Da Vinci Device
To compare the traction of nonskid surfaces, we followed the writings of Leonardo da Vinci and built a device similar to one he described in his studies of friction five centuries ago.
Leonardo da Vinci’s experimental setups for measuring friction were pretty simple. One of them was a variable incline plane with which he could measure the angle at which an object began to slide on a given surface. He then used a mathematical formula to calculate the coefficent of friction between the surface and the object. Today this is known as the static coefficient of friction.
To build a replica of da Vinci’s device, we used two straight and level boards hinged at one end. To the top board, we clamped samples of new nonskid material. For the object, we used a new deck shoe weighted with 11.43 pounds of lead sinkers, for a total weight of 12.35 pounds. OK, that’s a lot less than what a typical boater might weigh, but it was equally weighted for all surface testing, allowing us to draw conclusions about which nonskid materials offer the best traction.
Using an inclinometer, we recorded the angle at which the shoe began to slip with the surfaces dry, and then repeated the tests after pouring one cup of fresh water on each surface just before positioning the shoe (with a dry sole) and gradually increasing the angle. To learn what the da Vinci device taught us, turn the page.
Do the Math
You can use the da Vinci device to calculate how much force (F) is needed to move an object. First calculate the static coeffecient of friction by dividing A (measured when the object first slips) by B; then multiply that number by the weight (W) of the object, as in: F = (A/B) x W. This will tell you the amount of force needed to initiate slippage.