VO70 Mk2

Dadd on bulb weights, keel pin heights, sail sizes and other technical delights

While over recent weeks we have published the viewpoints of some key players in the Volvo Ocean Race about what should be done with the race, few people are closer to what may happen to the Volvo Open 70 itself than Chief Measurer James Dadd.

Introducing the Volvo Open 70 for the last race was a top move by the organisers as the class can rightful now claim to be the world's most high performance offshore monohull, the type of claim the world's premier offshore racing event should be able to make. The performance of the boats, monohulls achieving speeds previously only imagined possible from multihulls, seemed to stagger almost everyone, not least Volvo themselves who a couple of months prior to the start had to revise the estimated arrival times by as much a five days for some of the offshore legs. However this high performance came at a price with all manner of problems related to the boat's keel canting mechanism and ultimately the complete loss of movistar. Saying this, aside from the keel problems and some relatively minor structural issues after leg one with the ABN AMRO boats there were surprising few problems with the new 70s, a situation which Dadd believes they can only try to improve further with the next generation.

"We principally don’t want to change much," Dadd says when we enquire about what a Version 2 of the VO70 rule might look like. "We want to try and make sure that the developments the teams have learned this time round they can use next time. Whatever they have learned that didn’t work this time round we want to make sure that they can work on from that for the next version of the rule."

Dadd confirms that they will almost certainly introduce a maximum bulb weight as this, even more so than was the case with the VO60s, proved to be the prime performance driver of the 70s, with all teams shedding weight in the most extreme manner from the hulls to convert to lead on the bulb. "The important thing is we make sure we control it to where they are right now. We want to make sure the next generation of boat is encouraging a similar sort of performance to these boats but is also a step on from them. Realistically I think that is going to be around 5.5 tonnes which is what most of the teams have ended up with."

Introducing a maximum bulb weight will change the Volvo Open 70 development game considerably, but hopefully in a good way. For example this should effectively halt the weight shedding regime, making boats safer and more reliable and may even reduce cost if for example there is becomes no need to go for ridiculously expensive hydraulic rams made from titanium or carbon fibre.

"If you look at the America’s Cup Class their bulb weights, apart from when they changed to Version 5, have been pretty static since Version 3," says Dadd. "And with Version 5 the one tonne they have taken out of those boats has all come out of the bulb. So it is one of those things where they will be looking at refinements like the structure, trying to get that more reliable, so hopefully reliability won’t be a big issue next time. Hopefully everyone has realised this race that the crew need to have a boat that they can really push hard and the harder they can push the boat the more comfortable they will be with it and hopefully the higher up the podium they will be."

So if maximum bulb weight, one key part of the VO70's stability make-up is fixed, then teams will be quick to key in on other stability influencing aspects of the boat next time around. "I think they will be looking at the trade-offs with form stability, going for the wide boat with wide waterline beam." Aside from this Dadd reckons they still have a long way to go with research into appendages and trying to make the keel canting system efficient. "The keel canting system has to have the speed that’s required for the in port race and yet have the reliability that’s needed for the offshore legs."

Prior to this race Ericsson were investigating the use of a worm drive keel canting system (click here to read about this) instead of a hydraulic ram set-up all the boats ended up using. Would something like this be permitted? "I think it would be a bad thing if it wasn’t allowed," says Dadd. "This is a development class and I think we need to encourage development of that type. If we turn around and say it is going to be a one design keel rams I think it would be a great shame. You might find in five years time that the worm drive system has taken over completely from the ram system in which case we’d look pretty stupid."

One cause of a majority of the keel problems with the VO70s this time round stemmed from allowing the giant pins around which the foil cants to be mounted 150mm inside the hull. To allow the keel to cant this requires a slot to be made in the bottom of the boat and on the Farr boats it was the movable fairings covering this which were the main failure. "My view is that we should keep the pins where they are: 150mm inside the hull surface," says Dadd. "If anything maybe we increase that because it would allow them to go for bigger bearings. But I think realistically 150mm is fine. They know what to do with that now. I think we will also write that you aren’t allowed to have independent movable fairing plates. Although I am sure the teams have worked out how to use them now it is not a healthy development and when they go wrong they go wrong big time. I think having the keel pin within the hull, it was shown with movistar’s failure that it gave them that extra time to cope with the situation to get themselves sorted out and off the boat safely. So I think it works well to have the keel pin enclosed within a bulkhead rather than hanging off the bottom of one."

An area of development embraced by Team ABN AMRO from the outset following their background in Open 60s was of roller furlers for the headsails and snuffers for the masthead asymmetrics. It seems these type of efficient sail handling systems will see more take-up next time round. "Realistically I don’t think they need much encouragement - they have realised they need to have furling equipment. This time round we restricted the way that they were allowed to hoist the reaching headsails and the masthead spinnakers. They weren’t allow to furl the masthead spinnakers and they will be next time and the reaching headsails they had to hoist them on the forestay which meant that if you furled them you had to keep them up. I think those are two things we’ll get rid of them next time. I am pretty sure that every sail will be furling next time round and I don’t think we’ll have to push too hard in that direction."

It will then be a case of seeing if furling the masthead chutes is more or less efficient than the snuffer system ABN AMRO developed for this race.

