sail-world.com
 
 
News Home Cruising Photo Gallery Video Gallery
Sail-World.com : America's Cup: Ex-Oracle design chief looks at the Class of 2013
America's Cup: Ex-Oracle design chief looks at the Class of 2013

'Emirates Team New Zealand. shows the Y-structure used to support loads on their AC72'    Chris Cameron/ETNZ©    Click Here to view large photo

Mike Drummond has been involved in the design side of four winning America's Cup campaigns, starting with then Team New Zealand in 1987-2003, before joining Alinghi in 2007 and latterly was the Design Director for Oracle Racing in the 2010 America's Cup, and heavily involved in the development of the wingsailed 120ft trimaran USA-17.

That America's Cup regatta was his second Deed of Gift Match (sailed between just a single Defender and Challenger under the terms set out in the 19th century Deed of Gift which governs the America's Cup), Drummond was also involved in the design of the Big Boat for Sir Michael Fay, in the 1988 America's Cup.

Mike Drummond, NZ, former Technical Director, Oracle Racing -  MIAA   Click Here to view large photo
He was admitted to the America's Cup Hall of Fame in 2010 in recognition for his achievements in design.

Drummond left Oracle Racing to pursue other interests, during the current America's Cup cycle. He's also an excellent catamaran sailor in his own right, with several top performances in the singlehanded A-class catamarans and two handed one design catamarans.

Sail-World caught up with Drummond and asked his overall impression of the four designs currently working up towards the 2013 America's Cup regatta.

'From the design point of view there are three and a half groups,' he counters. 'Emirates Team NZ and Prada look like they have identical hulls and wingsails, but with different foils.'

'Overall I think Emirates Team NZ has a good, straight forward, conservative boat with lots of volume, and a well proven structural arrangement. The wingsail is straight out of a C-class evolution. They have correctly focused on foil over wing development.'

'Although they have added fairings, it looks like Emirates Team NZ still have a high windage platform - with their centre spine and rigging and so forth. That is not critical at this stage, but it’s a safe assumption their second boat will be similar, so there is a limit to the amount of drag reduction they can achieve.

The flip side is they’ve had a good robust package where they have been able to go sailing from Day 1 and learn about this new class of yacht which they can then feed into their second boat eventually.'

'These boats are very high speed and high on apparent windspeeds. Their windage as a proportion of their total drag is much higher than in monohulls and so it needs to be a higher priority in the design'

Emirates Team NZ first AC72 has a much higher drag from her support structure than Oracle Team USA’s cleaner approach with the use of the pod -  Chris Cameron-ETNZ©   Click Here to view large photo
He expands to say that the windage issue is not just turbulence around the rigging and the platform (multihull-speak for the combination of hulls, beams and decking) but also relates to aerodynamic efficiency. There is a very large gap between the Emirates Team NZ wing and the surface of the water (which Oracle Team USA have resolved somewhat with their central pod structure which forms an 'extension' to their wingsail and improves the effective span below the platform.)

'In light airs that drag and inefficiency is very large - of the order of 5% compared with a perfect seal - which is close to 5% of boat speed. The drag percentage reduces in strong winds but there is still a gap ', he adds.

Hence Oracle’s solution with a centre pod doing double duty as a structural member and forming a solid aero barrier, together with a horizontal deck surface. The effect is that Oracle is able to carry the lift from the wingsail much closer to the water surface. Beyond that Drummond wouldn't discuss further specifics of the pod or how it was designed to work.

Efficiency over structural stiffness

Emirates Team NZ and Oracle Team USA have taken quite different approaches in their first AC72's.

'Oracle has gone for an emphasis on the high efficiency and the greater speed potential. The tradeoff is in the structure. The class rule has a maximum weight and even lightweight fairings weigh something, so you can’t just add laminate without reducing material elsewhere'

Emirates Team NZ have opted for a Y-type structure (with two tubes running aft forming the top of the 'Y' and joining at the mast with a center spine which is also the prod, or sprit, running forward). Drummond explains that this Y-structure, similar to that first used by the 40’ Alinghi cat and later the 120ft Alinghi 5 catamaran in the 2010 America's Cup, is very stiff in torsion.

'Oracle dispense with that, so that the torsion is carried from the windward hull to the leeward hull through the twisting of the cross beams. The Oracle beams are much smaller in section and materials in torsion are less stiff than materials in tension or compression.

