Mainsheet Systems Compared: Why Paikea’s A-Frame Doesn’t Hold Up

In the Gunboat 68 mainsheet post, the traveller system handled twist and power as two clean, independent controls. Paikea runs something very different — a double-ended A-frame system, common on older-style French catamarans, with no traveller at all. Two sheets, one to a winch on each side, and every adjustment means working both at once. It’s worth walking through exactly why that’s a problem, because it’s easy to underestimate until you’re actually standing at the winch trying to make it work.

The gust that shouldn’t have been a problem

The clearest demonstration came on a beam reach, waves hitting the boat slightly on the beam, apparent wind around 60 degrees — exactly the kind of moment a gust needs a fast, reliable way to dump power. With no clear answer for which sheet actually controls depowering, both got tested in real time.

Dumping the windward sheet first: letting it go entirely, watching the boom — and it barely moved. No meaningful depower at all, sheet pulled straight back on afterward with nothing gained. Then the leeward sheet: releasing it showed real movement, the boom easing out — but the windward sheet was still holding tension, still keeping the sail loaded up. Even with the “working” sheet released, the boat stayed powered up enough that a real gust through that same setup would still catch a crew off guard. Neither sheet, on its own, actually solves the problem a traveller solves instantly.

A dangling sheet, and a jury-rigged fix

Even outside of gusts, the system creates problems on completely ordinary points of sail. Reaching under just the leeward sheet, the windward sheet has nothing to do — and nowhere useful to go. Left alone, it swings free and catches on almost everything nearby. The current fix is a shock cord and carabiner clip, rigged to hold the loose sheet out of the way. Workable, but it’s a patch on a system that shouldn’t need one in the first place.

Moving the boom: the guessing game in practice

Sailing upwind, needing to move the boom roughly 100mm to leeward, the two systems couldn’t be more different in what that actually takes.

On the Gunboat, moving the boom that same distance is one button press, or one pull of a traveller line — done, with sheet tension unchanged throughout.

On the A-frame, it starts with easing the windward sheet — by an estimated amount, since there’s no way to move the boom a known, specific distance. Ease it, then take up the leeward sheet to compensate. Except easing the windward side doesn’t just move the boom sideways — it also lets the boom rise and the leech open, changing the twist along with the position. So the boom ends up roughly where it needed to go, but the sail shape is now wrong: the head is stalling, twist has gone slack. That means going back to ease the leeward sheet slightly, then re-tension the windward side again, checking the twist again, adjusting again — several rounds of easing one side, tightening the other, checking shape, before the sail is actually trimmed the way a single traveller movement would have achieved in seconds.

What this actually means for sailing Paikea

None of this is a one-off inconvenience — it’s the reality of every trim adjustment, every gust response, and every reach on this system. A traveller gives one control for power and one for twist, fully independent of each other. The A-frame gives two sheets that both affect both things at once, with no accurate way to isolate either adjustment, and no reliable way to depower fast when it actually matters.

A track-and-traveller upgrade is on the list for Paikea’s refit, and working out exactly where it goes has turned into a genuine engineering problem in its own right. The cabin top looked like the obvious answer at first — it keeps everything out of the way — but building enough structure there to carry the load wasn’t achievable with the salvaged materials on hand, and the only workable track length would have run into the cutout needed for stepping in and out of the cockpit without hitting your head on the hard top. Running the track spreader-to-spreader would have solved the geometry cleanly, but the beam needed to carry that load would have to be heavier than makes sense, and it would conflict with a hatch that needs to open fully and the space already planned for solar panels. The current plan — down on the aft beam — comes with its own problem: it’s a Z-section, not a closed box, and a mainsheet load there will flex the beam unless it gets boxed in and stiffened first.

In the Members Library, the full breakdown of the Gunboat 68’s clutch arrays and deck padeye layout covers the hardware side of what a proper traveller setup actually requires — worth a look for anyone considering the same upgrade.

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