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Log Layout #10092 11/01/05 04:03 AM
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michael morningstar Offline OP
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Greetings Chris,
Hope all is well on the other side of the continent. Say, for several years now I've had some nagging questions regarding a few different log layout senarios. Perhaps you might have some insight?
My first question arose after viewing photos of Harrelson Stanley's bath house. That structure employed round/log noki keta in conjunction with transverse and longitudinal hari . In many instances, members that will have housings and female dovetails will be flattened, this of course facilitates quick layout and cutout. On such a piece, taiko , right??, the correct depth of housing and dovetail is easily obtained by indexing off of the created flat plane which is parallel with the vertical axis. What puzzles me is how to achieve the correct depth on a completley round member. One can layout these depths on the ends and transfer them to the surface as I noticed in a photo, but how to utilize them? Let's say that it was decided that backs of dovetails would be five sun from centerline and that the backs of housings would be six sun five bu from centerline. Three parallel, verticle lines representing center, back of housing, and back of dovetail would be made on each end, and six lines snapped between them. Also a horizontal axis would be established on each end representing the elevation of the bottom facet of the male log, and a line snapped. By using hikari to transfer the profile of the male log onto the female log, the lines representing the side facets would rise up from the bottom line and connect with the top "housing" line. The bottom "housing" line will lie below the bottom facet line and therefore doesn't seem usefull. It might in the case of a through dovetail, but not in this case. Help Mister Wizard smile Take Care, Michael

Re: Log Layout #10093 11/01/05 05:29 PM
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Chris Hall Offline
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Mr. Morningstar, you have surfaced. How is the new piece of land and work scene going?

You do ask a good question there Michael. I'm pretty sure I understand your question, but it's not utterly clear to me, so if I go off on the wrong tangent, let me know.

You question relates to how to fit hari to round keta. One point: taiko is the name for one type of treatment ("naguri") of hari, and refers specifically to hari that have had their sides slabbed off and the rest left in the round. It's also called "taiko-otoshi". Other treatments include hachi-men-tori (eight-face faceting), chouna-men (adze-dubbed face), uri-kawa-kiri ("melon-skin cut"), etc.
Now, the keta need to be of deep enough section to receive the hari when the drop-down dovetail connection is used. Typically, after the hari is connected, the amount of relish left on the face of the keta below the lower surface of the hari is 1/3 to 1/2 of the total height of the face.
It is a fact that these connections on round keta are going to be weaker than on square beams as there isn't as much meat there for the dovetail. It would be MUCH better to lap them with a cog joint of some type wherever possible. In either case, it is a joint that needs reinforcing with some metal. A better choice is to use rectilinear-section keta with log hari, but I appreciate you may with the all-log look for some reason. The beauty of logs is their strength in the round, and it doesn't make so much sense to compromise that by hacking deep housings into them.
When using round keta, and drop-down dovetails on the hari, you must try to keep the depth to the 1/2 mark, possibly a smidgeon over, otherwise you run into difficulties, as you noted, as the lower face of the keta continues around. It is possible to fit the hari lower down, even to parallel with the keta, but you may not be be able to use the drop-down dovetail (complicating assembly), or you will be taking so much meat out of the keta to provide adequate housing depth that is ends up weakend excessively. In cases without a post underneath, or some other form of support (like a cantilever above that is connected) the strength of the connection would be worsened - you want maximum possible amount of fiber of the hari supported, without leaving too little relish on the keta below it. Since the end of the hari is faceted to give flat bearing surfaces, you can drop it slightly lower than the theoretical 1/2 way mark.
The treatment of fitting to the same height is seen in the keta to keta connection under a hip on a veranda, with that funky keyway joint, but that's about it. If the butt of the hari is flared a lot so that it would be tough to keep it to the 1/2 way insertion mark, then the flare must be removed, but not so much that you end up weakening the hari excessively - and I know you know that so I won't elaborate further.
Getting back to the keta to hari layout - how to achieve the correct depth on the keta housing: you can establish the to centerline and the lower centerline on the keta quite readily. The keta can then be rolled on its side so that the top-bottom line axis is horizontal. Then, at each housing location, you need to be sure that the log is supported by something that is also level to this axis. You need to ensure that the log is not forced out of shape by being laid on it's side as well, by checking your top/bottom layour lines with a string line. with the log on its side, and a level reference surface underneath, it is a matter of measuring up plumb (you can use a pair of sashigane from your top and bottom lines to the housing depth you want. Then it is a matter of cutting down to the lines. With a pair of sashigane you can also confirm whether the housing is in plane with level or not.
Depending upon the shape of the log used, the housing can be kept uniform in relation to the top/bottom line reference axis, or you could vary the depth, making sure that you remember to adjust each keta housing to its hari as required.
And you could rig up a box to do the same cut out with the housing router mounted on it, or a regular router quite easily too. The box could be made to index against the top/bottom layout lines.
You also need to mark out the mizu-zumi line on both the keta and hari so that you can be sure you are bringing the hari down to the right depth. That line can be laid up off your reference surfaces too. On the hari, the mizu-zumi must be judged carefully in relation to the shape of the end of the log and how it will fit to the keta. On the hari the mizu-zumi is the primary reference line.
As far as the rest of you question, regarding determining the depths of dovetail, etc, it seems to me that once you have a reference face, all of the other depths you need are determined from that.
The issue with using logs for keta is that you must choose the hari carefully as there is less flexibility in terms of housing depth available for the hari. There is a narrower range of logs that would fit well to the keta. While deeping the housing makes for a wider face on the keta, it also weakens it, so you have less room to play with.

