Thu, 15 Nov 12 16:13

 So here we are. VESTAS Sailrocket 2 has finally begun the big reveal of the beast within. From our perspective, the speed wasn't any accident and certainly wasn't unexpected. We have been working in this direction for a long time now. We always said that we were aiming for speeds over 60 knots and that in the current speed sailing context it simply wouldn't be worth building a boat unless you were. I don't think anyone is really sure of what the potential of the kiters really is. Even the windsurfers are now showing that they had what it takes to get well over 50 knots. Everything about VSR2 was focused on 60+. We just hadn't found the right combinations to unlock the boats real potential. Being stuck in the low 50's was frustrating on one hand but very educational on the other. To be fair, the new foil didn't get stuck there for very long. We just needed to get enough runs in to work through a few theories. The change in performance once the fences were added was pretty remarkable. The way that the low wind performance changed was a big indicator that something fundamental had changed and we were itching to see how it would effect us in stronger winds. 

 

The last two runs were brilliant. That last run was truly great. It represented a real and undeniable breakthrough for sailing where the previous limiting factors were overcome. The good thing was that we did it in a pretty civilised manner on an open water course in winds that only averaged 24.5 knots on the shore station. I'm sure that we hit our peak speed in the high part of that average i.e. 28 knots but I'm also sure that that is about all we need to go even faster. The wind was ranging between 21 and 28 knots for those who are interested with a True wind angle of 99 degrees.

THIS IS THE LITTLE GPS WHICH WE TAKE ON THE COURSE TO INDICATE WHAT WE JUST DID. THE ACTUAL RECORD DATA IS ON THE BIGGER, MORE ACCURATE TRIMBLE GPS... BUT THAT DOESN'T HAVE A DISPLAY. IT INDICATED A LITTLE FASTER THAN THIS AS A PEAK ALTHOUGH THE 500 METER AVERAGES WERE ALMOST IDENTICAL. (I BELIEVE THAT SEB CATTELAN HAS HIT A SIMILAR PEAK BEFORE ON A KITEBOARD. I'M NEVER REALLY FOUND OUT WHETHER HYDROPTERE DID OR DIDN'T HIT 61 I.E. WAS IT A "SOMEONE-THOUGHT-THEY-SAW" SPEED OR WAS IT ACTUALLY LOGGED. I ONLY SAY THIS BECAUSE YOU HAVE TO BE CAREFUL ABOUT WHAT YOU SAY IN THIS GAME AS EVERYONE WANTS TO RUN WITH THE BIGGEST NUMBER AND THAT CAN LEAVE THE REST CHASING A MYTH... JUST LOOK AT THE ICEBOATING RECORD!

 

The target performance for VSR2 with these foils is 65 knots in 26 knots of wind. We figured that this should give us sufficient margin to get a 60 knot average and that we could make up for any unplanned inefficiencies by sailing in more wind if need by. You have to appreciate that you never get a solid 26 knot wind. Even on only a 500 meter run you might see 23 and 30 knots. At the true wind angles we are sailing we are bi-secting the gusts at a pretty rapid rate... not running along with them as you would on a deeper downwind course.

Now that we have looked at all the data we have seen that very little needs to be changed. The little 'yaw-string' wind indicator in front of the cockpit showed me that the fuselage was lining up with the apparent wind nicely. That's a good sign of the boats efficiency. The rudder loads and foil base pressures were all pretty good and the leeward pod was looking after itself nicely even at 60+ knots. 

TWO TEAM SHOTS. THIS ONE WITH BEN ON THE END AS HE JUST WARNED ME THAT I DON'T WANT TO MESS WITH HIS MUM BY EXCLUDING HIM FROM TEAM SHOTS... AND THE NEXT ONE...

WITH WALLY... THE NEW TEAM GOOD LUCK MASCOT. LAST TIME WALLY CAME OUT WE DID THE 54.4 KNOT PEAK WITH ADAM FROM 'WIRED' IN THE BACK. HE ONLY TURNS UP WHEN THERE'S A WHIFF OF FINE FRENCH CHAMPAGNE IN THE AIR. ANYTIME WALLY!

 

THE 500 Meter AVERAGE.

