Bullwhip

What is a bullwhip?

A bullwhip is a single-tail whip, usually braided from leather or nylon. It was made to drive cattle, and today it also turns up in cracking competitions. This is precision work: it asks for a lot of practice and a lot of room.

Why does a bullwhip crack?

A bullwhip cracks because its tip briefly moves faster than sound, which throws off a small sonic shock wave. The force behind that comes from the whip, not from your arm. With a paddle or a cane the power is in the swing; with a bullwhip it is in the whip itself.

The encyclopedia lays out the mechanism in short: in a well-executed crack, part of the whip passes the speed of sound, which creates a small shock wave. That happens because the wave you start with the handle keeps speeding up toward the thin tip. The broader entry on whips puts that at a factor of more than thirty compared to the speed of your own movement in the handle.

Goriely and McMillen describe the crack in Physical Review Letters as a shock wave created by the supersonic motion of the tip through the air, and they trace the acceleration to three things together: the tension, the whip tapering thinner and thinner, and the boundary conditions at the ends.

In practice that means the tip is the fastest part, and that is exactly the part you can steer the least.

What should you watch out for with a bullwhip?

With a bullwhip the first thing to watch is room. It is not a comfort but a condition. With a length of 1 to 6 meters plus your own arm, you need that whole distance clear, in every direction the whip can swing out, including behind you. A living room is out.

The cracker is the part to know. It sits at the end of the fall, makes the crack, and wears out faster than anything else because of it. You replace it more often than the rest of the whip put together.

Beyond that, the same placement rules apply as with spanking: aim for fleshy tissue and stay off the tailbone and the hip bones. The difference is that you have far less say over where the tip lands here, and that makes practicing without a person in front of you the only route. For myself, during impact play I stick to impact tools I can aim and steer in a room. A bullwhip is the far end you build toward, not where you begin.

Sources

• Shape of a Cracking Whip. Goriely & McMillen, Physical Review Letters 88(24), 244301, 2002. Establishes that the crack is a shock wave created by the supersonic motion of the whip’s tip through the air, and the role of tension, tapering and boundary conditions in the acceleration.
• Bullwhip. Wikipedia. Provides the definition as a single-tail whip of braided leather or nylon, the makeup with handle, thong, fall and cracker, the dimensions of the handle, fall and total length, the replaceability of the fall through a fall hitch, and the wear on the cracker.
• Whip. Wikipedia. Provides the description of the wave accelerating toward the tip past the speed of sound, at a factor of more than thirty compared to the movement in the handle.

Related terms

• Birch rod. The opposite extreme: many thin tips at once instead of a single point.
• Spanking. The placement rules that apply here too, with the zones you stay off.
• Bruising. What shows in the days after, and how long it stays.
• Flogger. The opposite from the same cupboard: many supple tails instead of a single point.
• Single tail. The family the bullwhip is one member of, with the members and their technical differences laid out.
• Impact play. The family the bullwhip is the far end of.
• Snake whip. The same principle without a stiff core in the handle, which makes it coilable.
• Stockwhip and signal whip. The other two members of the same family: on one the handle hangs loose from it, on the other the fall is missing.
• Whip. The umbrella name the bullwhip falls under, with the other three main types alongside it.