Vestas Sailrocket

2011... Knocking on the door but not through yet. 2012???

Fri, 30 Dec 11 02:01

Well it's been a full old year in the world of the VESTAS Sailrocket program. This time last year I was using the quiet Xmas period in the build shed to get all the spray-painting of the wing out the way!

We launched on the 4th of March and shipped the whole jam packed container to Namibia a few days later. After some low speed teething issues we drank the 20,30 and 40 knot bottles of champagne on consecutive days. Within 23 days from launch, this radical and highly compromised, one-off prototype boat was hitting over 50 knots. What's more, it was doing it using an unconventional ventilated foil section.

The VSR2 program is focused on making the breakthroughs necessary to overcome the conventional limits of high speed sailing. These are all centered around the performance limits of conventional foils. The kite-surfers don't rely so heavily on these and therefore, as they have so clearly demonstrated, they don't have the same limits. In order to test and develop foils at very high speeds, you need to fund, design, build, develop, maintain etc a craft that will allow you to repeatedly enter the 'laboratory' in a safe and reliable manner. This year I think we demonstrated that we have the right craft. At the end of the last session a couple of weeks ago in Namibia, we had shown that VSR2 could drag almost any foil we bolted onto it down the course at speeds over 50 knots. We were constantly banging our head agains the old limits. It does seem that many different craft and projects get stuck in the low 50's. We didn't make the breakthrough we were looking for this year but we are very definitely in the right laboratory with the right tools.

20/20

Now that I can look back, I can see where some of our assumptions were just plain wrong... but that's ok as our understanding of the bigger picture is right on track. The boat is great and it is only the highly modular foil that is wrong. It was our first shot at a ventilated/cavitating foil and assumptions had to be made. If we were just doing 60 knots then it would have been a lot easier. If getting through low speed transitions just involved pouring more fuel down the carburetor then it also would have been easier... but this is a sailing boat that has to accelerate from standstill using only windpower so the problem is a whole lot more intersting. Now that we have a whole heap of real world experience we feel that we are much better placed to re-visit the problem. Of course we are. VESTAS Sailrocket 2 is currently sitting all nicely packed away down in Namibia and can be made ready to do 50 knots plus again within a couple of days. All our efforts now are focused on getting the foil right.

SOLUTION

After our design meeting hours after landing back in the UK,

CHRIS, GEORGE, WANG, MALCOLM AND PAUL...

the current thinking is that we will scrap the L-foil configuration and go to a T-foil arrangement.

FIRST SHOT AT CAV FOIL ON LEFT AND PROPOSED T-FOIL ON RIGHT.

This foil does seem to have many advantages. We had discounted it previously as we though that the end plate would need to be much bigger to enable us to generate the low speed side force to get started. This would have meant that we would have had structural issues around the junction... especially if the top tip of the foil popped out of the water as this would put large torsional loads on the junction. Now that we believe we can go a lot smaller (as demonstrated by our 'chopped down' runs towards the end of the last session), we believe that the 'T' configuration has many benefits...

-we can use the existing composite 'head' of the foils.

-we can machine the new components out of metal which is far cheaper, quicker and will allow us to try many variations.

-we can make the foils much thinner as the bending loads are greatly reduced

However, there are issues that we need to resolve. Some of the aspects that need to be considered are as follows...

-what dimensions will we need to satisfy all criteria?

-what are the expected loads for all scenarios?

-What are the realistic performance expectations?

-How do we best gain the understanding of how the foil will perform and make the necessary flow transitions?

-if we do still want to use ventilation as a means of creating the upper surface cavity on the foil, how do we ensure it can get down to the foil?

-how do we maintain good ride height?

-How do we reduce the drag at the junction of the T as these junctions are always messy, especially when highly loaded.

There is just so much to learn. We have started by working on a 'T-foil' based spread sheet that will show us the effects on the various balance/load/ performance factors from changing various inputs. This shows us the basics. From here we need to understand how the one foil solution will make the transitions from standstill to over 60 knots in a sailing environment. The final foil solution needs to tick a lot of boxes. Whilst I have no doubt that our team could work through the problem if given the time and resource, I feel that it is time to start really bringing other brains in to help us solve these very particular problems. I know that our endeavours have been followed by some very clever people who are quite passionate about this dark corner of yachting that we are delving into. In many cases we have been contacted and this is much appreciated. If I have seemed a little slow in getting back it is only because we are trying to structure the problem so it can be best presented to fresh minds. There are many good ideas out there but first of all, the specific requirements need to be outlined. The spread sheet will help us do this. If all the requirements are met to satisfy the basics, then we need to have a program which then allows us to verify this. That is still an open discussion as we don't know exactly what resource we can apply to the verification process i.e. CFD, model testing etc.

If the T-foil does make it through all this and the manufacture is as easy as CNC milling out flat foils, then this may well allow us to try many different shapes. We'll see.

So here we are, heading into a new year and getting right down to the 'nitty gritty'. A world record would have been great but I can't allow that to overshadow what has been achieved this last year. Thankyou to everyone who has supported and encouraged us near and far. We will continue to share the journey even through this 'techy' stage as it seems that many of you find this as fascinating as we do. We don't intentionally hold anything back. Some times we just don't put things forward until we have some structured understanding ourselves. We don't feel we have too much to protect just yet as anyone who copies anything may well be simply copying our mistakes. VSR2 is still very much a work in progress albeit one that is more ready than ever for the challenges that await.

Have a Happy New Year and I'll see you all on the other side.

Cheers, Paul.

12 comments

Messy finish... Merry Xmas Rob...

