Craftsmanship in Wood

No, sorry, but we don't mean the same thing. They did not reverse the arrises on the drawing- and even if they did it is not the error anyway.

The issue is that they drop plumb lines down from the stick's cross-section to form the report line 'A'. Plumb lines reported 'A' then placed to produce the 'Vue de dessus' leads to a plan view for the crossing stick which is not the correct dimension.

Here's the 3D view of the problem - note the orientation of the arrises:

Oh, well... It finally sunk in!

I got stuck with my idea that they mixed up the arrises, that I did not realise that the correct orientation of a stick's cross-section would be perpendicular to the slope. And therefore the report line A must be aligned with the slope.
If doing it this way, oh wonder, then the arrises are all at the right place.

Thanks for leading me on to the right track.
Hope it wasn't too annoying.

Nice!

You're a lot closer to the answer, but not quite all the way yet. This is the correct solution:
I'm wondering if there would be any point in writing Les Compangnon Du Devoir a letter. I might do that sometime, but I want to work my way through some more of the book first to see if there are any other issues. So far, the plates after number 1 have all been correct.

Of course, you are right.
My measurements are at slope, yours are horizontal and therefore the correct ones to transfer them to plan view.
I overlooked that. *sigh*
It will be the best to draw it in order to cement my new knowledge.

From mind-drawing to real-drawing.

One last question: I wonder if it is necessary to rotate the report line to horizontal in this case.
The distances remain the same in both cases, right?

I appreciate your new blog-series by the way.

One last question: I wonder if it is necessary to rotate the report line to horizontal in this case.
The distances remain the same in both cases, right?

That's correct in regards to the distances remaining the same. I added the arc to bring the report line into a similar arrangement to what is shown in the text, and if you wanted to instead project the lines down and reflect them directly around a 45˚ line to the plan, the arc is the simplest means to do so.

Nice job on the drawing!

Chris Hall wrote:...and if you wanted to instead project the lines down and reflect them directly around a 45˚ line to the plan, the arc is the simplest means to do so.

I understand, then it makes good sense.

Considering how little sleep I'm getting of late, I'm surprised i'm making any sense at all