A Proa Perspective...  
By "Skip" Johnson - Houston, Texas - USA

... Matters of Balance

Adventure, experience, education; these were the goals driving the decision to campaign a proa in the Watertribe EC 07. Also high on the list was that I could have a partner that had done the race previously, Chuck “the Duck” Leinweber, but the window was only open for 2007. The OK to do this madness was granted with some trepidation from my wife Susie since I had already spent a lot of time building and campaigning a doubles paddle boat in the C100 earlier in the year. And she knows quite well the time and obsession involved in building a new boat in a short time frame.

Since Chuck and I were in the same boat at the same time, except when one or both of us were out pushing and pulling, I’ll let him tell the tale of the adventure, he took notes and pictures. (see May-June issue of "Small Craft Advisor" magazine - chuck)

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The experience was all I could have asked for and just a little more. Wind and waves aplenty for an old guy that usually paddles backwaters and looks for smooth skiing water at the lake. Also, the unspoken attitude as we traveled to Fort DeSoto was “I’m from the Texas gulf coast and I know all about shallow water”. A few days later I am in Florida and learning all sorts of new things about shoal water, tides and tidal currents. Mea culpa.

The driving force for all this effort was to see how a proa would perform in a real and challenging event, to find out what worked and what didn’t. Education at a visceral level.

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A shunting proa is a sailing vessel that has its axis of symmetry rotated ninety degrees. Instead of symmetry around an axis from bow to stern, symmetry is through a line from windward to leeward. Where one puts the various components of the boat determines whether the boat is a classic Pacific Proa or one of the variants. P52 is pretty much a classic pacific proa, a relatively long lean lightly loaded hull balanced by a float to windward. Comparisons to catamarans and trimarans are easy to make but inaccurate. A catamaran or trimaran transfers a significant percentage of its displacement from one hull to another to develop large moments to support large forces in the sail system to drive the hulls through the water. A pacific proa on the other hand unloads just enough displacement from the float to drive that long lean lightly loaded hull. A delicate balance foreign to a mindset that embraces trapezes and highly loaded everything. The only thing fairly highly loaded on P52 is the oar shaft that is mostly due to not having all the elements quite in balance yet.

P52’s hull is a simple long lean dory style hull with a fairly high prismatic coefficient balanced by a buoyant foil, both bilaterally symmetric (naturally) and longitudinally symmetric on the belief that a little leeway should provide all the lift needed and not add any extra turning moments or forces while traveling in a straight line. And it’s a little easier to build.

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I’ve got a strong desire to keep the rigging and time to water as simple as possible since there’s always the comparison to a car toppable solo double blade canoe, the gold standard in ease of use and return on investment (time, effort or money). So the float needed to either telescope or fold. Folding was selected so the possibility trimming the float back and forth a few inches to help balance and or trim the boat could be investigated. Initial trials were not auspicious and I now believe that a bilaterally symmetric boat would prefer to remain bilaterally symmetric. Overall the hydrodynamic portions of the design seem to work well together and I don’t see anything that cries out for significant change. The boat handled some pretty rough water in the run from Sannibel to Cape Romano and never buried the bow, stern or float.

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The sail system though, needs some significant reworking. Over sparred and over canvassed. I was moderately proud of the inexpensive lightweight cedar hollow birdmouth spars. Sixteen or so pounds doesn’t seem like very much until it’s swinging around high on the mast because lowering it brings the CE too far aft and everything goes completely out of control. I suppose pride goeth before too large a moment of inertia. This is the real visceral education I got on this event. The rules of thumb and coefficients for other types of boats may not be completely appropriate for a proa. The relatively high SA/WS ratio for a relatively crude trapezoidal/triangular shape should have been a clue. In any event, there will be a smaller sail cut from the current one, removing area from the back of the sail to move the CE forward and maintain harmony at home since Susie won’t need to restitch the difficult edges. The mast will be abandoned and one of the lighter yards cut down and retrimmed for a new lighter shorter mast. The other yard may be recut and retrimmed or there might be two new yards, time will tell. It’s interesting that the only hardware failure on the boat was the most expensive piece, a spinnaker pole fitting for the yard to shuttle shackle connection. To be fair there were some pretty high stresses going on at the time but it is disconcerting to have your whole sail system flapping in the (considerable) breeze from the top of the mast and trying to tear your boat apart [BENT]. I think I’ve come up with a simple solution to connecting the yard to shuttle that’s inexpensive, rugged and simple to remove.

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It turned out that most of the 200 miles we made were with a 40 square foot trisail cut at the last moment from a windbeaten plastic tarp. If I’d popped a little curve in the carpet tape we might have gotten there a little quicker but probably no farther.

After we anchored at the entrance to Indian Key Pass and watched the broken gussets at the float connection open up an inch or more as we bobbed in the chop [BROKE]I started to mentally break up the boat and catalog the salvageable pieces for its successor. But later that day watching the boat surf along at 17-18 mph pulling hard at the bit like a thoroughbred trying to pass the towboat I knew this boat deserved to be rebuilt and continue the quest [REDEMPTION - also see youtube video below].

The rebuild of P52 will have the sail/spar changes already mentioned along with a telescoping float system. The folding system worked well enough when extended and also when supported on the trailer (4500 miles worth) but was fragile in torsion while folded. Also to be corrected is the oar support at the cockpit, there needs to be an adjustable socket to raise the handle of the oar to stay in deeper cleaner water at times and to provide some more early warning when the shallows shoal. Incorporated in the socket will be some sort of tiller handle, there’s too much torque required at times to just twist the handle to steer. Also on the lower business end of the oars, there is going to be a removable end based on a double blade paddle ferrule to change out blades (experiment) or put on poling ends.

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On the same oar shaft, I would like to investigate propulsion based on what our water cousins the dolphins and orcas evolved untold generations ago. The hand-cranked propeller done in haste and desperation worked well enough though I did get greedy and lower the swing radius on the hand crank when I should have left it alone and increased the blade area a little bit. The issue is more philosophical than practical. The rudder on a kayak or racing canoe is the best way I know to describe the difference. A flat plate rudder will work but is terribly inefficient slowing the boat as much as turning. A well-shaped smaller 8-12% rudder blade will be a revelation, allowing sharper faster turns. But the blade may stall and you are then stuck with nothing but a smaller flat plate. However a well done scimitar shaped fin that spins a vortex off the tip will work almost as well as the shaped blade, and will do it every single time.

Finally if there is a successor to P52 there are a few things I know will be different and there is surely still more to be discovered. First the name will need to change, now that the boat is starting to prove its self, 5.2mm underlay is probably not the best choice for building. Then the boat wants to be 3 full sheets long, there is plenty of time to develop a cheap easy bi-directional masthead light and 7 knots at night can be a little slow at times. A little lower superstructure wouldn’t compromise the ergonomics particularly and would cut down on weight/windage a bit. Other changes/improvements await a season or two of development and perhaps another run at the EC, I can hardly wait.

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