Tinkering with a sail (2): making a trial version

This is the result of my first test sail, performed with a Wall Mart PVC tarp. See also my other post 'Making your own kayak sail' for making your own sail. 

Okay, it doesn't look quite right. The cause is the mast sleeve that I quickly sewed on as the last part of the work. The sleeve got on twisted, resulting in wrinkles in the sail. But a first test with wind force five soon showed that this sail generates a lot less heeling force for my kayak. This is mainly because the leech is much flatter than that of the original Falcon sail. This allows the wind to race past the sail more easily without drag at the leech. This improvement will therefore certainly return in the final sail in dacron. During the test I crossed the Kralingse Plas in Rotterdam, the Netherlands on a reaching, windward course in 9 min.15 sec. with moderate paddling along which was okay despite the strong wind. Then I did the same route with the original Falcon sail. That was quite a nightmare. The speed was considerably higher for the first ten seconds - I estimate about 13 km/h - but after that I had to lean out a lot to keep the kayak stable. Actually, I had no control over the boat. I tended to counterbalance the heavy leaning with an equally heavy paddle support on the water, causing me to lose speed and keep the boat turning into the wind. It became a wobbly crossing, at times at tremendous speeds, but then stalled again by the heavy paddlesupport and luffing. I was releaved to reach the other side of the lake in one piece, in 10 min. 25 sec. That is slower and much more restless than my unsightly test sail! Conclusion: a flatter leech is a big improvement in high winds. I have also brought the draft point (the position where the sail has the deepest point) a little further forward, so that I will hopefully reach higher upwind. The Falcon sail l is an excellent sail by the way, but in wind force 5 you have to be in good shape to handle the enormous speed without excessive leaning and supporting with your paddle blade, which again negates the great speed. Also I believe the Falcon sail has a very open leech - it furls round like the leaf of a tree - to keep the wnd in the sail a little longer. This generates more power on a beam course and down wind, but may work counterproductive going upwind for the wind needs to let go of the sail as smooth as possible at the leech end. The question now is whether my test sail also performs better in normal wind. I do not think so. The advantage is probably only felt in high winds.

My thanks go to Iede who accompanied me in his kayak during the severe weather test and to my wife Annemiek who taught me to operate her sewing machine.