Is Single Line Reefing
Right for Your Sailboat?

The single line reefing system is probably the easiest way to pull a reef in a mainsail and, providing the mainsail halyard and topping lift are led back to the cockpit, there's no need to clamber up to the mast to shorten sail.

But if the halyard and the topping lift are operated from the mast, then this is where the reefing pennant should terminate too.

On some boats the halyard is operated from the mast and the topping lift from the cockpit - which is just plain daft - but if this is the case it's best to keep the halyard and the reefing line in the same location, as you can deal with the topping lift before you leave the cockpit and when you return to it.

Clearly it makes a lot more sense to have everything all in the same place - either at the mast or in the cockpit - so you can deal with it on your own if you have to.

Pulling In a Slab with a Single Line Reefing System

It doesn't get much simpler than the external system shown here:~

single line reefing system for sailboat mainsails

Single Line Reefing - a Simple, Seaworthy System

Ease the kicking strap, or vang as it's also known, then;
Ease the mainsheet;
Head up towards the wind;
Take up on the topping lift to support the end of the boom;
Release the halyard and drop the main by enough to pull in the reef;
Pull in the reef and secure the reefing line;
Tension halyard and secure;
Ease the topping lift;
Adjust course, trim sails - and it's job done!

Internal Systems

Some spar manufacturers incorporate single line systems inside the boom, which, although looking neater is:

more expensive, and

is difficult to repair when something breaks, and

uses a two-part tackle which makes pulling a reef in easier, but

the mechanical advantage works against you when letting a reef out.

Trysail bagged and in its own track ready for use

There's only enough room inside the boom for the first two reef tackles, so the third reef - if there is one - has to be done with a standard slab reefing arrangement.

This means that in the very worst conditions you'll have to go to the mast anyway!

I know some offshore sailors that use this system have just two deep slabs in the mainsail, and rely on the trysail when things get really unpleasant.

The trysail should have its own separate track and be kept bagged but ready for hoisting at the foot of the mast, as shown here.