Published by the Open Canoe Sailing Group

area (which covers the whole of the Tay basin, but especially the much-paddled lower Tay) will take place in early March.



Performance And All That (JohnB)

It was very instructive watching our little boats on Loch Lomond in August as they coped with a wide variety of conditions. The quickest, by far, were TyroneC and KeithM, with Tyrone's boat having the advantage of an over rotating aerodynamic mast and it wasn't until F5 was reached that he appeared to suffer any disadvantage, although he was very expert at righting it and

Here's a space filler, just to keep you entertained. Did he really sail through?

getting under way again. KeithM was also very quick, particularly to windward.

In spite of the learned discussions that go on about the nature of the outrigger canoes, they did not appear to have any marked advantage. In light to moderate winds they tend to lose out because of their higher windage and increased wetted surface. Even in strong winds, say F4, the single hull boats can hold their own, only when the wind gets up to F5+ do they have a real advantage.

On the next two pages is John's latest thinking on canoe design, which he sent to GOSSIP last month. It is definitely not an outrigger canoe. (My first thought is that the daggerboard occupies a pretty central position. Not like Adam Wahl's leeboard.)

Tish 2 (JohnB)

This quest started some 10 years back with HamishS's Tishoo. This little boat, only 13ft. 6in. OA and very asymmetric, always did remarkably well in races, better than one would have expected with such a short waterline. She carried a rig of 45 sq. ft, 15 sq. ft in the jib and 30 sq. ft in the main, which had a very high aspect ratio of around 5.0. At the time the AR of our usual canoe rigs was about 2 - 2.5 and I assumed at the time that this was the reason for her success. It was not until I had read the work of Harry Luukkanen (In Search of a Sailing Canoe, 1997)

HamishS and Tishoo.

that I began to understand the significance of Tishoo's hull shape and from Harry's ideas evolved the hull of Tish 2. The resulting form will give about a 15% increase in speed for the same drag as an open canoe. This is probably significant as our boats not infrequently are sailing 'up the hump' and Tish 2 may well be able to get over the top and plane. Progress indeed.

The other great influence in the design of Tish 2 was Frank

All the detail presented above is based on sound scientific theory; this boat will be very fast and probably quite able to plane.

Bethwaite, an Australian designer and sailor of considerable importance and one must recommend his book "High Performance Sailing". Calculations have shown that if we can sit the crew out some 2.5 feet from the centre line we can increase the righting moment by about 25%. This would need a seat of say 5 feet, projecting by some 12 inches either side and as the rig we are proposing has a centre of effort some 6 or 7% lower than our convention una sail rigs, we have every hope of it being manageable. The rig itself has a high aspect ratio (6.5) 30 square feet fully battened reefable sail and a 14 square foot jib. Again, wind tunnel research and practice shows this to be the most powerful as well as having a lower centre of effort and hence a lower overturning moment. The sail drive, that is the drive that is actually pushing the boat in the direction you want to go, has also increased by some 25%.

A significant part of the rig is the aerodynamic mast with its unique turbulence creating after surface. Wind tunnel tests show clearly that the turbulent flow re-attaches to the sail more quickly than the laminar flow and is far more efficient in practice. All the underwater foils are NACA 0012 in section with an aspect ratio of 4.5. The centreboard is 3% of the sail area and the rudder 1.5% of the SA. The underwater surfaces should be finished to a high gloss and then kept polished for optimum performance.

Tish 2 represents my journey in pursuit of excellence. It has taken some twenty years but I believe that Tish 2 represents an ultimate sailing canoe and it is within reach. If I were younger and fitter I would build it. Nothing on Tish 2 is there without reason or because it looks nice. She is a highly functional machine and I have no reason to believe that she will not perform as designed.

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