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Hi!
Scattered comments on recent threads have suggested that PVC is currently held in low esteem as a dome building material.
I’ve made solid domes with different geometries from both metal and PVC, and they are both good or bad in the right situation.
While it is not perfect for all applications, PVC has different qualities than metal and at lengths over 4 feet or so, your PVC will flex but not permanently bend or break. Any but the $trongest metal will. And that PVC is never going to rust :-)
Common dome design tends to move towards short strut lengths since people want to build big, and almost always use the highly publicized icosahedral strut ratios. But if your dome is not too huge, and you use the low frequency octrahedral strut ratios, you will find that your strut lengths get to around 10 feet, which is great for PVC but lousy for metal.
Costs for both PVC and metal have gone up quite a bit, and dealing with 10 foot pvc poles has plusses and minuses versus 4 foot metal poles, so I leave it to you to figure out the cheapest and most sensible way to suit your own needs after considering the following design.
This is my design for an octahedral 2 frequency PVC dome that was on the playa for the last two years and performed like a champ.
It has a diameter of about 17 feet and a height of about 10 feet. The walls are close to vertical, so there is a lot of usable space. 2 people can put a huge tent underneath and live in luxury. We have also stuck 4 people in 3 tents under one, with room left over for an 8 foot long kitchen/utility table and some other stuff.
First, some pictures:
picasaweb.google.com/bruce.s...Octadome
Still interested? OK, here is how you build it.
Experienced dome builders can skip over a lot of the discussion of attaching vertices/hubs. On the other hand I hope that newbies can actually put one of these together with these instructions.
Remember, ALWAYS DO A TEST BUILD before you get to the playa.
Parts:
Structure:
12 x 10’ 2” OD PVC
8 (or 16 with bottomtubes) 7.6’ 2” OD PVC
9 x 4’ long 1” wide nylon straps* with metal cam buckles
4 x 6’ long 1” wide nylon straps* with metal cam buckles
8 (or 3 with bottomtubes) rebar candy cane or other ground anchors
*Nylon strap supplier:
www.ahh.biz/products/Pre...ock_Strap.htm
Cover:
1 x 20’ x 40’ tarp*
1 x 14’ x 16’ (or larger) air permeable cover—shade cloth, swedish snow camo, etc.*
approx 150’ – 200’ rope*
fabric clips* or other means of attachment
heavy duty zip ties or other means of attachment- as many as you have grommets along the 40’ length of tarp, plus extras.
Nylon straps or rope for fastening down the tarp in various places
*tarp supplier:
www.thortarp.com/consumer.htm
www.etarp.com/cgi-bin/import.cgi
*swedish snow camo tarps are now hard to find. Sorry!
*I bought my rope at www.majorsurplusnsurvival.com but their stock varies all the time.
*fabric clips at shelter-systems.com/gripclips/
I used 2” outside diameter PVC. You could probably get away with 1 ½” or even 1” OD, but you will be experimenting. Let me know how it works out on the playa.
One person can put this whole thing together, but it is easier with two or three, especially if you lack experience with these materials and construction methods.
You can build it with or without struts going along the ground (bottomtubes). There are pictures of both versions.
With bottomtubes you have the advantage that you can drag the assembled dome around to where you want it. You also have to put in fewer ground anchor points (rebar candy canes work best).
I prefer to build without bottomtubes. Why? You save yourself $ because you need 8 fewer tubes, and you have 8 fewer tubes to transport and fiddle around with. (There is a very small additional cost in extra rebar). In addition, the dome is a much more pleasant living experience without that tube going along the ground getting in your way when you want to go in and out. The dome has superior “indoor-outdoor flow,” as they say in the real estate business. It feels bigger because you aren’t drawing lines around it. You may also have something going on the ground that would be obstructed by the bottomtubes. It is a bit more difficult to assemble without bottomtubes. You will need a person or two to help at the end.
