Have you ever held a piece of paper up to your lips, pulled it tight and blew on it? If you did it right, you just turned a piece of paper into a musical instrument. If you are dealing with a $30.00 strap this same principal can ruin your investment and actually decrease the chance of the freight staying put on your deck. Here is an illustration of how air at speed can affect the object that it is flowing around. In this case a load strap. On the bottom near the letter "c" the air flow is minimal causing barely any movement in the object being affected by the air. As you climb up to "b" and "a", the vibrations increase. These vibrations can wreak havoc on load straps
In this picture, the straps are exposed to the air:
Here is a set of crates that were to be transported without a tarp. There is a picture of an umbrella on these crates and that means that this load should be tarped, but the customer did not want it tarped so it wasn't. The straps are clearly seen with a twist in them. The distance the straps are from the load and from the trailer to the top of the load is a factor. On a short load or where the load is as wide as the trailer is, a twist is not necessary.
If there were no twists in these straps, the air would cause vibrations in the straps. The straps would rub violently on the load at all of these points:
The twist keeps this vibration from happening. All there needs to be is one twist in the strap in between the top of the load and the trailer on this load. In addition to this the load requires strap protectors which are the small plastic pieces that cover the edge of the crates where the strap touches the load.
If you didn't twist these straps, they would vibrate and stretch and loosen up as you drive down the road. They also will rub on the trailer, the load, and wear the strap out. This load required 8 straps. They are about $30.00 each so that is about $240.00 worth of straps. Properly maintained straps can last for ten years on hundreds of loads in all weather conditions. Improperly maintained straps will last you one load. Maybe even two.