written by Rene K. Mueller, Copyright (c) 2006, last updated Mon, October 8, 2012
Heat Insulation: Leaf-like Segments, Multiple Lanes, and One Long Wrap
Instead of split bamboo other materials for the bows are also suitable:
- Willow: make sure the stick doesn't narrow too quickly, even diameter is an advantage; bind two together.
- Glassfabric: bows like used in modern outdoor tent construction
- PE (recyclable) or PVC (non-recyclable) 20-32mm pipes, as it was suggested by Daisuke Takekawa, yet, PVC has very limited temperature range (not suitable for below 0°C) so PE might be better choice
Since I focus on temporary buildings I tend to use white or colored PE pipe (2.5m, 3.3m or 5m long, 25 or 32 mm diameter) and bind multiple together at a time to get 10m long pipe as bow, and use three layers:
- rain cover: PE cover, using the leaf-like approach, using two-fold seam to sew the leafs
- heat-insulation: bubble-wrap or straw / hemp / shredded treebark filled blankets (quilted),
- leaf-like approach (more overhead, but best solution), or
- multiple lanes (simpler) or
- wrap one long lane from bottom to top overlapping (quick n' dirty solution)
- interior: canvas lanes, leaf-like approach
I made good experience with this combination with my yurt, as it provided some insulation while keeping the inside daylight bright. Laying all three layers over the bow skeleton, optionally the interior layer could be hung inside, but that's a bit more overhead to attach the canvas inside of the bow skeleton.
Since I'm considering to build the star dome in 6.4m diameter (10m long bows, in 4x 2.5m per bow), here a few preliminary notes on possible extensions. As I proceed and actually build one in full size also detailed "how to", illustrations and photos will follow.
Star Dome, Skylight Opportunity
One of the details to pay close attention of the star dome is the pentagon at the top. In case you want a simple tent it might even turn out to be a disavantage as you like to have one highest point, and not a pentagon where water can collect and make a dent. But for a skylight this pentagon is just perfect.
Star Dome Skylight Details
The side length of the top inner pentagon is l/9, the angle is 108° (3*180°/5), like I did for the yurt crown-wheel cover I plan to do the same for the star dome. Optionally also the larger pentagon (circumventing the pentagram star), then the side-length would be l/5.
Anyway, I would use the small inner pentagon with l/9, following construction I consider, adapted from my yurt construction I did.
The diameter of the required skylight is l/9 * (1 + 2*sin(π / 10)).
The base frame would be tied to the pentagon: drill holes into the base frame, and pull a cord through, tie them around the bow next to it.
Star Dome, Door Opportunity
The door is also handy, one of the five larger triangles at the bottom can be used to make a door. The original star dome comes with bamboo split bows and simple canvas, where one side of the triangle is let open to have it as rudimentary door, but for a temporarly building a solid door is recommended.
The side-length of the triangle (even sided) is l/5 (or aka s, which is circumference c/10), so the height is l/5 * sin(π/3).
Star Dome Door Detail
The hinge can be attached on the left or right, I personally prefer the right-hand side (from outside looking at the door), opening to the outside (opening to the inside won't work as triangle leans slightly inward at the top, and so the door would touch the ground, unless you would make the door smaller from the ground), with a simple locking mechanism.
I'm thinking of the making a l/5 long door frame with holes and attach it with cords to the bows, and the door opening to the outside.
Since the hinge will be on the side the door needs to be pulled upward so a light door is essential, otherwise it gets too hard to enter.
The angle of the frame struts are 180°/3, 60°.
I still need to work out the details, e.g. how to attach the rain cover, and ensure no water enters the door (the door slightly is leaning inside the center, not much, but the bottom door frame might catch steady rain water exposure).
On the previous page I provided the calculator to get the measurement (shape) of the leaf-like cover, since I'm thinking to make a star dome including thermal insulation, with unknown thickness (0.5cm - 15cm), the diameter base for the cover is variable.
Variable Cover with Fastener
In order to resolve this I thought about a solution where
- one leaf is wider than all others or
- all leafs are wider (5% than calculated)
and then attached two lanes to the leaf-seams: one on the left, and one to the right, and those two stripes or lanes have eyes where one or two cords can be pulled through, and then it can be pulled together like an old fashion shoe. To make it attractive I'm thinking to use white cord, and maybe cover it with a colored canvas over the fastener.
This solution would enable one to make the rain cover tight, and fitting the shape closely. It would be maybe suitable to have this fastener just at the side of the door as well (detailed illustrations will follow).
The rain cover needs to be attached at the base bows, and therefore a piece of rain canvas could be sewed additionally in order to put eyes on it and tie so the cover on the base; leave some extra rain cover reaching over and have the rain water flow away from the base (see illustration bottom detail). It's a notable detail, but it's required so no rain water actually flows into the shelter in case we just pull the cover under the base bows.
Below some options to do a circular floor:
Floor Layout Examples
The red outline indicates segments as whole pieces or segment to handle by a single person (to put up and take down). The first example a) requires a lath grid underneath so the laths can be put on - so personally consider d) most elegant.
More details follow later.
With high ceiling making a 2nd floor for beds is an interesting option, in particular in the winter-time when the heat from the stove rises.
2nd Floor Options in Dome
A few options I quickly drew, keeping the circular shape of the dome for the 2nd floor as well:
- "1/4 moon": 2 pieces and 5 columns, best light distribution from the skylight.
- "3/4 moon": 1 or 2 pieces, 4 columns
- "4/4 moon": 1-4 pieces, 4 columns
- "eclipse": 1 or 4 pieces, 4+ columns, the light from the skylight reaches both levels, the 2nd floor and also the base.
Star Dome with Stove
For the winter time a stove would be suitable, and I'm thinking to use an alike approach as I did with my yurt, and place the stove inside apprx. 1 - 1.5m away from the wall, and have the pipe go outside horizontally just through an opened leaf seam, big enough for the stove pipe with a thick heat insulator.
This way the canvas doesn't need to cut a hole for the pipe, but just wrap it nicely around the pipe. It's wisely not to have the pipe too high up reaching outside of the dome, as the higher the flatter the angle, and the more exposure of the heat insulator and junction pipe vs heat insulator where rain water falls unto. Maybe a little extra rain cover for the heat insulator will ensure water runs around it.
I'm not in favour when the pipe goes through the roof (e.g. in case of the yurt or other forms) as you battle with water leakages and I tend to prefer options where the water insulation remains simple and little to fiddle around.
A fan mounted near the skylight will ensure the hot air circulating properly within the dome.
Next Page >>
- Page 1: The Structure, The Construction, The Formulas, The Calculator, The Canvas, Pentagon & Triangles ...
- Page 2: Alternative Approaches, Extensions, Skylight, Door, Rain Cover, Floor, 2nd Floor, Stove
- Page 3: The Model, Todo, Real Life Example, Links