So you have a spotting belt, a trampoline or dryland board, pulleys, quick links and snap swivels. What’s missing?
But how much do you need - 50 feet, 75 feet, 100 feet? Confused? If you are then you have come to the right place … Here are the One, Two Threes of spotting Rope.
Spotting an athlete in a somersaulting or twisting belt requires the use of two lengths of rope – a short rope and a long rope. The short rope runs from the diver through the pulley closest to spotter and then down to the spotter.
The long rope must travel farther as it runs from the diver to the pulley farthest away from the spotter, then across to the closer pulley and then down to the spotter. So how do you know how long each of these ropes need to be? It is all determined by the dimensions of your spotting rig.
Height and Width
The height of the spotting rig is the distance between the floor and pulley(s). Since it is better to have more rope than not enough, a more appropriate measure of this distance to use for rope length is the total height of the spotting rig itself in the case of a free standing rig, or the height of clamps or crossbar used if the rig is attached to an existing structure. The width is always determined by the distance between the two pulleys.
For arguments sake, let’s create our own spotting rig that has a height of 20 feet, and a width of 15 feet.
To determine the length of the short rope, double the distance of the height of the spotting rig. But to be on the safe side, you should always add to that number. Adding an extra 10 feet is usually a good idea for most spotting rigs, but if you are setting up over water or have high ceilings and your pulleys are over 25 feet high, you may consider adding more than that.
Using our fictitious spotting rig as an example, if the height of the spotting rig is 20 feet, then your rope should be at least 50 feet: (20 feet + 20 feet) + 10 extra = 50 feet.
Determining the length of the long rope involves a simple calculation using the Pythagorean Theorem – an equation we all no doubt remember from high school!
Essentially, the long rope forms a triangle that goes from the spotter, through each of the pulleys and then back to the spotter forming a triangle. In reality, while the rope will not travel to spotter (due to being attached to the diver); it is better to figure the length in this manner to make sure that you have enough rope.
Since you already know the two sides of this triangle (the height and the width of the spotting rig), by determining the third side you can calculate the total length needed for the long rope – adding of course, an extra 10 feet.
In case you have forgotten this mathematical calculation, the Pythagorean Theorem states that the sum the squares of two sides of a triangle with a right angle equal the square of the remaining side - the hypotenuse. Confused? Let’s go to our spotting rig to make it clearer.
In order to determine the total length of the rope of our spotting rig example, we will take the square of the spotting rig height (20 x 20 = 400) and add it to the square of the spotting rig width (15 x 15 = 225) for a total of 625. The square root of 625 is 25, and thus we have the length of the third side of the triangle.
So to figure out the length of the rope you add the length of the three sides together, plus an extra 10 feet; 20 + 15 + 25 + 10 = 70 feet of rope.
Why The Extra 10?
It is always a good idea to have more spotting rope than you need. You do not need to go overboard and double the total, but that extra rope may come in handy when you least expect it – losing rope because you can’t untie a knot, a slight change in pulley height, etc. And you never want to feel like you are running out of rope while in the middle of spotting 3 ½ somersaults.
You can always shorten your rope, but if you don’t have enough to begin with then it’s back to the drawing board and the Pythagorean Theorem.