Hi, Chris here,

I asked Joel McCarty to set up this forum for those of you out there who might be interested in Asian timberframing, Japanese joinery, Japanese tools and such things. If you have questions about it, or discussions you'd like to embark upon, please feel very welcome to post. There is no such thing as a dumb question!
A little bit about me - Japanese timberwork is my professional specialty and area of tremendous passion. I particularly am interested in Japanese roof work, descriptive geometry and compound joinery. I am also keen to talk about tools, both hand and power.
I teach courses occasionally for the guild, including one coming up this Fall, and I look forward to meeting others in the community who share my interest in this area - hopefully in person, and if not, online.
I look forward to engaging and varied discussions!

Regards,

Chris

Hello Chris, my name is Michael Cran. I live in Nelson BC and run a small design studio. I am very drawn to the japanese spirit of workmanship. I recently stumbled across your Gabriola Island workshop and was sorry that I missed it by a year. Unfortunately the Massachusetts workshop is not an option for me.
I have recently been commissioned to build a Japanese style entrance gate which invlolves some compound joinery and as with all my other projects I said "Yes! I can do that". Now I have to figure out how. I have been studying 'The complete Japanese Joinery' and am learning much but I am still a little confused about how to calculate the angles and layout lines for hip rafters. This gate is not strictly a traditional structure, but my interpretation thereof based on the clients desires. I assume I should begin by determining the pivot points? Do I have the correct scales on my square? If I remember correctly they are makume and marume. I know I can calculate the circumference of a circle, or the largest square in a circle. Any use for hip rafters? Feel like coming to Nelson and giving me a hand? 20 bucks an hour and a floor to sleep on. Anyways, I'd appreciate any help you could give me. I will definitely be purchasing your book when it comes out. Feel free to contact me at minkastudio@gmail.com or 250 505 5421

Hi Micheal,

thanks so much for posting your question to this forum! I am happy to help you out any way I can, though I cannot, unfortunately, come out to Nelson as I am currently residing on the US East Coast. If I were still on Gabriola, well, then things might be different.
I am not surprised that you are finding yourself confused after reading the Nakahara book. It is intended as a general survey, just touching on various aspects of Japanese carpentry, and there are issues with the translation as it is. A good place for inspiration at least.
Since I don't know your grasp of hip roof framing generally, I am not sure how to advise you. The Japanese method of determining the cut angles for a regular hip are quite straightfoward in their own way, but it is nevertheless a complex topic. I f you could be more focused with your questions, I will help you as I can, but to explain the spectrum of Japanese hip roof framing in detail would be beyond this medium here I'm afraid.
The Japanese rafter square, sashigane, has a variety of scales on it, though some sashigane lack certain scales.
The front of the sashigane, omote-me (the 'me' is pronounced like 'may', in case you were wondering, and means 'scale'), has the conventional measure on it - whether in traditional sun and shaku, in inches, or in centimeters.
The back of the sashigane, ura-me, has several posssible scales. Typically it will have the kaku-me on the long arm, which is the front scale measure x sq.rt. 2 - this is the one used for regular hip rafter work primarily. This scale is the one that, if held across the diagonal end of a log (the top, not the butt) will tell you how large a square section log can be milled. There are transfer points from kaku-me to omote-me scales, and vice versa. Thus, if you look at 10 sun on the front scale, and note the mark at 10, you will see a mark carried over to the kaku-me, and it will read about 7.07 at that point (10 divided by the sq.rt. of 2). Conversely, if you took 10 on the kaku-me side, note the mark and turn it over to the omote-me side, you will see a mark at 14.14 - that is, 10 x sq.rt. 2. These carry over marks allow you to use the sashigane either side down most of the time.
The scale you mentioned, maru-me, relates diameter to circumference - it is a pi scale in other words. Hold this scale across the diameter of a circle, and the measurement you read will be the circumference of the circle. This scale has quite limited use and is sometimes omitted from certain squares. I decided to omit it from the square I designed a couple of years ago for Shinwa becasue it is just not particualrly useful. This scale is of no use for hip rafters, even if they are curved.
If you work in inches, I don't recommend the older inch-scale sashigane unless you plan to work in base 12. As Japanese roofwork is done in base 10, it is hand to have a sashigane that works on that basis. And if you are to work in base 10, it would be also handy to have a tape measure delineated in 10ths and 20ths too. I am thinking that Starrett might make one, but I'm not sure. If you intend to work in base 12, then a regular western framing square is the tool to use.
Okay, well, perhaps if you could post a drawing of the gate you are planning, or plan views, I could see more clearly what your ideas are.
I look forward to your next post Micheal.

Hello Chris, it seems that I can not post drawings to this forum, could you drop me an email? Your enthusiastic response is most heartening. My sashigane is in inches, with kaku-me on the back. minkastudio@gmail.com

Hello, much thanks! finding compound angles is a difficult task. Is the Japanese process different from other areas? I know how to find certain angles by using the triangle. Lifting up, laying down, finding points, laying down.......elevation, to plan, to elevation to plan. Do the Japanese use the same technique? Is the technique drawing (or drafting) based? Could you give us a summary of the process. Thanks, mo

P.S. minkastudio, search your topic of posting pictures within this site. There are some very descriptive remedies. I know I would like to see some more drawings.

Bueller......Bueller......Bueller.....sionara.

What is the major difference? Occidental and Oriental?

Hi Mo,

I guess I must have been quite preoccupied and missed your question altogether. Sorry about that! I know it is a little late in the game, but if you are still interested to know the answer I'd be happy to elaborate some. The short answer is: there are some similarities to western developed drawing techniques, however the Japanese also have methods that are not found in other systems.

~Chris

Hey Chris,

Thanks for the follow up. Sure I'd be happy to hear some differences. I know that developed drawing is hard enough to grasp with person to person communication along with actually doing it. So I can appreciate the fact that it might be hard to communicate the differences in this medium. If that's the case no big deal. I know your blog.

Thanks for the reply.

Mo

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

Hey Chris,

Thanks for the reply. That is interesting about shaping the wood to create a square section when a level plane is present. It seems that would add more work on the front end but then less when you get down to the joinery.

A few of us have been taught the french method and all I can say is that there is still a lot more to learn. If there was a scale of expertise of 1-10 I would say I'm at about a 5 with it. However, we have been taught the principles of it and the remaining problems should be able to be solved with them along with some head scratching.

I have inserted a drawing that our teacher gave us as one of the last studies. Basically take two pieces of wood and intersect them at any given angles to find how they join. Take a look. If you want I can try and get you a high-res pic of this via email.


As far as French text. I have had the privilege of looking through these volumes (that are in the link below). All I can say, is that it is the most extensive I have ever seen, and a masterpiece in itself. There aren't many of these present in the States that I know of, but do know of one set. If there is something you have been looking for, I can try to find it for you.

I would like to save up to purchase, but at a 1000 Euros, it will take some time. Rosetta Stone would not hurt either, but there is a ton of visual information. I'm pretty sure the drawing I have attached is from the volumes.

http://www.priceminister.com/offer/buy/7...Bois-Livre.html

Have a good day,

Mo

P.S. As I thought, the picture would not come up big enough in the forum. I'll send you one via email that is better.

Hi Mo,

thanks for that. I received the drawing by your email. I wish you hadn't sent me that link to the multi-volume set actually - like I needed something else expensive to tempt me. Sheesh! Tools and books are always finding new ways to extract $$ from me. It's vicious!

Good to be in touch.

Chris

That drawing you posted (and sent to me), BTW, is a good example of the 'devers de pas' technique being used for development...