Stop Dragging

Catamarans have massive windage. In a 25-knot blow, they pull back on the anchor chain like a freight train. You must set the hook properly and deploy the bridle, or you will end up on the rocks.

The Scope Equation

Scope is the ratio of chain deployed to the depth of the water (plus the height of the bow roller). Most charterers use 3:1. This is wrong. You need a minimum of 5:1 for overnight anchoring in standard trades (15-20 knots), and 7:1 if squalls are expected.

The Bridle is Mandatory

A catamaran must use a bridle (snubber) for two reasons:

It absorbs the shock loads. Chain does not stretch. Without a bridle, the windlass will rip out of the deck in a violent gust.
It keeps the boat pointing directly into the wind, preventing the boat from "sailing" back and forth at anchor (yawing).

Never leave the load on the windlass overnight. The load must be on the cleats.

The Back-Down Test

Once you let out 5:1 scope and attach the bridle, put both engines in reverse. Start at 1000 RPM, then ramp up to 2000 RPM for 30 seconds. Look at a stationary object abeam (on shore). If you are moving backwards, the anchor is dragging. Pull it up and try again.

Scope Calculator

Calculate exactly how much chain to let out.

Water Depth on Chartplotter (ft)

Expected Wind State

Common Mistakes

Mistake	The Reality
Anchoring in coral	Illegal, destructive, and the chain will wrap on coral heads and jam. Find the white sand patches.
Forgetting the windlass breaker	If the windlass stops working mid-deployment, you probably popped the heavy 100A breaker near the battery bank. Find it before you leave the dock.