This is all great information. I've learned quite a bit with this thread. I'm sailing today and will rake my mast back block-to-block to see if it helps some.

I like the look of those Nacras (500 and 570).

If there is a local fleet nearby, I would contact them personally. Most are eager to meet new sailors.

Well - We all knew didn't we - Didn't we ? <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
Just out of interest - 2 skeg cats: Dart 16 and Dart 18. The Dart 16 points much higher than the Dart 18 ! Nearly as high as a cat with boards, when the wind is up.

Sorry for the late reply, but I studied this issue and the conclusions surprised me and might interest some of you. I might be wrong, as usual, but... <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />

1) Resistance to Horizontal Rotation: we want the boat to tack around the daggerboard. Minimum resistance to tacking happens when the design achieves the same resistance to rotation forward and aft of the pivot point.
The hull's forward sections are more draggy when rotating horizontally than the rounder and flatter aft sections, so placing the daggerboard a bit forward from the middle minimizes the total resistance against the tacking rotation.
Conclusion: it is best to place the daggerboard forward.

2) Torque Generation: in order to tack the boat, the rudder has to exert a force (lift) that, multiplied by its distance to the centerboard, creates the necessary torque to overcome/equal the resistance against tacking and rotate the boat. When the distance from the rudder to the daggerboard is increased, the rudder generates more torque with the same lift or the same torque with less lift.
Conclusion: it is best to move the daggerboard forward.

3) Boat Placement after Tacking: When the boat rotates around a daggerboard placed further forward, it will finish the tack forward from the same boat performing the same tack around a daggerboard placed further aft. It may be one feet or four feet, but it is a very real advantage.
Conclusion: it is best to place the daggerboard forward.

Comments?

That all SOUNDS good Luis, but most if not all of what you say is negated if/when the bows are "lifted" during the tack by the crew "roll tacking" and taking their weight towards the stern of the cat through, and coming out of the tack. The fact remains that if the C/B's are well forward of the C of E of the combined sail plan, there will be weather helm which is not a very desirable situation, particularly if/when the helm makes your arms want to drop off on every beat. When boards are “too far forward” a tack can/will often be lost when coming out of it due to the boat wanting to immediately round back “up” after it has passed through the eye of the wind, all because of the “excessive” weather helm generated due to the C/B position, which can/will often cause the cat to “go into irons”. This same effect can also be generated by a crew keeping their weight too far forward coming out of the tack and creating a similar effect of having the C of LR too far forward and the associated weather helm rounds the cat back up into irons. One of the main reasons for “easing” the mainsheet during the tack is to obviate this “round up/weather helm” effect.