Need help finding the tapered angles of the faces

[Dimitri]

Hello Taff and members. I've been literally waisting a lot of time
finding the right solution for me, and then I thought that maybe maybe
making a geodesic dome in Sketchup was the way to go and it would find
me the angles. I did a search and found this wonderful group.

I am not a skilled Sketchup user etc. Anyway. I would like to make a
geodesic dome V3 with a diameter of 120cm but strutless. I want to
make this with ceramic terracotta tiles that are 41cm square and 1.7cm
thick.

I would cut the triangles out out of the tiles. I am not sure if I can
get a dome of 120cm with faces/triangles smaller than 41cm. I think
the triangle's largest edge is 49.5cm for a 120cm diameter dome. If
needed I can do with a 100cm diameter dome. I somehow going to glue
the tile's tapered edges, so calculations would also need to consider
this. I imagine each edge of a face will have 3 or 4mm mortar/glue
joints.

I downloaded one of Taff's Sketchup dome, and pushed in some of the
faces 1.7cm but for the life of me I can't get the angle of the
overlapping spaces the faces create with the protractor tool.

Can someone help me please. I would like to see one face in Sketchup
with the 3 tapered edges (with the angles mentioned) so I can start
cutting. Thank you

[TaffGoch]

Dimitri,

 

Using 41cm tiles, you should be able to construct a 200cm diameter dome/sphere, maximum.

 

I've posted a SketchUp model of the simplest of 3v geodesic domes, which is composed of only two triangle definitions:

http://sketchup.google.com/3dwarehouse/details?mid=41afae94f70855682137e32e8ebf2b1

 

With a large mortar/glue gaps, you may not have to worry about cutting the tile edges at the half-dihedral angles. The mortar/glue should hide the fact that the tile edges are cut at 90-degrees.

 

-Taff

[Gerry in Quebec]

Hi Dimitri and Taff,
With that simple 3v icosa geometry, the dome won't sit flat. Dimitri,
if you want to make a 4/9ths or 5/9ths dome, rather than a complete
sphere, it might be wise to use the Fuller-Kruschke version of the 3v
icosa, which has 3 triangle types instead of two and four edge lengths
rather than three.

Using the Fuller-Kruschke design, at a spherical radius of 57.07 cm,
which gives a floor radius of 56.06 cm, four CCD triangles (the
largest of three triangle types) can be cut from a single square tile
41 cm on a side.

I would bevel the edges, as Dimitri was planning to. I have made glued
models using plywood tiles and have found that the beveled edges help
to line things up correctly (having two or three extra pair of hands
would also be a big help!). Seven degrees for the beveling of edges
should be fine.

Beside's Taff's SketchUp model of the panel version of the Fuller-
Kruschke dome, the Info in the file 3v-icosa-classI-Fuller-Kruschke-
data.xls may be of use. Good luck.
Gerry in Quebec

On Aug 12, 3:16 pm, TaffGoch <taffg...@gmail.com> wrote:
> Dimitri,
>
> Using 41cm tiles, you should be able to construct a 200cm diameter
> dome/sphere, maximum.
>
> I've posted a SketchUp model of the simplest of 3v geodesic domes, which is

> composed of only two triangle definitions:http://sketchup.google.com/3dwarehouse/details?mid=41afae94f708556821...

>
> With a large mortar/glue gaps, you may not have to worry about cutting the
> tile edges at the half-dihedral angles. The mortar/glue should hide the fact
> that the tile edges are cut at 90-degrees.
>
> -Taff
>

>  3v_geodesic_dihedrals.png
> 86KViewDownload

[Dimitri]

Thanks Taff, the help bunny in your illustration was funny :-)

Uh, ok. Well, I was thinking of cutting the half-dihedral angles so
assembly would be easier, if I would do it with 90 degree angles, then
I would first have to make a support jig to glue the faces together.
Thanks for that drawing, let me see if I can find the angle withthe
protractor. ;-)

On Aug 12, 3:16 pm, TaffGoch <taffg...@gmail.com> wrote:

> Dimitri,
>
> Using 41cm tiles, you should be able to construct a 200cm diameter
> dome/sphere, maximum.
>
> I've posted a SketchUp model of the simplest of 3v geodesic domes, which is

> composed of only two triangle definitions:http://sketchup.google.com/3dwarehouse/details?mid=41afae94f708556821...

>
> With a large mortar/glue gaps, you may not have to worry about cutting the
> tile edges at the half-dihedral angles. The mortar/glue should hide the fact
> that the tile edges are cut at 90-degrees.
>
> -Taff
>

>  3v_geodesic_dihedrals.png
> 86KViewDownload

[Dimitri]

Thank you Gerry. I would indeed want half a sphere that sits flat. I
was thinking for the simpler 3v with 2 different triangles, then draw
a line halfway and cut out the tiles where the line meets. Would that
be an idea? So you have a sketchup file of your plywood dome?

Thanks!

> > 86KViewDownload- Hide quoted text -
>
> - Show quoted text -

[Gerry in Quebec]

Hi Dimitri,
I don’t have a SketchUp model of the plywood polyhedron. In any case,
it’s a full rhombic triacontahedron (30 diamond-shaped faces and 60
edges) rather than a geodesic dome.

If you prefer not to build the Fuller-Kruschke version of the 3v icosa
dome, you could use the conventional design (class I, method 1) but
alter the shape of some of the triangles in the bottom row of
triangles so as to make the dome sit flat. Alternatively, you could
make the base flat by replacing 15 of the 30 triangles in the bottom
row with 5 trapezoids. You end up with 10 sides instead of 15.

If you need edge lengths or a line drawing, let me know. Unfortunately
I can’t yet model domes in SketchUp.
Taff?
Gerry in Quebec

> > - Show quoted text -- Hide quoted text -