As are the others.

The jib will produce a header with respect to the main. This also mains that a sloop rig as a combon can operate to larger angles of attack of the apparent relative to centreline of the boat. The maximum angle of attack of a uni rig is smaller and for a given course this means that the uni main needs to be travelled out more.

But some may argue that due to this smaller maximum angle of attack that unis can point higher and have a better VMG. Sadly even this situation is more complex than it seems. Yes a uni rig can point higher, but this will not always translate itself in a higher VMG. Why ? Because to achieve a certain speed the rig needs to harvest a certain amount of energy; the amount that can be harvested is also influenced by the angle of attack. Less angle => less energy harvested with the same rig. Also this proces is a battle between positive and negative effects. In the beginning pointing will contribute more to VMG than other factors take away but after a certain point the effect is reversed.

But what if boat boats stay on the same course ? Than a unir rig can have another advantage that many over look. Without the jib the uni -rig can operate a smaller angles of attack. For high performance boats this is the last barrier which needs to be overcome for truelly high speeds. Or rather high boat speeds devided by windspeed ratio's. Something this effect is dramatic enough that a uni-rig on the same course as a sloop by virtue of higher top speed relative to windspeed can have a higher VMG than the same boat on a higher course than a sloop.

Sadly this "go faster because your rig can still operate at smaller angles of attack" is mostly influenced by the need to supply a absolute amount of power and this is closely linked to the overall drag of the craft which on a upwind course is mainly determined by hull drag and centre board drag.

So by making a boat alot lighter one reduces wave making drag but more importantly wetted surface friction drag. This in turn reduces the required sail force which will reduce the amount of force excerted on the boards which will lower the centreboards induced drag which results in even lower requirement of rig power.

This reduced rig power allows a crew to sail with less camber in their sails and have a rig that operates efficiently at smaller angles of attack ergo higher boatspeed to windspeed ratio's.


But for now the cats are still in the region of speed ratios where the angle of attacks are still large enough to have sloop rigs and not be limited in top speed to much. Only after designs with even less drag are designed will the smaller angle of attack benefit of uni-rigs really kick in. That is as long as these rigs can be harnest by the platform which till now is the more limiting factor.

Ofcourse this explains why Formula boats are often not very good reachers as their jibs and mains are cut to operate efficiently going upwind at small angles of attack. By thsi the sacrifize the big angle of attack efficiency which are found on reaches. On broad reaches this disadvantage is offset by flying a spinnaker.

And ofcourse this spi needs to become flatter with increasing downwind speeds which is of course the new trend in designing.

And so on and so on.

Wouter