Yes, I agree, I think we are talking about the same thing as far as compression goes. Let me add though that it wouldn't take any sort of thing added to a strut to apply any lateral force-- the struts all pull eachother through three dimensional space, and of course there is gravity, working both through the struts and on them. Add a little wind (or a lot sometimes on the playa) and you already have plenty of lateral forces on the struts.

If you put conduit through the 6' struts I think you will definitely be OK. In that case you could just use conduit and not even use the pvc over it...?

It occured to me this morning, and perhaps this was obvious to you from my earlier post (though it was not obvious to me <grin>) that you could do what fuller did-- build a two layer dome. In fact, since you are playing with nontraditional shapes you could build two layers on the top and bring the innermost layer down to meet the wallish part of the dome halfway down, and just do one layer from there.

Yes, I am totally with you there on the difficulty of modeling. For a while I was visualizing mentally, then doing a lot of math so that I could make paper cutouts and then assembling those with scissors and tape. It took forever!

What I do now is use Maya, the 3-d animation platform that is behind a lot of the special effects in movies nowadays. There is a personal learning edition that is free to download. The only caveat is that it requires a somewhat expensive graphics card, and a reasonably contemporary processor in your computer. You can also find cracks of the software out there, but that doesn't solve your system requirement issues if you have them.

But with Maya modeling is fast and easy! (faster and easier, anyway). You can easily create shapes and twist and bend and warp them, connect them with other shapes and move your viewpoint around to see it from different angles.

It is also possible, depending on your degree of measurement tolerance, to build a shape in Maya and then extract the strut length measurements directly from maya without ever having to do the math.

There might be some other software tool out there that is easier to use than maya-- it has a lot of functionality that is not used in the wire frame modeling work that I am doing, and all that other stuff gets in the way. Nor is Maya totally optimized toward what I am doing with it-- if there was something out there that was did less but was directed towards doing this specifically...

On the other hand, the lump of clay has an easy interface and you can do pretty much anything with it!

Oh, one other thing: this is the site of a guy in New Zealand who has been building nonspherical domes for a long time, some interesting info... I also have his book pdf if you want to check it out:

www.geocities.com/geodesics...ex.htm#idx

Bruce :-)