'Simplistically, Oracle's twist is coming from the fact that windward shroud has more load than the leeward shroud because it is supporting the wing and sails. That windward shroud is aft in the boat because it has to provide forestay tension. That offset results in twisting the beams.

'Everything deflects under load.'

Oracle Team USA showing platform twist, with the windward hull being pulled up at its after end by the force from the sidestay. Her approach to cleaning up under platform structure drag is clearly visible. -  Guilain Grenier-Oracle Racing©   Click Here to view large photo
Drummond's view is that the platform twist, which is a notable feature of Oracle's AC72 is stemming from the design choice made in the structure to support and distribute the rig loads into USA-17's platform. Oracle have decided to accept a less stiff structure to achieve lower aerodynamic drag.

'That is primarily where Oracle's twist is coming from. Emirates Team NZ will twist as well, of course, but that Y-structure has the loads being transferred by a structure that is in tension and compression rather than being one of torsion, which Oracle are running.

'Also on the Emirates Team NZ AC72, the truss-type structure naturally has a shorter path between the load points, whereas Oracle’s load path is longer and indirect going along the hull and then along the beam from shroud to mast step.

As the boat starts to heel the load difference between windward and leeward shrouds rockets up until the windward hull is clear of the water – when righting moment is maximum – thereafter the shroud loads don’t change very much. 'As soon as you start flying a hull, you begin twisting your platform, and when you are flying a hull the twist should be nearly constant. The boat winds itself up, but stays fairly constant in that wound state', he adds.
'There is some issue with the wings on the rudder, as to whether they are in the water or out of it. That is something for the designers and sailors to figure out - and get the right balance of heel angle or pitch angle of the winglet, and then just set up to that mark.

'Any load on the windward hull eventually gets reacted to by the leeward hull. If the windward hull is moving, the only thing causing that hull to move would be the load on the windward shroud.'

Drummond goes on to explain that if the load on the windward shroud is changing, then that can only be caused by changing aerodynamic forces from the wingsail being transmitted down the windward shroud, and into the after end of the windward hull which twists upwards in response.

Addressing platform twist

Drummond believes Oracle Team USA’s foils are of sufficient size to support sustained foiling -  Guilain Grenier Oracle Team USA©   Click Here to view large photo
Turning to the twisting forces on the leeward hull, Drummond says 'the leeward hull is reacting to water loads, such as buoyancy and foil forces. If you hit a wave - that wave is trying to pitch the bow up, or a change of angle of attack on your board, that will lift or drop the hull. Those loads will still get reacted through the windward hull.

'You would expect to see the windward hull follow the leeward hull, but there will be an inertial lag because the wing and windward have mass, so the crossbeams wind up a little bit before the windward hull moves.

'From what I have seen of the movements and the loads, I think that everything is coming from the leeward hull, and you see that in the behavior of the windward hull.

'I don’t think the windward rudder going in and out of the water has any significant effect on the platform structurally, but it must have a greater effect on the foiling balance and behavior.'

Of the 'three and a half' designs seen so far in the build up to the 2013 America's Cup, two seem to be foiling successfully, with the other two, not foiling at all, or having unstable flight.

So far, Luna Rossa and Emirates Team New Zealand are foiling very easily, but Drummond's view is that none of the teams are certain to the degree to which they are going to foil.

Artemis look like a semi-foiling boat – their boards and lack of rudder elevators mean they can’t fully fly. They can improve with new foils and large elevators but I don’t know how far they can go. Overall they seem to have emphasized wing development.

Luna Rossa and Emirates Team NZ seem to be able to fly at will -  Luna Rossa Challenge 2013  
'Oracle are expecting to fully fly but have a different solution to Emirates Team NZ in the fore/aft position of the boards as well as the foil design. Emirates Team NZ have found a stable foil design and my guess is this has allowed them to place the board further aft.

'When they launched no one would have been completely sure about how much time they would be foiling. It is mostly be dependent on boatspeed – upwind there will be less foil loading in all windspeeds, and downwind in light airs. The crossovers are what everyone is trying to find out, at present. Because multihulls get very little dynamic lift from the skinny hulls the wetted area drag is very significant at high speed, so foiling is essential to improve top end speed.