Anyway, I hope that answered your question. If not, let me know what areas you need me to focus on, and I'll do so.

Chris


My blog on carpentry practice, East and West:

https://thecarpentryway.blog
Re: Log Layout #10094 11/08/05 02:18 AM
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timberwrestler Offline
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I have a general Japanese-style log layout question. I've heard that there is some kind of flat pattern board that is used to scribe logs to square faces (like a hari to square plate). Is this how things are traditionally or currently done? I imagine this would work because, for whatever reason, logs always seem to sit over or sort of half-lap over the plates in Japanese structures. A week or two ago I was at a local timber frame house that had log tie beams connecting to a square plate. He had a very similar look to the Japanese log/plate joint, but instead of the whole housed dovetail Japanese thing he had a horizontal tenon, with some of the round left to lap over the plate. It was nice looking and I imagine both stronger and easier to cut than a housed, stopped dovetail.

I also can't figure out why in the world you would turn both the plate and hari on their sides to do any layout.

Thanks,
Brad

Re: Log Layout #10095 11/08/05 04:35 PM
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Chris Hall Offline
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Huh - I replied to this last night, but my post seems to have gotten lost somehow.
The Japanese method of using a "hikari-ita" to transfer the profile of the end of the hari to the keta is standard practice. There's also a method using a pair of sticks that are connected to a pair of crosswise sliding bars that can be set to the profile of the har and then transferred.
I went into some detail last night, Brad, on your comment about not getting why you would turn a keta over for layout, but I'm feeling like not repeating myself. Why don't you share with us your perspective on suitable methods, and elaborate upon what you find puzzling about moving the keta around for layout?

Chris


My blog on carpentry practice, East and West:

https://thecarpentryway.blog
Re: Log Layout #10096 11/09/05 01:43 AM
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timberwrestler Offline
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Chris,

Bummer your message disappeared. I hate it when that happens.

I read your message twice last night, and I must have it read it wrong both times. I thought you also intended to roll the hari on it's side, which didn't make sense to me because if the plate is on its side, the hari should be sticking straight up in the air--a precarious position to be scribing and cutting. So sorry. Too much sawdust in the head.

Is hikari-ita the method of putting a level plane below the joinery?

Brad

Re: Log Layout #10097 11/09/05 03:16 AM
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Chris Hall Offline
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Hi Brad,

okay, I hope that sawdust clears. Yeah, I was referring to keta layout, though the hari may also be flipped on its side for certain layout too - and the hari is not connected to the keta for this.

The hikari-ita is the transfer board (hika(ru) means "to measure" and ita means "board.

