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Semi Folding Pentayurt

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This page describes an adaptation of the Semi-Folding Hexayurt design to the Pentayurt aka H10. If you have not done so, read Camp Danger Hexayurt Hinge Technique first.

The Challenge of Five Sides[edit]

There are two differences between a Hexayurt and a Pentayurt that impact the semi-folding design.

A Pentayurt has an odd number of sides. This means splitting the yurt in half will not result in identical parts as it does with a Hexayurt.
The angles between panels are different. A normal loose hinge will not bend far enough for a Pentayurt.

Roof Design[edit]

The Camp Danger Design calls for two half-roofs made from three kites each. A Pentayurt has one less side and therefore one less kite. If you build a three-kite side and a two-kite side it will assemble, but it will not pack flat. To pack flat each side must have the same number of small-triangles. Each side will use a two-and-a-half-kite design. Also note there will be a left-side and a right-side half, and the halves are not identical!

Laying Out the Triangles[edit]

Each half-roof is made of five small-triangles. Unlike the Hexayurt design, you will need to form one tight-hinge and one loose-hinge on playa. When laying out the triangles be sure the leg of one half meets the leg of the other to form a tight-hinge, and the same for the hypotenuse to form the loose-hinge. If you build identical halves a leg will meet a hypotenuse and you will be unable to assemble the roof.

PentaRoof.jpg
Correct layout of roof.

[edit]

This is not a major concern for the semi-folding design, but may be useful to know if you care about pointing all the logos inwards. If you cut your triangles from the minimum of five panels you will be unable to hide all the logos. If you cut three panels logo down and two logo up you will be left with nine triangles with logo in and one with logo out. I know of two solutions to this. You can cover the offending logo with aluminum tape. You can cut a sixth panel and discard the extra two triangles. (Or gift them to another Pentayurt builder)

Hinge Design[edit]

The sharper angles of the Pentayurt require changes to the loose-hinges. The numbers do not come out as clean as they do in the Hexayurt. The required gaps for loose-hinges are as follows:

  • Roof: 0.853 x panel thickness
  • Wall: 1.176 x panel thickness

If you are interested in the math read on.

Trigonometry Homework[edit]

The important angle when finding the required tape gap is the angle formed between the panel edges. Imagine two wall panels without tape but otherwise placed correctly. There is a small V shaped gap when viewed from the outside. The angle at the base of this gap is the important one. I will refer to this angle as θ.

For a Hexayurt the angles are:
θroof = 29º
θwall = 60º

For a Pentayurt the angles are:
θroof = 50.5º
θwall = 72º

The ratio of gap/thickness is:
R = 2*sin(θ/2)

Assembly[edit]

  • Lay the half-roofs with the outside up and tape the two leg-sides together to form a tight-hinge. It is okay that this is taped on the opposite side from the other tight-hinges.
  • Lift the center of the roof until the hypotenuse-sides meet.
  • Make sure all the tight-hinges are fully open and tape the final loose-hinge. This last hinge will naturally form the correct gap if everything else is aligned and the ground is flat.
  • All other steps are the same as the Hexayurt.

In Use[edit]

I personally used this design during BM2013. I reused the same Pentayurt during BM2014. Another Pentayurt of this design was built for BM2014. Both yurts have performed well and will continue to be reused.

PentayurtPlaya2013.jpg