What is the letting-go circle radius defined as in anchoring calculations?

• A. distance from the horsepipe to the pelorus or radar or GPS antenna
• B. length of the vessel
• C. length of the anchor chain released
• D. distance from the anchor to the pelorus

Answer: (A)

In anchoring calculations you think in terms of a letting-go circle that is centered on the hawsepipe because that is where the anchor chain is attached. The radius of this circle is defined by the fixed distance from the hawsepipe to the vessel’s observation point on the deck, typically the pelorus or the navigation antenna (radar/GPS). This offset is important because you observe from that point, not from the hawsepipe itself, so the circle you plot on the chart uses the straight-line distance from the hawsepipe to the pelorus. That’s why the letting-go circle radius is the distance from the hawsepipe to the pelorus or radar antenna. The other options don’t describe this geometric setup: the vessel’s length, the length of chain released, or the distance from anchor to the pelorus aren’t what define the circle’s radius in this method.