What is FOC? Your Questions Answered
To get top performance from your arrows, you must understand a term called “front of center,” or simply “FOC,” to ensure consistent flight and accuracy.
FOC refers to the total weight in the front half of the arrow, and it has significant impacts on the arrow’s trajectory. Arrows with less than 10% FOC don’t stabilize quickly, which is especially important for bowhunters shooting longer distances or competitive archers abiding by FITA (Olympic style) regulations. Both must understand FOC and factor it in when building arrows to meet their needs.
You can see FOC by simply balancing an arrow on your finger. It’s important, though, to accurately calculate the weight in an arrow’s front half. Easton Archery breaks this calculation into this five-step process:
- Divide by 2 the arrow’s overall length (bottom of nock groove to end of shaft).
- Find where the arrow perfectly balances on your finger. Mark the spot with a permanent marker, and measure it from the nock’s throat.
- Subtract the arrow’s center measurement (Step 1) from the balance point (Step 2).
- Multiply the result in Step 3 by 100.
- Divide the resulting number from Step 4 by the arrow’s overall length. That’s the arrow’s FOC.
Some bowhunters rarely shoot past 30 yards, but Easton Archery still recommends a 10% to 15% FOC. You can change the FOC by adding or reducing your field-tip and broadhead weight, or placing inserts inside the shaft. You can also affect FOC by adding or reducing weight on the nock end. Although nocks, arrow wraps, and vane sizes and materials might seem to add minuscule weight, they affect FOC as much as the components in the arrow’s front half.
If you’re building arrows or want to increase FOC in your current arrows, don’t get too carried away. By adding 16% or more FOC to your arrows, you risk putting too much weight in the front half. That can make arrows nosedive at longer distances or difficult to paper tune.
With hunting season a few weeks away, you still have time for FOC experiments. Consider crafting four configurations per dozen arrows. Fletch some with lightweight vanes and extra inserts in front, as well as three- or four-fletch designs, and different field-tip and broadhead weights.
Calculate the FOC of all four setups, and shoot them side by side while noting performance changes. You’ll quickly identify the arrow setup that shoots the way you hoped.