This was pretty interesting and gives a great indication for what is to come. The speed graph is more of a spike than a solid average. We were accelerating all the way from 47 knots to nearly 62 throughout the average. VSR2 was still accelerating hard when I finally pulled the pin and eased the wing. In fact she kept accelerating even as the wing was going out. I have no doubt she was on her way to a much bigger number if more runway was available... and quickly. When I saw the gust I knew I wanted it. I had to see what it would do. We were already going quick and accelerating. That last bit was like a turbo kicking in. I hung on for a couple of long seconds whilst my mind raced through the rapidly developing issues. I was happy we had broken into new territory but was also determined not to do anything gung-ho-stupid and destroy the foil. It was nearing low tide and flamingoes were standing in the shallows at the far end of speed spot. If I ran up there I could easily destroy the foil and end this record session. Fortunately the whole show was brought to a stop in the usual manner albeit with a little more distance involved. I knew it was 60. It had to be. It's what I imagined 60 would be like. Hard and fast. The ride firms right up and the chop turns into a rapid chatter. VSR2 just locks into a course and begins to feel lighter as the loads she is torn between get bigger and bigger.

So the peak was 61.92 knots (71.3 mph or 114.75 kph). The average was 54.08 knots over 500 meters and the best 5 second average was 59.08 knots. As mentioned, the low speed on the 500 meter average was 47 knots. Even if we don't go faster, it shouldn't be hard to bring that 47 up into the mid 50's. That should do the trick.

The thing is that I don't trust the kiters. They make me feel uneasy. They're hungry for this game and they are not going to give this speed mantle away without a fight. I'm not sure what their real limits are yet. For all this time we have been trying to bag this outright world record but even now... before we have even achieved that... I am wondering if that will make me happy. I guess this challenge has turned into something bigger than the actual record. With this boat we want to push the limits of the sport itself. The performance of the kiters has forced us to build this wonderful machine and to aim high. With that last run we entered a whole new world of performance. It's a fascinating world full of possibilities. In one way it is akin to when sailing boats realised they could follow their powered brothers from displacement mode to planing mode. Our new foils have many similarities to that analogy. They no longer have long thin transoms but are actually at their thickest there with the aim of getting the water to seperate cleanly. It's no longer just water down there but now it is air and vapour mixing in weird and wonderful ways. These can be played with using all sorts of 'bolt-on' devices. It really is fascinating. I've been lost in this world for the last year and am still only just realising how little I know about it.

So I expect the kiters to oneday reach an average of 60 knots. I don't know how or when... but that's what I expect. I'm not entirely sure of what their physical limits are but I know they are hungry. We want to get to a 60 knot average now. I don't know if mother nature is going to help us out here but we will be on standby for any and every opportunity.

As we sprayed the Pol Roger champagne over the main foil the other night I joked that I hoped that this was the only type of cavitation that this foil would ever see.

Only yesterday when we hosed it all off did I really see/feel a certain 'chalkiness' to the normally super-smooth surface near the tip of the foil and along the suction surface near the TE. I'm pretty sure that this is pitting caused by cavitation. The interesting thing is why we haven't seen this before i.e. when hitting the 'glass-ceiling' at 52 knots? It makes me wonder yet again about what we are looking at.

I'm now sure that we can smash the existing record. VSR2 has showed her hand and it's holding some aces. I will also be the first to acknowledge that we haven't done it yet. there's a heap of ways not to get the record out there. I still have that slightly edgy feeling that comes when you have it all to lose.

WARM FRENCH CHAMPAGNE IN RESIN MIXING CUPS. WE TRY NOT TO TEMPT FATE ANYMORE BY CHILLING THE CHAMPAGNE BEFORE WE GO OUT. I'M NOT SUPERSTITIOUS... BUT I CAN'T AFFORD TO BE WRONG!

 

Despite our expectations, this is all new to us. Lying awake in the middle of the night and not having to wonder if the boat will ever really do it is a wonderful new sensation. I live and breathe this boat. It's great to be where we are at right now... with the expectation AND the knowledge. Yeah, we are aiming high... and yes I will be real happy when we grab that title for the first time.

 

One of these days this ride home is going to be that little bit more special.

Cheers, Paul

p.s. thanks for all the messages of support and encouragement. I read them all and reply to as many as I can. Many of you have been backing us for a long time. You're all part of this snowballs momentum.

Tue, 13 Nov 12 20:31

 Hi all, busy day today sorting out everything from yesterdays madness. Great to wake up in the middle of the night realising it's not a dream. The next potential forecast is for Friday/saturday. After looking at all of yesterdays data I know we can smash this.

