How many rafters are to be installed at a chord distance of 6' 3 18 on a W' diameter tank?

To determine the number of rafters needed for a tank with a diameter of W' and a chord distance of 6' 3 18", you first need to convert the diameter into inches and then calculate the circumference using the formula (C = \pi \times D). Divide the circumference by the chord distance to find the number of rafters, rounding up as necessary. Without the specific diameter value (W'), I can't provide an exact number, but the formula will guide you through the calculation once you have that measurement.