There are only 2 lengths of tubes, in a ratio of about 10 to 7.6. Since they are sold in 10 foot lengths, I made my domes with 10 foot and 7.6 foot tubes. 7.6 feet is about 7 feet 8 inches. Actually, I used 7 feet 10 inch tubes and I had no problems. This construction method is very forgiving of strut length variation.
Without bottomtubes you will need eight 7.6 foot tubes and twelve 10 foot tubes. Add 8 more 7.6 foot tubes if you want bottomtubes.
At the end of each tube, 1 or 2 inches from each end, drill a ¾” hole all the way through from one side to another. So each end will have two holes in it on opposite sides of the tube from each other. Try to keep the holes centered, but don’t worry too much. Look at the diagram.
You will also need to cut and bend your rebar. If you live in Berkeley or know someone who does, you are in luck because you can borrow for free a rebar cutter/bender from the Berkeley tool library.
Wow, you have cut your tubes to length, drilled holes, bent your rebar, and you are done with fabrication already. Easy!
Now to build it. I always have done this from the top down. If you build from the bottom up, let me know how it goes.
Start with four 7.6’ tubes. You can attach them with rope (not recommended) or 1” nylon straps with metal cam buckles, which you can get at american home and habitat:
www.ahh.biz/products/Pre...ock_Strap.htm
I like the 4 foot straps for the vertices/hubs that have fewer struts, and the 6 foot straps for the ones that have 6 struts. You get a deal on ordering these in lots of 10, and they are handy for attaching tarps and other things as well, so consider getting extra.
Take the fabric end of the strap and run it through both holes at one end of a tube. You will be following the same path the drill bit followed when it went through both sides. Then string the next tube on the strap the same way, and so on. Once the fourth tube is strung, run the end of the strap through the cam buckle and tighten it up. Leave some slack during construction, and then at the end you will go back and tighten them all as best you can.
Now you have a big “X.” At the free end one of the bars of the X, attach four 10’ poles and one more 7.6’ foot pole the same way, by stringing the ends of the tubes with a strap. Putting the tubes in the right order is a good idea—on your string the two 7.6’ tubes should have two 10’ tubes on either side. Look at the diagrams. On each vertex, you have 7.6’ tubes at 12 and 6 o’clock, and four 10’ tubes at 2 o’clock, 4 o’clock, 7 o’clock and 10 o’clock. Fasten and tighten the strap, and leave some slack.
OK, be careful here in this next part. The most common error in constructing these things comes from when you are supposed to use the other end of a tube you have already attached, but you bring in an additional new tube instead.
Go to the next free bar end of the X counterclockwise. Take the free end of the 10 o’clock tube from the hub/vertex you just did. This will be the 2 o’clock tube on the vertex you are now working on. Get new tubes for the rest, as above.
Go to the next free bar end of the X, doing the same as above, taking the free end of the 10 o’ clock tube from the vertex you just finished, and new tubes for the rest (except for the free end of the original X, of course).
Now go to the last free bar end of the X. The 2 o’clock tube comes from the vertex you just did, and the 10 o’clock tube comes from the first vertex of this group of 4. The 12 o’clock tube is the free end of the original X. When you are done you will have made a square base pyramid with a bunch of tubes sticking off the sides. If you don’t have a happy little square base pyramid you have done something wrong.
You will be going from having all the tubes lying on the ground to a three dimensional figure here. It helps to have someone lift the center of the X, where the four 7.6’ tubes met.
That was the hardest part—you’re almost done. The four free ends of the 7.6 foot tubes, one of which sticks off of each vertex you just did, is going to stay free for now. But the free ends of the 10 foot poles sticking out, that come from the 4 o’clock and 7 o’clock spots on each vertex are going to get fastened together in pairs. Each 4 o’clock gets fastened to its 7 o’clock neighbor. Take a look at the top view diagram.
Now you have four free 7.6’ ends and four 10’ pairs. These are your 8 ground anchor points.
If you are using bottomtubes, these 8 points get attached with 7.6’ tubes between them. You will probably want someone to lift up the centerward parts of the dome while you are fastening them.
