Saturday, May 12, 2012

The Story of the Gazebo (VIII)

One of the funny things about drawing in 3D is that while it can often help with visualization and problem solving, sometimes you really need to be able to set things up in 2D first. Case in point is the curved eave layout on this pentagonal gazebo roof I am doing as a design exercise. With hip roofs, the eave projection and rafter spacing are directly tied, and in Japanese carpentry practice one of the crucial aspects to getting a hip roof right revolves around getting the common rafter spacing sorted just perfectly. And with a eave that curves up, and a hip rafter curving up, the length of the eave changes from what it would be if the eave edge were straight.

It was in trying to move my drawing along a bit by adding in the soffit paneling that I discovered a problem with my 3d work. I had drawn the curved eave as a 3D construction in the first go-round, and the defects that arose because of this took a while to manifest. It turned out that I had so make a slight adjustment to the eave projection to correct the problem. So, it was back to the drawing board, and this time starting in 2D:

The projection traces, which are numerous, have been stripped away from the drawing to show it a bit more clearly.

With the 2D plans of the pieces figured out, I was able to construct 3D pieces from there, now including the soffit paneling and lattice (komai). Here's how that looks at this stage:

A view from underneath - at this point the material coloring is temporary and I will likely be making some changes before long:

There will be another soffit/ceiling, fitted between the wall plate and the outrigger plate, and I haven't started to draw that yet.

On top, I have roughed out the hanegi, the bowed cantilevers which support the eave:

So, it's moving along. At this point the hanegi are perhaps a little too thick, but their shape is about right:

Next up are the fulcrum beams for the hanegi, plus other framing details which associate, and then I will start on the lantern support framing and work out the actual roof profile. At this point I am thinking the roof surface will be moderately campaniform (bell-shaped, ogee-shaped).

In other news, I have been doing a little shopping for tools and wood and have a few new 'show and tell' items to post about in the near future. The Carpentry fundamental study group is on the cusp of starting project 2, which will be scissor-braced sawhorse. New members are welcome to join at any time.
Thanks for coming by the Carpentry Way.


  1. How are you creating the gentle curves in the top picture? Is it some sort of camber function in SketchUp? Is it something you developed yourself? Alright, I'm done shooting questions at you. For today. :) I'm having trouble envisioning how you would go about assembling this structure. I suspect it's a pretty specific process.

  2. Adam,

    "How are you creating the gentle curves in the top picture?"

    It's a Bezier spline tool plug in.

    The trickiest bit in terms of assembly is the reciprocal beam cluster, especially when it comes to fitting the last piece.

    Thanks for your comment!


  3. Wow. That's really cool. I didn't know about the plugins. Now I'm going to end up randomly attaching onion domes to everything I design for a while. Thanks for the tip.

  4. Very nice design Chris, and an interesting read as always! I've also done 3D work specializing in East Asian Buildings as well because of its intricate designs. I haven't used Sketch Up before, (I use 3Ds Max). My method to create gentle curves is to use a spline as a 2 dimensional blueprint and to pull the eaves up vertex by vertex; quite tedious :). Your comments above has taught me a new and faster way to do it since the program I use has a similar function.


    1. Frank,

      glad you found the above post provided you with some useful information - your comment is appreciated!


  5. Have you already finished this project? Can you publish the next (and final) steps, too? This really would be great! Thanks in advance! .-)

    1. Knispel,

      it was a design exercise - with the hope that a client might come along one day looking for a structure like this. So far, it hasn't happened.



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