Wed, 14 Dec 11 19:59

I would rate today as a bad day in the speed sailing office.

It felt like there was simply no magic out there today and everything we did just seemed to make VSR2 go slower.

Walvis gave us some ideal conditions. We tried to get some good speeds out of the conventional sub cavitating foil but for some reason it would just dig itself a hole and fall into it. The back float wouldn't even clear the water on the first three runs. It was horrible and generally in the low 40's. The fences had failed to work and then we were committed to pitch settings. We tried to play around but things just got worse. I have no idea why. It all ended when the mainsheet got weirdly fouled during one of the start ups and I hit the bottom with the foil. It wasn't that hard... but hard enough to destroy the foil. Good riddance. We plugged the chopped down ventilated foil back in (with end plates added). Walvis really had given us the perfect day. This foil effortlessly pumped out yet another 50+ peak and a 48.8knot average. It was great to have VSR2 back into its right mode. The run felt fast... but not fast enough.

We did 5 runs today. 3 slow, 1 grounding and 1 moderately fast run. I'm not happy. I can't believe we didn't even achieve a 50 knot average throughout this record attempt. I really can't believe it. Well it wasn't for lack of trying... or pushing.

I'll summarise the whole session in the next couple of days. In the big picture we have made some great progress... but damn I thought we would drag one of those foils AT LEAST over 50 knots down the course... especially after hitting 54.4 knots before the attempt even started. Sigh.

These foils were just wrong. We will get them right.

Righto, well Merry xmas Rob Douglas, you get to spend it with your nice outright world record once again.

I'm going to the pub.

Cheers, Paul.

20 comments

Another big push for the elusive transition. It's getting interesting now.

Fri, 9 Dec 11 07:04

It felt like it was going to blow all day... and it did!

We got in to the container on the lawns of the Walvis Bay Yacht Club early and quickly pulled VESTAS Sailrocket 2 out of her soft hangar. The wing was up in no time and Alex set to raking the whole beam and wing forward 6 degrees in anticipation for the loads that would need to be balanced if today we found the long sought after ventilated flow.

When the water breaks away from the suction surface of the foil and air is dragged down from the surface to create a cavity, It can be described as being ventilated. It can happen on any boat when the foils are used too hard and there is easy access to the surface i.e. transom hung rudders stalling whilst rounding marks. Now when one side loses grip, the other side, in this case the pressure side, usually has to do all the work. To do this it has to increase its angle so as to have a greater effect on the water around it. This is why the leeway angle of VSR2 increases when we step to ventilated flow.

Nick chopped another 15 cm off the tip of the 'wedge' foil so as to increase the area loading on the foil and hopefully make it lose grip and become ventilated. It is designed to be ventilated but has been operating in an attached flow manner to date. This has shown itself to be relatively fast... but it won't get records.

The day built strongly as expected and we headed across the Lagoon to speed-spot around 1 p.m . I rolled straight into a run figuring that it might blow out on us so best to get some runs in as soon as possible.

Run 1...

1 person, 30 cm removed from ventilating/wedge foil, 21-24 knots of wind, beam raked forward 6 degrees to 77 degrees.

Surprisingly easy start up and good acceleration for such a short foil. No doubt assisted by raking the beam/rig forward. Good control but nothing special speed-wise in the lightish winds. Peak speed 45.06, 500m avg. 42.44 kn. Actually quite surprised by ability to start up and go in such light winds with such a small foil.

LOOK MA, NO HANDS. VSR2 CRUISES ALONG IN THE MID-LOW 40'S.

Run 2...

1 person, same configuration as above but much stronger winds gusting to 29 knots. Another easy start up with good acceleration. Good control, no wierd noises or swerving. Foil felt draggy. Peak speed of 47.8 knots, 500m Avg. 44.71 kn.

This obviously wasn't working. That was windy and the boat was sailed as it should be. I was tempted to chop the foil again right then and there but decided that it would be best to try a big change to the foil configuration first. I used the full range of the pitch adjustment in order to angle the foil nose up as much as possible. The idea being to force the upper, more horizontal part of the foil to both lift and ventilate more. If this in turn makes VSR2 ride higher then the foil still in the water will have to work harder. Because the upper section of the foil now has a high angle due to the increase in pitch, it should ventilate and feed the air around the bend to the lower section of the foil more deeply submerged. That was the theory and this foils best chance before it would get the next big chop.

Run 3...

1 person, wedge foil with 30 cm removed in full pitch up mode. Very windy with gusts to 34 knots, solid spells over 30 and lulls to 28.

Had trouble launching the boat as it was just too windy. VSR2 launched hard from the nose tether to the transom tether and the boys in the support RIB couldn't hold it. I was dragging the RIB. The wing was stalled and VSR2 rolled to leeward. The whole leeward float submerged and the horizontal wing extension dug in the water. I eased the sheet quickly to unstall the wing and pop the float. The boys had set the tether free but I was no towing 30 meters of rope out the back. Fortunately no damage had been done to the wing extension. I pushed on with the run. From my perspective there was still no noticable difference although from the pics you could see the back of the boat riding higher. I could still feel the foil dragging hard with no tell-tale swerves to tell me she was letting go into a fully ventilated mode. It was damned windy and rough. We struggled to pull the wing down. 46.72 max, 42.31 avg.

As we headed back up the course I felt enough was enough. We pulled into the timing hut. Helena confirmed gusts now peaking at 35 knots. This was now officially bullshit. First we have long spells of no wind and then two days with over the top conditions. Something in the middle would be nice for a change. The trouble is that VESTSAS Sailrocket 2 is so well behaved and managable that you can easily be tempted out in conditions you simply shouldn't be in simply to try and use brute force instead of sophistication. It's not a bad card to have up your sleeve mind you. If that's what your given then you casn play it. I set the limit at 35 and was happy to stick with it. We had two issues on that last run where we nearly had damage and it was only due to general handling in very strong winds.