If you are not using bottomtubes, then figure out where you want your dome, and pound in your 8 rebar candy canes. The ones on the opposite sides of the rough circle you will be forming should be about 17 feet apart.
With bottomtubes, drag it to where you want it and put at least 3 rebar anchors on vertices spaced around the dome. One strongish person can do this.
Without bottomtubes, pound in rebar and then fasten ground attachment points described above to each of the 8 ground points. One or two people to help hold up the dome is really vital here.
When you have the dome in position, tighten up all of the nylon straps as much as possible. You will see from the pictures that some of the vertices/hubs are pretty slack and sloppy looking. That’s OK, just do what you can.
Now you need to cover it.
You can do whatever you want, of course, but here is what I suggest. Take another look at the pictures, taking note of the compass directions and where the openings of the tarps are on the satellite photo.
First, my core shade principles:
Orient main tarp coverage to South by Southeast, but cover tarp over ¾ of the sides, leaving only the north by northwest open.
2 tarp layers, outer layer breathable, inner layer solid and air/waterproof.
Do not make pockets at the top where hot air can be trapped.
Front and back ventilation allow a breeze.
I have used Thor tarp durashield 6500 as the bottom waterproof layer and swedish army surplus Tyvek snow break up camo covers as the top breathable layer.
www.etarp.com/cgi-bin/import.cgi
The swedish snow camo tarps are now popular and mostly sold out, expensive, and hard to find, and thor tarps is charging about 50% more than what I paid for my tarps 5 years ago, so your mileage may vary.
It is much more important to have at least 2 layers than it is to use any particular kind of tarp or cover.
So here is my technique.
Take a 20’ x 40’ solid waterproof tarp and attach 1 heavy duty zip tie to each grommet along the edge of the tarp. Don’t zip up the zip ties all the way, leave space. String rope through the zip ties along all edges. This is to allow easy rope threading and to prevent blowing out your grommets. At any rate, always make the rope tight and then attach the tarp to the rope. Do not tighten the tarp like it was a rope—tarps cannot take as much tension as ropes can.
Put your top breathable layer in the middle (or over the entirety) of the 20 x 40 tarp. I used grip clips shelter-systems.com/gripclips/ to attach the tarps. These clips are great for making hard anchor points on your tarps wherever you want them. Be sure to order some of the nylon cord they sell or you won’t be able to use the clips as an anchor point, you will just be able to use them to attach two tarps together. Order the largest clip size for use with heavy duty tarps.
Fasten the bottom 40’ edge of the tarp along the bottom of your dome. Spend a moment thinking about which is the top side and which is the bottom side of the tarp. The bottom side will be sort of up when you do this, and the top sort of down. This is because you will pull the loose 40’ edge over the top of the dome.
Tie or attach the rope running along the edge of the tarp at each ground vertex. This will take you about ¾ of the way around the dome. Make sure the unattached part is pointing North or North by Northwest. Leave about 4 –6 feet of slack in the tarp in the middle of the bottom edge. This will allow for ventilation later on, and the slack will be tightened up.
Now pull the top 40’ edge up over the dome, up to the top vertex. Fasten the rope at the top vertex and the 2 northeast and northwest corners. Leave one quarter of the top open—do not cover the hole top pyramid part of the dome. If you leave part open, it allows hot air to escape. If you close this part off, hot air will be trapped and your dome will be a less pleasant place. Fasten all the way along the edges down to the ground. This will take some fussing and fiddling to get everything tight and tidy. Put extra zip ties around the rope and through the tarp grommets where they are being attached to the dome vertices/hubs.
Take the slack that you left in the back at the bottom and gather it up, making a low triangle. Use a grip clip or some other means to hold it all together, and then run a rope, ratcheting tie down, or long nylon strap from this place up to the horizontal dome strut above it, and run a rope, ratcheting tie down, or long nylon strap to the strut along the ground, one of the ones to the side, or a new rebar anchor. You are trying to create an open spot in the cover that will always let air through, but since this is on the south side you don’t want it to be too high, or you will be losing shade.
Look at the pictures.
