Should Your Sidestays Break Before You Fly a Hull? No — Here’s Why
There’s a piece of catamaran folklore worth debunking properly: the idea that your sidestays should fail before your hull ever flies clear of the water. It gets repeated as a kind of reassurance — as if a rig failure is the safer outcome. It isn’t, and treating it that way is a genuinely dangerous misconception.
The Myth
The logic usually goes: if the boat’s about to capsize, better the rig comes down first. Framed like that it sounds almost sensible. It isn’t. Relying on a piece of your equipment to fail in order to keep you safe isn’t a safety margin — it’s a false sense of security, and it swaps one bad outcome for a different one you have far less control over.
The Car Analogy
Picture cornering too fast in a car, right at the point where it’s about to roll or skid. Nobody would say the tyres should blow out or the wheels should fall off before that happens — that’s obviously not a safety feature, it’s just a second failure stacked on top of the first. Wanting your sidestays to break before your hull flies is exactly the same reasoning, just applied to a boat instead of a car.
Why Rigs Fail on Heavy Cruising Cats
Here’s the uncomfortable part: on a big, heavy cruising catamaran, a stay genuinely can fail and bring the rig down before the boat ever gets close to flying a hull. That’s real, and it happens — but it’s not because anyone designed it that way as a safety feature. It’s a side effect of righting moment.
Righting moment on a catamaran scales with weight. The heavier the boat, the higher the righting moment, and the higher the righting moment, the more load the platform is theoretically capable of putting through the stays and the rig before she’d ever fly a hull. Building a rig and standing rigging genuinely rated to handle a heavy cruising cat’s full righting moment would mean something so oversized and impractical it isn’t worth building — the boat is extremely unlikely to ever actually reach that load in practice, so nobody engineers for it. The rig ends up as the limiting factor not by design intent, but because building it any stronger doesn’t make sense for a boat that will essentially never ask that much of it.
Flying a Hull Isn’t the Danger You Think It Is
None of this means flying a hull is inherently reckless. It isn’t. Watch Gunboats, HH66s, and similar performance cats fly a hull in a controlled situation and what you’re seeing is exactly that — controlled. It’s a managed part of sailing the boat well, not an accident waiting to happen. The comparison that actually fits: a Formula 1 car pushing hard around a circuit. Push past the limit and it will spin and crash, same as a boat pushed too far will go over — but the pushing itself, within the limit, isn’t the dangerous part.
Look further up the performance scale and the picture gets clearer still. A-Class catamarans, F18s, foiling beach cats — these boats fly a hull essentially all the time as a normal part of sailing them. The stakes of getting it wrong are higher at that level, but flying a hull itself was never the hazard. There’s a broader misconception that capsizing a catamaran is some kind of ultimate disaster. It’s a bad outcome, no argument there — but so is dropping a rig. Anyone who’s actually experienced either one will tell you neither is a situation you want to be in, and that one of them is a great deal easier to manage than the other.
What to Actually Watch
Managing the risk of flying a hull is genuinely more straightforward than managing rig load, because it’s visible. The first and simplest indicator: whether the windward transom is starting to lift clear of the water. Once that’s happening, the boat is telling you she’s overpowered, and the answer is straightforward — reduce sail. That’s an observable, controllable signal available to any sailor paying attention to their boat.
Rig load isn’t nearly as easy to see. The one instrument that actually measures it — a load cell in the shrouds — is fitted to a small fraction of catamarans out there, and even where it exists, load in a rig can spike and exceed a safe threshold faster than the crew can react to it. Watching how a boat is behaving and trimming accordingly will always be more manageable, and more reliable, than trying to keep tabs on rig load in real time. The responsibility sits with the sailor, not with hoping a piece of hardware gives way at the right moment.
In the Members Library
This ties directly into the rig-tuning content in the members library — how rig tension and rudder-angle feedback both tell you when a boat’s out of balance, and what “watching the transom” looks like in practice under sail. If you haven’t seen the free Understanding a Catamaran Rig content yet, start with How to Tune a Catamaran Rig and Cap Tang Misalignment: Diagnosing Rod Rigging Problems first.