'They all know they will be foiling to some degree, whether that is 70% of the weight of the boat is on the foil, and 30% is by hull displacement, or 100% is on foils.

'The aim has always been to 100% foil, but it is hard to manage without a control system. And you can foil at much lower speeds by having more pitch angle and more camber and more area on your foils. But the big question is 'is it faster?'

Drummond estimates that the critical speed to achieve foiling flight is around 18-20knts of boatspeed, but he stresses that is only a guess. In windspeed terms, and given that an AC72 will sail at around double the actual windspeed. It means that downwind foiling should be possible in 9kts of breeze or more, but upwind it would take substantially more wind to achieve the almost 20kts of boatspeed necessary to lift up onto the foils.

The question of upwind foiling in the AC72, while spectacular is not necessarily efficient in terms of getting upwind to the next mark as quickly as possible.

'On the AC72, you have this long slender hull which doesn't displace very much. Below 20kts it is very hard to beat that hull shape for drag. These boats are very efficient.

'When you are sailing at speeds over 25kts, that is when it really pays to get rid of wetted surface area', he explains.

Artemis Racing shows the long slim hulls of the AC72, foiling is really only beneficial above 20kts of boat speed -  Sander van der Borch_- Artemis Racing ©   Click Here to view large photo


In Part 2 - to be published tomorrow, we cover the trade-off with foiling and second generation AC72 issues and options, and Oracle's capsize.


by Richard Gladwell

  

Click on the FB Like link to post this story to your FB wall

http://www.sail-world.com/index.cfm?nid=105594

2:16 AM Tue 15 Jan 2013GMT


Click here for printer friendly version
Click here to send us feedback or comments about this story.

Click for further information on
2013 America's Cup

Related News Stories:

15 Jan 2013  America's Cup: First look at Emirates Team NZ's second AC72 + Video
13 Jan 2013  America's Cup Discovered: Episode 72 - Passion to Excel
11 Jan 2013  American Youth Sailing Force ready for battle at Youth America's Cup
11 Jan 2013  America's Cup: Emirates Team NZ and Luna Rossa '45ing + Video
10 Jan 2013  America's Cup: Luna Rossa skipper updates from Auckland
10 Jan 2013  America's Cup: Luna Rossa crew return to Auckland for final training
09 Jan 2013  America's Cup: Oracle Team USA's second wingsail arrives in San Fran
09 Jan 2013  America's Cup: Top designer still rates Oracle's chances of success
09 Jan 2013  America’s Cup Event Authority announces focus on 'Summer of Sailing'
09 Jan 2013  America's Cup: US events in America's Cup World Series cancelled
MORE STORIES ...






News - USA and the World

Photographer Ellen Hoke was on the water at the Farr 40 Worlds sailed from the St Francis Yacht Club, San Francisco, and provided this gallery of images from the Final Day - Day 4 ... [more]  

Photographer Ellen Hoke was on the water at the Farr 40 Worlds sailed from the St Francis Yacht Club, San Francisco, and provided this gallery of images from Day 2 ... [more]  

The Chinese entry Donfeng Race Team, has lost her lead on Day 9 of the Volvo Ocean Race, with boats on the east and western side of the course threatening. Two hours before the most recent sked at 0640hrs UTC, Dongfeng was still being listed by Volvo Ocean Race as the leader. But Team Brunel is now listed as the leader, but on a time taken projection basis, Team Brunel is fifth. ... [more]  

The 70th running of the Cruising Yacht Club of Australia’s annual Rolex Sydney Hobart Yacht Race is living up to expectation with 98 high-calibre entries received so far, from Sean Langman’s 1932 built Maluka of Kermandie, the oldest and smallest boat at nine metres, to the super maxis. The most talked about boat though, is the Verdier Yacht Design and Vplp 100 footer, Comanche. ... [more]  

Volvo Ocean Race: Dongfeng consolidates lead on Day 8 *Feature by Richard Gladwell, Sail-World.com/nz
After cutting between the Cape Verde islands, separating from the rest of the Volvo Ocean Race fleet, Chinese entry, Dongfeng gained an initial significant lead, which they are in the process of consolidating. One routing option for the then race leader Abu Dhabi Ocean Racing, gave the team the option of cutting inside the island group, they are close to the optimum course for Fernando off Brazil ... [more]  

