SAIL TRIM TUNING AIDS FOR FDBy: Lin Robson
As all of her fans know the FD is a boat that is highly sensitive to fine adjustments in the rig and sails. Receiving the most enjoyment out racing hinges in part on what long time FD sailor Mike Loeb said was “getting it less wrong”.
While there will never be a substitute for developing a proper feel, because the rig controls are multiple in number some sort of reasonable hierarchy has to be used to make what are found to be fast settings repeatable and understandable. Most of us start with the rake setting via genoa halyard tension, which really is the primary usable and available power setting. Other controls that effect twist in the sails and the sheets can be used to get closer to the right amount of power available, but the halyard sets the stage. As a consequence, it is good to have a clearly visible graduation scale on the aft side of the mast, set up so that the halyard end or nicropress fitting for the wire is set at zero when the mast is fully upright. That way it is easy to go right to the correct general area of rake for a given condition. I use the guide that if the boom end must be eased beyond the corner of the transom very often, you should rake a bit.
Arguably two of the most important goals with the main and genoa are finding the right lift to drag ratio and really tuning into the relationship between the genoa leech and the forward part of the main. For example in general while trimming the main I am always testing how much vang I can have on at any one time. Vang tension if appropriate to the pressure straightens the leech, adds power if the mast tip is not too limber, reduces induced drag, and allows the boom to be sheeted harder in first grommet conditions.
Sea state has a lot to do with how much vang can be applied. The more a boat is moving around the more likely that a certain amount of twist is desired to have a easier groove, being “less wrong” more of the time. We have been using mains with a bit less camber in the lower part, making adjustment of the lowers and outhaul more important, but using these controls has resulted in a wider effective range. This is because we can add depth when needed and truly remove it when desired.
I try and remind myself to be active on the main sheet, particularly as we vang sheet, because with the right vang tension it turns the main into a very effective directional tool as well as a source of power.
Historically most genoas for the FD were designed with the idea that more than normal leech curvature or “return” as I like to call it, was necessary to fool the boat that it had a narrower sheeting base than it actually does. Inboard movable leads help on today’s modern FD’s, but that condition still exists to a degree. FD genoas, particularly one intended for light to medium wind velocities does not look like a genoa you would see on a keel boat! The dilemma has been how much return should be built in for power and still have the sail be effective when it comes time to rake. This pertains to the optimal lift to drag condition we are always seeking. Just as an airplane needs additional lift via flaps down landing or taking off, but can retract them as speed increases, we need to be able to go forth with the same concept in mind.
While I think there will always be a need for a more dedicated light air genoa in our inventories, since the 2006 Worlds I have been using an all purpose design as my primary headsail. That sail, a North AP, has very good power down low for light to moderate conditions, but resembles a more conventional shape higher up. The idea is that when it is time to go to second or third grommet, a significant amount of that leech return goes away and you then have a genoa with a much flatter and cleaner exit.
I use the up / down and in / out adjustability of the genoa cars to try to fine tune the genoa twist and proximity of the aft end of that sail to the main. A very general guide is leech telltales fully flowing, and if the sea state and pressure are such, pulling the cars outboard can help with the straight line speed. If the boat feels bound up, ease and or rake to get her back in balance.
There is that magical moment when the sails are really working together, the rake, twist and centerboard position are right that make sailing these boats so much fun. I try to remind myself that as our boat is a very dynamic thoroughbred, we have to be active on rig changes and ready to go to the necessary settings. Hopefully as the puff or lull occurs, not after the fact. Watching FD’s in a trailing power boat can really show who is on top of these adjustments and who is not, with the condition of a generally constant angle of heel being the guide.See you on the water!