Please select your home edition
Edition
Fever-Tree 728x90

Sailrocket 2 on the way to an outright world speed sailing record?

by Paul Larsen on 4 May 2011
SailRocket 2 sea trials Day 1 Vestas Sailrocket - copyright http://www.sailrocket.com
In 2008, Paul Larson and his Vestas Sailrocket was on the way to an outright speed sailing record when his craft crashed in a spectacular fashion, damaging it badly. It has been a long road back, but Vestas Sailrocket 2 has arrived in Namibia for their next challenge. The aim of the team is to beat the outright world sailing speed record.

The team currently holds the B-class (150-235 square feet of sail)speed sailing record with a speed over a 500m distance of 47.36 knots (87.71 km/h), but in 2008, before crashing, Sailrocket had reached a reported unofficial speed of 52.22 knots. (See the video the end of this article and relive the exultation with their speed achievement, watch the crash and then sympathise with Larson's devastation at his dream's destruction.)

Sailrocket 2's construction:
The revised craft was launched March 8 at an empty weight of only 275 kg/605 lb. Fabricated with materials from SP-High Modulus, the main structure is an autoclave-cured sandwich construction, comprising carbon fiber/epoxy prepreg skins over an aramid honeycomb core.

Prepregs included Gurit’s Ampreg 22, SE84LV and SE70 and some dry reinforcements. Its wing-like sail is built around a CompoTech carbon tube that acts as a spar. The wingskins are a polyester heat shrink film. According to Larsen, the entire boat, including rigging, has the equivalent aerodynamic drag of a 74 cm/30-inch diameter sphere, and its revised design enables the pilot to maneuver the craft in much rougher water than the first version could handle.

Here's the latest from Paul Larsen on progress, and see the end of the story for videos of their current testing and the spectacular crash of 2008:


Yesterday evening we had our third session of tow testing of the bare platform. It was a beautiful evening as we towed the wing-less platform up and down speed spot with the whole team taking turns in the boat and in the RIB in order to observe all aspects first hand.

We saw on our second session the day before that the addition of the first trial 'step' on the front float made a big difference to it's ability to release from the water and step up into planing mode.

The new second 'step' on the rear underside of the hull quickly ventilated from behind at speeds as low as three-four knots. This enabled the up forces on the front of the float to win the battle and start lifting the hull upwards as speed increased. This in turn allows the first original step to 'get access' to the air and also ventilate. Voila... the hull keeps lifting and we are planing.

We wanted to see this work first hand before we went and added them to all the three floats. The back float was hence still suffering and struggling to break free from the water. We tried a few other trials with foils up and down and the beam swung fore and aft before deciding to head back in.

Yesterday, we went back out with steps on all three hulls. The leeward hull is so lightly loaded without the wing on that the step really isn't necessary. I was hoping for a bigger change on the rear float. Whilst the step was an improvement, it seems that we still have a low speed where the aft float gets caught in the wave pattern generated from the front float. There is every chance that this might just be a phenomenon caused by tow testing and that the addition of the side force of the wing could break the whole 'loop' so we shouldn't get too concerned until we conduct some sailing trials.



It was interesting yesterday to watch the foil behaviour. We were typically towing at speeds around 15-17 knots. The fact is that the foil was virtually doing nothing and you could hear it rattling around in its locking mechanism rather than being forced against either the upward or downward limiters. When the foil is fully submerged when the boat is stationary, there is as much lifting area as there is downward pulling area. The effect is that when it has an angle of attack created by any side force i.e. a sail or a tow-line, the overall force is neither up or down.

You have to remember that the foils on our boats are actually pulling the boat down into the water. On most hydrofoilers the foils are there to lift the boat up and out of the water. On the Sailrocket designs, the angled/inclined wing does all the lifting and it is the foil that keeps us down. So... when we start off and the full foil is submerged, there is no 'net' down force from the foil but the wing is pulling up. As we accelerate and the wing powers up, it gradually begins to lift the boat up with it. This means that the foil rises and the top section comes out of the water only leaving the angled lower part in the water and this is the bit that does all the 'down' work. When the boat is hauling along at full steam, the back of the boat will naturally ride at the height where the up and down forces balance. If it gets 'bumped' too high then the balance will try and pull it down and visa versa.

This means we can only do so much towing the boat around without the addition of the actual sailing loads.

It sure was a beautiful evening. It was a perfect opportunity to let every other team member go for a ride. I really enjoyed seein Ben in the cockpit. It always surprised me to see boat builders spend so much time building boats only to see them go out the shed and the next set of plans come in. Surely the joy has to be in actually seeing what you have spent so long building in its element. This way you can truly appreciate what it is you are creating. It has to make the whole experience richer.

Helena was all concentration. She knows that she will have the option to pilot this machine for a record attempt at some stage... and she knows that that day may well be approaching. It's not talk anymore. What she does and how hard she pushes it is soley up to her. There will be no restrictions and if she wants to go for an outright attempt... then that will be her call. Yesterday she also got to drive it for the first time..



The only one missing was Hiskia... but he'll probably get his turn today.

