Finally, the big leap off the drawing board...

 Hi all,

I'm happy to say that the new foil design is currently in transition from the drawing board to reality.

It has been a long, frustrating but necessary path to this point.

We have had to go back to school on this one. 

There has been a big shift in understanding from the last blog to where we are now. Some things just didn't fit into the high speed sailing forensics puzzle and we refused to neglect them. We had been constantly told how thin foils were the only way to go... and yet our big, 'fat', Mk1 foil had repeatedly hit over 50 knots. When we applied the theories and associated numbers that sent us down the path to superthin foils to the old Mk1 foil it showed that we would be very optimistic to even achieve 40 knots. It was obvious that something was wrong and that other options were open to us that needed to be explored. We withdrew from the outside world of expertise and chose to resolve the problem in house using our own small core design team. The fact is that you need to understand these problems very well yourself so that you can be in a position when dealing with outside expertise to ask A/ the right questions and B/ know the difference between bullshit and brilliance. I think it has taken us this long to achieve that status... and to be fair... we are yet to prove it. It has taken a long time but then this is an extremely complex problem of physics (as everyone keeps reminding us) and at the end of the day I'll be strapping myself into the final exam paper submission.

 

So, where are we? Well for starters the new foil is going to be a lot smaller than the original foils.

COMPARISON OF NEW FOIL TO OLD AS SEEN FROM BEHIND. THE MK1 FOIL IS THE BIGGER ONE.

 

They are also going to be made out of carbon composite instead of the steel option we were previously looking at. The reasons for this are many and varied. A lot has to do with our own particular operating requirements i.e. in a perfect, flat, high speed world we could use much smaller foils still but the reality is we are punching through high frequency chop even on the brilliant Walvis Bay speed-strip and these ideally small foils would not cope. In the end we have had to pick a span/depth compromise that we felt comfortable with. I am glad that we did those brutal foil modifications in that last sesssion last year. Chopping 15cm chunks of the foil one after the other gave us some great insights into how forgiving VESTAS Sailrocket 2 can actually be. The fact that she got up and going at all with 45 cm removed was pretty impressive. Mind you, we were sailing in top end conditions and we hope we don't have to do that again.

So whilst the new foils should see the same loads as the old foils, the lower spans should mean that they have lower bending forces. We believe that this will mean that we don't really need to use high modulus, pre impregnated carbon fibres. This reduces the complexity and cost of manufacture which in turn can be put somewhere more useful.

 

I am not going to give away too many details of the new foils. It has cost us a lot of time and money to reach this level of understanding. like most things in life, the answer is easy once you have seen it. We haven't shown that we have the answers yet but no doubt we will share things as they are truly revealed. In reality we only really understand our Mk1 foils now. Many of the explanations I may have given earlier wouldn't stand up to our current knowledge. I am as happy as can be with the logic behind our current path. I can't see any loose ends or aspects that we are deliberately overlooking. In fact, many of the previous 'weird' un-explained stuff now ties in with our understanding of the issues.

The tooling moulds will be put under the CNC machine tomorrow and we are pushing to have them ready by the end of the week. This means the actual build of the foils will commence next week. As soon as they are finished they will go direct to Heathrow where they will be accompanied on a plane down to Walvis Bay. Team members will be down there setting up the boat and base a week earlier in preparation. It's all go. VESTAS Sailrocket 2 is at a stage where we should be able to get up to the high speed stuff very quickly. As always we have to be careful not to make any silly mistakes along the way. 

It is pretty exciting from my perspective to be focusing on a return to sailing action. The kiters are planning another record session further down in Luderitz so Namibia is once again going to be the focal point for real high speed sailing action.

In these troubled financial times we have to remain as frugal as we can with our budgets. All our resources have been poured into resolving the design issues with the new foils. There are no retainers, rentals or wasted budgets. It's a big problem that we are trying to navigate through carefully and logically with a focus soley on the goal. We remain respectfully indebted to all those who have helped us reach this stage, big and small. We set out over 10 years ago to break the outright world speed sailing record and that remains the goal. At times we got pretty close but with Outright records, it's a one-step podium. We know our subject better than ever and the fire still burns. We'll get there.

