Not surprisingly Hutchinson is very coy about speeds reached by the Mule.
“Going to have to pass on that one,” is the inevitable response to the question that had to be asked.
“She goes very well. More than 40kts. We are seeing that speed in surprisingly low windspeeds,” is the only insight given in the Mule’s performance numbers.
“The most breeze we have sailed in is 23kts and we go out in anything from 8kts upward,” he adds.
“The interesting thing about the boat – which of hydro-drag versus aero-drag – is going to be the big limiter,” he says reflecting on one of the design imponderables of the foiling monohull.
“You have to think about the boat – outside that it is fun to go sailing – and think about what Auckland is going to be like in 2021. There’s a reasonable chance in March 2021 there will be 10-16kts SW breezes. We have to be smart about making sure that we balance that between just sending the Mule and having a good time.”
Of course, American Magic has gained a lot of insights from the Mule as to the merits and vices of the AC75, and what can be expected to see from the full scale America’s Cup class.
That includes what could be relevant to race management of the AC75 racing ahead of the America’s Cup World Sailing series – due to under way in Cagliari, Italy in nine months’ time.
“Under 9kts, they might want to give some consideration to wind limits,” he says. “You might spend a lot of time VMG sailing in displacement mode. I can assure you that it is quite boring.
“Yet the guys with the AC50 experiences who are on board say the Mule is matching those boats’ performance upwind. “The the boat is not going to have the same performance in lighter air. It is going to be too draggy. There is too much to slow it down. “It is pretty impressive when we do little things like trim the jib and try to take it all in and learn as much as you possibly can. It is very impressive.
“You learn to respect the boat very quickly for what it is capable of doing. Yet it feels quite a bit safer than the multihull – even though my multihull experience was with a non-foiling AC72 for about 10 days and the AC45’s prior to them foiling. In that regard this platform feels night and day different and safer.
“We’ve had a couple of good nosedives and the boat pops right back out and away you go. I suspect that with the AC75, while people might be a bit nervous about it right now, I would think that it is going to be quite a bit safer than the multihull – because of the ample volume that you have in the hull form.
NYYC American Magic – Pensacola, Florida – February 2019 – photo © Amory Ross
Like the AC50, the Mule, does have one serious vice, which may or may not be repeated in the AC75 which is almost exactly double the length of the AM38.
“You just have to be very mindful that the rudder elevator cannot come out of the water. It’s no more complicated than that. If the elevator breeches, it is all over Rover. She’ll just go where she wants to go. Managing the ride height is pretty critical,” he adds.
“Down-speed we have had our biggest snafus – getting off the tow,” he chuckles.
“But quite honestly once the boat is up and going it is at its safest time when you are foiling. You don’t feel that vulnerable. There is going to be a lot of technique to learn on how to manoeuvre the boat.
“We are pretty far away from any semblance of a foiling tack or gybe. You can see that there will be heaps to gain in that regard.”
The foiling monohull is also prone to the occasional nosedive. “It is pretty much like the TP52 or Maxi 72”, Hutchinson explains. “The bow goes under – a bunch of water hits you and you pop straight back out.
“The first time you do it – you get a bit of a rush! Then you knock Sean Clarkson off you and get back up and off you go!
“After a while it was no different from when we sailed the AC45’s – and we just had to get used to the mannerism of the multihull. With the Mule the nosediving doesn’t feel unnatural.”
One of the trade-offs that American Magic made in designing the AM38 was to develop the boat using the standard McConachy 38 hull. That meant there was no real opportunity to test various hull shapes – and maybe determine whether one style of hull will get the AM38 to pop up on the foils faster than another option.
Equally once on the foils the hull is a big drag item and obviously a smaller hull will have less aero-drag than a wider hull. In the AC75 class rule there is no beam or depth restrictions on the hull – just a distance from the centreline to the pivot-point of the foiling arm mechanism.
So, there is a margin for designers to explore on hull shape and work the hydro-drag versus aero-drag options?
“There you are touching on the uniqueness of the design and the decisions that all the design teams are going to have to face versus the simple side of gaining stability through hull form,” Hutchinson responds. “All the teams will have to face some harder decisions and it is going to be interesting to see the solutions that some people come up with.
“I’m not dodging the question – but I’m not quite sure that I know enough to be able to answer that question yet.”
