A couple of tricks that might help.
- get the old sail and stretch it HANGING by its three corners - you will see how much camber there is,
- build your sail with the minimum camber you accept,
- get stickyback tape, build the sail with this first,
- hang it (see point 1 above) to see if the camber is where you want it and as much as you want it (the sail will have no corner grommets at this point - use spikes),
- start with panels
, camber, then mow it (zigzag or triple step),
- build corners and other strong points, use stickyback to place them on the sails
(corner patches are built flat), mow them on,
- build tapes, attach them with big office stapler (I like to attach each end, then center, then each mid-center, etc.), mow them on, remove staples, remember about any trimlines (if they go into tapes)
- finish the corners (grommets or webbing) you will need grommet tools for grommets, webbing you just mow it on,
- if in doubt, build a polypro mock first,
- notice the shape of the edges - if they have any curve, build your sails with the same amt of curve, most sails have slight inward curve, unless they use battens (then they may have roach curve STILL keeping slight inward curves between the battens!)
ETC. Hard to express everything in a short msg but others will chuck in.