Theoretical woodworking

An on-going study exploring traditional carpentry layout techniques.
Sebastian Gonzalez
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Theoretical woodworking

Fri Mar 13, 2015 10:52 am

Hi Guys,

Long time no writing here... last months have been a bit crazy with the moving and packing things/finishing stuff from work/planing how to make the whole thing work. I will be traveling first to Chile in May while wife stays here with the cavies enjoying the summer. Then I pick them up in september. In the meantime I need to fix the house and set up the workshop.

Anyway, I packed almost all my tools and man I feel empty. I still have a month and a half here though and want to keep on learning... so I thought about descriptive geometry. But the good old way. Somehow I'm simply cannot use 3d drawing software. I mean, I even have problems with 2D so 3D is well beyond my means. Besides I want to step out of the glass screen for a while.

I've been doing a lot of reading in Chris' blog and some old books but I still could not make head or tails of the drawings till yesterday. Since I'm an impulsive person, instead of starting with the simple roof I went for the spherical dome:
Screen Shot 2015-03-12 at 6.39.57 PM.png
Screen Shot 2015-03-13 at 1.58.18 PM.png
It took me a while to understand it, and my calculus-trained mind was complaining all the time about the squaring of the circle going on there.

Eventually, I went back to a simple roof and it struck me: the drawing are static representations of a process. And you need to follow the construction to understand it. I guess that's why they call it constructive proofs.
Screen Shot 2015-03-13 at 2.07.17 PM.png
Today, I took another look at the splayed work from the "The carpenter's and builder's assistant, and wood worker's guide (1874)"
Screen Shot 2015-03-13 at 2.35.55 PM.png
I still don't understand this one completely (in particular the size of the plan), so I took the bevel angles and put them in my keynote:
Screen Shot 2015-03-13 at 1.13.54 PM.jpg
From the drawing you only get 2 bevels but the other two are reflections of those since the timber is square. Print it in paper, and fold on the lines:
Photo on 3-13-15 at 2.55 PM #2.jpg
It works. Sorry about the crapy picture but I'm in the office at the moment.

Now, as far as I can tell, by Thales theorem the same bevels should work for an arbitrary sized piece, so I could be able to make a mitred hoper now. Well, when I have a workshop again that is.

So, here my questions. Do you recommend any book for learning descriptive geometry? I found a PDF of la Charpente en Bois and seems really complete but a bit arid to follow, any japanese book maybe? Also, any ideas on how one studies this? You take the examples of the book and reproduce them in paper with different sizes/anlges/geometry? Make cardboard models of roofs? I'm a complete noob to drawing, so any help would be appreciated.
François Pernod
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Re: Theoretical woodworking

Sat Mar 14, 2015 3:58 am

Hi Sebastian,
a lot of different question in your post! First about the spherical dome, of course it's a squaring of the circle, you can't develop a sphere, so covering it with board is always an aproximation you have to finish with the plane, but the drawing principles of developing portion of the sphere are ok! think of peeling an orange!
The other drawings you show are a mix of carpentry and hopper problems mainly from English books I guess. First thing you have to understand is a shop drawing is a mix of everything you need to build your work, floor plan, cross section, true lenght of faces and angles, all this on the same piece of paper, so it can be quite confusing at first glance. And to further complexify, you have a big difference between carpenter and joiner drawing because carpentry is mainly structural and you have to deal with the roofer requisite, and the joiner have a different problem which is to have square faces so you can apply moulding to it, which lead to different solutions.
I will go through my library to pick some books French or English that are good compagnons and try to scan a few drawings to illustrate.
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Paul Atzenweiler
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Re: Theoretical woodworking

Sat Mar 14, 2015 10:08 am

I will be looking forward to observing the two members with the coolest names solve these problems. Francois, your statement about some drawings including so much information being confusing at first look is very true.
François Pernod
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Re: Theoretical woodworking

Sat Mar 14, 2015 10:13 am

Even more so when you do it full size on the shop's floor!
François Pernod
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Re: Theoretical woodworking

Sun Mar 15, 2015 10:46 am

Hi Sebastian,
I think the best way to go is to take two pieces of wood, draw and cut. For exemple if you take your third picture, the hopper, it works for any angle in plan and section. ABCDI is the floor plan with a mitered joint BD. E is the cross section of your rectangular piece of wood. L is the miter angle of face IJ and H is the miter angle of face IF. This is a shop drawing and not very clear if you're not used to it. Let's say you can put any section of wood inside AJI with faces paralel to AI and IJ,the miter angles will always be the same. You have one more angle on this drawing which is JID the level cut if you want to bevel your hopper and this is the angle for your circular saw to rip the cut.
Am I clear enough, pretty hard for me to teach geometry in English. By the way, I've never find any geometry treatese in Spanish, do you know any?
Last edited by François Pernod on Sun Mar 15, 2015 11:57 am, edited 1 time in total.
François Pernod
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Re: Theoretical woodworking

Sun Mar 15, 2015 11:53 am

I started scanning a few things.
The one in English i prefer is: Building geometry by W.J.Stone, 1st published in 46, I found this copy in a book shop in Cairo back in the 80's! I think you can find it on ebay.
I scanned a few pages concerning the hopper.
Well the order of the pictures are to be reversed and I can't add more than 5!
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François Pernod
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Re: Theoretical woodworking

Sun Mar 15, 2015 12:03 pm

This one for Chris,
I realize that scaning and putting on the blog is pretty long, it's ok for a few pictures but as soon as you want to put full chapters on the blog it's too complicated. Do you think there would be a solution, maybe something cloud based where we could exchange easily bigger volume of data?
François Pernod
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Re: Theoretical woodworking

Sun Mar 15, 2015 12:06 pm

Next batch of scans.
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François Pernod
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Re: Theoretical woodworking

Sun Mar 15, 2015 12:08 pm

I like this book because it applies to a lot of trades, not strictly carpentry.
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Chris Hall
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Re: Theoretical woodworking

Sun Mar 15, 2015 5:40 pm

This post is in the wrong section of the forum, so I will be moving it to the Drawing Study section.

Finding this topic a touch ironic after having written nearly 140 pages on the topic of hoppers in TAJCD Volume 2...

I encourage you all to delve into the topic of hoppers, and dig right into those old texts (as I have), but you won't find the same detail and thorough explanation in regards to the matter as in TAJCD II. One example: finding information on mortise and tenon hopper layout.

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