Peak speed 61.92 knots.

500 meter average 54.08 knots

5 second average 59.08 knots.

It's funny now to see that speeds of 52 and 53 knots are dragging down your average.

It's a new ball game now. Let's hope that mother nature comes to it.

Full report tomorrow... meanwhile here's the vid. Nice work Ben.

Boom, the 60 knot + run

Enjoy. 

 

Mon, 12 Nov 12 19:14

 Just in... 61 + knot peak speed and a 54. something average. Had to stop as the end was coming up fast.  Everything went into fast forward. I was saying " this is fast, this is fast" and then she took off again... "this is real f*****g fast"!!!

I thought we might have bagged the outright as well... as you would after hitting over 60 knots... but the average wasn't there... I think. We haven't downloaded the big TRIMBLE yet. Everyone is getting the data down now. We broke our own PB twice today... so that's 2 x triple rum and cokes in pint glasses... and of course the 60 knot bottle of champagne also falls. Happy days.

What a great relief.

I know the current world record is toast... hell, they can even raise it a bit if they want.

Life for VESTAS Sailrocket 2 starts at 60 knots. Today she walked on stage. She was beautiful to drive. Totally in control.

I got Helena to come down to the end of the course before I checked the speeds. I wanted her to be there. Unfortunately she had her phone in her drysuit pocket so that was the end of the Tweets.

Righto... lots to do.

The outright record remains to be beaten.

I'll let you all know the actual numbers when I know myself.

Happy days alright.

Nice work team... real nice.

Cheers from one beaming Australian in Namibia.

P

Mon, 12 Nov 12 13:33

 This is the best looking day we have had so far in this record attempt. The forecast has been good for a while and finally it has arrived. The day started in a promising way but then it just hung around for a bit. Everyone was in cruisy 'stand-by' mode. I went and did what I usually do when I want time to think, watch the wind build and generally chill out... I weeded the lawn. I wonder why I do it myself. I just find it calming and perfect for 'thinking'. I've never done any gardening in my life so odd time to start.

So it's blowing outside and we are all booted and suited. Let's see if we have the right pieces to assemble this puzzle... or are about to face-plant the glass ceiling again!

Helena will be sending tweets from the course.

I'm not getting on the emotional roller-coaster today. I'm just going to flat-line. What happens happens.

Cheers, Paul

Thu, 8 Nov 12 17:08

 We did manage to get out again a couple of days ago. The winds were still light but we made an effort for the practice as much as anything. You always learn something. On one hand we don't want to expose the boat to risk... on the other, not practicing as a team exposes the boat to risk.

The wind was moderate and we went on standby at the yacht club for a period before deciding just to go for it. The wind at speed-spot was once again around 17-22 knots... generally around 19-20.

A brand new GoPro 2 let us down by simply freezing up just before we started. Swearing at electronics has become part of my 'pre-flight' ritual. I don't know how many cameras this project has eaten through. The GoPro's are great bits of kit... essential really... but they earn their swear-time too.

The start up went very smoothly again. The back skeg had been chopped down by Ben after the previous run. The back of VSR2 still kicked around as it lifted out of the water but I will put this down to sailing in lighter winds. I was seeing wind gusts as low as 15 knots just before I released from the RIB.

Once I was on the course she felt fast and slippery once again. The speed was more constant than the previous run. The peak speed was 46.22 knots and the average was 43.85. Nothing flash in outright terms but very impressive for us considering the wind strength.

I had the little TACKTICK wind vane mounted just in front of the cockpit where I could see it... and I still didn't look at it! One of the cameras did catch it however and it was obvious that we are now sailing at a level of efficiency where the apparent wind is lining up perfectly with the fuselage. We are fitting all the little aero aids now as they will begin to have an effect.

 

Once the run was over we had an issue with the wing. A retaining collar had failed on the mast. It normally wouldn't be an issue when sailing but when at rest the wing can sometimes put the support strut under compression. This puts an up-force on the mast. The mast proceeded to rise up off the lower curved section. The rigging went slack. We all froze as our minds raced to what had failed and what was now being loaded abnormally. So often you can do the wrong thing at this point. The situation sort of stabilised in a wobbly way. Fortunately it was only light winds and we managed to understand the issues and get the whole thing down without causing any secondary damage. The wing has been under heaps more load than this before so it was quite surprising to see this. I'm glad we did as it would have no doubt ruined not only our next windy day (if it happened then) but also caused a lot more carnage and therefore ruined a week or so. The new part has already been made by Jose at BRUMAR ENGINEERING in Walvis and the wing will be re-assembled tomorrow. We haven't missed anything.