Enjoy :-)
Scattered comments on recent threads have suggested that PVC is currently held in low esteem as a dome building material.
I’ve made solid domes with different geometries from both metal and PVC, and they are both good or bad in the right situation.
While it is not perfect for all applications, PVC has different qualities than metal and at lengths over 4 feet or so, your PVC will flex but not permanently bend or break. Any but the $trongest metal will. And that PVC is never going to rust :-)
Common dome design tends to move towards short strut lengths since people want to build big, and almost always use the highly publicized icosahedral strut ratios. But if your dome is not too huge, and you use the low frequency octrahedral strut ratios, you will find that your strut lengths get to around 10 feet, which is great for PVC but lousy for metal.
Costs for both PVC and metal have gone up quite a bit, and dealing with 10 foot pvc poles has plusses and minuses versus 4 foot metal poles, so I leave it to you to figure out the cheapest and most sensible way to suit your own needs after considering the following design.
This is my design for an octahedral 2 frequency PVC dome that was on the playa for the last two years and performed like a champ.
It has a diameter of about 17 feet and a height of about 10 feet. The walls are close to vertical, so there is a lot of usable space. 2 people can put a huge tent underneath and live in luxury. We have also stuck 4 people in 3 tents under one, with room left over for an 8 foot long kitchen/utility table and some other stuff.
First, some pictures:
picasaweb.google.com/bruce.s...Octadome
Still interested? OK, here is how you build it.
Experienced dome builders can skip over a lot of the discussion of attaching vertices/hubs. On the other hand I hope that newbies can actually put one of these together with these instructions.
Remember, ALWAYS DO A TEST BUILD before you get to the playa.
Parts:
Structure:
12 x 10’ 2” OD PVC
8 (or 16 with bottomtubes) 7.6’ 2” OD PVC
9 x 4’ long 1” wide nylon straps* with metal cam buckles
4 x 6’ long 1” wide nylon straps* with metal cam buckles
8 (or 3 with bottomtubes) rebar candy cane or other ground anchors
*Nylon strap supplier:
www.ahh.biz/products/Pre...ock_Strap.htm
Cover:
1 x 20’ x 40’ tarp*
1 x 14’ x 16’ (or larger) air permeable cover—shade cloth, swedish snow camo, etc.*
approx 150’ – 200’ rope*
fabric clips* or other means of attachment
heavy duty zip ties or other means of attachment- as many as you have grommets along the 40’ length of tarp, plus extras.
Nylon straps or rope for fastening down the tarp in various places
*tarp supplier:
www.thortarp.com/consumer.htm
www.etarp.com/cgi-bin/import.cgi
*swedish snow camo tarps are now hard to find. Sorry!
*I bought my rope at www.majorsurplusnsurvival.com but their stock varies all the time.
*fabric clips at shelter-systems.com/gripclips/
I used 2” outside diameter PVC. You could probably get away with 1 ½” or even 1” OD, but you will be experimenting. Let me know how it works out on the playa.
One person can put this whole thing together, but it is easier with two or three, especially if you lack experience with these materials and construction methods.
You can build it with or without struts going along the ground (bottomtubes). There are pictures of both versions.
With bottomtubes you have the advantage that you can drag the assembled dome around to where you want it. You also have to put in fewer ground anchor points (rebar candy canes work best).
I prefer to build without bottomtubes. Why? You save yourself $ because you need 8 fewer tubes, and you have 8 fewer tubes to transport and fiddle around with. (There is a very small additional cost in extra rebar). In addition, the dome is a much more pleasant living experience without that tube going along the ground getting in your way when you want to go in and out. The dome has superior “indoor-outdoor flow,” as they say in the real estate business. It feels bigger because you aren’t drawing lines around it. You may also have something going on the ground that would be obstructed by the bottomtubes. It is a bit more difficult to assemble without bottomtubes. You will need a person or two to help at the end.
