Forming NFRC Domes

Shell structures, such as a dome, or Yurt, gain their strength through curvature, rather than materials you have to buy. One type is called the 2v Alternate, it is made of 6 pentagons, made of NFRC triangles, 10 equilateral triangles, and forms a hemisphere with a flat base. Domes are neat! However, you should first build a cardboard model to understand how they work. Iíve built several of different kinds, and have worked with coconut leaf NFRC. Iíll try to put this together for your greatest benefit.
  1. NFRC Domes should have these advantages:
    1. They are cheap owing to their inexpensive, often free building materials. They use Portland Cement only about ľ-inch thick, so it doesnít need much of it.
    2. They are light weight, and so should work well with floating islands. That doesnít mean that they wonít need extra flotation. Keep your eye on the island beneath yours as you add weight, and add flotation as needed.
    3. Owing to their curvature, they are strong in spite of being thin.
    4. Being made of Portland Cement, they are waterproof.
  2. Disadvantages:
    1. Building inspectors and most carpenters donít understand round buildings. And many enthusiasts donít either. The first one I built was a 24-foot diameter one of plywood. Later its new owner tore it down because it leaked. I asked him if he put shingles on it. He said, ďNo!Ē and wondered why it leaked? Thatís what shingles are for! Being round doesnít change that.
    2. In the underground one, the plumber didnít know where to put the toilet! So I laid out a square in the middle for him to measure from.
    3. The dome frame in Missoula, Montana, wasnít tied to the ground. The wind picked it up, and in walked next door.
    4. The one on Yap, in the Pacific, had sheet metal awnings over the windows, and no way to close them, a typhoon came along and it blew into the ocean!
    5. The one in Helena, Montana had plywood hubs. They twisted when I climbed on it, and was ugly covered with tar-paper roofing.
  3. But the steel fibrous, underground one works excellently. Itís been on the covers of 3 national magazines. With NFRC domes we can take lessons from each kind. But you still must work out the details for yourself. You can learn too.
  4. Unlike the Hex Island Segments, these are built with the outside up. Because we want the triangle connections pointing outside to shed water.
  5. They donít require floats, so theyíre easier.
  6. The edges are made similar to copper roofing, with the overlapping pieces made to shed water and add strength to each triangle.
  7. Unlike ferrocement, they are much thinner, lighter, and you donít have to do much concreting overhead.
  8. See ďDome Book IIĒ for lots of ideas.
  9. There are many ways to build domes, this is a simple one.

Construct each triangle of Natural Fiber Reinforced Concrete with a rainwater diversion piece of NFRC over the connections between triangles. The dome is thin, about ľ-inch made of 2 layers of crossed fiber. That should be plenty strong enough for an island in a warm climate. If you intend to build where itís cold, or need air conditioning, build 2 domes (one with a slightly smaller radius,) placed inside the other with insulation in between. The dome of radius R itself has:

60 A=R x 0.54653306 for 32-foot dome struts A=8-815/16 feet-inches that make up the pent centers. 2 legs of each pent triangle.

35 B=R x 0.61803399 for 32-foot dome struts B= 9-10 7/16 feet-inches.

Over 804 sq. ft. of living area, plus room enough for a small loft above the center bathroom for your bed.

  1. The triangle forms are made similar to the Hex Deck Island Segment forms, but of this different size. Naturally they donít need floats, and you may strengthen the outer edge with 3/8 rebar. Remember, that rebar only bends once, or use a torch. Bend it around the corners placing the connecting hole (you only need one.) so that the triangles may be bolted together. You can also weld washers at each corner. The rebar is buried in the NFRC so the whole thing is stronger. Note that this hole position is slightly beyond the triangle itself.

  2. Openings may be left in the middle of triangles for doors, windows, chimneys, etc., but donít cut any struts.

  3. Rake a flat place on the sandy beach

  4. Cut 2 10-foot 2x4s at 111.14į angles for the Pent forms

  5. Cut 2 10-foot 2x4s at 124.43į angles for the Equilateral Triangle forms

  6. Soak in diesel fuel or light oil so the NFRC wonít stick to it

  7. Place form pieces and screw them together appropriately

  8. Lay cement covered fiber criss-cross over the whole thing, and up the interior edge of the forms.

  9. Place the rebar with washers

  10. Cover the rebar with NFRC

  11. Stiffener walls should not be needed, but if you expect snow, put several down the middle.

  12. Write the date, your name and other pertinent information you may need later, while the NFRC is still wet.

  13. Sprinkle sand over the whole thing. Itís cheaper than paint and longer lasting.

  14. Have a beer!

  15. Make 30 pent triangles an 10 equilaterals

  16. Make a similar form for the rain covers

  17. Make one for each connection 20 for A-struts and 20 for B-struts

  18. When all are done and hardened for at least a week, put your dome together.

  19. Unlike other buildings, build from the top down. You donít have to, but itís easier.

  20. Build a hex by bolting together 5 pent triangles.

  21. Place it on a jacked-up scaffolding so it can balance itself.

  22. Add the lower row bolting them to the top.

  23. Remove the scaffolding and lower the whole thing onto your island.

  24. Check for sufficient flotation.

  25. Tie the base to the island sliding the rope through openings at the corners.

  26. Tighten the nuts

  27. Place rain covers over the connections

  28. Place rain covers of your choice over the bolts

  • Move in and have a another beer!

    It not only is on a movable island, but is thin, like a tent, and should not require a building permit, but laws vary. But you may want to register it as a boat, in order to get police protection. Check it out.

  • These Structures have not been engineered, there are too many differences with your specific needs. You are responsible for what you build, and to test pieces for integretary, nither Dr. Hait nor the Rocky Mountain Research Center bear any responsibility.

  • HAVE FUN!

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