my glasser told me about a new quad rear fin placement set-up.
the rear fins are now moved closer to the center/stringer and farther away from the rail.
if anyone knows about this,please tell me what you know/think about it.
He's likely talking about the McKee setup. A lot of people say it delivers the speed of a quad, but not the stiffness. There's the "rail" setup, with all four fins out on the rail, the "McKee" setup, with the rears much closer to the stringer, and the "Rusty" setup, that's somewhere in between. All are known, tested, reliable setups with distinct advantages and disadvantages.
As already said, it's a compromise. Moving the fins in any direction... fore/aft, together apart, spreading out the cluster or tightening up... affects speed, stability, sensitivity, drive, turning radius, etc. Combine fin placement with fin size, foil, cant, toe, base, flex, tip, etc... and you have a million different combinations to play with and fin tune your ride.
Then, start all over with your next board, because planshape, rocker, foil, etc... all has an impact too.
More info on two of the types of quad setups, I haven't shaped one with the Rusty setup (yet)
1. What I like to call a 'split keel' where the fins are close to the rail (like taking a large keel fin and splitting it, and spreading it out for water flow between the fins). The split keel is very pivoty and great on cutbacks and quick turns. Good for small to medium beach breaks.
2. Mckee quad setup where the quad trailers are more like a tri centerfin split and offset from the stringer a few inches. Mckee setups surf more like a tri fin with more stability but less turning. Good projection out of bottom turns though. Better on bigger waves and points.