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

At exactly 00:01 on the 29th January 2015, TeamVestas?' VO65 left VTE - Voltri Terminal Europa en route to Persico Marine in the foothills of the Italian Alps. The boat is now safely secured in a purpose-built facility near Bergamo, awaiting full assessment and the beginning of the repair process. ... [more]  

ISAF Sailing World Cup Miami Day 3 - There's a world of difference between skiing a long, smooth run and skiing on moguls. Today, forget the waves, it was the breeze on Biscayne Bay that was 'moguls.' Shift upon shift upon shift upon shift. ... [more]  

Ioannis Mitakis (GRE), the 2012 Finn European Champion, ruled the roost in Miami today with two emphatic race wins and moves up to third overall. Giles Scott (GBR) sailed his worst day so far, but still leads with a five point gap on Jake Lilley, and 12 points over Mitakis as the event reaches its half way stage. ... [more]  

The International DN Ice Yacht World and North American Championships are being held in Kingston, Ontario (right in front of our office). For the Kingston Yacht Club, we skated out to the middle of the lake, and put together a little highlight piece for them to remember the event by. ... [more]  

Doyle Sails had more success last weekend in the Auckland Optimist Championships, taking first and second overall in the 110 strong Open fleet. Six countries were represented in the event, and young sailors came the length of New Zealand to compete in the regatta that is a ranking event for World and International team selection. ... [more]  

EFG's Star Winter Series rules in Biscayne Bay by Connie Bischoff, Miami, FL
The third Star Winter Series presented by EFG (SWS) and hosted by Miami’s Biscayne Bay was a shining success. Not only have all five regattas had stronger participation than last year but the final one, the Mid Winters, grew 35% with 45% of the sailors international (CAN, SWE, BRA, UKR, ARG, ITA and GER). ... [more]  

2015 ISAF Sailing World Cup Miami - Day 3 photos provided by Ocean Images. ... [more]  

Day 3 of ISAF Sailing World Cup Miami, Presented by Sunbrella marked the midpoint of North America’s biggest Olympic and Paralympic classes regatta. With bright sunshine and fresh breeze in abundance, the world’s top athletes in 13 classes were treated to the conditions that exemplify why Miami is a preferred international sailing destination. ... [more]  

It was windshift upon windshift upon shift upon windshift on Day 3 of the ISAF World Sailing Cup Miami sailed on Biscayne Bay Presented by Sunbrella, the premier regatta has attracted 599 boats and 768 sailors who were adjusting all day to one thing or another. If it wasn't the wind direction that was changing, it was the wind speed. ... [more]  

Following the success of the Mount Gay Round Barbados Race Series that concluded last week, the dates of next year’s event have been confirmed for 16-24 January 2016. With overseas competitors from 11 nations represented a large part of the 47-strong fleet overall at the 2015 event ... [more]  

Ben Ainslie Racing, the British Challenger for the 35th America's Cup, have shipped two foiling Nacra 20 catamarans to Bermuda and have become the first team to commence sailing operations at the Venue for the next Cup. The team conducted an initial training camp in Bermuda, last week. ... [more]  

North U kicked off its 2015 season of youth match racing clinics around the U.S. with a successful clinic hosted by the Texas Corinthian Yacht Club in Kemah, Texas on Galveston Bay near Houston. Forty high school and college sailors spent two-and-a-half days learning about match racing and training in Sonars on flat water and 6-12 knots of breeze. ... [more]  

A fantastic week of sunshine, warm weather, big breeze and competitive sailing is what sailors were treated to last week in Key West. Several Canadians left the bitter cold of the north to partake in the fun filled week and a few even brought home trophies. Here's a peek at the fun in the sun! ... [more]  

At ISAF Sailing World Cup Miami, presented by Sunbrella, if the Chamber of Commerce had stayed up all night working at it, they could not have served up a better day for racing. ... [more]  