Thailand bids for 2016 IODA ‘Optimist’ World Championships by Jordan Rumsby, Royal Varuna Yacht Club
Pattaya's Royal Varuna Yacht Club has submitted a bid to host the 2016 International Optimist Dinghy Association World Championships, offering the world's most talented junior sailing teams a chance to experience the steady wind, sunshine, smiles, great food, and family-friendly attractions of Thailand's top dinghy sailing destination ... [more]  

Photographer Ellen Hoke was on the water at the Farr 40 Worlds sailed from the St Francis Yacht Club, San Francisco, and provided this second gallery of images from the Final Day - Day 4 Prizegiving ... [more]  

Bill Green - builder and sailor passes on by Malcolm McKeag, Scuttlebutt Europe
Bill Green, San Francisco-born sailor, Navy jet jockey (not a lot of people know that); US Coastguard; shrimp-boat hand (not a lot of people know that either); One Ton Cup winner and most latterly proprietor of Green Marine slipped quietly away from this life ... [more]  

Tom Burton (AUS) retained World #1 in the Laser after a tremendous fight back at ISAF Sailing World Cup Qingdao where he picked up bronze. The Australia had a tough opening day, finishing down the pack in both races but as the week progressed he worked his way up and sealed bronze on the final day to keep hold of World #1. ... [more]  

34th Student Yachting World Cup - France knew today its best day since the beginning of the competition. They spent the two races at the very first positions, even rivaling with the ultra-dominant English team. They showed today an astounding panache, and can now hope to improve their ranking before the end of the SYWoC. ... [more]  

Volvo Ocean Race: Blogs from the Boats - Leg 1, Day 8 plus Videos *Feature by Richard Gladwell/Sail-World.nz/com
Several of the On Board Reporters aboard, provide their unique views of Leg 1, Day 8 of the Volvo Ocean Race - in text, images and video. Catch a birthday at sea on board Team Brunel, and unravel the fishing net with Team SCA Hear and see how the crews coped with the front that came through in the nigh ... [more]  

Shala Youngerman and her team from Southwestern Yacht Club won the 23rd annual Linda Elias Memorial Women’s One-Design Challenge Sunday in this two-day fleet race regatta organized and sponsored by the Long Beach/Los Angeles Women’s Sailing Association and hosted by Long Beach Yacht Club. ... [more]  

After three days of racing in the Valparaíso bay, the Santander team was crowned champion of the Off Valparaíso Race, first stage of the Soto 40 South American Tour that was held in the Yacht Club de Chile with the participation of eight boats. ... [more]  

RS:X Youth World Championships - All set for Clearwater action by RS:X Olympic Windsurfing Class Association
Mild, breezy weather, temperate Gulf of Mexico waters and wide bands of sugar white sand - this is the place where 2014 RS:X Youth World Windsurfing Championship racing is about to start. 'Clearwater Beach is the perfect spot to play host to the young windsurfers gathering here from around the world for international competition', says Frank Chivas. ... [more]  

The first 24 hours of the Rolex Middle Sea Race has seen the fleet progress slowly up the eastern seaboard of Sicily towards the Strait of Messina. By 16.00 on day two, a mere ten per cent of the competition had passed through the Strait and started the leg to Stromboli, where they will turn west towards the Egadi Islands. ... [more]  

Volvo Ocean Race 2014-15 - If only it were that easy. Amazingly we did manage to replace the rudder and regain first position amongst the fleet however just hours afterwards, navigator Pascal Bidégorry was faced with an important strategic decision. ... [more]  

Ian Moore, navigator on Cookson 50, Mascalzone Latino, is no stranger to the Rolex Middle Sea Race, this is his fourth and Ian was part of the winning crew on Bryon Ehrhart's TP52, Lucky in 2010. Ian describes the tactical nuances of the first night at sea. ... [more]  

Top videographer and photographer, John Navas, was on the water for the final day of the Farr 40 Worlds being sailed on San Francisco. ... [more]  

The brilliant conditions of last week’s opening race of the season were duplicated today when the Australian 18 Footers League’s Major A. Frizelle Trophy race was sailed in a 20–knot North East wind on Sydney Harbour. Current JJ Giltinan champion Gotta Love It 7 team of Seve Jarvin, Sam Newton and Scott Babbage showed why they are the world’s best team. ... [more]  

