Can I get an estimate of a Skerry's Center of Lateral Resistance from the stem? (yeah, I imagine it moves around a *bit* when there are humans aboard)
Would it be somewhat close to the trailing edge of the daggerboard?
cheers,
-Kristofer
If you count the skeg---and you should---the Skerry's CLR is a bit aft of the daggerboard.
There are byzantine formulae, beloved of armchair sailors, subject to eye-rolling by designers, used to position sails and foils on small craft. The best known is that the CE should be positioned 10% of the waterline length forward of the quarter-chord of the fin. That works pretty well, but only for beamy, shallow-bodied hulls with transoms and prominent fins or centerboards---which describes an awful lot boats. Certainly that's the formula I applied to our small craft that fall under that description: the Passagemaker, Jimmy Skiff, and PocketShip.
In my experience, however, narrow double-ended boats don't subscribe to that formula at all, and tend to have pretty neutral helms no matter where the fin is placed, within reason. The Skerry, at least once it's moving, has almost no helm, or just a touch of weather helm, as is desirable. If you calculate the geometric center of area of the whole underbody excluding the rudder fin, you get an 8% lead of CE over CLR.
Thanks a lot for the considered reply. I appreciate it. -Kristofer
In my experience it moves around a LOT, depending on where I sit. The CLR of the hull is probably awfully close to the calculated point if the boat is settled in exactly on its designed waterline, and balanced exactly for and aft. Put 130 pounds of person in a position to knnock it out of exact fore-and-aft trim, and where the functional CLR is, can change wildly.
This is known by all dingy racing sailors. You can almost steer a performance dinghy with your weight, if the conditions aren't too extreme.
Add ing this together with Johns observation that the long, narrow double-ender hull is awfully forgiving on fin/foil placement and I'd hazard a guess that folks are over-stressing about where the *Exact* placement of the mast and boom and CE of the sailplan are. 3-4 inches one way or another isn't really going to matter much, and even if it does, then just sit a couple of inches for or aft to compensate for it.