5/4/2012
Editor’s Note: “Racing brings on head-scratching innovation,” said Peter Harken when asked about Harken’s long involvement in the America’s Cup. Read Ethan Brown’s article as he traces the development of the TTR AirBlock®—from the design team’s first “good idea” tested in the 2003 AC, to an award-winning block used by Grand-Prix racers, to the TTR technology found in Harken’s Black Magic® Big Boat line.
During our hardware development program for the 2003 America’s Cup, Harken Senior Engineer Chuck Lob designed the Super Sheave, which used high-strength stainless steel roller bearings with a stainless steel inner and outer race. This sheave could fit into our titanium ULC II (the state-of- the-art block for that Cup). More than one Super Sheave logged time on an AC boat, but the sheave was quite heavy and the outer race didn’t stay put in the sheave. These prototypes came back and sat in a box for a few years.
 The Super Sheave— stainless steel roller bearing/stainless steel inner and outer race. |
In late 2003, I began developing blocks for the TP52 class using a high-strength loop to handle the load-bearing portion of the block. This allowed me to save weight by replacing metal with cordage. In late summer of 2004, Engineering Manager Steve Orlebeke designed our first 2007 America’s Cup block. Based on a related "loop block" concept, he used the same well tested and reliable bearing system we had used for the past three America’s Cup cycles, but as usual we weren’t satisfied repackaging the "old" technology.
Despite its faults, the Super Sheave bearing set made the most efficient block we had ever seen at those loads. It was more efficient than the ULC II, or the more refined ULC blocks we were developing in 2005. Its biggest downfall was weight, a problem that the loop block concept was well-suited to address. The Harken engineering team also found solutions for other issues, including a coating to prevent the high-strength stainless from rusting in the marine environment.
THE BLOCKS
The SSR Loop
In late November 2005, I began playing with an idea that put the Super Sheave bearing into a loop block package. This became the SSR (Stainless Steel Roller) Loop block. The first SSRs were installed on an America's Cup boat in early 2006. As one would expect with a prototype, all was not champagne and roses. The blocks developed chafe points which had not been a problem during Harken’s in-house testing. Although our test lab is an extremely valuable tool, there is no substitute for on-the-water testing, with feedback from the AC teams a critical part of the process. Back at the lab, our testing showed that the bearing set was so efficient we could reduce the sheave diameter while maintaining efficiency of about ninety-eight percent. The reduced sheave made the whole block smaller, which, in turn, saved weight. However, the protective coating proved imperfect at inhibiting corrosion while adding cost and lead time, and the weight was higher than we wanted.
 The TTR—Titanium Alloy |
The TTR Loop
Further research into materials found we could use a titanium alloy instead of stainless steel and still maintain almost the same efficiency numbers. Our feedback from the teams led to improving the interface between the inner race and the cheeks and a refinement of the cheek geometry. Concurrently, we made adjustments to the bearing geometry. The titanium was the final piece of the puzzle. This made the Harken TTR Loop blocks smaller, lighter, and more efficient than the state of the art blocks we had used for the AC four years prior.
THE LINE
At the end of the 2007 America’s Cup, we only had two versions of the TTR block— the 5 tonne version was used at the mastbase and for spinnaker sheets, and the 8 tonne version was used for mainsheets and lower runners.It is a testament to the versatility of the loop block concept that In the spring of 2007, the J/V IRC 66 Numbers asked for a 6.5 tonne and a wide 5 tonne version. This gave us the opportunity to begin fleshing out the line. Later that year Numbers became the first boat outside of the America's Cup to have TTRs.
VOLVO 70 Class
 Volvo 70 PUMA |
The next demand for development came from the Volvo 70 class. the TTR bearings had shrugged off the high-load environment of the America's Cup, but longevity had not been a design priority, so our first response was to return to the test stand. After thousands of cycles at high loads, we were confident that TTR bearings could make it around the world. However, the extreme environment on a Volvo 70 uncovered new problems, specifically with the wide blocks. This sent us scrambling to make the wide sheave as stable as the narrow, and also to provide enough room to pass a changing sheet with a splice.
We went through several redesigns, before we had a complete solution. We revised the line groove to get the proper balance between a stable sheave and one in which the load can transfer between the original sheet and the changing sheet. The rollers were also tailored to the wide blocks. Finally, a longer cheek provided plenty of room for the extra sheets, and actually helped with the overall stability.
 Maxi Yacht SPEEDBOAT |
Banque Populaire 5 & SPEEDBOAT
The next challenge came on two fronts – one was the 130 ft (40 m) G-class trimaran Banque Populaire 5, the other was the over-grown Volvo-style 100 ft (30 m) Maxi Speedboat. Until the fall of 2007, we hadn’t made a TTR with a Maximum Working Load over 8 tonnes, and both of these boats would need blocks with MWL’s of up to 15 tonnes—a significant leap.
Perpetuating a fine tradition started by our fearless leaders, the Harken brothers, we said we could do it and then set about figuring out how. Fortunately the concept scales up quite well. Here again the loop block proved its flexibility as it allowed us to design a single block for each MWL of 10, 12, and 15 tonnes. With these few additions to the line, we were able to provide complete packages to both of these incredibly different boats.
Acceptance Beyond America's Cup
Our original path when developing the next-generation AC block focused on making the most efficient block, without regard for cost, and accepting that weight had to be a secondary priority. However, we were pleased to discover that the cost of the TTR blocks is not dramatically more than the ULC II Titanium blocks, and the weights are actually less for the same Maximum Working Load. This is for a variety of related reasons— the smaller sheaves use less material, the versatility of the loop block allows our quantities to be a bit higher, allowing some economies of scale, and making cheeks out of aluminum instead of titanium is certainly a benefit. As a result, the TTR line has found acceptance well beyond the America's Cup, which is quite rewarding. With this application of AC technology to many Grand Prix race boats, we continue to fill out the TTR line.
Trickle Down
The lessons learned from TTR development have been directly applied to our new Black Magic® Loop block line. The basic attachment concept is the same, with the loop going through the middle of the sheave, allowing us to save weight and get the most out of the loop attachment method. The cheek geometry is also similar, but we have added a pin at the center so that a continuous loop can be used to attach Black Magic® Loop blocks to the boat. Because of this added versatility, the Harken block available at your local chandlery is a small step ahead of the state-of-the-art blocks used by Grand Prix boats around the world.
