Do I still need a sight tape if I use the app?

You still need marks on the slider — the app produces them for your setup. What you no longer need is the trial-and-error of matching pre-printed tapes to two test shots.

Why does my tape read right at 20 and 40 but wrong at 70?

Tiny errors in the two calibration marks get amplified past them. Re-shoot the long mark at 60–70 rather than extrapolating from 40, and confirm the peep and anchor haven't shifted.

How precise do the calibration shots have to be?

As precise as your marks need to be. Shoot several arrows per distance on a calm day, use the group centre, and repeat the long distance twice if the groups disagree.

Sight Tape

A sight tape is a printed strip of distance marks fixed to the slider track of a single-pin or hybrid sight. Its spacing matches the arrow's drop curve, so the archer moves the pointer to the yardage on the tape and the pin is set for that distance without shooting it in.

Details

Every arrow setup has its own trajectory, so a tape only works if its spacing matches that setup. Historically archers found the right tape by shooting two known distances — say 20 and 50 yards — measuring where the pointer sat for each, and choosing the pre-printed tape whose marks fit those two points. Faster arrows produce a compressed tape; slower arrows a stretched one.

Applied correctly, a tape is remarkably accurate between its calibration points and slightly less so beyond them, because small errors in the two reference marks grow with distance. The usual advice is to take the long mark at or past the longest distance you intend to shoot, and to re-shoot both marks whenever anything affecting arrow speed changes — draw weight, arrow weight, string, or even a new release that alters your draw length.

Precision-cut marks are the modern version of the same idea. Instead of choosing the nearest pre-printed tape, the marks are calculated from your own calibration shots and produced for your exact setup, which is how BowSmith handles it in-app — there is no separate tape calculator to run, because the sight-mark tool does that calculation from your logged marks.

Whatever produces the marks, treat them as a snapshot of a setup, not a permanent property of the sight. Write the calibration distances and the date in the setup log, and check the long mark before any event where a yard of error matters.

Related on BowSmith

Glossary

Printables

Bow Setup Measurement Log

Common questions

Do I still need a sight tape if I use the app?: You still need marks on the slider — the app produces them for your setup. What you no longer need is the trial-and-error of matching pre-printed tapes to two test shots.
Why does my tape read right at 20 and 40 but wrong at 70?: Tiny errors in the two calibration marks get amplified past them. Re-shoot the long mark at 60–70 rather than extrapolating from 40, and confirm the peep and anchor haven't shifted.
How precise do the calibration shots have to be?: As precise as your marks need to be. Shoot several arrows per distance on a calm day, use the group centre, and repeat the long distance twice if the groups disagree.