[Good guy]

Well done marek, a great job. I look forward to seeing how you use it.
Tagwex, it's because you are looking at a surface that curves in three dimensions. Nothing is flat, other than the surface of each individual module. Go study ceramics and learn to throw teapots - making and attaching spouts to them will teach you a lot about the surface of spheroids.

[tagwex]

I still cannot see why the horizontal members are not all level. If you look at the bottom members of Mareks you will see that they are tilted to suit the joint design that he chose to do. By choosing a joint that could accommodate equilateral triangles this could have been avoided.

[marek]

Hi guys
Sorry Ive been away for a while.
Tagwex 5/12 represent a little less then half sphere. 7/12 is a bit more then half. 5/12 of the sphere makes my bottom level tilted slightly towards the ground and less prone to wind damage I hope. I'm not sure what you had in mind when mentioned the almost horizontal beams? Yes its partly due to the the joint I decided to use. They are, "off center" which is best seen at the bottom level.
Also there are two types (and sizes) of triangles used in the structure. Yes only two. One size makes pentagram and a slightly bigger ones makes hexagrams.Unfortunately there is also a mixed shape I called which is connects penta- and hexa- grams.
Best way to understand the geometry will be probably to use a website which I highly recommend. You can make a projection and turn it around as a 3D object. choose a detail level 3 and use carcass projection colors represent different beams sizes. the link http://www.spam.
Hope that will answer your question. Anyways I'm happy to answer any question to people interested in the project.
M

[marek]

[tagwex]

That explains it some. I thought it was a full hemisphere (a 6/6). Like I said previously if I was to make one I would appreciate the complexity more. I thought 5/12 was something to do with the proportion of the triangles, pentagrams and hexagrams. If I was to build one I think I would have the first 900 mm from the ground up vertical and then start the dome. You have done a fine job Marek, interesting too. I am just trying to wrap my head around the nuances of it.

[marek]

Yes Tagwex
The one, which you sent pictures of, are much more elegant. Id like to do this type of joint but just wasn't sure seeing how complex, and precise it has to be. With this kind of construction we are talking about 0.1 of degree precision settings (in the joint pictured in Wexford dome each element has 4 cuts to be made on each end) plus level of the ground the structure rest on, is also important. My dome seats on the grass in back garden, I didn't want to overdo it. As for the bottom vertical wall? Well its a matter of taste, in my opinion it messes a bit with elegant lines of the dome, but certainly it makes the edges of the dome more usable. If I was to build again, id rather build 7/12 sphere (little more then half). This way Id get usable edges without compromising structure lines. I know now that, having the bottom anchored to concrete blocks and edges of the skin buried in the ground I don't have to worry about wind. Sphere is pretty stable shape. Also if you have a skill, budget and machinery you can go even more complex. the higher the V number (my dome is 3V) the more triangles and levels, but also more timber, higher cost, and workload.

[tagwex]

There he goes again with the technical jargon! What is a 3V?
Two cuts at each end not 4.
I would imagine that if every triangle, pentagon and hexagon has the same proportions then by trial and error (if need be) a template could be made up for each cut end and with a chop saw all the cuts could be done at the same settings for each type.

[marek]

OK
3V- its hard to explain. like I said before best to have a look at the projection plan, play with different settings. That would include levels (2V, 3V, 4V), different joints and see how it affects number of different elements needed for the project.Simple example my dome is 3V, Tmak buid his last year (pictures on this forum) is 2V.
Each element is cut to different angle on each end. its a combined angle i call them vertical and horizontal - one allows elements to meet in the joint, the other allows the hole structure to curve. In 3V type of structure you have 4 types of elements if you add the joint, which you photographed in Wexford it doubles the numbers of cuts
Achieving level of precision with a chop saw and templates of course is possible but very laborious. I had a skill saw borrowed from a pro, unfortunately still had a problem with precise cuts of the vertical angle. I mentioned before, precision required is down to tenths of degree. There is a way around it. Acidome gives angles but also distances of each corner from imaginative end of the piece if it was cut at the right angle.
I have spent 2 days cutting elements. I wasnt rushing it but still it took 2 days to make 120 elements for my structure with "off ceneter joint'. If it was "star" joint"
it would take probably twice as long
P.S.
There is also a third way. Buy connector hubs. Then all you need to do is to cut your timber at right angles. Very easy unfortunately quite expensive.

[tagwex]

Well a chop saw would give the same angle on the cut everytime as you know. A skill saw is by hand and eye, basically on a wing and a prayer! I must look at that website tomorrow. The marking out must have been soooooo tedious.

[tagwex]

Clever little website that is. Would love the challenge of making one but I just don't have a need for a dome.

[marek]

My bad Tagwex
terminology yes it was a chop saw with a slider i used for the project and not a cheap one also. I was lucky I have a friend who has one. Without this tool I wouldnt even try