Years of development

Alex Adams talks about the radical new rotating wingmast on his Moth

Back in the early part of 2005 Adam May and Linton Jenkins of Full Force boats began discussing the idea of putting a rotating wingmast on a foiling International Moth. Now, finally, the concept has hit the water on Alex Adams’ latest boat.

In fact the mast on Adams’ boat is not designed specifically for an International Moth - it actually comes from an earlier wingmast that Jenkins designed for a Merlin Rocket,originally conceived by May and Jenkins before being put to one side. The idea then re-surfaced last year when May was off with America’s Cup commitments by Adams, who showed most interest in the project.

Originally the plan was to have the new mast ready in time for the World Championships in Italy in 2007. However, it soon became clear there was more work needed than just sticking the rig on an old hull. “It became obvious from early on that we needed a boat developed specifically for it,” Adams told TheDailySail. “The king post needed to be higher because of the kicker on it and it needed to take the increased kicker loads. So it got pushed back to now. I did put it up on the old boat, but it was not quite right for it.”

Above: Adams' new boat with large kingpost.

Since Garda, Adams has been busy with Jenkins building his new boat. Finally it seemed as though the project might go somewhere and recently the boat and rig were unveiled. The concept of having a wingmast on a Moth is a relatively simple one and is all about sail shape, achieving a smoother entry into the rig. However, we did wonder whether this also might be a way of stealing unmeasured sail area (the mast area does not form part of the measurement) “You gain a bit of area, but that it not really the reason for doing it,” Adams comments. “With the current rigs having a luff sock, you lose that bit of sail but gain a bit of mast - so it works out pretty evenly in the end.”

The rig itself is similar to those found on catamarans, with a mast spanner which can be used to rotate or tack the mast manually through manoeuvres. Because of this rotation the rig also has diamonds on it, though these are a fairly new feature. “The thing is that you have to use a lot less rig tension than in a normal rig,” continues Adams. “The leeward shroud has to be slack to allow the mast to rotate but this allows a lot of mast bend. The diamonds are there because the mast was bending too much due to this. About two days before the nationals I suddenly realised I needed to have diamonds and rushed to fit them.”

Of course on a boat that is as small, light and responsive as the foiling Moth getting to a spanner on the back of the mast is tricky, so Adams has rigged a rope system up to remedy this. Essentially rope comes out the back of the mast spanner and goes to a pully on the wing, before going across the boat, round a pully on the opposite wing and back to the spanner. This system means Adams can adjust the mast rotation simply by pulling the rope that sits just forward of his mainsheet strop. With this system it is easy to imagine the mast being rotated frequently, not only for tacks but also to flatten the sail or make it fuller. “At the moment I have not been adjusting it when I am going in a straight line. It just rotates naturally according to the shrouds. At some point I might play with that sort of rotation,” says Adams.

It seems clear to us that a system that adds more complexity to the already difficult manoeuvres on a Moth might be asking for trouble. However, as Adams indicated above the hope is that manually tacking the mast is only a temporary solution. “I think we are very close to having it self -tacking all the time, it is just a question of getting the friction and tension correct in the diamonds and shrouds,” Adams explains. As a demonstration of just how important diamond and shroud tension is on the boat, this week, while out competing in Kiel, Adams got the diamond tensions slightly different and the mast flat refused to tack. As for the future of the rope Adams seems unsure what might happen as the concept develops. “I think we will always have the mast spanner in it but what we do with it might well vary. At the moment I have the rope system but that might change.”

With the International Moth being a development class it is not surprising someone is trying out a wingmast, and it is perhaps even less surprising that this is not the first attempt at a wingmast in the fleet. In fact there were a number of Moths that had them back in the old scow days when the boats were much wider. The idea was also trialled by various sailors/designers when the class changed from scows to skiffs. However for the most part the idea was dropped because a wingmast is inherently stiffer than a normal tubular mast, so the rig did not offer enough gust response. Adams says this is not so much of an issue. “It depends in which axis you are bending the mast: fore and aft it is very stiff, but on the side section it is very similar to a normal mast. When you look at it the side section is a very similar diameter.” He adds that as the mast is rotated, the side to side flexibility of the rig become closer to fore/aft flexibility so there is plenty of de-powering going on.



Currently Adams is the only person (that we know of) trying a wingmast set-up, but that leaves him with some inherent problems when it comes to tuning. “Originally Sam [Pascoe] was going to do a two boat campaign with me, but he is now sailing the RS600ff instead. It would be nice to do something like that but at the moment I can still line up against other Moths or even a 600,” he says.

Obviously with no one else trying a wing mast and the rest of the fleet sailing around with conventional masts and sails that fit over them Adams has also had to look at different sails for the concept. “We had to start from scratch as there are no other examples out there. There are a few bolt rope sails from pre-foiling days but they are not right for foiling or for the mast,” he comments. “You need a much flatter sail as the mast is forcing a lot more shape into the rig. The Ka sails [the fleet standard] are very full when you let off the downhaul as they have so much luff curve. We do not need that luff curve to get the same shape so the cut is flatter.”

Of course inherent in the problems Adams faces with this new rig is not only does he need to work up a new sail and mast concept but his boat is also brand new and is still in need of some serious set-up time. This has led to him switching back to a standard rig recently. “At Kiel it was not working as well as I had had it working. Also, I wanted to do some foil evaluation and set that up and that is easier if I have the same rig as everyone else,” he explains.

One has to wonder whether all this effort is really worth it for what is presumably a slight performance gain. “At the moment I think it is probably a bit harder to sail with than a normal sail. I am told that downwind is where the big gains should be as we should get a lot more power. Right now I think I am at around the same speed as a normal sail,” Adams says. If downwind power is the major gain we wondered whether this might see Adams foiling earlier than the rest of the fleet in the lighter conditions. “The hope is that it might help early foiling downwind but I am yet to prove that,” he concludes wryly.

With only just over one week left until the World Championships get underway and with a lot of work still to do it is perhaps easy to assume that Adams will revert back to a more regular set-up for the regatta, however, he is hopeful this will not be the case. “I need to get another re-cut done on the sail following Kiel so that is my big issue. At the moment I also need to get the boat worked up with the old rig to give me a decent baseline. I want to stick with it for the worlds. If all goes well I will be sailing with it.”

As for the future Adams thinks he will continue with the concept and develop it further still. “The first thing to do will be to build a new mast as this one is fairly old and built for a Merlin Rocket,” he concludes. “It is about 1.5kg heavier than a normal mast at the moment and there is really no need for it to be heavier.”

So Adams is likely to be at the World Championships with his wingmast and will certainly be one to watch for the event. We suspect with the boat and rig all being fairly new his chances of putting a full competitive regatta together may be limited. However, there is certainly mileage in the idea and if all goes well and conditions are right, who knows how quick he might be?