America’s Cup knowhow harnessed for land speed attempt

Emirates Team New Zealand says it has always commissioned external contracts to keep the design team sharp. So, when an independently funded project to attempt to beat the Wind Powered Land Speed World Record emerged, ETNZ found willing designers, engineers and shore crew to put their talents to the test from being fastest on the water in the America’s Cup to being fastest on land.

Working with Glenn Ashby, whose objective is to: “Obviously design a craft that becomes the fastest wind powered land yacht ever,” the craft is already under construction at the Emirates Team New Zealand build facility on Auckland’s North Shore.

“The build is scheduled for completion in late March, for assembly and commissioning and preliminary testing in Auckland subsequent to that,” says construction manager Sean Regan, ETNZ. “The plan is to then pack the craft and equipment into containers and ship it all to South Western Australian and truck to the record attempt location where a small team will be based from July for testing and then ultimately a shot at the world record speed run.”

“The wind powered land speed record is something I have always been interested in, so when bringing a design challenge like this into ETNZ I knew it would be beneficial on a number of fronts to keep the technicians and the innovators of the organisation engaged during a down time with new, complex technical issues to solve with a cool project,” says Grant Dalton ETNZ CEO.

“Basically, from the point that Dalts said ‘let’s look at it’ after the finish of AC36, we have been all go,” says Ashby. “First job was a two-week in-depth feasibility study to ensure enough of a global understanding that this was something that could be done in a positive way for ETNZ and would not impact the team and its America’s Cup objectives financially or resource wise.”

Since then, the core group has been working through the new design and engineering challenges entirely focused towards beating the existing record of 202.9km/h (126.1m/h) which was set in 2009 by Richard Jenkins in Greenbird.

“As a team we explored some pretty creative and innovative conceptual ideas in the quest for more speed,” says Ashby, “however in the end our design and performance principles evolved into a concept reasonably similar in basic layout to the existing record holder, which really emphasised to us what a huge challenge this will be.”

Without a revolutionary design, and very much like what is predicted in the 37th America’s Cup with the next generation of AC75s, the gains will come down to the small improvements and refinements that add up to overall advancements and success.

“Like the America’s Cup we just need to be doing it better across the board by utilising our experience, skills and tools gained as a team to date,” says Ashby. “And then, like sailing, there is always the weather gods and doing everything we can to be ready when the right conditions are presented at the location.”

From a design and engineering perspective, Guillaume Verdier (team member) says: “This project is a really compelling one for all of us involved. There are a lot of similarities to what we do with fast sail boats in terms of the aerodynamics and structural forces, construction methods, materials etc, so we are well placed in many respects. But without doubt, no boat we ever design will go anywhere near as fast as we need our land yacht to go. So, with the increase in speed comes increased complexities, but we are sure these are complexities that we can learn from so we can make our next AC75 go faster.”

The obvious element of uncertainty and point of difference for all the Emirates Team New Zealand designers is tyre technology and the dynamic forces associated with tyres on the ground, as opposed to hydrodynamic forces on foils in the water.

“This is the big unknown for us,” says ETNZ mechanical engineer Tim Meldrum.

“Tyres on a flat salt surface going at over 200km/h is a whole lot different to foils in the water at over 50 knots. The rules stipulate we must run on a flat natural surface. The best ones we know of where it can be windy are dry salt lakes. With the tyres being the only point of contact to the salt it is a pretty important factor in finding the sweet spot in maintaining sufficient grip- with the least amount of rolling resistance.

“Our craft when compared to a speed record motorised car has a lot of differences. Firstly our “motor” – a wing in our case really delivers a small thrust force compared to a racing combustion engine. So, anything working against that thrust – wheel rolling resistance and aerodynamic drag has been a high priority to reduce if we want to hit high speeds.

“Secondly our wing creates a lot of side load over the main back wheels – so we need to provide grip to keep it tracking straight. A downforce aerodynamic wing like those used in F1 to assist cornering grip would rob us of too much speed, so we have opted to add variable ballast weight to allow us to tune our grip level. Extra weight mainly affects our acceleration time but does not compromise aerodynamic drag. The trade-off is we can go faster but we end up using more runway to get to our top speed. Luckily our racetrack is 8km across.”

Another contradictory problem to the norm in the America’s Cup is around weight. In the AC75s the less weight in the boat the easier it will be to fly and faster it will be. With a land yacht, weight is a positive in certain respects.

“In land speed, weight will be our friend if used in the right location,” says Regan. “So, we can refine our construction techniques that account for additional weight in certain aspects and not be so focused on weight savings. On the outrigger pod we are actively adding weight or ballast to counter the wind force on the wing sail, without which, the craft would just tip over. Not something we want for Glenn approaching such high speeds.”

Too little weight and the outboard tyre will come off the ground losing contact, too much it will add unnecessary resistance and lose valuable clicks of speed.

Any world record needs to be stringently verified and will require officials from the North America Land Speed Association to measure and record the run with a specific set of rules that must be adhered to in order to qualify for the world record.