Sailing Term: Cunningham

What it is, what it does, and why river sailors really should care

f you sail a dinghy for more than five minutes, someone will eventually say:
“Put a bit more Cunningham on.”

You nod wisely.
You pull a rope.
You hope for the best.

But what is the Cunningham, and why does it matter—especially on a shifty river like the Thames?

So… what is the Cunningham?

The Cunningham is a sail control that adjusts the tension along the luff of the mainsail.
It’s usually a rope or purchase system that pulls the sail downwards at the tack, separate from the halyard.

In plain English:
👉 it controls where the draft (the deepest part of the sail) sits.

What does pulling the Cunningham actually do?

• More Cunningham on

  • Pulls the draft forward

  • Flattens the sail

  • Opens the leech

  • Reduces power

  • Great when it’s windy or gusty

• Less Cunningham (or off completely)

  • Allows draft to move aft

  • Creates a fuller sail

  • Adds power

  • Ideal in light winds

On rivers, where the wind changes its mind every 30 seconds, this matters more than you might think.

Cunningham vs Halyard – why not just pull harder?

Good question—and one many beginners ask.

• The halyard gets the sail up

• The Cunningham fine-tunes how the sail works

Once the sail is hoisted properly, the Cunningham lets you adjust sail shape on the fly, without re-hoisting or disturbing other controls.

Why the Cunningham matters on rivers

River sailing is all about:

• Short beats

• Sudden gusts

• Tree-induced chaos

• Boats going from under-powered to over-powered in seconds

A quick tweak of the Cunningham:

• Depowers the sail without dumping the sheet

• Keeps the boat flatter

• Maintains flow over the sail

• Makes tacks smoother and less frantic

In other words: it’s a thinking sailor’s control.

Beginner tip

If you’re new to sail controls:

• Set it light to start with

• Watch the wrinkles near the luff

• Smooth wrinkles = too tight

• A few vertical creases = about right in light airs

And remember: if in doubt, ease it.

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Read the full explanation (with diagrams)

👉 https://pmrsailing.uk/sailing-lessons/sailing-terms-list/Cunningham.html