Here's the video of the run...

youtu.be/hCx7J9yBf2o

 

We remain plagued by light winds. Tomorrow is a maybe and Monday is playing with us. It looks like we are right on the edge of some strong stuff but it comes and goes with each forecast. I can't wait to let this boat go in a 25 knot plus day. Meanwhile we go over the boat... and sit and wait... and watch the news coming up from Luderitz where they are getting plenty of wind. Great to see the windsurfers beating their own records and edging ever closer to 50 knots. I look forward to sending some big numbers back down their way soon. Come on Walvis... jokes over.

Cheers, Paul

 

Tue, 6 Nov 12 14:27

 Hi all, here is a video which brings you bang up to date with this morning. Go Team. It goes hand in hand with the last blog.

Heading out again right now. It's another marginal day but good for training.

youtu.be/9t67XU0lhqc

Cheers, Paul

Tue, 6 Nov 12 10:17

 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.

NOT A 'FRICKIN' LASER I'M AFRAID... JUST THE TOW LINE!

HOISTING THE RIG...

PREPARING TO RELEASE FROM THE RIB. YOU CAN SEE HOW VSR2 IS NOW HANGING FROM THE RIB AT A POINT AT THE REAR STUB BEAM. THE WING IS OVERSHEETED AND STALLED SO THAT THE NOSE OF VSR2 SWINGS AWAY FROM THE WIND. I USUALLY WAIT UNTIL I AM AT ABOUT 90 DEGREES TWA BEFORE RELEASING.

 

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 5 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.

I THINK THEY'RE FREAKY... THEY THINK I'M FREAKY... PROBABLY BEST WE JUST AVOID EACH OTHER.

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.

THE FOIL IS RIDING NICE AND HIGH HERE. I LIKE THE PULSES IN THE SPRAY. THEY ARE MOST LIKELY CAUSED BY THE SMALL CHOP. THE COLOUR OF VSR2 IS INSPIRED BY THE BELL X1 THAT FIRST BROKE THE SOUND BARRIER. I BELIEVE SHE WOULD ALSO HAVE A SORT OF SONIC PULSE IN HER ROCKET EXHAUST. HUMOUR ME.

 

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. 

WE'RE ALL SURPRISED THAT THIS HUT IS STILL HERE. EVERY YEAR IT GETS A BIT LOWER.

 

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.

UNLOADING THE TIMING AND FILMING CREW BEFORE HEADING UP THE COURSE.

 

LONG TIME SPEED-SPOT RESIDENTS.

 

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... 

Cheers, Paul.

Mon, 5 Nov 12 12:53

 The Walvis Bay wind machine remains on safari... although we might get a chance to get out over the next couple of days. It has now been 16 days since we last had enough wind to get going. It's going from 'unusual' to ridiculous. The walls of the container begin to close in on us.

The WSSRC are now on-site so any runs we do from here will be officially ratified ones. Our record attempt period has started. The big TRIMBLE 5700 GPS is mounted on the boat. The gig is on!

The standby time has allowed us to think long and hard about our current performance predicament. We had our design meeting where Chris, Malcolm and myself had a long Skype discussion about likely scenarios. Basically we tried to reverse engineer the problem and our train of thought was as follows...

 

-The most likely candidate that would be giving us a sudden, large loss of performance regardless of power input is cavitation.

-The rudder is not loaded highly enough nor does it have the base area to give us such a sudden drop in performance... although we will continue to put sensors on it to make sure it isn't contributing.

-So... the most likely candidate for caviataion is the suction surface of the main-foil.

-The main foil shouldn't begin to cavitate around 52 knots unless it is 40% overloaded.

- How could the main foil be 40% overloaded at such a relatively low speed?

- If the upper portion of the foil, the part that enters the water, was ventilating (highly likely as it is at the surface), then what effect would that have on the boat?

- On checking the numbers, AEROTROPE deduced that if the transition (curved part of foil) was ventilating down its suction side... then we would lose about 30% of our lateral loading area. At 52 knots... this would lead to the lower section of the foil being overloaded by... wait for it... 43%!

