A-Cat Worlds 2017, Exploder D3 devel: Interview with Gonzalo Redondo

Photos: Gonzalo at Sopot Worlds,  Heli shot by Paula Kopylowicz – Brewin, Jakub Kopylowicz, Gonzalo –  Bundock by Helena Darvelid/Sailrocket – The winning Z22 foil, Stephen Brayshaw by Helena Darvelid/Sailrocket . –  Exploder/D3 Wingmast tested by Kuba Surowiec. –  2017 WC Steve Brewin foiling upwind by Helena Darvelid / Sailrocket . –  Video by Kostas Trigonis.
Left: Gonzalo with Santi Estevez & Anton Paz. Below with Luc Dubois —-

2017 was a perfect year for Exploder: Mischa & Stephan grabbed F18 Worlds with the Scorpion at Denmark and later the long awaited A-Class Title at Sopot by Steve Brewin. Both crowns have long stories behind, Mischa on his decade of pursuing the F18 top podium, and the A-Cats 5 consecutive titles for Dna seemed a wall too high to climb. But Jakub Kopylowicz kept working and joined forces with Gonzalo Redondo from D3 Applied Technologies.
Together they embarked in an intensive development process to aim for the A-Class World Title.

Interview below focus on the devel & testing aspects to get the crown, which of course was possible in the end thanks to the great team riding the Exploder D3. Check Brewin’s own path to the title here

R&D in the A-Class has given us great foiling rides, Gonzalo along Jakub have provided sailors with current top notch flying solution. Just watch Kostas Trigonis video above, he is a good sailor of course, but see how the platform is doing it’s own work. Previous A-Cat foiling setups needed plenty of sailor’s input. Thus this footage resumes pretty much the result of Exploder/D3 Applied Technologies work: Smoothless  stable flights.

Q&A below will be also avaible in next “Foiling Magazine” first digital edition.
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Interview with Gonzalo Redondo , owner/head designer at D3 Applied Technologies / d3appliedtechnologies.com

– Since when you started working with Jakub / Exploder in the A-Class project?
Gonzalo Redondo: We started working together in September 2015 I believe as I remember working on the original platform concepts at the airport coinciding with the Monaco Yacht Show. I knew well the great job Jakub was doing and had fantastic references from everybody. By that time I was sailing on a foiling moth.

– Which was the initial plan and objectives?
Initially we thought about designing new foils for the A15 which was performing already pretty good. After some R&D we went from Z5 to Z10, which ended up being the production boards until Sopot. Also, we wanted to develop new rudders and decided to develop Ts and Ls until both would be refined. From the beginning we did not think it was fair to make conclusions based on undeveloped concepts. From a theoretical perspective Ls would make sense but from a practical one we ended up selecting Ts after a few months.

We thought about taking it easy with regards to the new platform, the Exploder AD3, but I believe Jakub had some issues with honeycomb stock in January 2016 so he suggested to put all his resources in the new tooling. Hulls were already designed so March 2016 we launched the new boat and it proved to be faster and also lighter than the A16.

There are some aspects of the platform design that simplify development. For instance, the longitudinal chine you see at deck level right in-front of the forward beam provides a consistent beam to deck intersection, which enables Jakub to move beam position without any effort or extra tooling. For instance this is why it is so easy to ask for custom configurations. We even tested one with everything forward 30cm.

– Which was the time frame you guys established to reach a targeted level of performance you showed at Sopot?
Hehe, there is no schedule in a development class. It is very simple, we do all we can until we run out of time. At this stage we know we can go from design to machining moulds and then testing in less than 2 weeks. I believe once it was 1 week. After Medemblik priority was on boards and rudders. Also, some construction and fittings have improved to make the boat more reliable.

– How was the coordination with the Polish/ Spanish & Australian teams, in terms of equipments (both tested the same at same time for ie?)
Very good. The sailors are committed to the development of the platform and usually we received most of the feedback via Whatsapp. Jacek is very reliable and communicates very well with Jakub, then Stevie and Bundy are key testing and bringing ideas, and for me it is also very easy to communicate with the Spanish guys. For instance Manolo tests equipment in waves and Antón Paz and I in flat water. Moreover, the Australian part of the team is key to develop over Northern Hemisphere winter, although we try to sail throughout the whole year at our place. Kostas is also helping the team in many ways.

– We know Jakub likes to develop, build and test . Which were the limitations (if any) on the R&D build/test process?
Software tools are always a limitation, and we have a continuous development program in the tools as well. There is always a limit on what you can model and so it gets to a point in which we cannot be certain about designing better foils, so when that time comes we need to get into our cave and figure out how our tools could be improved. Other than that, we had a plan to go to the Worlds with Z21, but ended up going with Z22 which is a variation of Z15, which was the first of what we call the new generation.

The board numbering accounts for the design iteration. After Z10 we designed and built Z
11, Z12, Z15, Z19, Z20 and Z21, so 6 foils before the final one. Some of the foils are CFD’d and VPP’d but are either not good enough for manufacturing or we feel we can do better straight away. Sometimes we get additional feedback that changes the way we approach the design. These boats are pretty dynamic so sometimes there are things you just can’t see with the tools. It is a nice experience because it is quite a practical design project.