Volvo Ocean Race - The fleet has finally left the West African Coast. They are now in the trade winds, making the westerly course across the Atlantic Ocean to FernandoThey will find the Cape Verde Islands in the way and that will cause some issues of navigation. ... [more]  

2014 ISAF Sailing World Cup Qingdao - It was a light wind, big wave finish at ISAF Sailing World Cup Qingdao as the medallists were decided across the six fleets competing on the waters of the Beijing 2008 Olympic Sailing Competition. ... [more]  

2014 Rolex Farr 40 World Championship - In life, timing is everything. And, after seven years in the Farr 40 class, the timing was right for New York financier Alex Roepers to achieve a long-held goal of winning the Rolex Farr 40 World Championship. ... [more]  

Watchstanders at Coast Guard Sector Hampton Roads received a report from a concerned friend at 10:30 p.m., Friday stating the two men had departed on a planned 20-minute trip, but had been gone for approximately two hours. The reporting source also stated that the men did not have radios or cell phones aboard. ... [more]  

The Soto 40 fleet that competes in the Off Valparaíso Race was able to complete only one race in a day characterized by a lack of wind. Today’s winner was Horacio Pavez’s Mitsubishi. Eduardo Souza Ramos’ Phoenix achieved a fourth position in the race and continues leading the overall, with only two points less than Jorge Araneda’s Santander. ... [more]  

Volvo Ocean Race: Welcome to Al's Ocean Cafe by Brian Carlin, Team Vestas Wind
On Board Reporter, Brian Carlin - (from Ireland, where else?) gives a quick tour of his below decks domain aboard Team Vestas Wind. As On Board Reporter, he gets to run the cafe aboard the Swedish flagged round the world racer. You don't need to have a sense of humour to sail aboard, but it certainly helps. ... [more]  

The Royal Bermuda Yacht Club has announced that the Argo Group Gold Cup is still set to sail, albeit on a compressed schedule, starting Wednesday, October 22. Using the one-day-delay plan announced last Wednesday, the Argo Group Gold Cup will be compressed to five days of racing and organizers will take advantage of the fine weather expected after Gonzalo. ... [more]  

Volvo Ocean Race: Dongfeng regains lead after incident packed Day 7 *Feature by Richard Gladwell, Sail-World.com/nz
The Chinese flagged entry, Dongfeng Race Team has regained the lead at the end of Day 7 in the Volvo Ocean Race. Course routing from Predictwind shows that the race leader is just five days away from the turning point of Fernanado, Brazil. Includes latest 'Inside Track' video ... [more]  

Uncut video of Dongfeng Race Team replacing their rudder at night, after collision with an underwater object while leading Leg of the Volvo Ocean Race. What makes the change even more remarkable was that it was undertaken at night. ... [more]  

Volvo Ocean Race - Team Alvimedica bounces back by Amory Ross, Team Alvimedica
Volvo Ocean Race 2014-15, Day Seven onboard Team Alvimedica. There’s nothing like filling the void of a difficult day with some trade wind sailing. Yesterday was a tough one: we came out on the losing end of quite a few gambles and fell far off the lead pack, but the boys have bounced back well and the mood on deck in these near-perfect conditions has returned to one of humor and laughs. ... [more]  

Volvo Ocean Race 2014-15, Day Seven onboard Team SCA. There's an age old saying: expect the unexpected. It pretty much sums up offshore sailing. However, there is also a degree of dealing with the expected. And there is a slight dance to be had-- to not be too shocked by either spectrum of a situation, and to handle all events with grace and control. ... [more]  

Thousands of spectators lined the Valletta Waterfront to witness the start of the 35th Rolex Middle Sea Race. 122 yachts started the race, a new record for the Mediterranean classic offshore race. Under blue skies and brilliant sunshine, the international fleet of yachts from 24 different countries set off on the 608 nautical mile race. ... [more]  

It was a light wind, big wave finish at ISAF Sailing World Cup Qingdao as the medallists were decided across the six fleets competing on the waters of the Beijing 2008 Olympic Sailing Competition. Byron Kokkalanis (GRE) had wrapped up gold in the Men’s RS:X the day prior but intriguing battles for gold across the remaining fleets played out in a tense day of competition. ... [more]  

