Roubo bandwagon

I have received my copy of the third tome of 1977 edition of "L'art du menuisier ebeniste". Now I will slowly start looking for the previous 2 tomes in the same edition. I may look into obtaining the antique editions down the road.

I quickly read a few pages and apart for the antique units, I can read it no problem. The nice thing is that now I know the exact specs of the monster resawing frame saw: a blade at least 4" wide and less than 1/12th of an inch thick at the teeth, tapering towards the back with no set... the blade should be filed rip at about 2 TPI (points 5/12th to 6/12th apart).

TIL: antique French units

A ligne is an antique measurement equal to a 12th of an inch. The ligne itself was composed of 12 points and it took 12 inches to make a foot. Up to this point (har har), it's logical albeit duodecimal. After that, it gets messy... 6 feet to the toise, 3 toises to the perche-du-roi, 20 feet to the "perche ordinaire" and 22 feet to the "perche d'arpent".

French cathedral builders used a measuring system based on 5 numbers from the fibonacci sequence: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987...

Their measuring stick was called the "king's cane". That cane measured a total of 555 lignes (around 125cm)

It was subdivided in five different measures, each connected through the addition of the previous two measures.

34 lignes in a hand (palmus minor)

55 lignes in a palm (palmus major)

89 lignes in a span ( a hand + a palm)

144 lignes in a foot ( a span + a palm)

233 lignes in a cubit (a foot + a span)

That may be a fun easy project to make with a large piece of scrap wood.

For you imperial lot, the reason the cane doesn't seem to add up is that the French inch of Roubo's time was a smidge above 17/16th of an English inch (1.06575)... to make it easy. :)