I had seen enough. This foil wasn't letting go so it was time to chop another 15 cm off. This was now 45cm in total and over half of the main foil. It's not the ideal way of getting a smaller foil. It's pretty brutal in fact but this foil isn't working as is and drastic measures needed to be taken in order to find this ventilated flow. The foil now only had 30 cm until the radius of the bend. there wasn't going to be much left in the water. Maybe it was a step too far.

I pondered all this whilst we sat and waited to see if conditions would abate. It blew it's arse off for about 70-90 minutes before I saw longer steadier spells back down in the high 20's. The call was made to go for it again. We are on a mission here.

It was pretty rough just heading up the course and there were still some strong gusts around. The foil looked really silly now. Of course I had doubts... look at the thing and consider what I was about to try and do with it.

On the other hand this was perhaps the last windy run for this record attempt before we head back to the UK. we need to understand what works. We have learnt so much and already accept we need to try new foils. This would perhaps be the most educational thing we could do with this foil here and now.

As the RIB lowered me out onto the course I mentioned to Jeff over the helmet comms 'well, this is why you put harnesses in these things'.

Run 4...

1 person, 45 cm removed from wedge foil, full pitch up. Winds 25-31 knots. To my great surprise, VSR2 still managed to start up and accelerate pretty well even with so much foil now removed. The back of the boat was riding much higher but it all felt nice and stable in the cockpit.

THE REAR FLOAT IS RIDING HIGH AS I ACCELERATE ONTO THE COURSE. WE WOULDN'T WANT IT ANY HIGHER AS IT DECREASES THE PITCH ANGLE OF THE FRONT FLOAT. HIGH 'PUCKER' FACTOR HERE.

Due to the rough water I tried to get in nice and close to the shore. I could still sense the drag. I was a bit nervous about this run as there really wasn't much in the water and what was in there was a rough stab. Just past the timing hut I could see a gust on the water.

THIS LOOKS TO ME LIKE IT'S DIGGING A DITCH BUT WE DON'T HAVE THE LEEWAY OR CORRESPONDING RUDDER ANGLES TO BACK THIS THEORY UP.

VESTAS Sailrocket 2 accelerated hard. It felt like I was being released from the drag. It felt like something was changing. I quickly considered what the hell I was doing and eased the sheet.

The run had been too slow to start for a record run and we were running out of course as low tide was upon us. I could potentially be closer to the edge than I knew. It was a good peak speed that could have been much higher with a second similar run. Peak speed 51.41 knots, 500m avg 46.57kn.

The wind had continued to drop into the low medium 20's and the sun was heading for the horizon. It was too late for another run. So that was it. We had pushed hard again. Maybe with that last 51+knot surge we had glimpsed a transition but I can't be sure. Now that I have looked at the masthead camera... it still looks like the foil is travelling close to the forward rudder wake. That tiny little, high riding, unfenced, stumpy, thick-as-hell-tipped wedge that I still call a foil had just ripped out a 51 + knot peak and not ventilated. If it was ventilated, then why is it pulling the boat harder to windward than the large conventional foil? Christ, we have 4 fences on our long conventional foil to try and prevent any ventilation and this little thing just goes and does that. Right now I'm a bit lost on that one although I already have theories how to improve what we now have. It's late, I'm tired and I need to talk to some people. All I know is that our next foils are going to be tiny in comparison to what we have now. I know now that we can get started with a lot less than we expected. You always learn something extra on the side.

So we have 1 week left now. One week with no big winds forecast. Things change and a one week forecast can't be treated as fact. We will, as ever, go forward with optimism. that last surge was encouraging. It was the best peak in the last two days which started with a full foil. We still haven't finished with the conventional sub cav foil yet either.

Yes... it is frustrating to not be hitting the big numbers.

Another big day in the speed sailing lab. Every result is a result.

Cheers, Paul

22 comments

Big Wednesday and a big hard push. Still no Breakthrough.

Wed, 7 Dec 11 21:53

What a big day. I don't think we have ever done 5 runs in a day let alone in such top end conditions.

We went out there and went for it today. There were things that I needed to see. The conditions were, of course, just a little too much. The wind was gusting to 34 knots but I couldn't afford to procrastinate. Throughout the day I had come to realise that we are wasting our time down around 50 knots. The whole VESTAS Sailrocket 2 program is based around making ventilated foils work so that we can hit speeds over 60 knots. Small incremental gains around 50 knots is not what we are about now. I had a joblist to work through, a tough boat and a solid team who are comfortable handling her in strong conditions. It was time to push.

All runs were done with the ventilated/wedge foil

Run 1

Day still building so still a bit light, 1 person onboard, Easy run with a peak speed of only 44.3 knots. Nothing remarkable. No vibrations or unusual handling. Did a weave down the course with the rudder simply to see how the boat behaves and if any play in the system misbehaves. It didn't. We can reference this change from positive to negative loading later.

Run 2

Day building strong, 25-30 knots. 2 people on board (Helena's first proper run in the boat). Still a bit difficult to start with two people but nevertheless a good run. Peak speed 48.87 knots. Nothing remarkable again. No vibrations or unusual handling. Pod flying towards end.

Run 3

Wind 25-33 knots. 1 person onboard. Decided to try to max out the boat in tope end conditions. If it was going to ventilate... it would do it now. It didn't. This was this foils last chance. We maxed out at 50.8 knots.

