Domes from Karl

Editor’s note: As usual, Prell and his friend Karl are thinking up innovations for survival. – John

 

Dear G.,

Want to tell you about some domes we have made. I figure we may need them for personal shelter and to store some of our possessions in. With clear plastic they could be used for growing plants, of course.

Both are made of schedule 40 PVC in three quarter inch size. Hubs were a problem at first. Then someone suggested using lids from 5 gallon pails. Someone figured you could wire the struts to the lids using twist wires. I bought a little tool at the hardware store, a hook that swivels on a handle. It is used to secure rebar before concrete is poured. The lids are very strong and flex to give you the curve the domes need. Also, the lip at the edge of the lids gives you an angle too.

The second dome uses sections of 4 inch diameter PVC pipe for hubs. Holes are drilled for the struts using a 1 and 1/8 inch spade bit. Each end of a strut has two holes drilled through it and galvanized nails are pushed through the holes, one inside and one outside the hub. You can put this design together without any tools. Seems like it would be loose, but the curved form of the dome creates tension and makes the parts lock up.

What do you think G? Could these little shelters be used by the New American Peasant?

If anyone is interested I can supply details.

Karl

 

 

Click here for info on domes without hubs.

Click here for a few tips on building domes for survival shelter.

 

6 thoughts on “Domes from Karl”

  1. Thanks for your inquiry. Here’s info Prell passed along. There’s a fairly simple formula for making the struts. Cut a 10 ft. PVC pipe into 3 sections. Multiply 1/3 of 10 ft. by .884 to derive shorter pieces. There’s more online, but I don’t have exact web links at present. There’s info on a site on making domes from rolled up newspapers. I understand a site on the Burning Man event has info.  The Burning Man does it all as far as calculating. Just type in overall dimensions and it gives the struts. You can even start with the strut lengths and it calculates the other way.

    You can see another post on this blog about making domes without hubs at http://www.destinysurvival.com/2009/04/10/look-ma-no-hubs/

  2. How mush spacing on the holes in the pvc hubs ? Is there a 4 and 5 hole ? Does the hub make it stronger ?

    Thanks
    Larry

    1. Karl had problems leaving a comment, so e-mailed his reply to me and asked me to reproduce it here.

      Larry,

      The holes in the hubs are spaced at regular intervals. The five hole hubs are at seventy two degrees apart. The holes for six hole hubs are sixty degrees apart. You can Google “protractor” for a large one to print out.

      A convenient way to mark the holes for drilling is to make a cardboard collar with holes at the various angles. I used one made from an oat box with a piece of tape over a gap that allowed me to just slip it over each piece of pipe. You can mark this collar by laying it on the protractor and eyeballing where to make the holes. Make a small hole over each mark. Slip the collar over the blank hub pieces and make dots on the hub with a marking pen or a pencil.

      When all your hubs are marked put the point of your bit on these dots to drill. The spacing does not have to be exact. There is a looseness to this design. If the hub holes are evenly spaced around the middle of the hubs, the struts will adjust themselves OK. Just drill at a ninety degree angle to the surface. As you assemble your dome the shape will automatically form. I have found the hubs are the strongest part of the dome.

  3. Hi John and Karl,

    Thank you so much for providing this information about your success with engineering these types of Geo domes. I am going to be utilizing your ideas with a 4″pvc hub this summer to build a greenhouse for a community winter garden. I do have one question, if you could please answer that would be excellent. As for the base ring hubs with 4 connectors, I assume two of the connectors are parallel with the ground. What are the angles I need for the two connector holes that form the upside down triangles around the base? would it be 72 degrees or 60 degrees? Sorry… you may have already answered the question but I am a little confused on the base hub hole positions, but understand the rest perfectly.

    Thank You very Much!
    Charlie
    Orcas Island, WA

    1. I’ve been asked the pass along this reply.

      Dear Charlie,

      I will tell you about the bottom hubs on the dome I made. It is the one in the video. I used 6-hole hubs with 60 degree angles for the bottom row. I figured the two bottom holes might be useful to help anchor the dome in high winds, but it has never been necessary where my dome is. I hope this helps.

      Sincerely,

      George Prell

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