 

Cheers, Paul

Comments

Reply re: Tubercles

 I have read about these but I think we are aiming for speeds with our new foils that even the fastest fish/mammals would not achieve. From what I understand they might be effective for certain hydrodynamic issues that aren't relevant to our speeds and angles. Still interesting stuff though.

Cheers, Paul.

Just a passing thought...

But from someone who spent hours discussing windsurfer fins with a NASA hydrodynamics engineer under the gazebo on the beach in Key West.

Have you ever heard that the row of serrations on the leading edge of a humpback whale's fins are for turbulence control?

Go to the link and check out the explanations. Anything there that tweaks your mind"

http://phys.org/news/2012-09-scientists-purpose-vortex.html

News?

How can I possibly fill in my lunchtime without some juicy Sailrocket news to follow.
How's it all going. Must be close!

I'm sure there are delays. CNC moulds like that are not easy to do quickly.
We just finished machining a very bloody hard (literally at rockwell 52+) monoblock Titanium propeller for a very wealthy russian so we know the headaches cause by R&D. Took a long time to get the machining technique down so if you need a titanium foil, let me know.
Pete

RE.... News?

 Hi Peter, Well rest assured that it will all be coming thick and fast soon. I expect to head down to Namibia around the 20th. The new foil is currently being built in Bristol and might make it onto the same flight down. This one, as mentioned, is being done in composites. Titanium propeller's eh? Interesting choice. Well we haven't proven that our new foil is the answer yet so we will leave all other options open. We may still eventually go down the metal path in the future and it really isn't our field of expertise... so keep some of those metal off-cuts.

Cheers, Paul.

Propellers?

High speed racing props must be in your fields of study? How do they relate?

Reply re:Propellers

 Yeah high speed racing props are very interesting... but once again they have quite different environments and issues. We often discuss their design and reference our own understandings to this. At the end of the day our respective applications and general performance requirements are just too different to apply similar solutions to both. Nonetheless, I could no doubt sit and discuss the hydrodynamics of these propellers with those who design them for hours. I'm sure we still have a lot to learn and some times it's the small details which are the most fascinating.

We'll see how our Mk2 fast foil goes first. I don't think I have seen a propeller that uses the same principles... but I have seen many high speed power boat rudders that do. The rudders are perhaps more interesting to us. Even the high speed RC guys have done some interesting work on them.

Cheers, Paul

Progress

Great to hear of your progress Paul and all the best to the team. My question is a simple one: Do you know of anyone evolving other yachts - not record breakers - along similar lines? The notion of not relying upon ballast and taking out the downforce is an obvious one and one that I sketched up some years ago. On my reckoning a practical boat can be evolved.

with thanks & regards,

Patrick Irwin
Melbourne

New Foil - On the road again

Hi Paul,

I read with great excitement of the continued team VSR2 progress.

Based solely upon keen interest in the foil progress, I'm going to expose my ignorance in the approach to a high-speed foil design.

I start by noting the kite-boarders' apparent solution to counteracting the kite power at high speed: a greater attack angle of the windward board rails. From the videos of the super high-speed kiteboard runs (I.E. Douglas @55Kt), it's hard to say that the board skegs served as important a function at speed as did the edge of the board shovelling a lot of water downwind. In fact, it doesn't even appear that the board skegs are in the water, so it would appear that the kite boarders are not burdened with the high-speed foil issues.

So, my question: why can't the VSR2 solution be similar to the kiteboarder's solution?...I.E. a long, shallow skeg with the long edged arranged roughly parallel with the VSR2 upwind beam.

I'm aware that the person in control of the kiteboard must be making multiple and instantaneous corrections to the angle of the board in response to the energy of wind gusts or water surface changes, which would be hard to reproduce in a fixed mechanical foil system on VSR2. But what other factors account for the foil system you pursued rather than a foil system styled from the kite boarders?

