Sunday, July 19, 2015

Project Mayhem: second round

It's been a bit more than a month since we started. We are 4 joints older and perhaps a bit wiser too.

I guess we all have enough time for the joints, and we are not yet struggling to finish the homework before deadline. We only have one miss and 2 late entries in 12 occasions, that's a pretty good stats if you ask me.

So, I'm raising the bar.

There are two areas I'd like to develop more: architectural joinery and mathematics.

You didn't see that coming, did you?

First, what do I mean by architectural joinery? As people say, cutting the joints is the easy part, the difficult part os to draw them. But you also need to know what to draw and where. Using a double tenon or hunched, a goseneck or dovetail, and so forth and so weider. For that a theoretical problem will be given and you need to post your solution to it. For example, a client asks you for a saw horse. Draw all the members with their respective joints and justify why using one instead of the other. (This is not the real exercise, it will be slightly more complex and more of an architectonic nature.)The following week when it's your turn to pick the joint, you need to give us also one of this theoretical problems. I'm thinking of problems that are useful to us, design the roof joints for Jason, another canoe holder for Steve... catch my drift? You will see more with the example of wednesday.

Now, mathematics. Why? First answer because I think that in a proper world, people not only knows a few languages, like english, french and C++ but they also have a good base of calculus and classical mechanics. The answer that may interest you, because Chris' books start with a book on "mathematics for carpentry", so if you want to reach the hopper you first need to understand Pitagoras.

Without having read any of Chris' books, there is something I noticed in his drawing and in the forum posts, is that people don't really get mathematics from a user point of view. What do I mean? Chris' drawings give measurements to the 1/10000th of an inch, some people in the forum write numbers till the 20th significant figure. That's a 2 microns shaving and the size of an atom respectively. Neither make any sense to describe the length of a rafter or a saw horse leg.

So what's the answer? Trigonometry from a physicist point of view. I will be giving problems each week and some resources to read. The problems will be take from my university book, and I did them when I was 16 and in high school, so you should have no problem whatsoever to understand them. I will link you to a proper american class in youtube from MIT or whatever so you get the base to solve the problem.

What's my idea?

Look at this picture:

How many joints are here? How many variations for each joint? What's the length of that hip rafter? How do you label the pieces so you don't mess the whole thing up?

We are probably not going to build any house but that kind of knowledge is useful for any project we may undertake. I hope by the 9th month of study we are closer to understand this.

So, from next week onwards, the problems for project mayhem will have 3 questions: a joint, design and mathematics.  It would be great if you let me know what your mathematics level is to plan the problems for wednesday. I'm thinking of Pythagoras' theorem, sin and cos, and one or two more things (approximate any square root amongst them, so you can cut a rafter with .2mm precision and do that by hand with pen and paper) so after a month we can pass to the next thing. Roof model someone?


  1. Eeeek!

    Mathematics has always been a struggle for me. Sadly, I will need to go through a very substantial review on even the most basic aspects of sin, cosine, and tangent. I will definitely be the trailing end of the curve here, but this is actually a very important point that you raise.

    Back when, people actually were required to know these basic mathematical functions. Now all we have to do click a button. Even the measuring is done for us, if you get one of the fancy digital read tape measures. One of the aspects that I am so enjoying about the Japanese joinery, is the continued reference point back to the tools we use. We layout the tongue of the joint at 15 mm, 30 mm, whatever, because that's the thickness of the leg of the sashigane. Fast and practical, though not truly engineer friendly in terms of designing the member for the intended load. This reference back to tool dimensions feels a little like the "eyeball" measure.

    I have a bunch of short lengths of 2x12 laying around. I intend to begin my trigonometry practice with laying out the "hopper" form that gets used in the Japanese carpentry curriculum. Hoppers make great garden planters! I'm going to use a calculator, I don't care what you guys think!

    Also....we are most likely buying property here, so I might be especially time challenged for the foreseeable future.


    1. Actually..... If we are looking for practical applications here.....

      I need a relatively simple structure that can be built using found materials, approximately 12' x 24' that would incorporate 3 rooms, two bedrooms, one living area. Kitchen will be separate, as well the bath. Purchased material should be of 12' length of less, to fit into my minimally sized car. Joinery is a reality here, ha-ha!

      Tin roof, single wall, no electric... Very simple. Suggestions are encouraged!

    2. Ooooo, big verandas/awnings as well! Elevated post and pier construction.....

    3. LOL

      That was precisely my idea, crowdsourcing ideas for projects. But you need to wait your turn, I need help with mine first :P

  2. This should be great! When I cut the roof of my house it took quite a bit of study for me to understand the valley rafter and jack rafter cuts. Its the kind of thing, use it or lose it. I calculated lengths for the rafters on a pure mathematical basis as well as direct measurement, as things in the real world are never perfect. Just what we need, geometry is our friend!