– Having such intensive devel program  the build / test cycle must result in some interesting data for your theoretical work on CFD and initial design intent.
 Which conclusions you can drive out of the results your system were showing to actual feedback from Aussie/Polsh/Spanish camps?
There are 2 aspects very tricky to fine tune, these are ventilation and turbulence. As of today I am surprised of the little ventilation we get on the daggerboards. The rudders are trickier in this respect but the combination of area, foil section and stiffness of RB21 (current production rudder blades) seem to be effective. As of turbulence, this is quite a funny one as there has always been plenty of talking on the subject and nobody is really certain. We have got an idea of what works and what does not, and then it depends how much you want to risk it. Sometimes it is great to come up with unsailable appendages as they set the limits of what is possible.

– Are you able to adjust your predictions now , based on the on the water results? Which is the gap of CFD to actual perf ?
The VPP is very accurate on average VMG. I am surprised about top speeds tough. Also, the Australians were the ones that uncovered their own upwind foiling technique which was not predicted by the VPP due to the previous aero package.

– Tank testing is now obsolete? or serves still a specific purpose?
I have only run tank tests myself at the University and even tough I am 33yo that was more than a decade ago. We still get some tank testing results for some commercial projects but they match pretty well. No matter what, the truth is that tank testing as a design tool does not really work within our new design methods. Nowadays a CFD simulation can give you a better insight on boat dynamics than a simple tank test, particularly when it comes to sea keeping. It is not all about resistance. The environment of a towing tank is just different.

Moreover we always end up testing dozens of hull or foil designs so it would not really be viable as a design tool. In my experience, what really makes sense is to build development platforms which you can test in real world conditions, i.e., scale tests in which you can jump in and check if what you are feeling is indeed what you are looking for. I quite like the new AC protocol banning towing tank and wind tunnel testing. For instance when I was part of the design team of the latest VOR70s we did not do any tank testing.

– New foils have less chord than previous Exploder Z versions, any structural compromise was addressed or the use of high modulus carbon can by pass the lesser material used?
We have not broken a single board and that is of some concern! Errors and breakages are fantastic to speed up learning curves. Jakub is already using high modulus carbon.

– Seeing your latest Foils, they resemble some of the latest designs we’ve seen in the AC, seems the classical elliptical planform continues to be up to date and alive. Which are the overall benefits over a straight taper for ie on a Z board?
Well, for me the definition of an elliptical wing is the one of the Supermarine Spitfire (you may find a nice pic to attach). The current planform is just an attempt to improve the effective aspect ratio of the foil. The taper is not straight so I would not say a straight taper is beneficial. Also there are some structural implications related with hydro elasticity that we need to be careful about. Even ventilation is quite affected by the planform shape.

– You have specialized yourself also in foil section development, how key is to nail the foil section aspect say over planshape or overall shape on vertical/horizontal/tip?
On one hand an incorrect foil section can screw up any design. On the other hand I am really impressed by how some funny foil sections work. We extended the trailing edge of a foil and you would not notice the max. thickness was effectively moved forward, which is a very important parameter with regards to turbulence. I think next year we will work a lot on foil sections as the shape and platform of the foil seems to be quite efficient as of today, although for sure we will try to develop it. Anyway what looks ok today will be outdated in the near future, that’s for sure, and not knowing what’s next is very exciting as well!

– The foil section devel is now fully automated? Of course you still need to input and target specific goals , but can you set those parameters and let the systems develop at will to reach final result?
We do have a few foil section algorithms to automatically develop sections. However, in my humble opinion, the experience, understanding and thinking of a person is critical to drive those algorithms, as they sometimes go wild. Understanding the effect on performance of every foil design feature is what really matters. Then you can go and boost the design work with algorithms and tools, but no tool will design you a foil on its own.

– How important is to have dedicated and specialized hardware/software packages like you guy shave a D3 Applied Technologies to reach such level of refinement?
Key, which is why our biggest investment is always in cluster and software development and licenses.

– You decided to embark yourself in a intensive training sail program towards Sopot, we ‘ve seen some really stable foiling and how you improved. I’m  always praising those developers that can actually tests their designs, of course some might not be able to and having riders is as good and efficient method, but how flying your designs iterations helped you along the Pro riders feedback to continue developing further?
For me this is very important as well. As of today I’m really satisfied with my flatwater performance. Our training venue is perfect as the biggest waves I’ve seen there are coming from motorboats. This allows Antón and I to do a lot of 2 boat testing so that we understand the performance and dynamics of every prototype. Then we compare our feedback with that coming from Australia and Poland. My first day in Sopot was ok. The second was very wavy which was a pain for me as I had a pretty wild wipeout injuring my knee. I wonder if Gordon Upton has pics of that wipeout as I do not know if I spinned once or twice on the trapeze! The next day was superlight and that’s a condition I don’t perform at all. Will definitively work on it.