REPLY- On the road again...

 Hi Tim, 

VESTAS sailrocket 2... and VSR1 for that matter are based on completely different overall concepts than those used by kitesurfers for speed. We each operate in very different environments to suit our respective concepts. There are a few reasons why we have chosen different foils for our craft but one biggy is that we are actually using our foil to pull us down to the water as our inclined wing is trying to pull us out. it is pretty hard for a pure planing surface to do this as it needs to hook into the water. Another aspect is the fact that the overall efficiency of a rail biting into the water is relatively poor. A higher aspect ratio foil is much more efficient. Kite surfers have shown they canbe very quick upwind... but only when they resort to foils as against just edging upwind. There are however many good things about how these inefficient foils/edges work that has resulted in them having (currently) a significant speed edge over the craft that use conventional foils which includes windsurfers, VSR1, Macquarie Innovations and Hydroptere. They are largely only using the inclined/edging high pressure surface of the board to give lateral resistance to the kite. They are not using the low pressure, suction side of the board as they are standing on it! As we approach high speeds into the 50's it is this suction side of the foils that is subject to cavitation and all the associated speed sapping drag. So they aren't using the power of this suction surface and therefore have to operate the surface they are using at twice the angle to do the same work. This is also draggy. A large part of their current performance comes from sailing at deep angles downwind in very, very strong winds. They are not so much opposing the wind as going with it. Don't get me wrong, I'm not saying thats bad or anyone's better... it's just how the physics work. Let's face it, they have the record and ultimately they are the first to use a ventilated foil to break the outright world record. There is a lot more to a kiteboarder than just using a kite. Overall I have a huge amount of respect for both the craft and the riders. We have chosen to sail in much less wind and use the build up of apparent wind to generate our power. We can do this because we have no net overturning forces due to the concept around which our boats are based (thankyou Bernard Smith). By sailing on a beam reach we build up a huge amount of apparent wind and can turn 25 knot winds into 60 knots. The loads on the wing and foil are immense. The boat feels like it is sailing upwind and thus needs a very efficient foil i.e. a higher aspect foil otherwise we would just have to turn and run more downwind... which would lead to less apparent wind... which would require us to sail in more wind... and so on and so on.

So, we can sail our complex (currently) craft in an open water course in relatively standard condition whilst the kiters sail a simple craft in a complex, man-made course. To each their own. 

As we do go faster i.e. deeper into the 50's, we do have to use elements of ventilation and/or cavitation to make our foils work. You simply can't avoid it. If you want to make these foils more efficient you would most likely look at increasing the aspect ratio. This results in longer, deeper foils. The kiters do still have a host of options for increasing efficiency and I look forward to seeing how they evolve.

The above is a quickish response to a subject that I could talk about forever from many angles. I hope it helps answer your question.

Cheers, Paul.

Paul-On The Road Again

Before following the VSR2 ventures, I never even knew the scientific subject existed involving ventilated high-speed foils, never mind caring about it. Now I'm talking to my kids about it.

Quickish response to the subjct question or not, your ideas and writing on the subject are a good read. If you ever produce a dissertation on the subject, I'll read it cover to cover.

All the best as you build and test your new foil. I'll continue to follow with fingers crossed for the team. Safe travels.

Tim

New Foils

Great to hear of your progress. Eager to see the results! All the best to you and the team.

Cheers,Bob Imhoff

New foils

When they are finished can we see pictures of the moulds and manufacturing set up. Sorry I'm a sad engineer but a happy sailor ;+)

The technology fascinates me and the challenge inspires me.

Go team Sailrocket.

Reply.,, New Foils.

