What can you tell me about trimming a furling mainsail without battens?
Sue & Larry respond:
Our first cruising boat had an in-mast, roller-furling mainsail and we found only a few differences in trimming that from a conventional mainsail.
With no battens to support the leech of a traditional mainsail, it will flutter away and be very inefficient. To help reduce this problem on mainsails designed for roller-furling use, the sail has been modified by cutting away some of the leech and leaving a much more concave looking shape. This certainly helps with the fluttering leech problem, but doesnít entirely remove it.
The boomvang is your best help here. By tightening down on the boomvang, the end of the boom is pulled down, resulting in the leech tightening and allowing the sail to hold a good shape with no flutter. The snugging down of the boomvang, in combination with some outhaul tension, always gave us a reasonable sail shape for sailing upwind. As we bore away from the wind, we would release some of the boomvang pressure and some of the outhaul tension. Youíll find that as you point further away from the wind, the leech has less of a tendency to want to flap, and the leech tension is no longer needed, nor desirable for good sail shape.
Just a tip we learned about using our in-mast roller furler: Itís often necessary to fully release the vang tension prior to furling in the sail. This will help eliminate any snags as the sail is rolled into the extrusion. Good luck.