This was not enough. Still no signs of the evil vibration. We should in theory be doing over 70 knots in these winds. Time to go under the knife.

Run 4

Wind 25-33 knots. 1 person onboard. water rough. 15 cm removed off the tip of the foil. I was expecting to see ventilation or at least the return of the vibration to show we were headed in that direction. I dipped the wing extension in a wave trough during the launch and did some minor damage. Peformance wise it was still fully functional. After a quick over the shoulder assessment I went for it. The start up was noticably less 'crisp' but VSR2 still hooked in and took off. She felt a bit more lively. As I beared away onto the course she did a big weave that took a fair bit of rudder to correct. This could be the foil switching between attached and ventilated flow. It felt like there were moments of 'release' in there and even the run itself felt faster.

It was rough though and this always adds drama and a sense of speed. It felt better although the peak speed was almost the same at 50.52 knots. The average was lower at only 46.02 knots. Oddly no vibration or sense of ventilation apart from that weave at the start.

Run 5

Getting dark now. Swam ashore to do a BBC radio interview whils the boys towed VSR2 up to the top of the course. The sun was setting and I wanted to do one more run with the new trimmed foil before trimming another 15cm off it. I ran up the beach to catch up with them and we pulled the wing up one more time in similar 26-32 knot conditions whilst the African sun set (first flamingoes present). 1 person. Good run with no weave or vibrations. Noted the hard surging of the boat which feels like it is pulling a lot of drag. Peak speed of 50.24 knots, (average 47.78). Damnit. 50 knots is boring now.

So, where are we? With limited footage and data downloaded I can still tell you that we are fully attached even with 15cm of main foil removed in strong, fully sheeted on conditions. No bad vibrations were felt although there was that big weave on the start-up and bear away of run 4. We will look at that one more closely. It's pretty surprising that reducing the area of the foil didn't initiate the bad vibration but then maybe that was caused by other more subtle situations. I am keen to chop off another 15 cm. I want this thing to ventilate. We will discuss it further and sleep on it.

Overall it was a very good day. We pushed very hard in as strong a conditions as we should ever need to sail in. We did more runs than ever before and brought the boat back intact and ready for more tomorrow. Of course it's annoying that we didn't break through but days like this will create our end result. The whole team did a great job to keep the ball rolling and not fumble it.

Helena got a new PB of 48.87 knots but just missed out on becoming the second female ever to cross the 50 knot barrier on a sailing craft. I'm sure she will do it many times in the future.

In the end I had no issues with chopping the foil. It's only purpose is to go well over 60 knots and it simply isn't doing it. The rest of the boat is waiting for the right foil solution to set it free.

The boys have gone home after the other great team at The Raft sentg pizzas, extra big burgers and some beers around to the container for the data transferring session. It's 20 to 11 now and we will be up and at it early tomorrow. We will double check and reconfigure the boat. The beam and rig will be moved forward in anticipation of the greater leeway angles generated by a ventilated foil... and most likely another 15 cm will be trimmed off. VSR2 will be remeasured for reference and calibration purposes. Then we will head out and do it all over again.

The good news is that Saturday is grunting up and may be useable.

It's not over yet party people. As always, we will push it right to the end. We aren't just hanging around here. From the perspective of our teams performance today, we did very well. I doubt we could have squeezed much more out of the day. We just have to find what makes this dog hunt.

Righto, gotta call Malc.

Cheers, Paul.

7 comments

Two days to go. Optimise or breakthrough?

Wed, 7 Dec 11 11:49

It has been forecast to blow today for some time. The winds have been very light recently so this has been eagerly anticipated. I just walked outside when I heard the first rustlings of the wind. The first 'fingers' of breeze were finding their way across the glassy lagoon being led by a pod of dolphins. That has to be a good sign if you're into that stuff (which I'm not really)... but there it is, a pretty sight in anyones books.

We have been busy trying to understand what is going on with our foils and working out explanations for VSR2's behaviour on the last runs. I must thank those of you who have had input and put forward suggestions as they are all considered. There are some very learned people who know a lot more about some of these high speed phenomenoms than us so it really is great to apply their understandings to our situation. Whilst we still can't explain the tendency of the conventional foil to bear away hard at around 50 knots, there is a consensus growing regarding the performance of the ventilated 'wedge' foil. We believe that it is too big and therefore not travelling at the correct angles which would allow it to hold a stable ventilated cavity. When we get that horrible vibration it may be because it is travelling in a 'no-mans' land mode where it has lost grip but can't lose grip enough to hold a stable cavity. It is obvious by the photos taken from the masthead (shown in the previous blog) that the cav/wedge foil is not 'sliding' as it is designed and therefore is not operating in the mode it should. The fact that it is travelling quite well with the water attached to both sides of the foil could explain why we have pretty good low and medium speed performance all the way up to 50 knots but are struggling to go faster. This odd foil is sort of behaving like a conventional foil. We did however go faster in one run with two people on board so really don't know what speeds it is capable of in this mode. We suspect that we will not be able to generate the angles of attack this foil requires to side ventilate i.e. shed the water off the suction side (probably somewhere above 5 degrees) unless we reduce the area of the foil. Cutting the foil is a one way path.

Now, based on the forecast, it looks like we may only have two good sailing days left before our current record attempt is over. Today and tomorrow. We may get some bonus days if the long range forecast changes but they are not obvious now and it would be risky to assume they are coming. This means that we have two paths which we can follow. We can try and purely optimise what we have in order to get the best result we can in this session, or we can make the call to go down the one way path of cutting the bottom of the cav/wedge foil and going for the breakthrough.

