The main advantage of squaretop over pinhead sails is that the airflow over a squaretop sail is more laminar (a pinhead will always have wind going up the leech, trying to find shortest distance.)
Extra advantages : better gust response, better efficiency of area in sail that is somewhat away from edges (=middle section); more efficient use of the area that is in the top (the upper section of a pinhead does nothing but create drag); More area up high, lifting hull early and possible milking more energy from higher air layers. Better distribution of total sail area. (A sq mtr on the bottom near the foot doesn't do much in the top it does even when its efficiency is less than the middle part).
HOWEVER : If you are slightly oversheeted on a squaretop sail, the drag is higher than on a pinhead, since the pressurised air "jumps over" the head, causing a lot more drag.
Drag is related to size of the pressure zones. a square top can just create larger pressure zones there and so larger drag.
Am I right in assuming that a pinhead sail would be a bit more forgiving in this regard, since the air has no head to hook over, or would it be even worse as the air is already travelling up the leech to a certain extent ?
It is difficult to say in one simple phrase. It is not that easy. Pin head suffer from the mast section being very big in relation to the pin head area as well for example. On the race course however, pinheads are uncompetitive and that should say enough.
If my assumption is correct then correct settings while sailing with a squaretop is more critical than a pinhead sail.
??
Yes.
But the rewards when trimmed right are just a significant.
Wouter
