A storm jib is familiar to most sailors and can be a very useful addition to the cruiser’s sail plan as it offers a robust, useful headsail that can usually be relied upon to combine well with a reefed mainsail, a tri-sail or even a mizzen sail to provide a stable and effective sail plan in anything over say 30 kts of true wind.
Usually small and very robust, a storm sail is made of durable, heavyweight fabric and is normally set either on the forestay or an inner forestay. The tack is usually set by way of a strop which is itself attached to the deck. This allows this relatively small, yankee-cut sail to be rigged quite high off the deck, clear of any green water that is likely to be washing across the foredeck in a heavy sea.
The luff is probably best hanked onto a steel forestay with strong, brass piston hanks, but with the common use of furling headsails on modern cruising yachts these days, storm jibs are sometimes hanked onto a strong nylon sheath which envelopes the furled headsail and is hoisted (attached to the jib and sheath by a second halyard).
When setting the storm jib make sure to rig it sooner than you need it. If you are able to set it on a second forestay or inner forestay this gives you maximum flexibility when choosing when to reduce headsail or furl away the remnants of your genoa. If you use the sheathing method the best you can hope for is to set the sheath around the partially furled genoa (but above the furling mechanism) and make sure that when you furl away the headsail you don’t trap or damage the sail or the furling mechanism.
Then, you’ll need to secure the genoa sheets and re-run the storm jib’s sheets, making sure to run them properly through the cars and back to the winches. Make sure to set the car positions and have the sheets run properly at the shrouds. If sailing upwind, it’s not unusual to have to set the sheets inside the shrouds to allow proper trim.
It’s good practice to have the storm jib kept in a bag with its own sheets securely attached to the clew so that it can be rigged on the foredeck without too much hassle. Make sure you attach the tack first so that you don’t lose the sail! Then hank it on and run the sheets and attach the halyard as appropriate. If you can run everything in parallel with the working headsail then great, if not, make sure everything is properly secured and keep an eye on sheet runs and halyards. Make sure your new halyard isn’t twisted when you hoist, especially as it may be at night. After all, weather always seems to be at its worst after dark!
It makes sense to practice all of this alongside whilst the kettle is able to be regularly boiled and the biscuits are within easy reach for a relaxed debrief. Rigging storm sails for the first time in a severe gale is just asking for trouble. And the biscuits will get soggy too.