Chris


My blog on carpentry practice, East and West:

https://thecarpentryway.blog
Re: Log Layout #10098 11/09/05 11:36 AM
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Mark Davidson Offline
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chris, this thread is interesting, but I can't understand the japanese terms. Could you provide a translation of some of your basic carpentry terms, or point toward a site which would have this?
It may be an idea to create a separate thread with this info, then that thread could be bumped to the top when a question like mine comes up?

Re: Log Layout #10099 11/10/05 12:08 AM
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Chris Hall Offline
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Hi Mark,

thanks for your post. The terminology is a bit mystifying for sure. With the two folks I've been having this discussion with so far, I know that each of them is fairly familiar with the terms I'm using - but not the general audience. I think another thread as a glossary isn't a bad idea.
I have an article coming out in the next TFG Journal, where some of the terms for the various components in a frame will be explicated.
Until then, here's a rundown:

keta: the wall plate/building perimeter beam. Also the name for the beam used along the veranda to support the decorative rafters - called the 'noki-geta'. If it's a round log, it's often termed a 'gagyo'

hari: tranverse beams that run across from wall plate to opposing wall plate (keta to keta). There are different types of these, and if the word 'hari' forms a suffix, it becomes '-bari', as in 'koya-bari-gumi' (hut beam construction)

taiko: the name for a hari that has been slabbed on two sides.

mizu-zumi: lit. 'water-ink'; the horizontal reference line established on timbers at a pre-determined height

I think that covers the terms used so far. If you are not clear on the meaning any of these terms, or any other Japanese carpentry words that you may have come across, please let me know.

Chris


My blog on carpentry practice, East and West:

https://thecarpentryway.blog
Re: Log Layout #10100 11/11/05 03:18 AM
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michael morningstar Offline OP
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Thanks for responding Chris smile ,
The notion of using sashigane as winding sticks occured to me awhile ago, but I must have suppressed it in hopes that an easier method dawned on me. A Smatlevel perhaps ?
You've brought up a very important point regarding the soundness of the hari to log keta connection. The more I reflect on it, I realize that Harrelson's building is the only structure where I recall seeing this done. I'm curious as to the joinery employed in round engawa-keta hip junctures? Aside from the "funky" joint shown Wood Joints in Classical Japanese Architecture?
Also, are you aware of a general stategy for organizing the layout of many hari , overlapping each other longitudanly and transversely. My only experience is with transvere hari , which is very straight forward. The dense web we see in many minka roof structures baffles me confused James showed me a picture of logs that had layout marks on them from a shop in Japan. It seems that what I was seeing was the ten line and then lines representing distances above and below ten . Do you suppose that a system of mapping might be used? Thanks for your knowledge.
Michael

Re: Log Layout #10101 11/16/05 02:11 AM
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Chris Hall Offline
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Michael,

please excuse the delay in responding, I simply forgot.

The alternative engeta joints I've seen are simplified versions, ofter with a stub tenon, detachable nose, and all-thread to pull it all together.

Fitting multiple hari together can be done in a variety of patterns. It depends upon what sort of logs you have - in terms of their shape. If using taiko, then there is a mizu-zumi (water-line) established on the flat sides, which is used as a reference. Otherwise, you are scribing, one by one. Lay a transverse hari - or several going in the same orientation, depending upon the pattern you desire - lay it out, do the cut it out and then fit it. Then take the hari that is to fit crosswise on top of it, orient it to plumb, and scribe it using the hikari-ita. The crossing points for the hari-to-hari are usually a form of cogged partial lap joint. With taiko, it is a pretty straightforward procedure to transfer layout marks; with round or multi-faceted logs you will be scribing, plain and simple.

I hope that answers your question well enough. Personally, I quite like the idea of 'weaving' the hari; say one across the short span, then one crosswise on top spanning the long axis of the building, then another crosswise on top of that on the short axis. You need particular shapes of hari for that, ones that do not have a consistent bow, rather an accelerating curve or a curve concentrated on one end of the log, or a wiggly log.

Chris


My blog on carpentry practice, East and West:

https://thecarpentryway.blog
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