One 'optimisation' path, which has two options(one for each foil) is unlikely to yield an Outright record but may get us a few scalps further up the speed sailing ladder, the other 'breakthrough' path is perhaps our only chance of making the jump to realise the potential of the boat (It's great writing this down as it all starts to become obvious).

1/ OPTIMISE EXISTING OPTION...we try and repeat the performance where we achieved 54.4 knots, improve on it and bag the 'fastest boat' and Australian record. To do this we use the cav foil and simply try and re-find that performance now that we have changed a few things i.e. stiffened it. To do this we will try a few different pitch and inclination settings.

2/ BREAKTHROUGH OPTION...If none of this works then we should proceed to chopping off the tip of the foil. The idea is to try and make the break from attached flow to ventilated flow. This foil is meant to work this way and it is not ideally suited for the way we are using it anyway. The consensus seems to be that it is simply too big to operate at the angles it requires to ventilate properly and this is causing this oscillatory flow where we are neither here nor there. This may well be the last time we ever use it so we should learn from it. Firstly remove 15cm to see what effect that has (we expect it will make it worse before it may make it better). Secondly by removing another 15cm (30cm total) to see what effect that has.

3/ OLD SCHOOL OPTION...Try again with the sub-cav section. Two additional fences have been added. One at half-way around the transition and the other 25% down the second foil.

In a perfect world we would have a great couple of days that allows us to do 8 runs in similar ideal conditions so that we could scientifically progress through the above options in order. This way we could have our cake and eat it too.

If these are our last two big days then we do want to leave here having made every effort to glimpse the real potential of VESTAS Sailrocket 2. This boat is designed to drag a super-ventilated/cavitating foil through the water over 60 knots. If we only manage to make a few runs then I may have to make the bold call to chop large chunks off the very expensive and difficult to replace ventilated foil and just go for it. I know you're all probably reading this screaming "CHOP IT. CHOP THE BASTARD NOW WITH A BLUNT AXE!!! We want 60 and we want it now (in HD preferably)". Well, it's on the cards (the hacksaw is packed and the lines are marked on the foil) but the thing is that it may well not guarantee a result. The foil may just be wrong. It may prevent us from even getting started. It will however give us a point on the graph to reference future design decisions against. If it fails then we go down the 'old school' path.

So, we will see what we get weather-wise and take it one run at a time. We do need to be lucky on this front and it is out of our hands. The conditions may well not lend themselves to our proposed scientific method. We still have so much to learn.

Let's see what happens.

Cheers, Paul

9 comments

A bonus sailing day although no big numbers!

Fri, 2 Dec 11 20:24

Today developed stronger than we expected although we were ready to get out there. As the wind started to whistle we switched from data processing to 'gig's on' mode.

Obviously the results from the previous session has been on our minds as it showed that we have some big issues to resolve... but we also have a heap of data to point us in the right direction.

Take these two pics for example...

There is just an immense amount of info in these two shots. They are taken in very similar conditions at very similar speeds... with two totally different main foils plugged in. The top one is the with the cavitating, wedge shaped foil and you can see how close the foil is tracking to the bubbly, ventilated wake of the rudder. It's almost in it. The lower photo is with a conventional foil and it is travelling well clear of the wake. The rear pod is flying in both and the fixed angle (but self retracting) rear skeg in the back float is just kissing the crests. You can see the wave impacts of the front float as it jumps across the crests. The fact is that the Cav foil is built with 3 degrees of angle in it as it was always assumed it would be travelling in a fully ventilated/cavitating mode. these shots show that it clearly is not. The flow is most likely fully attached back to the base of the foil and... it's performing quite nicely. The trouble is that it's now subject to the standard foil issues and that won't give us that glorious sonic 'boom' that we crave. All good evidence.

The rudder loads were similar for the two runs with low loads around 5-30 kg. This would suggest that loss of grip at the front/rudder was unlikely. What is interesting is how submerged the main foil is in both instances. VESTAS Sailrocket 2 should be riding on her transition. This is the curved section of the foil. Instead she is sitting much lower with a large part of the 'first foil' (the upper more horizontal foil) submerged. This suggests that the foil is pulling down too hard... or we have stood the rig up too much to stop the leeward pod from flying and thus reduced the net up lift... blah blah blah. I could go on... really I could. I hate to cut it short for you technoheads out there who are no doubt getting right into this... but that's how it goes when the wind starts to blow and you have to drop everything, make a quick call on what changes will be best to try out and then get out there.

That's what happened today. I was calling Chris and Malcolm whilst climbing into a MUSTO drysuit and discussing options. I had already reduced the incidence of the main foil and pitched it up slightly. This should reduce the downforce and create more lift on the upper horizontal foil section. I discussed wioth Malcolm the possibility of quickly 'whipping off' the bottom of the foil... but we had no time.

We got over to speed-spot. Conditions were gusty and shifty. We had wind peaks to 27 knots but lows to 17 and the angle was changing. I knew it wasn't record breaking conditions so didn't spend ages with the details of the boat. It was going to be a day for collecting more data and trying things out. Helena's seat was fitted in the back. many of you have mentioned the fact that we went faster with two people on board. It doesn't make sense... but we can't discount it yet.

I did the first run one-up. I didn't feel that previous horrible vibration although the run wasn't that fast. There were some big holes in the wind. I noted that the foil seemed to be travelling higher. I did the full run. It wasn't strong conditions.

FOIL IS DEFINITELY RIDING HIGHER. WE ARE NOW RIGHT AT THE START OF THE TRANSITION RADIUS HERE... EVEN IN LIGHTER CONDITIONS.

We tried a second run with Helena onboard.

