Monday, 30 August 2010

Dutch Nationals technical wrap-up

The Dutch Nationals provided us with more data about how to get the best out of the DNA.
There is a trend toward more mastrake. That way we keep the bows form burying downwind in big gusts which helps the boat acelerating to speeds over 20 knots.
Although the beam is clearly behind the middle the mastrake balances the boat better upwind and downwind.
Upwind all forces are centered around the daggerboard. The helmsman is standing in the trapeze at the daggerboard as well and the boat feels light and fast.

It is so importrant to keep the bows up in breeze to keep the boards working for you. If the boat dives the boards give less left and become draggy. The same effect as if you would sail downwind the straight boards completly down. The fastest way to sail the boat is the nose just touching the water, both burying and high up are slower.

In 24+ knots you can choose how to sail the boat downwind; to sail it flat with the daggerboards up or with even more mastrake on one hull and boards down. If the boat nosedives you can still bear away; the boat will not cartwheel but plough through the water before it comes back. Chris sailed it in 24 knots of breeze downwind on one hull with extreme mastrake and was excited about the speedthrill.
We have not seen any trapezing downwind in this Nationals, mainly because the wind was so gusty and sofar only Chris and Jaap have experince in doing so in force 5 and up. You definitely need toe loops to do so, although nosediving is minimized once you stand on the transom of the boat. (according to Jaap and Chris)
Now the first DNA's have arrived in Australia we will soon get more reports about this new style of of downwind sailing.

We also believe now that in over 18 knots we can reduce the rake of the boards a little because at the high speeds you get so much lift from the boards. When I overshoot te first mark in a 20+ knot breeze and had reach to the first mark the boats started to jump, which looked spectacular but felt a bit scary. So next time I will reduce the angle with half a degree to have better control and lower drag for even higher end speeds. Decreasing the amount of lift is easy on the DNA because we have our sliders with which we an easy adjust the amount of lift.
Upwind you can sail the boat in two modes; one is going for maximizing straight line speed with a slightly twisted sail (Roeland style) or sail it with a tighter sheet and sailing 'bananas' in gusts. With bananas I mean that you not really steer up to to handle the gust but instead sailing a slight curve to gain height. It feels as if the boat is climbing up into the wind. I used this technique to pass a boat with straight boards. It only seems to work on a boat with curved boards.

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