 Hi Chewie, sure. Although we are still working out how to build certain details. The moulds have been swiftly moved from where all the blank blocks were assembled to another CNC specialist as the machine we were going to use had mechanical issues. Thankfully we could find someone who could do the two halves in one go on short notice and very little time has been lost. The team is in full swing finishing drawings and getting structures checked whilst I try and make sure it all moves forward smoothly. We are machining epoxy tooling block which is very dimensionally stable. We will make female moulds and will most likely infuse the foils in a couple of stages. The interesting detail will be around the transition (elbow) as this is where we have large bursting loads. It is here that we need to incorporate some form of shear web. the laminate should be solid there so we will have to do something clever. We're onto it. I hope the moulds will be finished either at the end of this week or early next week and we can go directly into build. If the whole lot was done in 3 weeks... it will be in Namibia a couple of days later where VSR2 will already be set up and waiting. We are keen to make the most of this weather window. people in Walvis Bay are already e-mailing saying we are missing some good days.

Cheers, Paul.

Nice to hear things are coming together...

Not looking for you to reveal you hard earned secrets, but did you ever come up with an explanation for that run 2-up that was faster than subsequent runs?

Why we went faster on that 2-up run...

Hi DC, I was asked the same question recently so will post the reply here for all to read. 
 
Good question and one that puzzled us as well. It was the first time I ever took a passenger on a fast ride and we all thought that it would just be a nice, fast-ish ride to take a journalist on before conditions built in the afternoon. The top speed was a true surprise. 
It has taken a long time to fully understand what happened and why we never replicated it with that foil again. As usual it came down to a number of factors. I think that we now understand it in its entirety.
Basically the foil had an internal fracture that meant although it wasn't going to fail, it wasn't as stiff in deflection as it should have been. This means under big loads it would begin to flex and straighten out. When it flex's/straightens it stops pulling down as much as the wing pulls up and the boat begins to ride up on the foil.
We now know that that foil was way too big and this lead to it travelling at extremely low angles to the water flow at high speed (low incidence, almost negative). So low that the cambered pressure surface would some times go negative at the leading edge (as described in the last blog). This would lead to cavitation on the pressure surface of the foil which is extremely draggy. It was our limiting factor. One way to stop this is to reduce the area of the main foil. Now when the foil was flexing the back of the boat would ride high which would result in the foil coming out of the water and therefore the area submerged would be reduced. This reduced area would be subject to the same load and therefore would have to work harder per square inch... so the foil would travel at a greater incidence (angle of attack) and this would reduce the likelihood of cavitation allowing the boat to go faster.
I think the fact that I happened to have a passenger on board when this happened was not relevant to the real issue. We probably would have gone slightly faster again 1 up as the back would have ridden higher with less weight aft along the fuselage. 
The videos confirm that the back of the boat was riding very high.
We discovered small cracks in the foil the next day and carried out some pretty full on repairs. The result was the foil no longer flexed and the boat would ride at its correct height... and begin to cavitate at the old 49-51 knot speed. It all seems to make sense and all the evidence stacks up. It ties in with our overall understanding of the foil issues and we have designed accordingly.
Cheers, Paul

Fast run explained...

Thanks for that.

Interesting that it was the foil flexing, not the approach angle during startup, flow disrupted by the forward rudder, etc. Best of luck getting that new foil in place.

I trust the rest of sailrocket has been keeping safe in the interim.

New foils, new day

Here's hoping that the new foils do the trick. I always look forward to hearing from you, even if the news isn't all good at times! Good luck with the winds, and the attempt in general.

Russell.

New foils, new record?

Hi Paul and the team, great to hear you are all on the go again looking forward to updates etc. this is the year of the big one I am sure
regards
Mike

The search for the Grail continues

Hi Paul
Great to hear that the project is on track again. In the present economic climate that is not always a given. In the light of your previous achievements and the research done into the foil design I hope that this stint is going to be the big one. Looking forward to seeing you all at the WBYC again.

Regards

Uwe

Foils and back to Walvis

Hi Team

Good to hear some news, we were wondering if funding was becoming an issue in the current climate but great to hear you will be back in Walvis soon
.Pat and I are back down on 29th August for three weeks, so hopefully we will cross over.
Let us know if there is anything useful we can do, Pat has unfortunately not lost much weight so ballast availability can continue!

This year feels good!

Kate and Pat Chilton

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