It really was such a pleasure to be finally sharing the experience with her. Christ she has put in some work... and faith in this project. We didn't get going as the wind began to fade but in a way it really didn't matter. I really enjoyed that and we will share the speed later.

So a lot more was learned. Data was gathered and we are coming to understand certain aspects of what we have on our hands a lot better.

I love reading all your input. I can understand how hard it must be from the readers perspective not to have all the data we have to form an opinion on. The thing is that the picture is constantly changing and one opinion can fade with a new bunch of data or by slightly adjusting the timeline which changes the order of things.

I still believe that we can do this. The boat itself is awesome and it constantly takes us up to the record door for us to knock on it. One day we'll get the combination, burst on in and trash the joint.

I love this laboratory.

The weekend looks pretty windless. It might be time to get away for a day or two before we go mad. The wind will come next week. VESTAS Sailrocket 2 is in great shape. The brains trust are at it back in the UK. Today was a bonus and I think we made an improvement. all is good.

Cheers, Paul

7 comments

A good day...but what is going on with these foils?

Wed, 30 Nov 11 21:46

Walvis Bay rose to my challenge today and delivered a near perfect speed sailing day for us. This is why we come here.

VESTAS Sailrocket 2 is in the best shape of her life. The whole boat is starting to feel like a finished piece and I am really happy with her.

We did 3 runs today. The first one we did with the conventional foil in. We have added two fences to prevent air from getting sucked down from the surface. One fence is just below the bend (transition) and one is right at the top. It felt like I got ventilation on our last outing when VSR2 went into a big bear away so we added these fences to stop this.

The first run today went well and was very smooth. All the little details were making the whole experience so much enjoyable and as mentioned, it was near perfect conditions. The new launching system meant that I got up close to the beach much sooner than previously and this makes for a much longer run. The leeward pod was flying high but I was easily able to lower it using the flap control on my left.

The run was very enjoyable. Fast and effortless. Just after the timing hut she performed her old trick again and went hard into a bear away. I put in a couple of turns on the wheel to correct it and immediately stopped the run. Hmmmm. It would seem that fences didn't fix that then.

I still managed a top speed near 51 knots and a 500 meter average around 49.38 knots. This would be a new 'B' class world record for craft with our sail area... but I'm not that interested in that. I went faster with a passenger a month or so ago. We are after bigger game here.

Conditions were building so considering we hadn't discovered the magic to make that foil work I decided to do the ol' switcharoo over to the new ventilated 'wedge' foil. The guys had to go back to the container to collect it but in an hour or so we were back up to the top of the course and ready to roll. The start went great but even early on in the run I got this terrible noise and shuddering vibration coming from the main foil. I was only doing about 30 knots but there it was. It sort of felt like what I would assume cavitation would feel like. Not a cool or sophisticated noise... more like an engine throwing a rod! When I turned onto the course it smoothed out and the run went very well again. Once again I enjoyed it and it felt fast. VESTAS Sailrocket 2 is just effortless to sail now and I can savour the speed sensation without fear. She cruises at 50 like a car down a highway.

The, just past the timing hut again, she made that horrible noise which felt like running the tip aground on concrete. The drag pulled me from 50 back down to around 30 and once again I was forced to abandon the run. This was weird. Once again I hit a peak speed around 51 knots. This really is weird. I mean with effectively three different foils i.e. conventional-no fences, conventional-fences, ventilated, we have hit nearly the identical speed in very similar winds. Maybe it's a coincidence involving many factors but either way, there it is.

Conditions were still epic. It was just soooo flat along the shore. Gusting 28 knots and glassy in close. Pure speed sailing porn! We were so close to getting some bigger scalps than the B class record. I want to get the Australian record which is just over 50 knots and the unofficial 'Boat' record off Hydroptere which is around 51.4 knots or 2 knots quicker than my previous run. Either of those would be a nice way to finish the day. I stated the third run but once again I got that terrible draggy shudder. This time it was more persistent and I canned the run at the timing hut. I had only peaked at 30 something knots. What the hell was going on here. We went over the main foil and rudder but it all seemed fine. No obvious signs of cavitation. No damage. Basic boat settings. More Hmmmmmm.

we dropped the rig at sunset.

We have been sitting back here in the container downloading data and digesting as much varied info as we can get. We get a lot from each run. 6 High Def cameras, 1 Cosworth data logger, 3 GPS systems including the mighty TRIMBLE used for record ratification and a TACKTICK wind system with data logger. Multiply that by 3 runs and It's no surprise that we are still here at 10:30 p.m. having just downloaded it let alone digested it.

Funny thing is that I'm pretty happy with today. Breaking this record is like solving a big puzzle and today we got a whole bunch of clues. We did get some great data. The boat itself really impressed me. She is a real noble beast who now feels like she is trying to help us. The boys have done a great job sorting out the details on these windless days gone and I can really notice it. She's slick.

So we will digest all this new info. I already have a few things I want to querie. It appears from the masthead camera that the foil is running very close to the ditch created by the ventilating forward mounted rudder. It should be about a meter away. We have already double checked this whole aspect and remeasured it all to triple check. It seems very odd. Has VSR2 dropped into a mode of sailing that we haven't planned for and that she needs to be shaken out of. VSR1, our first boat, used to drop into a mode where she would drag sideways down the course at about 12-15 degrees. We couldn't believe it as it was still doing 38 knots. It was something you couldn't model or predict and yet there it was. Once we became aware of it and accepted it, we made the mods and began to unleash the potential.

I'm beginning to feel that there is something big we are missing here.

