Proas: Pacific, Atlantic, or Tacking?

Part 3 in a series from adventurer Stephen Ladd

See first article in this series here. —Eds

Article by Stephen Ladd

The greater the length-to-beam ratio of a hull, the less its immersed cross-sectional area, which is the principal component of drag. A proa is a boat with a long, skinny main hull stabilized by an outrigger held to one side by crossbeams. The outrigger contains no accommodation, so is even slimmer for its length than the main hull: little more than a floating spear. As with other multihulls there’s no ballast.

The most common, and only traditional, type of sailing proa is the Pacific proa. These keep their outrigger to weather, and “shunt” rather than tack. That is, to resume windward progress on the other tack (or should I say on the other shunt?) 1) the sheets are freed, 2) the “old bow” falls off the wind while the “new bow” points up, 3) the sails are somehow reversed 180 degrees, 4) the rudder in the “old stern” is lifted, 5) the rudder in the “new stern” is dropped, and 6) the helmsman steers the “new tiller.”

The Pacific proa, which keeps its outrigger on the windward side, must have evolved millennia ago because the far-flung archipelagos were all colonized long before Europeans arrived on the scene. The Polynesians had no writing, and their boats were entirely perishable, so we don’t know how they evolved. This is unfortunate, because it would seem safer to put the outrigger on the lee side. Surely an outrigger’s resistance to immersion, due to buoyancy, must exceed its resistance to being lifted into the air, due to weight. Yet windward outrigger placement defines the Pacific proa. Why? Only one reason presents itself: it’s faster! As the wind loads the sail the outrigger unweights and may even fly out of the water. Now there is only one skinny hull, which is optimum for speed-to-power ratio at higher speeds. (At low speed a more bulbous monohull may be more efficient due to less wetted surface area.)

The Pacific proa sailor prevents capsize through careful sheeting and reefing. Also, modern versions usually have a voluminous above-water leeward protrusion in their main hull to catch the boat and prevent it from turning turtle. This “lee-pod” has a somewhat boat-like shape, so the boat skids along, not quite tipping over, until the sailor corrects the situation.

The Atlantic proa is a rare latter-day invention. Its progenitor was Cheers, an American boat that took third place in the 1968 OSTAR single-handed trans-Atlantic race. It shunts just like a Pacific proa but it carries its outrigger to leeward. The more power the sail(s) develop, the more the outrigger digs in. This adds drag, but you don’t need a lee-pod.

The third type of proa, also extremely rare, is the tacking proa. Only a few have ever been built. Its logic is as follows.

1. If the Pacific and Atlantic proas are both feasible then a boat that is “Pacific” on one tack and “Atlantic” on the other must also be feasible.

2. There is no need for a second rudder.

3. There’s no need to come to a stop with each come-about.

4. There’s no need to reverse the sail plan with each come-about, which seems to be inherently awkward.

Basically, a tacking proa is a trimaran with one outrigger instead of two. All else being equal, the crossbeams of the tacking proa would have to be longer than those to either side of the main hull of a trimaran. This is because in a trimaran the leeward outrigger contributes stability via buoyancy while the windward one does so via weight. Each does double duty. With one gone you’d have to give the remaining outrigger more leverage.

Proas are rare. Boattrader.com has no category for them. Neither does Sailboatsforsale.com. And tacking proas are vanishingly rare! A few can be viewed at https://www.tackingoutrigger.com/index4.html.

I’ve chosen to turn a Pacific proa into a tacking proa because I want:

• only one rudder,

• a central cockpit convertible into a tent, which was impossible with the mast in the longitudinal center, and

• quicker coming about.

Nor was disposing of the rig that came with the boat wasteful because it consisted chiefly of some bamboo poles and a ripped Tyvek sail. That is, it wasn’t a fully developed boat. I still have never shunted a proa, and possibly never will.

Quite arbitrarily I am extending the crossbeams to port, so she will be a Pacific proa on port tacks and an Atlantic proa on starboard tacks. I don’t know which I’ll like better! I may have to carry less sail on the port tack than on the starboard tack. The idea of non-symmetry doesn’t bother me, while the minimalism appeals.

Above are some pictures of my proa in her former, Pacific, life. Her name was Palindrome, as in a word that can be spelled in either direction! That’s no longer appropriate, so she will get a new name. Renderings of her as a tacking proa will come in a future article. •SCA•