There are only 2 lengths of tubes, in a ratio of about 10 to 7.6. Since they are sold in 10 foot lengths, I made my domes with 10 foot and 7.6 foot tubes. 7.6 feet is about 7 feet 8 inches. Actually, I used 7 feet 10 inch tubes and I had no problems. This construction method is very forgiving of strut length variation.
Without bottomtubes you will need eight 7.6 foot tubes and twelve 10 foot tubes. Add 8 more 7.6 foot tubes if you want bottomtubes.
At the end of each tube, 1 or 2 inches from each end, drill a ¾” hole all the way through from one side to another. So each end will have two holes in it on opposite sides of the tube from each other. Try to keep the holes centered, but don’t worry too much. Look at the diagram.
You will also need to cut and bend your rebar. If you live in Berkeley or know someone who does, you are in luck because you can borrow for free a rebar cutter/bender from the Berkeley tool library.
Wow, you have cut your tubes to length, drilled holes, bent your rebar, and you are done with fabrication already. Easy!
Now to build it. I always have done this from the top down. If you build from the bottom up, let me know how it goes.
Start with four 7.6’ tubes. You can attach them with rope (not recommended) or 1” nylon straps with metal cam buckles, which you can get at american home and habitat:
www.ahh.biz/products/Pre...ock_Strap.htm
I like the 4 foot straps for the vertices/hubs that have fewer struts, and the 6 foot straps for the ones that have 6 struts. You get a deal on ordering these in lots of 10, and they are handy for attaching tarps and other things as well, so consider getting extra.
Take the fabric end of the strap and run it through both holes at one end of a tube. You will be following the same path the drill bit followed when it went through both sides. Then string the next tube on the strap the same way, and so on. Once the fourth tube is strung, run the end of the strap through the cam buckle and tighten it up. Leave some slack during construction, and then at the end you will go back and tighten them all as best you can.
Now you have a big “X.” At the free end one of the bars of the X, attach four 10’ poles and one more 7.6’ foot pole the same way, by stringing the ends of the tubes with a strap. Putting the tubes in the right order is a good idea—on your string the two 7.6’ tubes should have two 10’ tubes on either side. Look at the diagrams. On each vertex, you have 7.6’ tubes at 12 and 6 o’clock, and four 10’ tubes at 2 o’clock, 4 o’clock, 7 o’clock and 10 o’clock. Fasten and tighten the strap, and leave some slack.
OK, be careful here in this next part. The most common error in constructing these things comes from when you are supposed to use the other end of a tube you have already attached, but you bring in an additional new tube instead.
Go to the next free bar end of the X counterclockwise. Take the free end of the 10 o’clock tube from the hub/vertex you just did. This will be the 2 o’clock tube on the vertex you are now working on. Get new tubes for the rest, as above.
Go to the next free bar end of the X, doing the same as above, taking the free end of the 10 o’ clock tube from the vertex you just finished, and new tubes for the rest (except for the free end of the original X, of course).
Now go to the last free bar end of the X. The 2 o’clock tube comes from the vertex you just did, and the 10 o’clock tube comes from the first vertex of this group of 4. The 12 o’clock tube is the free end of the original X. When you are done you will have made a square base pyramid with a bunch of tubes sticking off the sides. If you don’t have a happy little square base pyramid you have done something wrong.
You will be going from having all the tubes lying on the ground to a three dimensional figure here. It helps to have someone lift the center of the X, where the four 7.6’ tubes met.
That was the hardest part—you’re almost done. The four free ends of the 7.6 foot tubes, one of which sticks off of each vertex you just did, is going to stay free for now. But the free ends of the 10 foot poles sticking out, that come from the 4 o’clock and 7 o’clock spots on each vertex are going to get fastened together in pairs. Each 4 o’clock gets fastened to its 7 o’clock neighbor. Take a look at the top view diagram.
Now you have four free 7.6’ ends and four 10’ pairs. These are your 8 ground anchor points.
If you are using bottomtubes, these 8 points get attached with 7.6’ tubes between them. You will probably want someone to lift up the centerward parts of the dome while you are fastening them.