-It would cavitate

- AND... the back of the boat would ride very low... as it has been doing...

- AND... pitching the foil up would most likely have little effect and may actually make it worse by leading to more upper surface ventilation (as we have often seen)

 

So, this all seems to fit together very nicely. This in itself kind of makes me suspicious. Nonetheless it is a great starting point. Some parts are kind of obvious i.e. that we are getting ventilation near the surface of a shallowly (?) inclined surface piercing foil but others aren't. The foil was already twisted so that it would be lightly loaded near the surface to prevent ventilation. The fact is that what happens at the surface is very hard to predict, especially in chop. We have added substantial 'fences' to the foil to try to prevent the curved part of the foil from ventilating. We have started big as it is easier to chop them down than build them up. We have fences on both sides.

 

Looking at VESTAS Sailrocket 2  sail past, it is easy to see the energy lost in the spray that is thrown into the air by the high pressure side of the foil... but nearly impossible to see the energy that is lost by air being sucked into the water on the opposite suction side of the foil. Both need to be considered.

It is only our 6th run with this foil. In this respect I think we are developing it in the right manner.

I think our logic is sound and obviously I look forward to seeing what happens next. We may not get the fences right first time. We have other options for modifying the foil if this doesn't work. We'll see. One at a time.

 

We have begun to make a few changes to the foil as we always expected we would. Subtle changes at the speeds we are already travelling can make a big difference. I'll hang onto a some of the pictures, data and details for now. If there is one thing that the past year has taught me... there is very little real-world info about the hydrodynamic arena we are about to enter into. There are lots of theories but getting the hard data from the real world to verify them is the hard bit. Some of those theories strongly oppose the path we are taking. The data we have received already validates some of our decisions. It has been expensive to come by.

 

Ben has also made a new asymetric rear skeg to help VSR2 get started.

So far we have just been using the old original rudder off Sailrocket 1. It has worked OK but quite often its effect was marginal. The new foil is nearly twice the size. The purpose of this foil was to help our small high speed foils give traction at low speed. VSR2 starts in a highly stalled state and makes a lot of leeway. As it is skidding sideways, the weight of me in the front makes the front float sit low and this drags the nose of the boat into the wind. She won't bear away and I just sit there. If we add more lateral resistance at the back of the boat i.e. the new big skeg... then there will be more drag at the back and if I fully over-sheet and stall the wing, VSR2 will bear away to an angle where I can sheet out the wing and start sailing. Hopefully I can get up enough speed for the small front rudder to get a grip before VSR2 turns head to wind again. You have to remember that the boat is set up to be perfectly balanced at 60 knots. This particular boat and concept is more sensitive to its static set up than most other boats as the sail/wing has a large offset from the opposing foil.

The skeg will kick up as VSR2 accelerates. If not then I will pull it up manually as soon as VSR2 begins to accelerate.

 

For now, we sit on standby. VSR2 sits outside fully tooled up and ready for action. The wind is blowing nicely already but we have lost confidence in its ability to build as it normally would. The team is now milling about as we wait to see if it will build enough to go sailing. I want to get out today... even if it is just to see how well the new skeg works at low speed. Tomorrow is forecast to be stronger... but then the wind drops off again until the weekend. A big day is predicted next Sunday but I don't put too much faith in forecasts that far away.

Come on Walvis... reward our patience. We're waiting.

Cheers, Paul

 

Wed, 31 Oct 12 16:18

 The Walvis Bay wind machine seems to have broken down. The powers that be that make this one of the best and most consistent speed sailing venues in the world have taken a break and left no message as to when they are coming back. It has been 11 days since we have had enough wind just to get started in and the forecast doesn't indicate anything strong enough on the horizon. It's very unusual for this time of the year. In my four years on location here I haven't seen it this 'flat' before. It's weird. It's slightly depressing to be honest.

As mentioned in the previous blog, we have had to commit to booking a WSSRC ratified world record attempt without even knowing if we have the performance to achieve our goals. VSR2 is still very much being dialled in. We have only done 5 runs since we arrived, 2 of which we didn't even get going over 10 knots. The last run was pretty good in 'boat' terms... but pretty average in 'Outright' record terms.

As a team, both here and in the UK, we are all scratching our heads as to why we are hitting this 'glass ceiling' at around 52 knots. Consider the simple facts we have seen to date...