In general I feel I can ride the boat fast but I’m still to novice to sail properly around the course. Pending task for this winter is upwind foiling. Anyway I’m very proud I made it to Gold fleet as I had no expectations at all. Next Worlds I know I’ll just try to do better, knowing that when the regatta starts I am not the designer of the boat anymore and just an amateur a-cat sailor trying to enjoy the ride and share it with others.

– We’ve seen at Sopot how upwind foiling payed for the first time. We’ve been talking on how stable and early lift were goals for latest versions. There is a limit for the full foiling A, in terms of flying upwind say in 6kntos like a Moth?
Mmm, the moths do not have efficient hull shapes, whereas the A hull is very high performance. It is normal that in low wind you better float. However with Z22 we lowered the wind to make upwind foiling pay to something like 10 knots. Upwind foiling is already possible in 8 knots tough, it’s just that the hull is pretty good too!

– Rig devel: A wingmast was tested by you guys but was discarded for the Worlds. Short masts were tested by many but also discarded by Brewin for ie. So in terms of rig design this Worlds haven’t seen any breakthrough or definitive new solution. Which direction you think the Class will take in the future and previous mentioned alternatives have any future in your view?
This was an experiment to kick off a long term project. The mast project is not commercial but raw investigation. Anyway I would like to remark that winning the Worlds with a boomless sail is quite a breakthrough for me! I sailed for fun a Dart 18 for a few years and I liked the boomless idea a lot. I’ve also been testing myself a Brewin sail and I like it too. He deserves great credit for bringing that to the class.

If the next Worlds are going to be in a windy venue then short masts would be the way to go probably. However current rig developments are constrained to Fiberfoam and Saarberg masts. They are doing a fantastic job but obviously this is quite restrictive in terms of testing different solutions.

– Which are next steps, if any in the foil/rudder area?
Hehe, as long as ideas keep flowing… I know what we would do today but we don’t know what we will do tomorrow. I think we have ticked all the important boxes with the new platform so now it is time to look at some detailing probably.

– How about the offsets setting some are using ?
With the latest rudders we use 0.5deg positive rake. As you know I have made a 3D printed inclinometer jig to help with that. It was not my intention to sell it or anything but it is hard to say no to sailing mates.

As of the rudder offset, it works as you gain righting moment by creating downforce with the windward rudder. Many have tested it this year. However complicating systems on boats like the A-cat adds weight and you loose focus on the things that really matter. I would see it as a nice feature if it was linked to other existing controls.

– Platform: With all the test done on beams positions, can we say we have a rather standard placement now to remain for 1-2 seasons at least? Or still room to test & devel in that area too?
I think so. However if anyone wants to order a different configuration I believe it is possible as I explained previously. At the end this is a development class so the same way some of us take the risk to order platforms, I don’t see why it would not be possible for any sailor.

– Overall impression of the work done which ended with the title at Sopot
I am proud of the team effort but eager to keep going. I don’t think being satisfied is really possible in a development class.

– Future overall R&D plans
Even tough we have ideas to keep testing, we will focus for a while in ways to improve our design tools before we get back to R&D mode. But be certain we’ll do our best to keep performing next season.

– So outside of the A-Class stuff, what other projects is D3 office involved with at the moment?
We are very lucky  to be involved in so many projects. The office has only been up and running for less than 5 years and I believe we will finish 2017 having started project 100! As of catamarans, we are working on some foiling designs now which are already under construction. The Flying Phantom Essentiel is a joy to sail and we look forward to continuing working for them.

Lately we have been involved in a very special  multihull project, for which we have set up a very strong design team with Luc du Bois, Adam May, Marc Menec, Mannerfelt Design Team and Bob Graham with support from Gio Belgrano on the structures. The experience has been so good we are considering establishing the design team somehow. Adam, Luc and I are A-cat sailors and good friends, so it is very comfortable to work together as we share that practical view, and I believe like we complement each other very well. Marc Menec, he is one of my closest friends and the best 3D guy you can find. He runs his own firm but I consider him part of the D3 team as well when it comes to foiling cats.

With Mannerfelt Design Team we started helping them a few years ago in their high performance powerboat projects. Running hydro simulations at 120 knots to design racing powerboats is one of the trickiest things you can do!

Other than that we are also working on Olympic campaigns, drone designs, both power and sailing megayachts, watersports gear (windsurf, kitefoil, electric jets), high speed ferries, ocean support vessels, floating houses for Dubai… We even designed the linesplan of a 30m fishing vessel which ended up being Ship of the Year 2016. There are also some Civil engineering projects in the office. I like the idea of being multidisciplinary as it keeps our mind open and we can share solutions from one sector to another.

– Final toughts? 
I am very thankful to Jakub. I would say thanks to every eXploder D3 owner and for sure our team riders. Then to my team at D3 Applied Technologies and also Marc Menec, who also collaborates with us in this project. They deserve all the credit.

–ends—
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