Another avenue Dadd is considering is allowing deck-stepped as well as keel stepped masts. This has been a common feature on Open 60s for decades as it allows the integrity of the hull to be maintained in the event of a dismasting. "We hummed and harred about it for the last version of the rule and the reason why we didn't go for it was because most of the guys involved in this event had more experience with keel stepped masts. This time round I think we just need to allow them some development on that side. We also didn’t anticipate this time where the relative mast and keel positions would end up - it has ended up with the mast stepped bang on top of the forward keel bulkhead. It is a very complex area and there is enough going on there as it is, so if you can put the mast at deck level it simplifies that whole area substantially and it will allow them to be more conservative with the structure because they will be worrying about it have to do one job rather than two."

One of the principle changes for teams next time round will be developing a new Volvo Open 70 for the new course including anticipated visits to the Middle East and Asia with more sailing in the tropics and considerably less in the Southern Ocean. Volvo Ocean Race meteorologist Chris Bedford is currently undertaking a study in the weather on a variety of new routes prior to making his recommendations to Volvo but it is expected that the average wind speed for the race will drop considerably.

"Right now we don’t know what that course is going to be, but it looks like there is going to be lighter conditions," says Dadd. "I think it would be a great shame if we lost the rough conditions that we got but at the end of the day the roughest conditions they saw this time were in the North Atlantic. I think it is important to keep the extreme element because that is where all the good footage comes from. The footage which sends a chill down your spine is when these guys are in the rough weather and when they are doing the long day runs where they average more than 500 miles - that is what gets to people."

While it is generally felt by most sailors we have spoken to in the race that they liked or would have liked twin rudders, this is one area of debate that may be renewed thanks to the new course. The choice of having one or two rudders is dictated by the beam of the boat and on the lighter course it may be that the drag of the hull becomes a more important factor in the VO70's design.

Dadd is less convinced this will be the case. "We don’t really know how these canting keel boats are going to work best because you have to remember that in low wind speeds you have a large lump of lead hanging under the boat that you can cant around so these boats are always sailing at an angle of heel. On the next course I doubt we’ll see a CBTF-style very narrow boat working. They are always going to be powerful boats. If you think about it these are seriously overpowered boats and you are still going to want the righting moment you get with a fat boat so you can keep those big sails up the whole time."

Interestingly for the last Volvo Ocean Race none of the teams chose to go with the maximum size of sail allowed under the rule. For once there was no one hammering a corner of this box. "I was really keen to get rid of all the sail measurements for these boats completely but the teams felt that was going a bit too far. We have reached the natural limit which is nice because if the natural rules work then that is the best way to do it. You can try and cheat us, but not nature." Saying this if the next course does prove to be lighter Dadd thinks it highly likely that teams will increase their sail acreage and will have to adapt the hulls beneath them to cater for this.

If the wind speed is less than Dadd is also considering increasing the length of the bowsprit. "It will look more in proportion with the boats and it will give them more opportunity to play with big drifters.You are still going to see very high performances and you are going to need to if you are going to do long legs in light conditions."

Following the loss of Hans Horrevoets presumably they are looking at ways of making life on deck safer. "It is a tough call. We are looking at it but we are unsure what to do. We might make the coachroof more practical. That area will change slightly but I am not sure to what degree. They work at present. We also thought about increasing freeboard but if you look at these boats alongside other 70 footers they have a huge amount of freeboard already. The problem is that if you have a boat going that fast then it is going to be wet and it is supposed to be life at the extreme, where the guys are having a hard time of it. We don’t want to wrap them up in cotton wool."

Another area up for consideration is the internal water ballast. While the boats rely on their canting keel to increase their athwartships stability, boats are allowed to carry up to 1 tonne of water ballast in a tank inside the transom to life their bow up in big downwind conditions.

"I was against putting water ballast into these boats from day one, because I think if we add more water ballast in the back of the boat all that will happen is that designers will look at it and say when the going gets tough we can put a lot more weight in the back of the boat which means that we can make the bows finer," maintains Dadd. "So you are not going to make the boats any drier or safer, you are just going push the designers in another direction. If we got rid of the water ballast tank or if we increased the size of the ballast tank we’ll put them on to a steep learning curve again. We want to try and reduce the cost of these things and one way to do that is to stop them going through another steep part of the learning curve. "

As a result Dadd reckons it is most likely they will leave the amount of water ballast as it is. "Brunel is the only boat with enough rocker to make decent use of the water ballast and they are also the only boat which has enough volume up forwards that they don’t have a particularly wet boat, so they got ride of their water ballast tank because they didn’t need it."

When it comes to crew and sail numbers Dadd says that it doesn't particularly matter - teams will work out the sail inventory and sail handling systems to suit whatever Volvo propose However he recommends crew numbers staying the same for the offshore legs but bumping it up for the in-port races to get closer racing, better mark roundings and creating more of a spectacle.

Dadd is totally against the suggestion being pushed by Grant Wharington to allow power winches, even one powered winch for the halyards. "I believe this is a physical sport and powered winches should be the reserve of cruising boats. If cruising boats want to go racing fair enough. I don’t even agree with them on boats like Wild Oat s."

Dadd expects to publish the new rule for the Volvo 2008-9 Volvo Ocean Race on 8 September this year - three years to the day after the first version of the rule was published and 33 years to day after the start of the first race... A draft document it is understood is already circulating between designers, sailors, etc. All that is needed then will be a finalised route...