DESIGNING A LEAN, MEAN MACHINE

More than ever, the responsibility of being the principal structural engineer in an America’s Cup campaign is daunting, regardless that the design and build of an AC72 is a team effort. At Emirates Team New Zealand, where Dalton’s boys operate a lean machine devoid of the frills and extra dollars that some of the other campaigns have at their disposal, the Kiwis appear to have designed a solid boat that has successfully transitioned from the Waitemata Harbor to San Francisco Bay.

Fifty-two-year-old Giovanni Belgrano, principal structural engineer for the team, has worked in the Cup for 25 years on and off as a partner in a composites consulting company called SP Systems and specifically with ETNZ in 2007, Luna Rossa in 2000, and America3 in 1992. Here Belgrano explains how ETNZ has managed to keep it all together thus far.

What’s the specific goal of your job?


GB: The design is structurally driven, so I work with the design team to come up with the best solutions in terms of getting the most effective performance that we can and the structural stiffness and strength that we need to go fast. We’re now in the final stages of development which include final refinement but mainly monitoring performance of the structure and making sure we’re ahead of the game--sailing the boat harder now that we’re in the venue, learning the San Francisco conditions.

What have you learned about the conditions in San Francisco?


GB: We sort of knew them, but there’s nothing like actually being here measuring the loads and recording the structural behavior of the boat. To give you an idea of my day today, it was a sailing day, and I have to prepare the boat and get it in the water. Then I sit on the chase boat with an iPad and look at the strengths and loads in the structure. We have a number of values that we have reached in the past, and every single maneuver and every single angle that we’ve tried in race training. I carefully look on the water at what’s happening, then what I’m doing right now back in the office is typing a memo with a list of things to check after today; that’s because we’ve hit a couple of records in a few areas. Every day we try something different and record all the strains and the values with fiber optics on the boat, so I make sure that I can report which areas have been loaded more highly than usual today. There are only two areas today which is quite good.

Can you tell me what those areas are?


GB: The mainbeam starboard--we’re keeping an eye on the fibers in one of the main beams, and there’s an area on one of the boards which today has reached a higher level than before, so we’re going to look carefully at that also, in addition to the standard checks that we do. The shore team has a set of checks that they do post-sailing, and they’ll go on the boat and check those areas more carefully.

Are you able to “see” any issues that may be occurring on the boat as you’re following on the chase boat?


GB: We work on several levels; one is that you can visually look and see that the boat is going fast and the team is developing new maneuvers and racing techniques. The other level is that you can check on the computer from the boat instruments how fast they are going, how much wind, what angle they’re sailing, etc. The final level is ... if we get too close to anything we’re going to get an alarm warning if we reached a certain level. We also reference all the records we have achieved, like the highest levels we have reached with certain loads. We load test the boat before she goes in the water, then we do another load test in the water. So that’s what I’m doing: monitoring loads while we’re sailing.

Have you seen changes in the structure over the 33 days that your second boat has been on the water?


GB: No, the structure has stayed the same. The only change is the way that we sail it, the maneuvers we do. They’re like kids--you have to keep an eye on them every single second because to prevent a failure, even to anticipatem we need to visually see, then we discuss the maneuvers the guys are doing. Then we have a much better understanding when we look at the data. It’s a high priority, but we only have one thing left to do ... win some races.

What is a fiber optic load sensor and how are you using them?


GB: It’s a fiber made of glass not much thicker than a hair that transmits light. Little grooves are made in th epoxy, and the fibers are dropped into those grooves--the same as is used in telecommunications. The fiber is embedded in the laminate all over the boat: in the rigging, the daggerboards, etc. If you stretch or compress certain areas, a certain amount of light transmits through the fibers which provide us with data on how much stretch or strain has occurred. We spend all our time monitoring how much everything is stretching, whether it's rigging, or laminate on the boat, or the daggerboards or rudders--how much they are bending.

How do you monitor its behavior within the structure?


GB: There are things called interrogators which can handle about 40 channels each, and they send light through these cables. At each point where we want to know what’s happening--it’s only sensitive at a given point, every 2 meters or 1 meter or 250 mm, they are manufactured for us to the specs that we want--at that point it stretches and the light will go faster through that part of the fiber. Therefore we know how much force there is on the laminate at that point. There is a computer in each hull, and we see the data via WiFi. Then we download it when we get back to shore. It’s pretty cool actually to see the boat highlighted and everything that is happening. We initially used to go on the boat to try to look at the data, but it's nearly impossible with the spray; then the iPads go haywire and you have no screen! So we watch from the chaseboats instead, see the data, and talk to the guys on the radio.

 How long have you been using this?


GB: This is new for ETNZ, and it’s our first time using it as a primary active system. It’s typically used for very specialized testing. It’s not that commonly used as it's very delicate and complicated.

How were you previously managing the observation and monitoring of structural issues?


GB: A more old-fashioned but still more reliable electrical resistance system called strain gauges. They’re embedded into systems called load cells which are everywhere. Fiber optic supplements the load cells and the pressure sensors. There’s a lot of hydraulics on these boats (most of the controls on these boats are hydraulic)--all the hydraulics have pressure sensors so you can measure the pressure and therefore understand the force.

What’s the procedure if something looks suspicious while you’re out on the boat?


GB: We call them on the boat and discuss what we’re seeing if the loads are unusual. The boat gets synced to a thing called the blueprint: a number of standard settings. They don’t improvise, they sail by the numbers, and they can see the loads on board through all the load cells I’ve described. They do most of their adjustments against those load cells. They are very load conscious on the boat.

What’s been the advantage of the fiber optic system?


GB: We have more detailed information about what is happening. It’s actually a lot more to worry about! The more information you have, the more concerns you have.

How’s your speed out there?


GB: I think we’re building up to the regatta. Right now we’re focusing on venue development, understanding the venue--it’s very tricky to sail here--and of course skill practicing. There’s never enough time to practice enough and perfect all the maneuvers, meantime the boat has to hold together. We’re going faster all the time and trying new tricks all the time. Each time is a new experience.

Your thoughts on multihulls/AC72s in the America’s Cup?


GB: They’re a significant challenge engineering and design-wise. We’re not doing this because we like working on it, it’s what we're told to do if we want to challenge for the America’s Cup. I don’t mind them--they’re interesting, but they’re certainly not practical. Technologically challenging, and generally speaking, totally impractical!

* As published: http://www.sailingworld.com/blogs/racing/americas-cup/designing-a-lean-mean-machine?page=0,0