- 2 different boats with 7 wildly different foils have all hit this speed

- The boats have been sailed in winds from 22-34 knots and only twice just exceeded this speed. Remember that in theory a 30 knot wind has nearly 50% more power than a 25 knot wind.

- Both boats accelerate very hard up to this speed and then flat line.

- VSR2 is designed to sail at over 60 knots and is sheeted accordingly. If anything she is a little oversheeted at 50 knots. The tell tales are all flying and she accelerates from 40 knots up to 50 with the same sheeting angle. We have eased the wing out a few degrees to allow for the fact that we aren't achieving the polars.

- The foils are specifically designed not to cavitate until at least over 60 knots. They are base ventilated wedges and we have gone to greast lengths to prove that the base is ventilated well down to tolerable/expected pressures throughout the run.

 

So, if it was simply a question of power... then we would go significantly faster in higher wind strengths. This hasn't proven to be the case. If the drag increase was gradual or even linear... then we would go faster in stronger wind strengths... we don't. The aerodynamic drag is only a small part of the overall drag picture. The front planing surface is the only thing in the water apart from the rudder and main foil at high speed. A simple V'd planing surface should have an almost flat drag curve as speed increases. The new rudder is smaller and more efficient than the last one in all dimensions. We are about to measure its base cavity pressures to make sure it isn't choking/cavitating... but am sure it isn't at speed (when the wind returns we will find out).

Thanks to all the sensors and the COSWORTH data logger package we have a lot of very useful information from each run.

LOOK AT THAT ACCELERATION ON THE YELLOW LINE. YOU CAN SEE HOW THE ACCELERATION LEVELS OFF EARLY AS THE WING IS ONLY PARTIALLY SHEETED UNTIL I BEAR AWAY ON TO THE COURSE AND SHEET FULLY IN TO 10 DEGREES. THE ACCELERATION THEN SHOOTS UP AGAIN UNTIL WE HIT THAT GLASS CEILING AT AROUND 52 KNOTS. IT STAYS THERE DESPITE SAILING THROUGH GUSTS UNTIL I SHEET OUT AND BEAR AWAY TO SLOW DOWN.

 

We are able to see how each aspect relates to the other. This graph above shows Boatspeed (yellow), rudder angle (red), rudder load (spiky purple... note it follows subtle steering inputs closely), Course over ground (lower grey), wing angle (playing up but still useful bottom dark blue), wind strength/angle (missing on this run), there are a couple of other load sensors in there.

We sit and stare at these graphs for ages, then we ponder them, lie awake in bed thinking about them... and come and check them out again. We question the accuracy of all the data and wonder how we can improve it. At moments like this when we don't have all the answers, we wonder if they aren't staring us right in the face. These light wind days give us time to ponder such things in depth.

So it comes down to this... if the nature of the drag was progressive or power dependent, sailing in significantly more wind would reward us with significantly higher speeds. We have simply hit 50-52 knots too many times now. This would suggest that the rapid rise in drag has been brought about by the foils in the water. Nothing else in the air or water could give such a rapid increase in drag. We know we are fully in the region where cavitation is likely. I can understand where the sub cavitation foils are failing as we are potentially near their limits, I can even understand where the first try at a ventilated/cav foil was failing (too big, too cambered)... but this new one is a hugely different foil in all aspects. It is specifically designed not to do the bad things that the first foil did. The new foil is the safe, reliable option and yet it simply hits the same glass ceiling as the last foil. That seems odd to me. 

So we are all going over the boat, the data and having a fresh look at the basic principles. What are we missing? There is almost 100kg of thrust or drag not accounted for at our current speeds. It's a lot. Malcolm and Chris are meeting up at AEROTROPE in Brighton tomorrow to discuss the problem in depth. I'll skype in. If the wind was here we would be working progressively through the problem but it's not... so we have to work with what we already have.

 

There's a little bird outside that has become quite accustomed to us. It now hops into the container with one dodgy foot in search of crumbs. It hops right past me even as I type now. It has this weird problem where it is actually very territorial. When it catches sight of its reflection in the shiny underside of one of VSR2's pods it attacks it. It flies into its own reflection time and time again and we think it's silly. From it's perspective it might be watching us going out time and time again smacking into our own glass ceiling. Neither of us will give in. It's not about the ceiling of course but rather the desire to own the territory on the other side of it.

