Hi Mo,

its a large topic, and i can hardly claim expertise with any layout system. I've studied the Japanese methods for a long time and in recent years have spent a bit of time, well a few thousand hours, studying the French methods. So, i have some points of comparison, and I'll give one example.

The primary French method I am aware of is 'devers de pas' which is a way of determining the layout lines based upon their projection to the floor. Part of this method entails placing a view of the x-section of wood which is to be compound sloped upon the drawing and developing projections from that. Then one develops views of the same piece, now at slope, and develops a new x-sectional slice. For example, a square section leg, if on a compound slope that is the same in both x- and y-axes, will have a horizontal x-section at slope of a diamond. Another way of saying that is that the leg, if cut to meet the floor flush, will meet it as a diamond shape. To deal with this, the French might rotate the leg to one direction or another so as to place one face of the sloped leg in line with the actual floor plan. This solves joinery problems on one axis at least.

That's not a method the Japanese use. First off, they would often choose NOT to use a square section piece at compound slope, because the resultant diamond-shaped horizontal section creates problems in joinery (awkwardly shaped tenons and mortises) and aesthetics. So the Japanese practice is to reshape the leg section, using one of various different drawing method to determine the shape, so that when the leg meets the floor, or any horizontal plane, it is square in section, not a diamond. The Japanese also use a system based upon subdivision of the main slope triangle into sub-sections to determine the cut angles in regular plan, regular slope compound work, a method, as far as I can tell is unknown to the carpentry traditions of other countries. This is the 'ko-ko-gen' method. It's very easy to learn and use in comparison with a lot of other systems, in my opinion.

I do like the French method for certain things, however I find their traditional lay out texts, like Mazerolle's, quite frustrating because of the numerous errors and misleading pieces I find in them. One of the newer French texts I have, Charpente en Bois, also has mistakes. It's quite rare to find any mistakes in the Japanese texts on layout, I have found, so I feel I can trust them more.


That's just a small slice of a large pie I'm afraid. Thanks for the question and getting back to this topic.

Cheers,

Chris