Section 9  Recognising seamanlike sailing rigs

Introduction

When I was racing model yachts I used to watch other people setting up their boats for racing. They looked at them from every conceivable direction and tweaked this and that and I wondered just what mental images they had that could be so accurate. I never found out and one must also consider the possibility that it was really “mind games”. On occasion I would watch a really good racer just take over a boat from a novice and sail it into second or third place just to show that the boat could do well in the right hands and that it was good enough for the novice to use to learn how to sail. I now think that I do know what rigs should look like when they are set up properly but it has come from physics and observation and not from experience.

 

In this book I have offered an explanation of the way in which sails can be made to work together to drive a boat and how they can be used to improve the upwind performance. I said that I find that I can now “see” how a rig should be set up. It seems to be appropriate to give some examples. I have no regular access to photographs of yachts that are sailing but they do appear in the press and I collect them. The pictures here mainly come from that source. [1]

 

Seamanlike rigs

There are lots of designs for sailing rigs and they cannot all be seamanlike. I need to interpret that word “seamanlike”. There are rigs that have evolved to a point where the users of the rigs are satisfied that they are as good for their intended purpose as they are ever likely to be. The dhow used on the Nile, the Norfolk wherry and the Thames sailing barge, with its Dutch equivalent, are typical cases. They look to be primitive when compared with a modern racing yacht. But they are all working boats that have always had to earn just to continue in existence. They are cheap to build and are operated by a minimum of crew and they work in special situations. Any unbiased assessment will recognise that these boats and their rigs are seamanlike. They work.

 

By comparison there are other designs of rig that seem to have come about just to be different or for some special purpose such as sail training when a hybrid rig is mounted on a hull. Some designs seem to spring from optimism.

 

I argued for the flow over the windward face of a sail being orderly and free from eddies and swirls and that this is the best that can be done. I came across the picture in figure 59 of a “super” yacht. It is a radical design. There must have been very good reasons to set the sails in front the mast and disturb the flow on the windward side. I cannot think what they might have been.

 

I discussed the mode of operation of a single soft sail and a Bermuda rig. In figure 60 we have two small boats both of which are racing and presumably going as well as they can. They are beating in the River Fowey but probably not quite as close to the wind as they might be. We can see where the single sail of the Topper is set to the wind and I have to suppose that this is the best position for this isolated sail. On the Troy the mainsail is set with its main boom a few degrees off the centre line. If it had been the only sail it would be in the same position as the sail on the Topper so it is not set to drive the boat but it is in the best place to interact with the jib to let the jib drive the boat. This is to be expected from the physics. As a design the Troy has been unchanged for 100 years. It looks to be quite modern and I do not think that anyone would regard it as anything other than seamanlike. (They have no inbuilt buoyancy and they do sink from time to time but they are recovered.)

 

We can see a compromise that has been taken in the rig on the Troy. The boom must have a kicking strap and must swing across the cockpit freely. This requires space below the boom for the kicking strap and the sailor and the boom is fitted some way up the mast. But the jib is low down and not in the best position to take advantage of the flow round the main. The compromise is typical of yacht design and whilst it seems to be likely that if the jib could be raised there would be an improvement in upwind performance the additional complication of the rig is a great disincentive. As the Troy must conform to its racing rules to be eligible to race, there is no problem.

 

However one of the small dinghy classes has a very exaggerated vertical misalignment of the two sails. One wonders whether there is any interaction at all between the main and the jib.[2]

 

If the Bermuda rig has been developed to improve the upwind performance of a yacht we should be able to see it at work. In figure 61 the yacht is beating and we can see the angles of the two sails. They are consistent with the jib working in the diverted flow in front of the main. Note that the jib is set low to close the foot of the sail with the foredeck and the also that there is space under the main to accommodate the kicking strap and provide working space for the crew. The flow over the main will leak though that gap but yacht design involves compromise. This yacht is big enough for the rig to be affected by the wind gradient and the twist in both sails is evident.

 

If the Bermuda rig involves setting the jib at an angle to the main for beating what about rigs with two or three jibs? The main and the inner jib will, between them, divert the flow more than the main by itself. So we might expect to find the forward jib at an even greater angle than the inner jib and that is what we have in figure 62 where the yacht is some way off the wind. The interactions still give an advantage over the single sail at this point of sailing.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 63 is of a catamaran that is beating and we can see that the aft sail has a very small effect on the mainsail because the two sails are the same size and set too far apart to act together. The two jibs are set just as might be expected and the three forward sails are acting together as a rig. When I first looked at this rig I thought that it was too far forward relative to the hull but recognised that I did not know the position of the fins and thought that that the boat would not be balanced. Look at the wake off the two rudders; they are being used to prevent the boat turning to leeward where a balanced boat would tend to turn to windward. The designer of this boat may have good reasons for this set up but the drag from those rudders must have been a significant factor in the design compromises.

 

Figure 64 shows the yacht on the cover. It takes this rig to new complexity with three mains and three jibs all fore-and-aft. There appears to be no interaction between the three mains. The inner jib looks to be not in the best position but the other two jibs are where they might be expected to be.

 

If you accept my argument for the interaction of sails then you can also see when a rig is “wrong” and the inner jib should be in a position that is consistent with the rest of the rig.

 

In figure 6 the yacht has furled square topsails. It also has furled top-sails on each mast. I do not understand the use of square sails in this way and I can see no way to find out what they do and how they do it.

 

 

 

 

 

 

I have looked at lots of pictures of boats under way and they all seem to fit in with this idea of making the sails interact to get the jibs into the best position to drive the boat. I have also seen some that seem only to be comprehensible if the basis of the design is to fill in every available space in the standing rigging regardless of any interaction. I have not saved pictures of such rigs.

 

The Bermuda rig extends the performance of a given area of sail to windward. The only way to improve the down wind performance is to add area in the form of one or two spinnakers. Figure 65 is from the dust cover of “ The Shell Encyclopaedia of Sailing” edited by Michael W. Richey. It is hard to see how much more sail could be added.