I’m sure everyone knows by now that I believe 100% that the camber over the first third of the sail is critical, and that the run aft should be flat. With this conviction it should be obvious that whenever I look at a rig I look for camber forward and flat aft as a method assessing how well a rig will perform. If trying to draw a single cambered panel I would plan the maximum camber point to be around 35% and no further back that 37% chord.
In sailing, as with life, it’s not what you put in; it’s what you get out. No matter where you plan your maximum camber position to be, you have to assess what you end up with under sailing conditions. By the time the parrels have pulled it this way, the halyard that way, gravity the other way and then the wind blows, what do you end up with? Looking at the various photos of Poppy I know I have not got what I wanted in the first place, and thought I had sewn into the sail.
The problem with looking at photos is that they are just a snap-shot in time, and do not necessarily show the average situation, but sometimes they are all you have to go on. The boat of the month photo of Footprints is a case in point. Look at that snap-shot in time, and take a horizontal line about one third to one half way up the sail where the airflow should be somewhere around horizontal. Then try to draw the shape that the airflow will experience as it passes along the sail from luff to leech. As there seems to be is a crease running from the top of the luff of each panel to about 50% chord at the moment the photo was taken, then it would appear that this crease has removed the extra material over this most important (in my eyes) area of the sail and flattened the camber, pushing the maximum camber point further aft than planned. As Arne has pointed out this increases weather helm, and reduces the sailing performance.
It could be that by swinging the rig forward to the more balanced position used for off wind sailing helps reduce these creases and returns the camber to the planned shape and improves the performance by reducing the weather helm. Please remember that these comments are really a stab in the dark, based on one photo. I think it is an attractive rig and am disappointed to hear that it is not giving the planned performance, yet. It is interesting and useful to see how things are working out with Footprints.
It is easier for me drawing split rigs as I feel it is appropriate to put the centre of area of the sail in the same position used by the Bermudan rigs. I have no problem with masts distorting the forward part of the rig, and the higher balance rig does not try to distort the camber shape. To those who haven’t tried it, designing a rig always seems to produce a few problems that you haven’t planned for. For example at the moment I am trying to define the practical range of the ratio of panel height to panel length for a well cambered sail. PJR gives answers for flatish sails, which is no real help. There is still so much to learn.
Paul, I understand that camber forward makes a sail less critical to heading and easier to find the ‘grove’.