What is a Triatic
A triatic stay is a piece of standing rigging that runs between masts.
On a ketch it runs between the main mast and the head of the mizzen mast and is used to stop the upper section of the mizzen mast being pulled backwards. The same job can be done by forward shrouds so not all ketches have triatic stays, it depends on the specific rig set-up on the boat.
Cons
I once sailed with a delivery skipper who, on seeing a ketch sail by, said “I’d never sail on a boat with a triatic stay. If one mast comes down it would bring the other down and you’d lose your whole rig”. He said this while we were sailing on a sloop, where if the one mast came down we’d have lost the whole rig…
On Speedwell of Rhu our main mast is keel stepped. If the mizzen were to fail it’s likely that the triatic stay would break before the rather more substantial main rigging gave way but even if it didn’t a main rig failure would result in the main mast breaking part way up rather that the whole mast going overboard. So I’m confident that in the unlikely event of a rig failure we’d be able to salvage something for a jury rig.
Pros
The triatic stay removes the need for any other forward stays from the head of the mizzen mast. On our boat the original forward mizzen shrouds set a limit on how long the main boom could be, by getting rid of these we’re been able to fit a longer boom which moves the main sheet away from the helm’s head and gives us space to fit a bimini. The simplification of the mizzen rigging also makes it easier to fit our wind generator to the mizzen mast (there’s now enough space between rigging wires to let the blades spin).