The tails of most skis are a collection of round surfaces making it nearly impossible to get an accurate DFT (Distance From Tail) reading. Here’s a simple way to take most of the variability out of measuring your ski fin’s DFT. By introducing a flat surface underneath the caliper in the form of a shim, most of this variability can be eliminated.
To get the right shim size, use a straight object to bridge the gap between the ski’s edges. The shim should fit perfectly into the gap between the straightedge and the ski’s base. If the size of your shim just barely touches the straightedge, your DFT measurements will be both accurate and consistent.
The shim doesn’t need to be brass either. It can be anything that’s relatively firm. You can even cut a shim out of paper or a business card. Anything that makes contact with your straightedge will deliver an obvious flat spot to rest the caliper against while measuring.