sail-world.com -- Improvement all around for Vestas Sailrocket 2 + Video
Improvement all around for Vestas Sailrocket 2 + Video
Wed, 7 Nov 2012
Paul Larsen, Vestas Sailrocket 2 project leader and pilot, discusses how the team has now been able to get out on the race course and make all around improvements.
We managed to get out on the course yesterday in slightly marginal conditions. The wind was between 17-24 knots... mostly around 20. We were happy to have Dave and Gordon Cameron out as guests today. No one gets a free ride though and they were both happily put to work taking photos and assisting with the launch.
I was keen to see how the new double-sized rear skeg would assist us during start up. The answer is that in light winds that we normally wouldn't even get going in... it transformed the boat. I could now ease the wing out to get the flow attached and hold a straight course without having to drag the small front rudder along at full lock. I was in control at five knots... you know... like a normal boat.
This will make a huge difference to how we do the following start up procedures. VSR2 lifted nicely up onto the plane as I accelerated towards the beach.
I made an effort to raise the skeg as it had done its job and we were going fast enough for the main foil to be pulling effectively. It then got a bit funky. The new rear skeg is too big to fully retract even when raised to its limit in the rear float. This means it can still steer the boat if the rear float isn't flying.
As I bore away onto the course and accelerated further, the rear float raised clear of the water. It was obvious that the boat was steering was still being affected by the rear skeg because when it lifted clear, the boat jerked to windward. I responded with a heap of rudder, the back sank, the skeg kicked in, I steered, we accelerated, the back lifted etc...
We only went through a couple of rapid cycles before we accelerated enough to settle into a flying mode. It was a little un-nerving. No issues at 25-30 knots but it would be a big issue at high speed.
The good news is that for the rest of the run the rear float was flying high enough for this to have no effect.
The fact we were even sailing in this wind was good news. VSR2 felt slippery. Towards the end of the course she got her skates on and took off. She felt real slippery. We were not going fast enough to fly the leeward float but when I looked back at the rear foil It seemed to be riding at the fences. There was still a lot of spray.
So it wasn't a fast run... we only averaged 41.3 knots but peaked at 47.3 knots. When I looked at the data from the shore weather station throughout the run there was one gust to 21 knots but generally the wind was around 19 knots. This marks a huge improvement for this boat in these wind ranges.
On reviewing all the onboard footage afterwards I could clearly see the new fences working brilliantly. In fact they perfectly determined the ride height of the boat. If they stopped working then we would simply lose a bit of ride height until they became effective again. This means that we now have a lot less foil in the water and that the foil that is submerged is working well. This could explain the high boat to wind-speed ratio we saw towards the end.
It was a great little shake-down run and I was itching to see all the Cosworth data at the end. The SMD pressure sensors we used on the rudder to test base cavity pressures showed that everything was A-OK up there. Oddly for such a low speed run, the rudder side loads were quite high. This could be a good sign as it could be a reflection that we are sailing at low apparent wind angles (with higher lateral loads)... and hence higher efficiency.
I decided to only do one run as it was obvious that we needed to slightly reduce the dimensions of the low-speed skeg. If we were going to sail the following day then we would need some time to do the 'chop' properly (it's done now. We are once again ready for sailing. Trouble is that the forecast has dipped again. Ho hum.)
Yesterday was a good day. Our theories seemed to be proven correct. We made some basic setting up mistakes with regards to recording data that was a bit annoying i.e. the masthead GoPro wasn't turned on, the onboard wind-speed oddly recorded everything but the run itself(????) and I didn't mount the little wind indicator in front of the cockpit which gives a nice simple, clear indication of how efficiently we are sailing.
The fact is we need to be out sailing more often so all these procedures become routine. Last year we were sailing all the time and the team got very slick. The weather has not been so kind to us this time.
So we will try and sail again today but to be honest, I don't expect there to be much wind. I will still try and get out for the sake of the teams practice. We need more wind now to see if we really have found a way through the 'glass ceiling'. The only ray of hope on the forecast is next Sunday. It looks pretty strong so we need to make sure that we are ready for it when it comes. It looks like those days are going to be precious.
The whole team are quietly excited about how the new foils are progressing. The real proof will be when we start punching out the big numbers. We haven't done it yet. Until then we have to keep a lid on it. I do like what I'm seeing though. Yep, one of these days...