2007_02_11

Home
Up

After spending the night at Toms house at Mount Best listening to the wind and rain all night long, I was keen to get down to Sandy Point, to catch up with Andrew and get some testing in on the new V7. On the way down about 9.30am I had another delay from a fallen tree on the narrow winding road from Toms house through the rain forest. It seems every time i go down there the wind howls and blows trees over! I can't figure it out... 

After a short spell at Andrews house at Sandy Point we all headed down to the inlet to find the wind a bit up and down and hard to predict what it was going to do. We all struggled with choices as the wind strength ranged from 10 knots to 35 knots. Finally we hit the water, most of us on 5m sails. It was not (usually) worth going out too soon because we know that the fins operate better at or just before full low tide.

But this was my first session on the TM45 V7 Super Carbon and I was keen to see how it went in all conditions. And I was very pleased with how it performed. Not so much because of the top speeds achieved as they were quite moderate considering the peak wind speeds, but more because of the way the fin did it, able to produce terrific speed whichever direction I pointed it. Which is a distinct change from the V6.

The V6 is an exceptionally fast fin in stable water conditions. It is not so much affected by the short wind chop because the fastest I have recorded was on the V6 in quite significant chop. But it seems to be affected by turbulent or disturbed water. And the number of sailors on the course might have an affect also, possibly due to cross chop having more of an affect than regular chop.

The course on this day was different from our usual east bank conditions. With the wind so far around to the ESE, there was little distance you could travel at the right angle before venturing into the larger chop. And I was not too keen to venture there for a number of reasons, not the least of which was that it was a borrowed board and it would be an expensive exercise if I dented it!

So on my first shakedown run I stuck closer to the bank and tighter to the wind. Fortunately there was plenty of wind on that first run and I was able to let out the back hand quite a bit and let the sail suck me across the wind through the very flat water behind the bank. The top speed on the GPS was 42 knots on that first run, heading into an outgoing tide. This was a very good speed for such an angle and water state. Perhaps with the V7 I had solved this final riddle of why fins can work so well one day and so poorly another. I backed that run up with quite a few runs that day over 42 knots with a max 2 second peak speed on the GPS of 44.3 , and again working against the tide and about an hour before low tide.

The return runs back up the course were interesting also in that the fin went very well up wind. I should have been surprised but knew that although these asymmetrics are designed for going one way, they can still have some surprising upwind ability going the other way. The V7 did not let me down and always managed to point high back up the course and felt solid. What is often interesting is the speed of the return trip. My V6 likes to run at about 15-17 knots, but the V7 liked to run a bit faster at around 20-22.

There was another interesting statistic. The average wind during my sailing session was 23 knots, with many gusts but also many deep lulls. I spent a lot of time dragging my bum in the water trying to get going in some of these drawn out lulls. But I very regularly got peak speeds over 40 knots even in some of those lulls, which might have been 20 knots or even less at times. My peak speeds are rather short but interesting how often they got over 40. I had the distinct feeling the fin was flying in the light stuff even when running only the 5m Stealth and on a tight course. I expect that more testing on the west bank in consistent wind will back this up.

My goal for the TM45 has always been to build a fin that will get up to 45 knots more regularly and in a wider range of conditions. In particular, I was trying to solve the issue of fins sometimes working and sometimes not. After suspecting the water state as the cause of the problem I developed a unique foil for the V7 to try to encourage the drag bucket to exist in a wider range of conditions. The way this one performed I think I have finally achieved this significant design goal and am feeling very satisfied about that. Especially after all the hurdles I have had to overcome.

I am tempted to give this foil a name to identify it from other foils that might have different design goals. Perhaps I should call it the Vario section, to signify its goal of operating in a wide variety of conditions. This way I can identify this section on other fins I make that share the section design, but might differ in other ways. For example, I was considering building a speed slalom fin and I think this Vario section in a symmetric design would work extremely well.

Here are the graphs of the best runs (pink range is 10 seconds):

Trackpoints at 20211017_095951.gpx

 

 

 
 
 
Copyright © 2007 Parametrix Pty Ltd
Last modified: February 15, 2007