We are very definitely in the lab. We'll get to the bottom of this one. Two weeks to go from tomorrow. Come on Walvis, give us a few more like that.

Cheers, Paul

21 comments

A bonus day yesterday but nothing today.

Thu, 24 Nov 11 14:32

We managed to get out on the water for the last two days but today looks like it won't get going.

On Tuesday we went out to try some stuff but it was too light to get started. I was still contemplating driving down to Luderitz to see the kiters go for it and deliver the WSSRC observer but it all got too last minute. After many calls back and forth with Seb Cattelan based on organising the long trip and our ever changing forecast, we decided to stay and hope for a sail. We had all but called off yesterday at 4pm when the wind began to build over 20 knots. I took a good reading with TACKTICK instruments and got a steady gust of 21 knots. Everyone was relaxing in the container doing e-mails and stuff. In one hour and five minutes we were at the top of the course with the wing up preparing for a run. It was a pretty good scramble all in all.

We have decided to have another look at the conventional foil and see how far we can push it. We mounted it on VESTAS Sailrocket 2 but didn't have any fences on (Fences are like little skirts around the foil which stops air from getting sucked down from the surface). The wind was lighter today and this foil should be a whole lot more efficient. It should be capable of runs well over 50 knots in steady winds around 24-5 knots. It was obvious quite quickly that we had made the right choice to head out. Helena was getting gusts up to 29 knots but there were big holes in the wind where it would drop down to 17. It was an odd day.

The first run went pretty well and VESTAS Sailrocket 2 accelerated hard. The pod flew early and I was able to control it with the flap control line on the right of the cockpit. Just past the timing hut she did a big yaw away to leeward and I had to apply a fair bit of rudder to bring her up on course. I thought something had let go but everything still seemed in place. I slowed down and bailed out of the run anyway. We still managed a peak speed over 49.5 knots but the average was down due to the holes in the wind. I was pretty sure that we had suffered ventilation and that is what caused the yaw down the course. Fences are pretty critical at high speed, especially with surface piercing foils that don't have a boat on top of them to separate them from the air.

THIS SHOT SHOWS THE SPRAY FLYING OFF THE TOP SURFACE OF THE FOIL AS IT GOES INTO THE WATER, ALSO VSR2 IS RIDING LOW AT THE BACK. THIS SUGGESTS THAT THE UPPER SECTION OF THE FOIL ISN'T WORKING VERY WELL NEAR THE SURFACE. THIS IS EXPECTED. WE WILL SEE HOW THE FENCES CHANGE THINGS.

I did another run but experienced the same sort of drag.

We called it a day and headed back in happy that we had been out at all. It was a very productive day.

Now that we are in the midst of a record attempt we have to give ourselves every chance of success by any means. We still believe that the future will be in the usage of the new ventilating foils however we can also use this fantastic craft to find the limits of conventional foils. Many people have suggested that if we have the power to drag the new wedges down the course at over 54 knots then we should effortlessly be able to pull a much sleaker conventional foil at the same speed and even higher. Even if it does start cavitating we may have the power to drag it up to the current record. This is why we have one of each type of foil here. If the forecasts are lighter then we will use this foil. We have VESTAS Sailrocket 2 setup so we can quickly switch between the two setups. Yep... the ol' switcharoo!

So, figuring that we had pushed this conventional foil as hard as we could without fences, we now have to try it with them on. They can make a massive difference. Apparently the mighty Hydroptere would barely even work without them on her big surface piercing foils.

We have fitted two fences today and we are ready and waiting for the wind to fill in. It's a beautiful day today... but no wind.

Every day VSR2 just gets better and better. It was so easy sailing in the lighter wind conditions. Effortless.

The kitesurfers had very strong conditions down in Luderitz the other day and Seb managed a 53+ knot run... but no new outright record. Rob Douglas remains the man to beat at 55.65 knots.

We are ticking the boxes and constantly illuminating the path forward. We will get there.

Cheers, Paul.

5 comments

Last time I dare this place to show me a good blow... Cheeerist!

Mon, 21 Nov 11 20:50

Jeffro looked at me funny the minute I said "C'mon Walvis, I dare you to blow" earlier today. You really shouldn't messThe wind was filling in late and I was worried the forecast was going to struggle to materialise. We didn't head out until around 3p.m. The wind was filling nicely. It was 25 at the timing hut so we went straight to the top of the course. We had changed a few things and wanted to make sure things were right. It was just as well as the rig was raked too far forward and we had to mess with it for a bit to get it right.

The wind kept building and Helena was calling out 32 knot gusts by the time we started to get in shape for a run. The funny thing is that we are getting used to these winds now. I messed around too long in the cockpit as I was getting eased out onto the course by the RIB. I had dropped the quick release mechanism for the safety harness and pondered just doing the run without it. I looked around at what I was doing and decided that that was the typical decision you explain later from a wheelchair. I eventually found the piece and got harnessed up. It was pretty damned windy and rough. I was keen for a big run though and this is what I wanted. VESTAS Sailrocket 2 was released but once again struggled to bare away from the wind. Something about the wind and waves makes her weathercock in stronger winds. I tried a few tricks but she just sat there head to wind. I had to gently try to ease her forward on the edge of stalling the tiny rudder before she bit. The trouble was that I feared I had damaged the horizontal lifting, roll control flap as the leeward pod buried between waves. Sure enough as VSR2 accelerated the flap came free. It was hanging on by a small control line but eventually broke free.

NOW THAT'S NO WAY TO TREAT A LADY!

