It seems that since TT rely on their edge to grip the water
(and to a lesser extent their fins), a relatively sharp (thin) square edge seems to work better than thick rounded edges. Although I can't say that I understand the hydrodynamics, I have been told that the rounded edge allows more water to get past it thereby reducing the pressure the board can apply against the water. Without the pressure pushing back against the board, it must have a greater tendency to get pulled downwind.
NOTE that some boards have edges which are needlessly sharp and add more danger than any improved performance is worth.
My first board was a "medium" size which I think was 165cm X something like 38cm.
I weighed 185lbs and was riding in 12-20+ MPH and would be decently powered at 15 MPH. I was so unable to go upwind that I built a board with a moveable little "keel" hoping to be more like a sailboat (it didn't work).
More by chance than design, I got a "large" board that was 183 cm X a tapered 39-40cm.
Although it had significant rocker, it also had relatively sharp rails and a 5th fin in the heelside middle. I can still remember the first time I could really go upwind cause I was SO happy.
As can be seen from my old boards, boards used to be MUCH bigger and (like all kiting stuff) have been getting smaller and smaller WITHOUT becoming any cheaper. I’ll assume that manufacturers costs have motivated them to reduce the size.
However, it is common knowledge that smaller boards require significantly more power to get on a plane, and somewhat more power to stay on a plane than a larger board of the SAME SHAPE.
Therefore, they've substantially increased the width relative to length because greater width allows getting up and planing with less power but still minimizes the amount of material, shipping costs, storage/display space etc.
But the downside to greater width as pertaining to upwind ability is that it is harder to hold an edge and therefore there is a significantly smaller window of range of power where the board can hold a SOLID edge in order to create the pressure required to go happily upwind. The fact that chop etc. also causes a wide board to bounce more than a narrow board also reduces its ability to hold an edge.
These facts suggest that the reasons my 183 seemed to go upwind noticeably well is twofold.
First, since the edge creates the needed pressure, it seems logical that the MORE EDGE THAT IS IN THE WATER
the harder it will be to get pulled downwind and the 183 had a LOT of edge in the water. Second, the fact that it was comparatively narrow allowed it to be relatively unaffected by chop etc.
thereby staying more securely in the water. Although the 5th fin undoubtedly added some resistance, I think the vast majority is caused by the long sharp edge.
It probably needed more power to get up on than would have been required with a wider board but not too much more once riding.
It should also be noted that beginners generally need NOTICEABLY MORE POWER to go upwind
because they don't have the skills which experienced kiters use to create the efficiency that enables going upwind with less power. This being the case, it is easy to see how a beginner in the required reasonably strong wind might have extra difficulty holding the necessary edge with a relatively wide board .
So my question for anyone still awake is, what are the flaws in this theory ?
Specifically, that very long, relatively narrow TTs with sharpish square rails should make it easier to go upwind and especially in the case of beginners.
Malibu Kitesurfing - since 2002
(310) - 430 - KITE (5483)http://www.MalibuKitesurfing.NETkfRichard@MalibuKitesurfing.NET