How do sword makers draw the curvature of a sword's profile?

[red4]

My question is about double-edge swords that are symmetrical. I understand that when one side is established, it is drawn on paper, then the paper is folded in half and traced to create the other side. However, what I'm curious about is how the first side is drawn. A lot of these swords have shallow S-curves (as seen below). The S-curve looks almost mathematically precise. It doesn't look like freehand lines. How are these lines drawn in the patterning stage? Do they use enormous compasses? The blade in the picture below is about 3 feet long, with a very shallow concave in the S-curve, which looks like it might have a radius of 4 or 5 feet. That's doable with a compass, but is there a different technique?

 

[Teddz]

off the top of my head...

a set of French curves, flexible ruler used for long curves...

And in some cases, with a master craftsman, the curves are done freehand.

 

[ARKM]

Yeah my guess is free hand.

 

[RobertMuldoon]

Depending how that sword was made, it could have also been drawn in an computer and made with a CNC or waterjet/laser cut out of the steel.

 

[Miker]

You can make a large compass with pencil and string, of course I have no idea if that applies here.
I would hypothesize that once one was happy with a given shape they may keep that around as a pattern to trace for future use.

 

[sonicfreak04]

smiths would just hammer it to shape using the horn of the anvil or use fullering and drawing dies which have curved that would force the metal to spread out into a more curved shape

 

[tcsmit29]

I've made similar curves in woodworking projects. French curves are what I've used.

 

[lmgill]

By eye. "A machine is a device for replicating the skills of the master craftsman, for the non master."
After 40 years of crafting, and having started in a machine shop, in many cases I can see differences of +/- .005" of an inch.

 

[red4]

I've made similar curves in woodworking projects. French curves are what I've used.

They make really big, almost flat french curves? I hadn't heard about french curves until the replies in this thread, and have since googled them. All the french curves I'm finding seem to be too small for the sword in the picture I posted.

 

[Bioshutt]

Years Of practice and a dang good eye for detail

 

[tcsmit29]

They make really big, almost flat french curves? I hadn't heard about french curves until the replies in this thread, and have since googled them. All the french curves I'm finding seem to be too small for the sword in the picture I posted.

What I've used in woodworking is a thin piece of plywood that is bent to the desired curve and then the line is traced onto the project wood. I had always heard guys refer to this as a French curve. It might be a slightly incorrect usage of the term but the concept is the same.