At 0210 UTC in the Volvo Ocean Race, Dongfeng Race Team hit an unknown object in the Atlantic Ocean just off the coast of Africa and broke their rudder. This resulted in the team performing an emergency rudder replacement, a difficult operation in the pitch black of night, in less than two hours. ... [more]  

Volvo Ocean Race: Race closer than leaderboard suggests - Leg 1, Day 6
Volvo Ocean Race: Dongfeng Race Team break rudder after collision
2014 Rolex Farr 40 World Championship - Famous breeze frustrates
2014 Off Valparaíso Race - Day 1
Sunfish World Championship - Victory for Argentina's Francisco Renna
Volvo Ocean Race - Feeling the pressure six days in
Volvo Ocean Race - Alvimedica cautiously cruising down coast of Africa
Volvo Ocean Race - Team Brunel still within striking distance
Volvo Ocean Race - Testing times for Team SCA + Video
Beijing 2008 Olympic legacy lives on in Qingdao + Video
La Torche PWA Grand Slam - A return nearly 20 years in the making
ISAF Sailing World Cup Qingdao - Game on for remaining fleets
Farr 40 Worlds: Day 2 Image and Video gallery *Feature
Day 5 of the Chris Benz Lüderitz Speed Challenge: 4 more records!
Volvo Ocean Race: Coastal racing at its best - Leg 1, Day 5
Chris Poole new number one Open Match Racer in U.S.
Rolex Farr 40 World Champs - Plenty leads as Struntje Light impresses
2014 Soto 40 South American Tour - Back in action
Volvo Ocean Race - Mail arrival brings excitement for Team SCA + Video
Volvo Ocean Race - Jens Dolmer getting restless onboard Team Brunel
Volvo Ocean Race - Too close for comfort as fleet pushes on + Video   
Foils or not? Explanations from IMOCA Class President Jean Kerhoas   
Ben Ainslie's Olympic Finn sails are up for auction   
Volvo Ocean Race - Team Alvimedica goes to school   
Volvo Ocean Race - Intensity level rises for Dongfeng Race Team   
China Cup Regatta - Olympic medallists and offshore legends to race   
St. Barth Cata Cup - Friendly US rivalry on the Island   
ISAF Sailing World Cup Qingdao - Tight and tactical racing + Video   
Farr 40 Worlds: Day 1 Image and Video gallery   
Team Ulrikkeholm new WIM Series champion   
Podium finish in sight for top Alpari Tour teams   
Intercollegiate Offshore Regatta: A rousing success with over 50 teams   
Rolex Middle Sea Race 2014 - Taller than the Burj Khalifa   
100 foot limit raised for 2015 Rolex Fastnet Race   
2014 Rolex Middle Sea Race - Shockwave prepares for race   
2014 Rolex Farr 40 World Championship - Land of plenty   
Volvo Ocean Race: Blogs from the Boats - Leg 1, Day 4 plus Videos   
Old Pulteney, US Sailing host third Annual Maritime Heroes Award   
Argo Group Gold Cup - Hurricane Gonzalo delays start   
Volvo Ocean Race: Life at the Extreme - first episode of weekly video   


For this week's complete news stories select    Last 7 Days
   Search All News
For last month's complete news stories select    Last 30 Days
   Archive News







Sail-World.com  


















Switch Default Region to:

Social Media

Asia

Australia

Canada

Europe

New Zealand

United Kingdom


http://www.sail-world.com/event_images/image/Twitter_logo_small.png http://www.sail-world.com/event_images/image/FaceBook-icon.png  http://www.sail-world.com/event_images/image/RSS-Icon.png

United States

Cruising Northern

Cruising Southern

MarineBusiness World

PowerBoat World

FishingBoating World

 

Contact

Commercial

News

Search

Contact Us

Advertisers Information

Submit news/events

Search Stories/Text

Feedback

Advertisers Directory

Newsletter Archive

Photo Gallery

 

Banner Advertising Details

Newsletter Subscribe

Video Gallery

Policies

 

 

 

Privacy Policy

 

 


Cookie Policy

 

 



This site and its contents are © Copyright TetraMedia and/or the original author, photographer etc. All Rights Reserved.  Photographs are copyright by law.  If you wish to use or buy a photograph contact the photographer directly.
XLXL NEW US
LocalAds   DE  ES  FR  IT