Your Tired Old Mainsail

Your Tired Old Mainsail

One topic of discussion that I hear about all the time around the marina has to do with skippers having their boats overpowered to the point where the boat is no longer under control.  Frequently these discussions include graphic descriptions of water washing the ports (windows), rounding up violently, and so on.  As often as not, the skipper relating the story has an older 22 to 27-footer that is still sailing with a twenty or thirty year-old main sail.  The sail works okay on light wind days… but when the wind pipes up, the sail is so blown out and round that the sail develops too much sideways thrust instead of forward thrust and the boat tips excessively.  What are some options???

One option of course would be to buy a new mainsail.  And, that is probably the most efficient “fix” - - and this one will last longest.  Other options might be to significantly increase Cunningham and clew outhaul tension.  This tends to flatten the sail – but the older and more blown out the sail is, the less effective this second option becomes.

A third option might be to “pre-bend” the mast.  You do this by tightening the forward lower shrouds or by increasing tension on the backstay… or both.  If your boat has a pair of lower shrouds that angle forward to chainplates ahead of the upper shroud chainplates, it should be fairly easy to increase the tension on the forward shroud by simply turning the turnbuckle at the bottom of the shroud.  Do this evenly until the mast is bent in the middle about three or so inches.  The pre-bend will flatten the middle half of the sail and make the sail less powerful in the gusts.  If there are aft angled lower shrouds too, you will need to loosen those turnbuckles.  And, on many boats, if you increase the tension on the backstay, the mast will also bend in the middle and depower the mainsail.

Increasing the tension on the backstay also increases the tension on the forestay and helps the jib to keep it’s shape - - and not sag off to leeward in the gust - - again creating sideways instead of forward energy.

So, if you are not quite ready to buy a new mainsail, pre-bending the mast may help in the short run.

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