Hitch Configurations, Capacities, and Basic Knots
Hitch type sets the capacity
The same sling has different working limits depending on how it is attached:
- Vertical - 100% of the single-leg rating.
- Choker - typically 75–80%, because the sling is choked on itself; a tighter choke angle reduces it further.
- Basket - up to 200% when the legs are vertical, since two parts of the sling share the load.
Sling angle is where loads are lost
Once legs leave vertical, each leg carries more than its share. The tension per leg is:
T = Load ÷ (number of legs × sin θ)
where θ is measured from horizontal. Equivalently, multiply the vertical capacity by sin θ. Common factors: 60° = 0.866, 45° = 0.707, 30° = 0.500. Legs at 30° carry twice the tension of vertical legs. Keep included angles at or below 90° where practical, and never assume two legs share equally - the center of gravity decides.
Knots and rope
In rope work, a bowline forms a loop that will not slip, a clove hitch ties off to a rail, two half hitches finish a tie, and a timber hitch grips a log. Any knot costs roughly half the rope's strength, so spliced eyes are preferred. Knots are never permitted in a sling - a knotted sling is out of service.
Worked example
A 10,000 lb load in a two-leg bridle at 60° from horizontal: T = 10,000 ÷ (2 × 0.866) ≈ 5,774 lb per leg. Each leg must be rated at least 5,774 lb, not the 5,000 lb a careless split would suggest.