Pete
David suggests 30° between the after part of the batten parrel and the batten. That makes sense, and should ensure low friction. However, there is a bit more to it than that. In general, the closer the CG of the sail sits to the mast, the less it will want to fall forward, and the less are the forces needed (from batten parrels or other lines) to hold it back. In plain English this means that high-AR sails, and sails set with a big balance, are more forgiving in this respect. The worst are the low-AR sails set with very little balance.
The challenge is to land on a compromise where the sail sits where we want it to, and where the friction between batten parrel and mast is acceptable.
The sails I have made lately are in the “difficult” class, being quite low and broad. On the hi-res photo, below left, I have shifted the sail of my Ingeborg maximum forward without moving the batten parrels. I did so by lengthening the standing tack parrel, TP. As can be seen (enlarge the photo), the batten parrels will restrict the sail from falling forward when reefing. The friction is noticable when hoisting and lowering, but the sail still comes down by itself without jamming, so it is OK. A glance at the halyard shows that it is next to vertical, so it is not pulling the sail forward.
On the photo to the right, taken recently, the sail has been pulled just a bit further aft with the throat hauling parrel, THP, after hoisting. The TP has also been shortened again, just a few centimetres, to make the PVC jacket on the boom reach the mast.
On a schooner the AR of the sails are generally much higher than sloop sails, so there is a good hope that you will get away with fairly little balance and short batten parrels. It is important that the mainsail is restricted from falling forward, as the clearance between the two sails tends to be on the short side.
A final advice is to make the masts tall enough so that the angle between it and the halyard stays within 20-30°.
Arne