I pointed wildly to the support boat and they retrieved it whilst I began to line up the course. Damn it was rough and there was a hell of a lot of spray in the cockpit. I struggled to see the beach and just had to bare away when I felt it was right (ah, the good old days of VSR1). The forward flap was smacking into the waves and the leeward pod was sitting hard on the water without the lift that is normally generated by the departed flap.

The boat just felt draggy. I sheeted in hard but we just weren't accelerating as we should. I feared that the mods to the foil had created too much drag. I was still getting spray in the cockpit which is a very bad sign as it means we are way underperforming. Oh well, that's that box ticked then. I parked the boat without drama and waited for the boys to eventually come along after retrieving the undamaged flap.

I had no idea how fast I had just been as the bastard GT31 gps we use is about the most useless piece of equipment we have on the boat for providing simple speed data. I despair at the people who design that crap! Later we saw did just shy of 48 knots and about a 45.2 knot 500 meter average. Nothing flash and about what it felt like.

We really shouldn't be sailing in that stuff.

We lowered the rig and went back up to the timing hut. The run was a mess. I watched the video of the rooster tail and saw the change that the foil mods had created.

NICE PLOUGH EH?

I got Nick to wet and dry off the small ridges we had added to the back of the foil. We managed to remove the wing extension and took it into the igloo hut where we reinstalled the horizontal flap.

The wind was already hitting 36 knots.

Walvis had come to the party... and trashed it!

We stayed on nonetheless to see if it would abate. It was a very low tide but strangely enough the water was still blowing over the beach from the lagoon behind.

We waited and waited and eventually came home at sunset as the wind peaked at 37 knots.

I'll admit to feeling a little dejected. The whole day just felt messy and there was no magic involved. There was no breakthrough and no big numbers. The fact that it was also the only reasonable looking day on the forecast didn't help. Oh well, I guess we ticked a box. It was a rough trip the long way around the shallow bars that guard the lagoon. The whole yacht club was whistling in the wind. Still, we managed to put VESTAS sailrocket2 away in one piece. I gave her a pat on the snout. We'll work out what makes you tick yet girl.

So the forecast looks flat. It gets hard to trust when a day like today overperforms so much. I will watch tomorrow closely before we decide to head to Luderitz to watch the kiters and deliver an observer. I really would like to see them in action though.

Righto, so that's our first run out the way. We are still in development and that is part of it I guess. We are a little bit smarter after today and have a whole new job list as well.

I'll never dare you again Walvis. Like I say, I'm not superstitious... but in this game I can't afford to be wrong!

Here's a pic of Gordon and Ian from Scotland who came over to see the action. we distracted them from other tourist activities as we told them that seeing a boat like this in action is truly one of the rarest things you will ever see. They chucked a few notes our way for the post-record piss-up. Nice on guys, glad you came out!

Cheers, Paul

4 comments

First record run...COME ON WALVIS, We're waiting!

Mon, 21 Nov 11 10:19

It's Monday and it's forecast to blow today. This forecast should give us gusts to 30 knots and with this we should see some good speeds.

VESTAS Sailrocket 2 is really still a work in progress but now this progress has a sense of urgency as it is being done under the watchful eye of the WSSRC (Record governing body).

We are super keen to get on the water today. The weather has been very flat and looks to continue being flat for the forseeable future after today. Come on Walvis, we're more ready than we have ever been, give it to us!

More fairings are now present on VESTAS Sailrocket 2. The strut now has a feathering fairing fitted and the front float strut now has a trailing edge fairing fitted. Little details are constantly being improved and systems refined.

The kite-surfers down in Luderitz finished their record attempt a week or so ago which freed up the WSSRC record commissioner to come up and watch over our 28 day period. The other day I has Sebastien Cattelan contact me and ask me if he could have him back for this coming Tuesday and Wednesday as they have a good 'blow' on the way and desperately want to have one more shot at the title. I basically said that this would be fine by me providing that our attempt takes precedent and is not hampered in any way i.e. if our forecast means we are not sailing then by all means he can have him but if things change on short notice then he must come back regardless of the situation in Luderitz.

I thought that the big problem would come from the WSSRC not authorising this arrangement but this proved not to be the case. They stated that they didn't want any bureaucracy getting in the way of a proper attempt if possible. I totally applaud this stance. We could of played games with keeping the commissioner on site here to hold the competition back but I simply don't want to see that type of crap enter this game. It's hard enough to get to this stage for any project without having different projects trying to undermine each other. Still, you do have to consider all the implications and the risks it now introduces to your own project. You have to be aware that you may expose yourself unnecessarily to risk by having your 'man' stuck next to a rolled over car in outback Africa as you try to whizz him back and forth over 700km of semi-dirt roads. Any number of scenarios now come on the table. It's a tough decision but we will try and be as helpful as possible as the shoe could just as easily be on the other foot in the future.

I told Seb that I would wait until midday here to make the final call.

If our own forecast is flat on Wednesday then I will try and get down to luderitz myself to go and see this trench in action. I'm sure it's a spectacular sight/site.

The first 'fingers' of a SW wind have just wafted across the glassy lagoon here. The cool breeze has taken the sting off the morning sun. Come on Walvis... COME ON!

We have so many ideas and theories about what is happening with our boats performance and we still have so much to try. The matchstick camera has arrived and we have made a tiny streamlined fairing for it so that it can be attached to the main foil hopefully to film the ventilation and/or cavitation taking place. It will be absolutely amazing if this camera works. I give it a 50/50 chance. It won't be on for today but it will be for the future.

Righto, let's see what the day brings. COME ON WALVIS!

We will do a twitter feed from the beach today and it will come up on the front page of the website as well (you need to keep re-freshing). I believe all the links are on the front page for the live-feed.

Cheers, Paul.

3 comments