“You can simply look at that through the lens of all the traditional monohulls we sail.
“A beamier boat with more stability is going to go faster but is going to have more drag to it.
“The same philosophy may apply to the AC75. But in listening to the conversations, I’m not sure that anybody knows. The solutions are going to be interesting to see.
“The thing that the Mule has taught us is that by being a stock McConachie 38 it forces us to focus on other things. But you can certainly see the limitations of the hull form as well.”
While American Magic may have had the design handcuffs on when it came to hull options for the Mule, that was not the case with the rig and double skinned mainsail – which is a unique feature of the AC75. Then there is the return of the Code Zero, last seen on the AC72 catamarans, and freedom of jib design.
While the other Challengers and Defender are expected to head to North Sails, American Magic will be using Quantum Sails. One of the Team Principals, Doug DeVos, is also an owner of Quantum Sails.
American Magic has gone with with a sail development team that has been consistent and successful in the Maxi 72 and TP52, with five world championships won by Bella Mente and Quantum Racing since 2014.
“Everything is to scale with the AC75,” says Hutchinson. “As the project grew, we made the conscious decision that when we were comparing the 38 ft apple to the 75ft apple, that we were doing it as close as we can.”
“I’m not saying anything that people don’t know, because we have had the Team New Zealand spies up here watching us. Ineos Team UK have been here watching us and so has Luna Rossa. Hutchinson confirmed that the Mule was fitted with a double skinned mainsail, which will make its debut into the racing world aboard the AC75.
“In the aero-world (rigs) it is going to be quite an interesting one to see how it all develops. There is a lot of gain to come out of it. The AC75 rig is way more complicated than just the two skins. Without going into too much detail there is a lot of good gain to be had there,” he hints.
“The point with the rigid wing is that out of every manoeuvre you knew what the rigid wing was going to do. With the AC75 it is a lot more complex – simply because of the soft sail, with battens and all the things that go in with it.”
Flying’s the only way to travel – the Mule heads out for a training session – NYYC American Magic – Pensacola, Florida – February 2019 – photo © Amory Ross
One of the features of the AC75 is the development of the radical foil arm and canting mechanism which are supplied parts on the AC75 and are currently under development in a joint project between the Challenger of Record and Defender.
That was another area where American Magic had to go it alone in the development of the Mule and designed and built their own foiling infrastructure based on what was available from the AC75 class rule and available design drawings.
“Our setup is relatively similar to the AC75”, Hutchinson confirms.
“If you look at it as a team as to where we are just simply balancing strengths and weaknesses, so many of our decisions were based around circumventing time. So here is another opportunity where we can do that.
“The Mule concept was conceived prior to the rule being released – but we didn’t get into it until after we saw the Rule.
Being generally ahead of the Class Rule and Protocol development process, another challenge for the American Magic is whether multiple Foil Wings (attached to the end of the Foil Arm) and an area of free design within a shape template, will be permitted during the Regatta.
Yet to be determined is whether the Challengers will be permitted to change their Foil Wing daily, as happened with daggerboards in the 2017 America’s Cup Regatta. Or, if they will be allowed to be changed between Rounds in the Prada Cup. Or, if no changes will be allowed at all, except for breakages, once the Prada Cup starts.
For the Emirates Team New Zealand, the situation is simpler as the Defender only has to target the conditions that will prevail for the Match starting on March 6, 2021. The Challengers have to get through Qualifiers, Semi-Finals and Finals scheduled from January to February 2021, before attempting the Match in March.
That’s span of weather conditions is expected to ask plenty of questions of the Challenger designers, as the same issues could occur with hydro-drag on the Foil Wings as happened with the light and heavy weather daggerboards in the AC50’s
“We are still waiting for the Challenger of Record and Defender to decide how we are going to approach the racing”, explains Hutchinson.
“The Defender has been pretty forthcoming in saying that we are going to race the Match in one configuration, with a “No Change” period. It is up to Team New Zealand and Luna Rossa to sort that one out.”
“Team New Zealand has been very clear on their position for the Match. So, it is going to probably get to the point where how far out from the Match do we have to declare a Certificate, and then what do the Challengers want to do through the Prada Cup.”
“None of it is written yet, but verbally we have it from Team New Zealand that you will have to call it well before the Regatta.”
