peak measurement, astonishingly captured on film at the moment of failure, was 156.0 kilograms or approximately 344 pounds. To be clear, strength will vary somewhat based on material and slingshot size, however this should be adequate safety margin for a Harpy in good condition to run bands of normal reasonable force.
We size our 3D printed slingshots on a virtually continuous spectrum based on the width of the hand at the knuckles. This measurement is taken in millimeters and provided to us at the time of purchase. We will scale your slingshot to match your measurement.