I’ve been on a bit of a French Carpentry drawing tear for the past couple of weeks. With the lucarne biaise (see the previous post) out of the way, I moved on to the next dormer in the line-up, the fan-tailed dormer, or lucarne éventail.
When I last tackled (<– a link) this drawing, I got hung up on a part of the 2D drawing concerning the ridgepole and the alignment of it's undersurface to the body of the roof:
“With a little reverse drawing from the completed 3D parts on top of the 2D plan, I was able to determine the correct arrangement. I still don’t get everything on the drawing, but had enough to produce developed views of all the parts in the end.”
While I solved it using 3D, the impression I had formed is that the drawing in the book was defective, and that was where my study left off last year. Again, I had some useful recent correspondence with Tim Moore in France, and he pointed out that the picture of the ridge pole cross section on the 2D plan had to be showing an oblique section of the ridge. That made perfect sense. If one cuts a housing on a beam for a hip rafter, for example, the lower surface of the hip rafter, while square to the hip itself, forms a sloped line on the face of the beam which receives it. Once I got that – and it seems obvious in hindsight – I realized that I could probably work the remaining drawing bugs out after all.
Here is the (mostly) completed 2D plan drawing of the fantail dormer:
I left off developing the lines for the rotated hip rafters and associated jack rafters, as those are fairly straightforward. It does end up with a lot of lines on the page all the same.
The éventail dormer completed (right), and placed into the model with it’s neighbours, the nolet biaise (middle) and nolet carré (left):
A view of the same, looking the other direction:
As you can see in this plan view, the fantail dormer takes its name from the spreading rafter plates:
To further add complication, the ridgepole descends on the dormer roof:
So, I am caught back up to where I left off last year and am now wanting to forge ahead with some more Mazerolle study. There are two more dormers to deal with in the text, and that is what I will focus on. Next up: Lucarne Et Nolet Sur Arêtier (dormer on a hip corner). I hope you’ll stay tuned to the Carpentry Way.
6 Replies to “Following Mazerolle: Lucarne Et Nolet Éventail (III)”
Your level is simply awesome, I love to read your blog, God bless you man, thanks a lot for sharing your knowledge
very kind of you to say that. I am struggling with parts of the Mazerolle layout, and can hardly say to have much 'down' yet, but it has been a most interesting journey so far. I'm thankful to the insights I gained through my collaboration in this process with Tim Moore.
Glad you are enjoying the blog and many thanks for your comment!
The sloping ridge edge bevel geometry on fig. 3 plate 11 Louis Mazerolle's book looks wrong. Did you use a different method to correct/establish the sloping ridge edge bevel?
Here's what I used to establish the sloping ridge edge bevel.
it has been many months since I looked at it and remember having problems with the drawing initially in regards to the sloping ridge but resolved them later. The drawing in the book did work – I assume you're talking about the backing cut?
Yes, I was referring to the backing cut on the ridge. Since the ridge is theoretically a hip rafter.
that section of ridge drawn on plate 11 is an oblique section cut of the ridge, not a true section cut. It's to do with the hip rafter upper end cut layout.