Are Roller Reefing Mainsails Worth Having?

Take a look at any modern cruising boat and the odds are it'll have a roller reefing system on the forestay. Some may have two; one for a lightweight genoa and another just astern of it for a working jib. If the boat is cutter rigged, then it's likely the staysail will be set on a roller furling gear too.

Hunter 356 Exhibit A anchored 2With an in-mast mainsail furling system on fractionally rigged boat, the system will perform better if the mast bend is released by slackening the backstay.

Not so long ago, we cruisers were quite content with these roller furling gears on our headsails and simple slab reefing for our mainsails.

Not, it seems, any more...

Most spar makers offer roller reefing mainsails  as an option to their standard masts and booms, and some are markedly more successful than others.

With headsail roller reefing systems, it doesn't matter too much if you've been a bit sloppy rolling a reef in. Perhaps the sheet was a little slack and the sail was flapping around. OK, it won't look very pretty and the sail shape will be awful, but at least it's in - and you can pull it back out and start again.

But not necessarily so with roller reefing mainsails, which are contained (and that's the problem) either within the mast or within the boom.

In-Mast Roller Reefing Mainsail Systems

in-mast roller reefing system for mainsails

At best, this is a quick and easy way - providing you get the procedure right - to reduce the area of the mainsail in a rising wind.

But it can go wrong; and if it does with the sail jammed in the mast groove you won't be able to get it in, out, up, down or do anything much at all with it - short of a bosuns' chair and a sharp knife.

Sails used with this system are flat cut, have little or no roach - or even a negative roach - and if there are any battens at all, they'll be vertical.

Halyard tension is critical; too much and you'll have a job getting the first few turns in, and the boom has to be adjusted just right, so you'll need a rod kicker. If your sails are new or in good shape, then you've got a good chance of this system working at its best, but it your sails are past their first flush of youth, and maybe a little baggy then you could be in for an interesting time.

And there's a penalty to be paid in additional weight aloft as a result of the all the hardware inside the mast.

You may have guessed, I'm not a fan...

In-Boom Roller Reefing Systems

Sailboat boom furling systems use a fully battened mainsail and are conceptually more seaworthy than the in-mast type, because:

  • if the sail jams in the boom slot, it's still possible to ease the halyard and drop it.
  • a sail jammed in the boom slot will be much easier to sort it out than one halfway up the mast.
  • reefing the sail in the boom lowers the centre of gravity, unlike the in-mast system which leaves the weight of the sail aloft.

For successful operation the angle between the boom and the mast is critical. In some systems this is fixed by a rigid kicker, whilst others allow a degree of articulation and rely on a spring in the kicker to return the boom to its correct angle.

The double swivel arrangement found on headsail furlers is also incorporated in some in-boom systems, which flatten the main without reducing its area.

But why Bother?

Both in-boom and in-mast systems are mighty expensive, and far from risk-free unlike a slab reefing system with lazy jacks which is:~

  • Simple
  • Effective
  • reliable
  • cheap
  • and you can fix it if it breaks

Mainsail roller furling/reefing systems? I just don't get it.

Cruisers' Questions:

Any tips for operating an in-boom mainsail furling system to minimise the risk of problems when reducing sail?

Here are some tips for successful operation of an in-boom mainsail furling system:

Understand your system: Check inside your mast at which way your system should furl. If your furling system has the option, put a winch handle in the furling mechanism at the mast and turn it the direction indicated to make sure the sail is going into the mast in the correct direction.

Assess your sails: The biggest cause of problems is the sail itself – how old it is and the material it is made from. Make sure that your sail is in good condition and that it is made from a material that will work well with your furling system.

Adjust halyard tension: The halyard tension should be adjusted so that the sail is not too tight or too loose. If it is too tight, it will be difficult to furl the sail. If it is too loose, the sail will not furl properly.

Check the backstay: The backstay should be adjusted so that there is no slack in the leech of the sail. This will help to ensure that the sail furls properly.

Smooth it out: When you are furling your sail, make sure that you are doing it smoothly and evenly. This will help to ensure that the sail furls properly and that there are no wrinkles or creases in the sail.

My in-mast furling mainsail has jammed inside the mast on more than one occasion. How can I avoid it happening again?

To avoid problems with your in-mast furling headsail, you should keep an eye on the furling drum and on the masthead swivel to avoid halyard wraps or other problems. You should also avoid using the winch to furl the sail away.

If the sail gets jammed during furling, it is probably due to the sail being rolled up too loosely. In this case, you should try to pull the sail tight on the roller profile inside the mast. To do this, hold the outhaul and roll up the sail again a bit, keeping the outhaul well under tension. Then unfurl again; if necessary, repeat this maneuver several times.

If that doesn't work, it's back to the bosuns' chair and a sharp knife!

Dick McClary responded to Cruisers' Questions, and used GPT-4, OpenAI’s large-scale language-generation model, as a research assistant to develop source material. The author wrote the final draft in its entirety and believes his input to be accurate to the best of his knowledge.

Read more about Rigging and Sail Handling...

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