SIMBO SAILING: Modern Twin Headsail Rig

I’VE RECENTLY RECEIVED an e-mail from Iain Simpson advising me that he has just launched a website dedicated to what he calls the “Simbo,” or Simple Bow Rig. In plain English this is a twin headsail rig, very similar to what bluewater sailors used to advocate for downwind tradewind sailing back in the 1950s. Iain has updated the concept for modern roller-furling systems and employs it on his Najad 570 Song of the Ocean. He is quite keen on it and has been proselytizing on the subject for a few years now.

The concept is really very simple. Instead of hoisting a single headsail up the furling rod on your headstay, you hoist two identical sails (in two separate luff grooves) on a single halyard. When sailing on the wind, the two sails lie one on top of the other, forming in essence a single two-ply foil. When sailing off the wind, you can split the sails and fly them wing-and-wing on two separate whisker poles. When you don’t want to sail anymore, or if you want to reef a bit, you simply roll the two sails up together on the furling rod they share.

Back in the day the notion was you’d fly twin headsails with the mainsail down. This way sail area would be perfectly balanced across the rig and by leading the two headsail sheets back to your tiller you could easily coax a boat to sail herself downwind without any special self-steering gear. In the days before Blondie Hasler invented the servo-pendulum windvane, this was considered a very useful little trick.

Example of a twin headsail rig from the 1950s. Here the sails, which are bent on with hanks, are set on twin offset stays

Iain likes to fly his twins downwind with the mainsail up, which obviously increases sail area quite a bit. His theory is if you trim the main to an angle of 45 degrees it will spill wind into the windward jib, which in turn will spill wind into the leeward jib, keeping all the sails full and happy.

I’m not sure that’s exactly how the aerodynamics work, but as you can see in this video he in fact has no problem keeping all sails full when running off.

Iain and Jan Simpson aboard Song of the Ocean

You can learn more about the details of flying sails this way by visiting Iain’s new site. Once there you can check out some other ideas he has on modern sailing systems for cruisers.