On day 2 of ISAF Sailing World Cup Miami, Presented by Sunbrella, the rainstorms of yesterday vanished but the excellent wind conditions remained in place on Biscayne Bay. A more conventional day of racing saw US Sailing Team Sperry athletes finish the day in the top 10 in 5 Olympic classes and 2 Paralympic classes. ... [more]  

Bringing Dragon Sailors from around the world to Antigua. Harmony Hall Yacht Club, with the support of the Antigua Yacht Club Marina and the Inn at English Harbour, will host the second Annual Antigua Dragon Yacht Club Challenge with nine races scheduled to take place over five days in fantastic Caribbean conditions on identical Petticrow Dragons. ... [more]  

There are so many ways that the Dongfeng Race Team could have lost the chance to win the light-air marathon from Abu Dhabi to Sanya in China. Leading from the first 24 hours to the finish, 23 and a half days later, 5,403 nautical miles sailed and eight different gulfs, oceans and seas, is not necessarily the most advisable way to try and take the spoils. ... [more]  

Sydney photographer, Michael Chittenden was on Sydney harbour last Sunday and captured these images from Race 4 of the NSW 18ft Skiff Championships ... [more]  

New Zealand short-handed sailor, Conrad Colman is on his second two handed round the world race, this time aboard the Spirit of Hungary with Nandor Fa sailing in the Barcelona Round the World Race: I had noticed a couple of chafing zones on the mainsail so I prepared some patches and the Dr. Sails flexible epoxy glue so we could drop the main quickly ... [more]  

2015 ISAF Sailing World Cup Miami- Photos provided by Ocean Images. ... [more]  

Photographer Ingrid Abery was on the water at 2015 ISAF Sailing World Cup Miami and provided this gallery of images. ... [more]  

2015 ISAF Sailing World Cup Miami - It may have been a day late for Australia Day, but on the second day at the Sailing World Cup Miami, the Australian Finn sailors were on a charge with some sparkling performances. Giles Scott (GBR) still leads after winning the opening race of the day, while Jake Lilley (AUS) won the second and moved up to second overall. Ed Wright (GBR) is in third. ... [more]  

2015 Pineapple Cup – Montego Bay Race is set to begin Friday, February 6. The 32nd edition of the venerable Pineapple Cup – Montego Bay Race will start in Port Everglades, Florida, and send its 12-boat fleet on a challenging 811 nautical mile course to Montego Bay, Jamaica. George Sakellaris’s (Framingham, Mass.) 72-foot Shockwave will be the largest boat competing, so it should be interesting to ... [more]  

VX One momentum is growing with ever larger fleets showing the pure fun and easy performance of this true thoroughbred one design. ... [more]  

Last Friday, former Oracle Team USA team member, Matthew Mitchell issued a media release stating that he has lodged a complaint with the International Sailing Federation over the actions of a fellow crew member, Simeon Tienpont, and inaction by the International Jury for the 34th America's Cup, in San Francisco. ... [more]  

Volvo Ocean Race: A warm and colorful welcome for Team SCA into Sanya by Richard Gladwell/Sail-World.com NZL, Auckland, NZ
The all-female crew, Team SCA, arrived to a warm and colorful welcome including fireworks, Chinese dragons, orchid garlands and traditional costumes into the city of Sanya on Hainan Island in southern China early Tuesday evening (local time). 'It was a really different leg. I wouldn’t say it was hard in terms of the physical side but it just had lots of things coming at all angles ... [more]  

Touch2Play had the great fortune of participating in what would be the largest yet gathering of J88’s to date. Quantum Key West Race Week would serve as a chance to see how boats lined up against one another in conditions that covered the full range. For this event we had Rob and Sandy Butler, Steve Leibel, Keven Piper, Coleen Walsh and myself, Larry Huibers. ... [more]  

As the Barcelona World Race leaders race to the Crozet Islands, once again their paths have diverged – Neutrogena around 200 miles to the south-west of first-placed Cheminées Poujoulat on the water, and gaining around 40 miles in the past 24 hours. ... [more]  

