In-mast furling mainsail: Pros and cons

30th May 2022 Elena Manighetti

In-mast furling mainsail: Pros and cons

In-mast furling has become more and more popular on modern sailing yachts. Some sailors love it and some hate it - as it happens with most technologies when it comes to boating, after all.

In this article, we look at the advantages and disadvantages of this system, so you can decide if a boat with an in-mast furling mainsail is right for you or not. But first, as always, let’s answer some common questions on the subject.

What is in-mast furling? 

In-mast furling is a furling system which allows you to furl your mainsail inside the mast of your boat. The mast is hollow and contains a tube around which the mainsail wraps. To wrap it and unwrap it, you pull on an outhaul line or an inhaul line. 

Can you reef an in-mast furling main?

Yes, in fact you can furl as much of the sail as you like, which gives you greater control over how much canvas you put out.

in-mast furling

in-mast furlingIn-mast furling mainsail pros

Some sailors and cruisers find in-mast furling extremely handy. Here are the reasons why:

  • You can easily reef the mainsail from the cockpit

  • Reefing can be done quickly by solo sailors

  • You don’t need to fold and store the sail in a cover.

Being able to reef from the cockpit gives you a great advantage, as you don’t need to step on deck or onto the flybridge in order to reef. That’s great especially for solo sailors. The ease of the maneuvre is also a plus when hugging the coast in variable winds. While in-mast furling can be expensive, you won’t need to create and install a mainsail cover, which increases windage on deck. 

Finally, you won’t need to fight with the sail to fold it and push it into its cover at the end of a sail. This means you will never leave it out in the sun, even for a few hours after a long passage.

In-mast furling mainsail cons

Some sailors are completely against in-mast furling because:

  • The system can jam or fail

  • You have less control over the shape of the sail while underway

  • In-mast furling needs to be carefully maintained.

Newer furlers tend to be more reliable than older models, so they jam and break less often. However, if you don’t handle the sail properly, you could end up bunching it up and jamming the furler. When this happens, a portion of the sail usually flaps in the wind uncontrollably. It’s also worth noting that mainsails that furl away don’t have battens, so you can’t control their shape as much, especially when reefing them. 

Finally, you’ll need to maintain the furler regularly and to replace your mainsail before it becomes baggy in order to prevent any issues. 

in-mast furling

In-mast furling vs in-boom furling

There’s an alternative to in-mast furling: in-boom furling. This is when the mainsail reefs inside the boom. While the two systems are very similar on all aspects, boom furling offers an advantage: if the furler jams, you can drop the sail onto the deck or into the cockpit and remove it. This is an excellent safety feature.

Another benefit of in-boom furling is that it can be added to an older sailboat, as many companies produce furling booms, which you can fit to your boat. If your boom sits very high or is above a flybridge, a furling boom will allow you to raise and lower the mainsail from the comfort of the cockpit. 

Finally, in-boom furling systems are reefed to a full-length batten, which means they allow you to pull the foot of the mainsail straight and flat. This means you can achieve a better shape.

in-mast furling

As you probably know, sailors have strong opinions about everything to do with sailboats. You’ll find both cruisers who love their in-mast furling mainsail and racers who would only ever buy a yacht with a traditional mainsail.

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