American Magic is the first team to put out the call for bulk rental accommodation in Auckland – looking for around 100 units. However, their plans for arrival and final set up in Auckland are still a little fluid because of decisions yet to be made over the first of the America’s Cup World Series regattas – tentatively scheduled for October 2019 for Cagliari in Sardinia.
“Right now, our plan is to be on the ground later this year – we are waiting to hear what is going to happen with the Prada Cup event in Cagliari – so that will be a driver,” Hutchinson explains.
“Our plan is going to be based around what is best for us to win.”
He says it is not an option to come to Auckland with the Mule.
`The Mule` American Magic’s surrogate boat shows the foil arms lowered, and the T-foil rudder – photo © Amory Ross
“We are not set up operationally to run a bunch of different boats. So, if the Mule is sailing, the AC75 is shut-down. When we come to Auckland the plan is to come with [AC75] Boat 1.”
“The guys down there, Andy Nottage (ETNZ) have been really good and very helpful about getting information to us about getting our slab (base) and getting all that together. I’m not directly involved with the Auckland setup – a couple of guys from within the team are taking that on – there is a lot that has to happen.”
One of the claimed features of the AC75 was its intended ability to self-right if it capsized.
The simple physics of the AC75 mean that it is highly reliant for “push-up” stability from the leeward Foil Wing. It generates that force as a function of lift from the AC75’s speed through the water which offsets the heeling moment. Take away the boat-speed, and there is no lift from the Wing Foil, and there is really only hull volume and crew weight to offset any heeling moment.
The animation of the AC75 showed both Foil Arms being lowered and the combined weight of the Foil Wing and Arm (about 925kg each) being sufficient to bring the AC75 upright.
In real life that doesn’t happen and the on the water support team need to go through a similar procedure to that employed in the Semi-Finals of the Louis Vuitton Trophy in Bermuda to right Team New Zealand’s AC50 when it pitchpoled as she crossed the start line.
America’s Cup AC75 – the capsized boat is not expected to perform as per the Operations Manual – photo © Emirates Team New Zealand http://www.etnzblog.com
What happens when the Mule capsizes?
“You call in the chase boats”, says Hutchinson. “Everyone has a good chuckle. You hook up to a bow tow and a side tow – much as you did with the catamarans – and you just give them a good pull and up she comes.”
“I suspect that if you didn’t have the mainsail up that the Mule would be self-righting. It is hard to see it being able to self-recover with the water weight. The water weight inside the mainsail alone makes it pretty tough for the boat to come upright.”
“Good or bad we’re getting practice at it,” he laughs.
“It’s only happened a couple of times. First time was while sailing, and then the next time was just getting off the tow at down-speed.
“One time was getting stuck in irons when you have zero steerage and getting hit by a puff and blown over.
“If it is shifty and puffy and you get at the wrong angle when you are going too slow, there’s not really a lot you can do to stop it happening.
Hutchinson says they do get lift from the leeward foil wing almost as soon as the Mule starts moving.
“But the other trick is not to take the windward foil out of the water too quickly so you don’t roll over to windward. Once you are going at six or seven knots and Dean gets steerage it’s a lot easier to sail.”
The AC75 is expected to suffer from the same light air downwind malaise as the AC50 – which were unable to make effective VMG downwind in less than 6kts of windspeed. On a couple of occasions, including one race in the Challenger Final, races were abandoned as the AC50’s reached back and forth unable to be able to sail downwind with advantage.
The first day of AM38 sailing from their summer base in Bristol. – photo © Amory Ross
From what they have seen with the Mule, Hutchinson believes the AC75 will have a similar issue – maybe more acute.
“Yes, the wind needs to be a lot more than 6-7kts,” he says. “There’s going to be a lot of sitting to leeward and just hanging out because there’s not going to be a lot of action. It will be quite boring if there’s 6-7 knots of windspeed.
“You can’t sail directly downwind in that windspeed – you’ll be sailing back and forth just trying to get her to pop onto the foils.
“I don’t know if the Defender and Challenger have thought about how they are going to approach that situation. It will be quite boring.
“You think back to 2013 and the race that got abandoned for Team New Zealand when their AC72 didn’t make the time limit. I can remember watching the first run with their Code Zeroes deployed – it wasn’t too exciting.”
by Richard Gladwell, Sail-World.com/nz