For the Tokyo 2020 Paralympic Games the International Paralympic Committee (IPC) will announce on Saturday (31 January) at 10:00 CET the final line-up of sports. ... [more]  

On a high octane first day of the ISAF Sailing World Cup Miami on Monday (26 January) Giles Scott, Alison Young and the Paralympian Sonar trio of John Robertson, Hannah Stodel and Steve Thomas saw the best possible start to their 2015 sailing seasons with double race victories. ... [more]  

On the opening day of racing at ISAF Sailing World Cup Miami, presented by Sunbrella, it was sunny and bright. It was storming and raining sideways. It was sunny and bright. ... [more]  

On the opening day of racing at ISAF Sailing World Cup Miami, presented by Sunbrella, it was sunny and bright. It was storming and raining sideways. It was sunny and bright. ... [more]  

RC44 World Championship Leg 1 gets underway on 24th March until 29th March 2015. The RC 44 Class is unlike any 40 foot sailing yacht ever designed, and the reason for that is simple. She is a high performance one design yacht created for top level racing in international regattas. If one was to compare this concept to racing cars, then we would be talking about the F1, NASCAR or similar. ... [more]  

ISAF Sailing World Cup Miami - US Sailing Team Day 1
ISAF Sailing World Cup Miami -Finn class -testing conditions on Day 1
ISAF Olympic classes regatta Miami 2015 images by Ingrid Abery
Volvo Ocean Race: Team Alvimedica wins first podium place in Sanya
Volvo Ocean Race: Dongfeng scores historic victory for China
Volvo Ocean Race: Dongfeng release first DroneCam video from Leg 3
Volvo Ocean Race: Chinese team set historic first with home port win
Volvo Ocean Race: Team Vestas Wind arrives on time in Genoa + Video
America's Cup - Virgin considers backing Ben Ainslie, BAR
Bell's Beer Bayview Mackinac Race - Changes
Alpari World Match Racing Tour - Monsoon Cup preview
Barcelona World Race - A game of chase
Quantum Key West Race Week: Four GC32's make spectacular USA debut
Volvo Ocean Race – Frostad says Caudrelier proving them wrong *Feature
Volvo Ocean Race - Last day drag race to Sanya
Volvo Ocean Race Leg 3 - Tense onboard Abu Dhabi Ocean Racing
Volvo Ocean Race Leg 3 - Dongfeng Race Team pushing hard!
Volvo Ocean Race: Leg 3 Finish - Video - Delayed feed
2015 ISAF Sailing World Cup Miami - Countdown begins
Volvo Ocean Race: Donfeng set to create a piece of sailing history
Barcelona World Race - First of the iconic Great Capes has been passed   
Classic 18fters racing on Sydney Harbour   
Volvo Ocean Race - Can Dongfeng still hang on for a Sanya win??   
Stephanie Roble, 2014 Rolex Yachtswoman of the Year   
Barcelona World Race - Taking advantage   
Oakcliff Awarded Joe Prosser Award at US Sailing NSPS 2015   
20 Nations head for 2015 St.Maarten Heineken Regatta   
Volvo Ocean Race - Less than 500 miles to go   
2015 Quantum Key West Race Week - Fantastic finish   
Barcelona World Race: Weather beacons launched midrace   
2015 Quantum Key West Race Week - Day 5   
Mount Gay Round Barbados Race – Gala prizegiving marks end of event   
2015 Quantum Key West Race Week - Day 5 images by Ingrid Abery   
Volvo Ocean Race Leader - Dongfeng - the right place at the right time   
ISAF Youth Match Racing World Championship - Notice Of Race online   
Volvo Ocean Race: Changes to Team Vestas Wind crew   
McDougall+McConaghy Moth Worlds: Highlight video released   
America's Cup: Oracle crew mate lodges complaint against Tienpont   
2015 Quantum Key West Race Week - Day 4 images by Ingrid Abery   
2015 ISAF Sailing World Cup Miami - US Sailing Team preview   


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