Today is a post about progress, the sort one makes by taking a step back and then two forward. Yes, another wormhole was discovered, and I surely fell on into it. I was trapped in there for a good while today.
Here’s the problem – a little matter that all started with a couple of lines that weren’t quite matched up:
If you click on the picture, you’ll see that just a hair to the side of the solid line is a little dashed line. Trouble is, that dashed line was the reference, and the solid line snapped slightly over to the side for some reason. A solid line I based a whole bunch of stuff on….
Damn that SketchUp – I shake my tiny fist…
That little kafuffle with the line had effects when I started placing one of the developed fan rafters into place on one of the purlins and things just weren’t quite adding up. That’s how I found it – tracking backward until I located the discrepancy. Unfortunately, in the end I realized that the repercussions of that line being just a hair wrong were going to have numerous down-stream effects, and more importantly, it meant that I had to re-draw all of the curvilinear parts. -gulp-!
Here’s the thing – while the drawing will look absolutely fine upon inspection, unless you magnify in, way in, continuing on with the drawing when it is based on an error, no matter how slight, means I cannot rely upon the data points I have acquired so far in the drawing process. You see, once the drawings are completed, I will be spending quite a while re-drawing key portions of the 2D so as to make a whole bunch of templates with which to shape parts and check alignments. The 3D allows me to be absolutely sure of my results, but it absolutely punishes me if I don’t have the 2D portion just perfect. Nothing painful mind you – I imagine some future version of the software might be configured to give the user little jolt of they make an error, who knows. Just kidding, I think…
By getting the 2D perfect, I can rely upon the drawing directly when I draw the templates in full scale, and I will be able to take off various heights and measures from the virtual into the actual with total confidence. So, it’s worth taking on the error and fixing it now. That’s my stand at least.
Questions of deciding whether to fix an error once discovered or to carry on and either build on top of it or try to compensate for it some way come up all the time in construction. It’s all about the best laid plans of mice and men, and this mouse is trying hard to get the plans laid as right as he can.
So, 10 hours later at the drawing board, and I am only just managing to stave off going completely ’round the bend, but here we have it, the Mark II:
Though I had completed the hip rafter layout to the point where the fit between components was decent at the exterior intersection…
That little gap above the hip arris where the kaya-oi meet on their lower surface had been bugging me, and I had decided after that previous trip down the wormhole that I would, you know, how do they say it? Oh, yes: ‘deal with it later’.
Trouble was, I hadn’t really found a solution for determining the backing cut on a gradually curving hip rafter with a curving purlin meeting it. I have virtually every Japanese layout book there is, and, strangely I might add, none of them seem to cover this matter of the backing on a curved hip rafter with curved kaya-oi. There is one illustration in one of Togashi-sensei’s books that shows the hip nose layout including the backing cut, and I had followed it faithfully, several times over in fact, and the results were plain enough: it didn’t come together right when the parts were assembled in 3D. The drawing above is proof of that, a product of that method, and when I drew the new hip rafter and kaya-oi, I had the same problem again. So much for the aforementioned ‘later’.
I have other roof carpentry layout books in French, German, English, and even Yankee, but the topic of curved hips is really not covered in any semblance of detail. The few odd methods I have come across in those texts I have tried but they don’t work when the eave purlin which lies atop the hip is also curving up. They only work for curved hips with with straight parts laying on top of them. A curved hip with flat strips or boards laid upon it is no big deal, but if the eave purlin, kaya-oi, is curved, the backing cut is a tough nut to crack. It has stymied me for a while now.
Well, was a tough nut to crack, for I managed to solve the layout on that today! By determining the correct method, through some reverse-engineering and a sudden flash of insight, I was able to also determine what exactly was wrong in the illustration in Togashi’s book. That, my friends is the very first error I have ever discovered in the master’s work. While I derive little satisfaction in finding his little mistake, I am tremendously pleased that I have at last solved a vexing puzzle. Maybe I’ll write him – not sure if he is still alive though.
In the end, I had to construct new hip rafters, kaya-oi, and komai. So far I have placed the new hips (sumi-ki) and kaya-oi on the roof, and things are fitting just as they should:
Here’s a look down that hip rafter, showing the curving and slightly twisting backing cut:
Thanks for your visit and comments always welcome. –> on to post 6