Compound angles in Oregon Dome-style triangular frames

[Gerry in Quebec]

I took a closer look at some computer models of triangular panels based on the Oregon Dome method. That's where you bevel-rip struts through the wide face and assemble them into triangles with butted joints. It now looks to me like there are indeed some compound cuts involved, namely at one end of each strut. Earlier, I thought there were only simple bevel cuts.

 

For the Buckyball panel domes that Bill Fisher is thinking about building (https://groups.google.com/forum/#!topic/geodesichelp/8MX7SJ9vd_4), which consist of pentagons and hexagons rather than triangles, there are no compound angles to cut. This is partly due to the fact that the joints are mitred, not butted. But for most triangulated panel domes, there will be some compound angles to cut, even with the Oregon Dome method.

 

Attached is an Antiview image of a computer model of a dome panel frame. It's a simple example of the Oregon Dome method applied to the equilateral triangle of a 2v icosa half-sphere. The compound cuts are the three exposed strut ends.

 

Here's a link to Paul Robinson's great little Youtube video on building triangular frames:

 

https://www.youtube.com/watch?v=U32KTMtp5kU

 

At the 6 min. 20 sec. mark, Paul pulls out a handsaw to make the final three cuts on his frame. These, as far as I can tell, are compound angles (though he says at the outset of the video there are no compound cuts involved). The advantage of Paul's setup is that the simple triangular "pattern" (or jig) he has created allows him to make these cuts without having to calculate any compound angle saw settings. The other three end cuts, done before the three struts are placed on the jig, are all simple bevel cuts, calculated from the face angles of the particular triangle he happens to be working on.

 

- Gerry in Québec

[Paul Kranz]

Gerry:

The last Oregon-type dome I built had compound angles, but not in a single pass. Everything was cut perpendicular to the wood and it was only after the bevels were cut from the side members that the compound angle were formed before they were racked in a jig.

Paul sends...

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Very high regards,

 

Paul sends...

ReviveTheFlame.com

[William Fisher]

I still think Oregon Dome makes a nice product. If I was going with larger than my plans, I would use their method (but using Gerry's 4x4 idea).

[Gerry in Quebec]

Thanks, Paul. It would be great to see some photos of your domes.

So far, I haven't used the Oregon Dome-style method to build a panel dome or even a dome model... only a 5-triangle cap serving as the roof of a small lakeside shed I built last year. But I like the relative simplicity of that construction system and hope to build a scaled-down model of an 18-triangle cabin once the snow is gone. For that I will bevel-rip 2.5" x 2.5" rough-cut lumber in half to make pairs of struts.

Meanwhile, we have so much snow here in Quebec's Outaouais region that my dome workshop is looking more and more like a huge scoop of vanilla ice cream.

- Gerry in fluffy white Quebec

[norm...@gmail.com]

Hi Gerry, can you share a pic of the ice cream cone?

We've hadn't had much snow in south central WI this year

Paul, you sure make using plastic sheeting look tidy!

[Gerry in Quebec]

I took this pic a few minutes ago. Even the cupola is buried. Luckily the camera didn't freeze. Including wind chill, the temperature is minus 35 degrees C (minus 30 F).

- Gerry in Québec, imagining a beach in Hawaii

[Paul Kranz]

Gerry:

Please find attached what I went through to make an Oregon Dome-like panels.

Paul sends...

[norm...@gmail.com]

thanks for posting that Gerry.  That's neat.  We've had the cold but not much snow.

[Gerry in Quebec]

Thanks for the file with pix, Paul. Looks like you bevel-ripped 2x4s for your triangular frames .... so 1.5" thickness roof-side and a little less ceiling-side. Nice setup.

[Paul Kranz]

Gerry:

Thanks, man, it was loads of fun!

Paul sends...

[Gerry in Quebec]

Here are three drawings and a caption to illustrate how an icosahedron could be built with dimensional lumber such as 2x2s using the Oregon-Dome approach to panel construction. I have not built this myself; it's an armchair exercise -- too blinking cold to work in the shop these days.

- Gerry in frigid Quebec