• Kemp Sails

The Main Choices

The mainsail is, by definition, the Main Sail: this might sound trite, but it’s rare for a boat to carry more than one on board, and whatever the proportion of area it contributes, the balancing effect it provides to the sailplan means it is the most-often hoisted sail.

This single sail is then expected to perform all the way from motorsailing through dead air to act as a stabiliser, via ghosting along in 3-5kts of breeze to driving the boat perhaps under a 4th reef in 60kts: selecting the correct options is very important! This applies to mizzens equally: we make these just like our mains, but smaller, and even tougher.

Be realistic about how often you expect to reef though, and reflect this against how good modern weather forecasting is. It’s unusual inshore to meet unexpected weather, and an experienced skipper will always be prepared to reef once or twice. How you do it (conventional slab with horns, single line, or dual line, or even roller boom) is up to you, but it is a rare day sail in the bay that you find you need a 3rd reef unexpectedly..!

Planning for multi-day and/or offshore passages is a different matter. Fitting a third reef is prudent if you’re cruising, and it is a requirement to be able to reduce your main luff by a minimum of 40% if you are racing offshore, and this is the approximate height of a third reef. In fact, in his excellent series of articles on storm sailing, Skip Novak recommends a 4th reef as an alternative to a Trysail when cruising too, as this is already a familiar operation. Your mileage may vary, as they say.

Another factor that merits some thought is the length and number of battens. A standard main will usually have 4 short battens supporting a modest roach, but longer battens, even extending as far as the luff (“full battens”), make mainsail handling, in combination with lazyjacks and/or a packaway, a breeze: on rigs without a backstay they can support an enormous amount of extra sail area too. Inevitably the extra hardware required to brace full length battens away from the mast add cost though, so as with so many things, the trade-off is cost.

If you’re cruising for an extended period, or you’ve bought a boat with a system included, in-mast furling brings its own unique set of choices. A more stable fabric pays itself back in terms of longevity, since unlike a conventional main (where you can hoist up pretty much any shape sail and get blown along!), a sail that furls inside a spar will cause problems if it is not fairly flat: therefore, replacement should be a consideration if you are experiencing furling issues.

The convenience of furling up your main like a roller blind comes at a price: as well as the potential for shape (desirable) to cause furling problems (undesirable!), a sail without vertical battens needs to be cut like a genoa on the leech, with a concave, or hollow, edge. Adding battens not only adds weight, but adds complication in build, and risk of snags in use, but does allow us to add area, and helps to stabilise what can become quite a ‘fluttery’ edge with use. It is a trade-off that needs careful consideration.

Detailing on either type (conventional or in-mast) makes a difference to not only ease of use, but to pleasure of use: often, what we fit as sailmakers in the final stages make a huge difference to how the sail can be used, and we are careful to try and think about the various situations the sail will be used in. As a bespoke supplier, most things can be (and probably have been!) incorporated...

To highlight just one example: ordinarily, the leech line - a small diameter control line for the flutter on the back edge of the mainsail - is terminated at the clew in a clam cleat. We not only provide exits and extra cleats at each reef point as standard, we offer metal cleats and also the option to have the line go ‘over the top’ of the sail, offering the ability to adjust it at the luff. Just the thing when your boom is over your head, or out of reach to leeward!

So whatever you need, Kemp Sails has huge experience in the selection and specification of mainsails, and enjoy the strong support of all the major cloth suppliers in the UK: before you make any decision, come and have a chat with us.


Owain Peters, January 2019

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