Clew outhaul and cunningham

Flattening a mainsail can be made easier by adjusting your clew outhaul and cunningham

With two of its three sides supported by spars, the control of the mainsail should be painless. And in theory it is. Luff tension can be adjusted by hardening down or easing the halyard. The clew outhaul will do the same for the foot. When beating or close reaching, the mainsheet takes charge of leech tension and twist, with that role being transferred to the kicker when running. Finally, a lightweight leech line provides a useful tweak to suppress any fluttering.

To be denied complete and readily accessible control of your most important sail is frankly ridiculous, yet that’s the reality many cruisers live with. In fresh breezes it’s very common to see mainsails that are too full, with the draft too far aft. There couldn’t be a better way of enjoying excessive weather helm and heeling but, if you prefer a more comfortable mode of sailing, the sail should be flattened to de-power it. In marginal conditions this is an easier option than taking in a reef – assuming you have the wherewithal, that is.

Those with masthead rigs (I venture to guess the majority of offshore sailors) find themselves denied the ability to flatten the main by introducing more mast bend. Flattening the sail is usually achieved by increasing luff and foot tension.

For the racing brigade this is no problem. Their mainsails (and ours on Shindig) are loose footed with the clews attached to RCB (recirculating ball) cars at the end of the boom. It’s a no more arduous task than trimming the mainsheet. This contrasts with many cruising mains which have bolt ropes along the foot and a solid slider at the clew. The friction is horrendous. Whereas the racing system can be adjusted under load, cruisers might be obliged to luff up before they heave on the clew outhaul, then bearing away to fill the sail before they see the results. If not satisfied, they must repeat the process.

A similar situation exists with luff tension – but worse. Not only do you have the side-loaded friction between the slides and the luff groove but, in tightening the halyard, you’ve also got the weight of the sail to overcome.

Once the mainsail is up, racers rarely bother with the halyard. Luff tension is controlled by the cunningham – an exquisitely simple and inexpensive arrangement that deserves a place on every boat. The cunningham offers some significant advantages. Firstly, the pull is downwards so you’re neither struggling to lift the sail or overcome the cumulative effect of all the slides between the head of the sail and the gooseneck. And, secondly, it tightens the lower luff first – exactly where you want to remove all that bagginess.


Incidentally, go easy on the cunningham. On cross-cut mainsails the sailcloth is run perpendicular to the leech, meaning the luff is on the bias. Sweat the cunningham down too hard and you can permanently stretch the sail. The last time I tendered this advice I got flak from a friend of the whack it down hard persuasion. Well, that might be OK for a radial cut sail but certainly not for a cross-cut.

For my money both a loose-footed mainsail and a cunningham are very welcome shipmates on our boat.

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