(CNN) Science, secrecy and subterfuge have become as much a part of the America's Cup scene as the sailing itself.
Two years out from the 2021 America's Cup in New Zealand's Auckland, this covert phase of design and testing is in full swing, with teams working feverishly to dream up a speed machine capable of winning the "Auld Mug."
The boats for the next edition of sport's oldest international trophy will be radical 75 feet long foiling monohulls -- dubbed AC75s -- which means they will lift out of the water on canting hydrofoils to "fly" at speeds of up to 50 knots.
The concept is cutting-edge, and a departure even from the high-tech foiling catamarans that made up the last two editions of the Cup.
Visit CNN.com/Sport for more news, features and videos
With the first action not scheduled until the autumn, D-day for the launch of the teams' first of two race boats is March 31. The favorite mantra in Cup circles these days is, "The only thing you can't buy is time."
But it's at times like these that the Cup can potentially be won or lost. Or possibly even changed forever.
New design, technology and innovative thinking is the cornerstone of the Cup. From wooden hulls to carbon fiber; from the revolutionary winged keel that helped Australia II snap America's 132-year stranglehold on the competition in 1983, to giant foiling catamarans, control systems powered by cyclists, speeds in excess of 40 knots and real-time performance data pouring into chase-boat computers, each edition pushes the boundary.
Some gains are incremental. Some represent giant leaps forward.
Two years out from the 2013 competition in San Francisco, one of the challengers Team New Zealand was working secretly on a concept that took the Cup into a new realm -- the air.
Away from prying eyes in Auckland, the team was conducting covert experiments to see if they could get a small catamaran -- which they nicknamed the "Waka" -- to rise up on foils when towed across the flat Lake Arapuni in Waikato.
"To anyone walking the dog around the lake, we probably just appeared like a few old battlers towing a beat-up old catamaran down the lake for fun," Team New Zealand's Australia skipper Glenn Ashby said on the team's website recently.
READ: The world's best yachting destinations
After weeks of experimentation, the dream of souping-up their AC72 catamaran was becoming a reality.
Foiling wasn't new in sailing, but getting a giant America's Cup multihull, which weighed the same as five saloon cars, to lift out of the water on a hydrofoil the size of a kitchen table -- and then racing it -- certainly was.
"Some of those evenings where we would sit around the table, knowing we were pioneering absolutely new ground in the America's Cup and in foiling multihulls and foiling boats was a pretty special feeling," added Ashby. "Sitting there with the designers and the sailing team really knowing that you were part of such a special period of America's Cup history in the making."
READ: Confessions of a superyacht stewardess
News of the Kiwis' eventual breakthrough spread like wildfire, and the other teams had to scramble to catch up.
Team New Zealand may have ultimately lost 9-8 to Oracle Team USA in what was labeled one of sport's greatest comebacks, but they changed the face of the sport.
Their design bods were at it again on the AC50 boat in Bermuda in 2017, which had "cyclors" turning the winches with their bigger leg muscles, and they clinched the Cup in style.
As winner, the Kiwis got to choose the boats for the next edition in conjunction with Italy's Luna Rossa, the principal challenger.
But mindful of potential ingenuity, the Kiwis have even stipulated that for 2021 crew "...shall all be human beings." So cyclors are out in an effort to return to a more traditional sailor-oriented competition.
READ: Britain's richest man plots America's Cup coup
To get a head start in this Cup cycle, Britain's Ineos Team UK and new US challenger American Magic have built scaled-down foiling test boats to begin to understand the challenge of sailing the complex AC75.
Ineos, backed to the tune of $140 million by Britain's richest man, petro-chemicals billionaire Jim Ratcliffe, has adapted a 28-foot Quant yacht by attaching foils on canting arms and has been trialling it on the Solent on the south coast of England.
Skipper and team principal Ben Ainslie said the boat -- dubbed T5 -- was "pretty wild" and told the Yacht Racing Podcast there have been some "pretty big wipeouts" as they learn the craft while the 40-strong design team works on the first version of the team's AC75.
"There's been a lot of swimming," he told CNN.
READ: New York Yacht Club: Return of the greatest team you've never heard of
It's an open secret that the teams have spies watching their rivals' every move, and Ainslie admitted "there's certainly been quite a lot of reconnaissance, as you would understand."
Over in Florida, American Magic, a new syndicate for 2021 bankrolled by businessmen Hap Fauth, Doug DeVos and Roger Penske, has been busy trialling its own scaled-down test boat. The team has revamped a 38-footer, dubbed the "Mule," and has been testing on the flat waters of Pensacola in the northwest of the state.
"The evolution started out the first day I was on the boat and we foiled. It was quite windy, some of the systems weren't operating perfectly and the boat was a bit loose and were we a bit out of control," skipper Terry Hutchinson told the Yacht Racing Podcast.
"It was almost like getting into a car with my 16-year-old son driving for the first time. Just wondering what could possibly go wrong."
Cup veteran Hutchinson describes sailing the Mule as an "unbelievable experience" and "some of the most fun I've ever had sailing."
"The sensation of speed is impressive. I've spent the better part of a month sailing around at 30-something knots and it's becoming normal," he added.
"But every single day the guys are coming off the water with more questions than answers."
READ: Weather analysis the 'super gain' for Kiwis in America's Cup
The bulk of New Zealand's early testing has been done on a state-of-the-art virtual sailing simulator with sailors and designers working hand in hand, an innovation pioneered for Bermuda by technical director Dan Bernasconi's six-year stint with the McLaren Formula One team. They do, however, plan to launch a test boat, too.
In Italy, Luna Rossa have also been using a simulator allied to testing on a small foiling catamaran, mainly to work on concepts for the new double mainsail.
Certain elements of the AC75 are one-design, meaning they are built centrally in Auckland so all the teams have the same equipment. The foil arms and canting systems are part of that package to save on design time and costs.
Racing may be some months away, but for the America's Cup teams the design battle is raging.
"If we don't have a fast boat I'm quite certain it doesn't matter how well we race a slower boat, we're not going to win so we have to make sure we work hard on developing a fast boat," added Hutchinson.