Is it possible to straight-stitch sail seams, or do they need to be zig-zag? Our youth boat-building group inherited a "canvas machine" sewing machine that we had expected we could use to build a sail kit, only to learn that it only does straight stitches, not zig-zags. Do we need to keep looking? I'm aware we can try to press a home sewing machine with zig-zag feature into service if necessary, and have done it on my own projects, but we were hoping this donated machine would set us up for good. Thanks.