If you are not using bottomtubes, then figure out where you want your dome, and pound in your 8 rebar candy canes. The ones on the opposite sides of the rough circle you will be forming should be about 17 feet apart.
With bottomtubes, drag it to where you want it and put at least 3 rebar anchors on vertices spaced around the dome. One strongish person can do this.
Without bottomtubes, pound in rebar and then fasten ground attachment points described above to each of the 8 ground points. One or two people to help hold up the dome is really vital here.
When you have the dome in position, tighten up all of the nylon straps as much as possible. You will see from the pictures that some of the vertices/hubs are pretty slack and sloppy looking. That’s OK, just do what you can.
Now you need to cover it.
You can do whatever you want, of course, but here is what I suggest. Take another look at the pictures, taking note of the compass directions and where the openings of the tarps are on the satellite photo.
First, my core shade principles:
Orient main tarp coverage to South by Southeast, but cover tarp over ¾ of the sides, leaving only the north by northwest open.
2 tarp layers, outer layer breathable, inner layer solid and air/waterproof.
Do not make pockets at the top where hot air can be trapped.
Front and back ventilation allow a breeze.
I have used Thor tarp durashield 6500 as the bottom waterproof layer and swedish army surplus Tyvek snow break up camo covers as the top breathable layer.
www.etarp.com/cgi-bin/import.cgi
The swedish snow camo tarps are now popular and mostly sold out, expensive, and hard to find, and thor tarps is charging about 50% more than what I paid for my tarps 5 years ago, so your mileage may vary.
It is much more important to have at least 2 layers than it is to use any particular kind of tarp or cover.
So here is my technique.
Take a 20’ x 40’ solid waterproof tarp and attach 1 heavy duty zip tie to each grommet along the edge of the tarp. Don’t zip up the zip ties all the way, leave space. String rope through the zip ties along all edges. This is to allow easy rope threading and to prevent blowing out your grommets. At any rate, always make the rope tight and then attach the tarp to the rope. Do not tighten the tarp like it was a rope—tarps cannot take as much tension as ropes can.
Put your top breathable layer in the middle (or over the entirety) of the 20 x 40 tarp. I used grip clips shelter-systems.com/gripclips/ to attach the tarps. These clips are great for making hard anchor points on your tarps wherever you want them. Be sure to order some of the nylon cord they sell or you won’t be able to use the clips as an anchor point, you will just be able to use them to attach two tarps together. Order the largest clip size for use with heavy duty tarps.
Fasten the bottom 40’ edge of the tarp along the bottom of your dome. Spend a moment thinking about which is the top side and which is the bottom side of the tarp. The bottom side will be sort of up when you do this, and the top sort of down. This is because you will pull the loose 40’ edge over the top of the dome.
Tie or attach the rope running along the edge of the tarp at each ground vertex. This will take you about ¾ of the way around the dome. Make sure the unattached part is pointing North or North by Northwest. Leave about 4 –6 feet of slack in the tarp in the middle of the bottom edge. This will allow for ventilation later on, and the slack will be tightened up.
Now pull the top 40’ edge up over the dome, up to the top vertex. Fasten the rope at the top vertex and the 2 northeast and northwest corners. Leave one quarter of the top open—do not cover the hole top pyramid part of the dome. If you leave part open, it allows hot air to escape. If you close this part off, hot air will be trapped and your dome will be a less pleasant place. Fasten all the way along the edges down to the ground. This will take some fussing and fiddling to get everything tight and tidy. Put extra zip ties around the rope and through the tarp grommets where they are being attached to the dome vertices/hubs.
Take the slack that you left in the back at the bottom and gather it up, making a low triangle. Use a grip clip or some other means to hold it all together, and then run a rope, ratcheting tie down, or long nylon strap from this place up to the horizontal dome strut above it, and run a rope, ratcheting tie down, or long nylon strap to the strut along the ground, one of the ones to the side, or a new rebar anchor. You are trying to create an open spot in the cover that will always let air through, but since this is on the south side you don’t want it to be too high, or you will be losing shade.
Look at the pictures.
Enjoy :-)
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