Okay, need some really basic (yet reasonalby accurate) means of measuring the following on a beachcat:
Mainsail luff curve
Mast prebend
Mainsail draft


I would seem from my reading that the easiest way is to turn the boat on its side (I guess support the mast at the hounds) to measure sail draft..?

The luff length is easy to measure directly from the sail lying on the floor, as well as the luff cord (curvature).

I would take pictures of the others and see if it suffices.

Pictures of the mainsail as seen from the tramp (or from the ground, if tramp removed) reveal a lot. Pictures of the mast taken from the mastfoot or from the ground inform a lot about prebend.

Bug, just go sailing! Why in the world are you worrying about luff curve when you haven't been wet it what.... 4 years? And another thing...pictures or it never happened.

Mainsail luff curve:

Peg head to ground (or tie around a post), pull "tight" from the downhaul clew and peg / tie to another post, put some twine from center of one eye to the other (head eye to DH eye) and tighten; and then measure the difference between this line and the BACK of the bolt rope.

Mast prebend

1, tie a thin line or whipping tewine to top of the mast and then pull tight and tie around the gooseneck fitting on the mast. Tape the line to the mast at the black band at the top of the mast (if you have one) or have a "class measuement point"; Same at the bottom so you have the line right beside the mast.
2, take a sail batten and place this across the back of the spreaders resting on the diamonds; Measure distance from mast track to the bit of line.

Never really measured sail draft.

It's part of my "dreaming out loud" thing.... But Ksurfer did offer an invite to Hirams if he still has a boat in one piece by then....

And it's probably been closer to A BILLION years <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />

Offer still stands for Hiram's. I did get a box of parts in the mail and the boat is going back together this weekend!

Your #2 is a measurement of spreader rake Simon

Luff curve - loosen the battens and lay sail on flat surface

Prebend - eye up the back of the mast or tension the main halyard down the back [on windless day]

Sail draft - tip rigged boat on its side. dropping a ball on the sail is always interesting to see where it goes!