Our ratified record attempt starts in a few days. No wind is forecast. Maybe it's a good thing. Maybe we are being afforded the time we need to work on the problem without distraction. I still have faith that there are great leaps and surges of speed waiting for us once we gain the understanding. I just hope that mother nature gives us a decent shot.

Cheers, Paul.

Fri, 26 Oct 12 13:53

 If there is something to 'blog' about I will. Unfortunately we have had a long run of very flat weather and it looks set to continue. We are working through odds and ends but basically we need to keep doing runs to follow a process of elimination. We need to see what is stopping us from getting through the mid-low 50's. We doubt it is lack of power. We think it has more to do with an excess of drag.

Once most of the priority jobs were done, we took the opportunity to take a couple of days off. The days can be very long and relentless when the wind machine is on so you have to take these opportunities to get away from it all when you can. Namibia is an awesome country and it is always a pleasure just to load the car and disappear out back. They are filming the new Mad Max 4 film "Fury Road" out here at the moment. We often get members of the crew coming down to check out the boat so it was a real pleasure to have the team invited to check out their workshops. It is mind blowing what they do... and the cars... holy s**t! The Australian petrol heads are going to explode when they see these things. The cars will be the stars. As we drove out towards Brandberg mountain we drove right through the set and saw all the 'beastly' cars. In the landscape they were designed for... it was pretty impressive.

FURY ROAD... WELL THE C32 ANYWAY. A TOTALLY VOIDED LANDSCAPE WITH THE MAD MAX 4 SET WAY OFF IN THE DISTANCE. 'SHITE-RIDER' IN THE FOREGROUND!

 

So we camped and braii'd and hiked and stumbled across two bull elephants down a riverbed and basically enjoyed this beautiful part of the world.

I WAS JUST SAYING TO BEN HOW THE ELEPHANTS COULD BE RIGHT BESIDE YOU AND YOU WOULDN'T KNOW... WHEN WE HEARD A BRANCH BREAK. ONLY ONE THING DOES THAT. A MOMENT LATER TWO OF THESE FELLAS WALKED OUT.

... WHICH SENT US STRAIGHT INTO 'BABOON MODE' ON A ROCK WALL.

Late that night I sat outside the tent reading under a bulb. everyone was in bed and the campsite was pretty deserted. the sky was clear and a half moon was up. I noticed two low shadows about 20 meters away. It took me a while to realise what I was looking at. Nothing else moves like large cats. They were highly on edge and I couldn't move an inch or they would clock it. They walked around the perimeter of the light and down a dry river bed. I stood up and they melted into the bush. We checked the tracks in the morning and worked out they must have been cheetahs.

A very lucky encounter in the wild.

So we came back to Walvis Bay as I always have the fear that we are missing out on something. The forecast was very flat but we moved into standby mode just in case. This basically involves still doing jobs but being ready to sail on short notice in the afternoon if the wind goes against the forecast. It did this yesterday. We got winds over 20 knots at the container so headed across to speed-spot. The wind over there was gusty between 14 and 24 knots. We tried a run but didn't really expect to get going. I was surprised that we nearly did. It's a real trick at the best of times. We were close yesterday on a number of occasions but 'close' doesn't get the rabbit.

So we are on standby again today. It's already past 2p.m. here and we have very little wind. The rest of the week looks terrible. It is pretty unusual for this time of the year... and hence pretty frustrating. 

WHAT IT MEANS....

Well, it means that we have had to book the WSSRC without actually seeing if we can break the outright record. We have to roll the dice. For a program on a modest budget like this one is... we try not to gamble too much. We have always hoped that we could demonstrate to ourselves definite record breaking runs before we call in the officials. I think you would all agree that it would be a pretty nice position for a project to be in. For a start, you could actually plan for it media-wise. Now if we do set records, we will all be seeing it for the first time before the WSSRC. It will be the real deal. We had to book the WSSRC well before now but we didn't have to book flights and all the extras yet. That time has now passed and we are committed all round. The record period will commence from the 1-3rd of November and run throughout.

Even now we are hoping to do some big runs before this period... but the forecast looks unlikely. It can change of course. We will be ready.

I have been reading and giving lengthy replies to all your comments on this blog-spot. There was a glitch there as we sorted out a spamming issue but I'm onto it now. There is a bunch of info in those replies for those of you who are into the details.

Here is the video... youtu.be/4OCkcuy-TfE

Enjoy.

Cheers for now, Paul.

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