The warm East wind was blowing lightly this morning which would indicate a nice but relatively windless day ahead. We will do one more session of tow testing where we will actually measure some of these loads... and then we will roll straight into the wing trials. We might be able to do both of these today if this wind settles a little so as not to corrupt the numbers.

I must admit that I am still a little concerned about the 'hump' drag. In respect to our situation, this 'hump' is the amount of drag that builds up before the boat makes the transition into 'planing' mode. You often see it in fast powerboats where they need to use a lot of power to get started but once they are up and planing on the surface of the water, they don't need so much power. This is because they have overcome this transition from low speed displacement mode to high speed planing mode. Some shapes do it better than others. We are discovering how big our 'hump' is right now and will try and use a few tricks to bend it to our will.

To follow the progress of Sailrocket 2, go to their www.sailrocket.com!website








The following video was taken during the 2008 record achievement and shows the spectacular crash:

Wildwind 2016 660x82Barz Optics - FloatersAncasta Ker 33 660x82

Related Articles

New addition to North Sail for Volvo Ocean 65 racing machines
Their sails have powered eight out of nine Volvo Ocean Race winners since 1989-90, with Steinlager 2. Instead of assembling cloth panels into a particular sail shape, the Volvo Ocean Race sails are composites. This means that 3Di material 'tapes' are laid in a specific arrangement, offering stable structure to the sail where it is needed most.
Posted on 24 Apr
America's Cup - Practising in Bermuda's Great Sound - April 23 - Video
Emirates Team New Zealand had their first solid day of training on Bermuda's Great Sound on April 23, 2017 Emirates Team NZ had their first solid day of training on Bermuda's Great Sound on April 23, 2017. Winds during the session were averaging 10kts gusting 15kts. As with the other video it is impossible to gauge boat speed, or form an accurate impression of relative speed. However the infrequency of splash down is apparent, as is the very slick gybing and tacking while remaining foil borne.
Posted on 24 Apr
America's Cup - Tech Tuesday - Why AC50's sail bow down - Video
OTUSA tactician Tom Slingsby (AUS) explains why the AC50's sail with bow down trim Why do the America's Cup Class catamarans sail with bow down trim? It's a common question. Helmsman and Tactician Tom Slingsby? provides a detailed answer in this #TechTuesday feature.
Posted on 23 Apr
America's Cup - Touchdown and take-off for Emirates Team NZ in Bermuda
Today the team's America’s Cup Class race boat was out sailing on Bermuda's Great Sound for the first time It is just over three weeks since Emirates Team New Zealand was sailing in New Zealand, and today the teams America’s Cup Class race boat was out sailing on Bermuda's Great Sound for the first time under inquisitive gaze of an armada of competitors' chase boats getting a first hand glimpse of the kiwi boat
Posted on 23 Apr
America's Cup - Emirates Team NZ has first sail in Bermuda + Video
Emirates Team NZ has just completed for their first sail in Bermuda, in preparation for the racing phase of AC35 Emirates Team New Zealand has just completed for their first sail in Bermuda, in preparation for the racing phase of the 2017 America's Cup campaign. The team, the last to arrive in Bermuda, returned to their base in the Royal Dockyard around 7.15pm local time (1015am NZT).
Posted on 22 Apr
America's Cup - Images from Practice Race Session 2 in Bermuda.
Images have just been posted by America's Cup organisers of the second Practice Session conducted between April 6-7. Images have just been posted by America's Cup organisers of the second Practice Session conducted in Bermuda between April 6-7. Images are not available from the third session which finished on April 12. The next Practice Session is a five day one beginning on April 24 to April 28.
Posted on 22 Apr
35 days to go until the start of the 35th America's Cup
Friday 21st April is another milestone in the countdown to the start of the 35th America’s Cup Friday 21st April is another milestone in the countdown to the start of the 35th America’s Cup as it marks exactly 35 days to go until the greatest race on water begins in Bermuda.
Posted on 22 Apr
Crewsaver appointed as Official Safety Provider to 35th America’s Cup
Crewsaver has announced today that it has been selected to be the Official Safety Provider to the 35th America’s Cup Crewsaver has announced today, 21st April 2017, that it has been selected to be the Official Safety Provider to the 35th America’s Cup, which will take place in Bermuda from 26th May to 27th June 2017.
Posted on 22 Apr
America's Cup - Oracle Team USA's Jimmy Spithill does a flying leap
Oracle Team USA skipper, Jimmy Spithill became the latest AC50 sailor to go overboard Oracle Team USA skipper, Jimmy Spithill became the latest AC50 sailor to go overboard with an epic leap after he crossed the AC50 during a manoeuvre and was unable to stop when he reached the new helm position. In a split-second decision the twice winner of the America's Cup had to decide whether to drop, slide and try and grab something, or just keep going and leap clear of the rudder foils. H
Posted on 21 Apr
America's Cup - Practising in Bermuda's Great Sound - April 20 - Video
The America's Cup Teams were training on Bermuda's Great Sound on April 20, 2017 The America's Cup Teams were training on Bermuda's Great Sound on April 20, 2017 including Oracle Team USA, Land Rover BAR and Groupama Team France in AC50's.Sailed in moderate to fresh breezes the teams seemed to be sailing OK but with some significant splash-downs and broaches.
Posted on 21 Apr