A= depth of rope space on drum, inches: A=(H-D-2Y)/2
B= width between drum flanges, inches
D= diameter of drum barrel, inches
H= diameter of drum flanges, inches
K= 1.58 for 3/8" rope
Y= depth not filled on drum where winding is to be less than full capacity, inches
L= length of rope on drum, feet
L = (A+D)*A*B*K
Mike