The LONG ones'd be say 16 inch or so . Youd only copy & use the usefull looking ones , or derivatives . ( might tryn scan suma mine )
One ends up putting pencil mark datums on them , doing ribs and consecutive shapes .
If one curve matches LE at Root ant at Tip , @ differant sector , the two marks devided by the number of the bays , gets datum
( mark on curve ) for each rib .
Getting more tecnical than me , you could use a progressive diffrentail variation between the two datums . And Go Cross Eyed
marking it out .

2H & 3H are finishing / Final pencils ( Leads ) and are softer & Smudge Easier .
6H is pine line ( like wot for them rib layouts ) and wont show on a print , if light .
4 H is more usual layout pencil . ( use good one , Staedler etc )
A Fine Sharp Tip ( maybe sharpened rolled on sandpaper ) a draftsmans pencil is sharpened on a Fine Taper , NOT a short one .
A Well Sharpened 6H , Draw Two Lines ONE millimeter apart .
Split That.
Split Those . ( parrallel Lines all )
Youve Got 1/4 mm's . BUT . . .
Two staggered overlapped lines between them now , will get you clear defined 1/10 th m.m. devisions . Which should be close enough for
general drawing .
Just use EQUAL Devisions ( divided by multiples ) of whatever youve got . Measuring Stick . Knotch marks . Knots on string , etc .
