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Making a quonset-style PVC Tunnel ("Monkey Hut")
The flexible nature of PVC pipe allows curved structures with their own internal tension, negating the need for outside bracing or guy lines. You can make a half-round tunnel roughly 10 feet wide by around 7 or 8 feet tall that can easily be set up by one person, absurdly easily with a helper. The materials you need are schedule 40 1" PVC pipe, 1-1/4"pipe and tees, some thin rope or strong webbing, and some tent stakes to anchor it into the ground (if building indoors or on concrete you'll need a different anchor system, I'll get to that later). And some duct tape, of course. Always duct tape. BTW, all these pics are linked to larger uncropped versions for a better look.
http://i36.photobucket.com/albums/e31/pjhawke/revenant/PVC1ingredients.jpg
The 1" pipe is the actual structural material of the frame. The 1-1/4" pipe is just used for connectors so you'll only need 1 or 2 lengths of it as you'll be cutting it into smaller pieces. With schedule 40 pipe, these 2 pipe sizes are unique in that they very neatly slide into one another; snug enough that there's no jiggle but loose enough to slide and rotate.
The 1-1/4" pipe serves as the sleeves that connect the 1" pipe sections, and as reducers in the openings of the tees. The pipe sections in the straight-through section of the tee can be small, say 2", since they're just acting as bushings. The piece in the 90-degree position should be longer, around 4-6".
This allows the tees to function as pivot joints or hinges on the lengths of 1" pipe that are your ground rails. The 90-degree section on each tee is the "foot" that joins your rib strut to the ground rail.
Each foot/tee needs to be anchored to the ground to keep the bowed ribs from pushing the base apart on the ground. Using some thin but strong rope or webbing, make loops big enough to connect around the tee as shown in the picture with enough loop left over to get a stake through. 20-22" should do it.
Each rib strut is composed of 2 10-foot lengths of 1' pipe, joined in the middle by a 1-foot section of 1-1/4" pipe. It's a good idea to mark the rib lengths at 6" from each end, so you know you have the connection properly centered in the tube.
Don't use actual 1" PVC couplings for this; since the pipe is flexible, the bending stress on the joint will pop the pipe out of the shallow sockets of the coupling unless it's cemented, which would give you 20-foot lengths of straight pipe to store. No thanks. Use the 1-1/4" pieces as connectors and just duct tape the ends to keep from sliding and you'll be in fine shape.
So, to recap: For each rib, you'll need 2 full lengths of 1" pipe, 1 1-foot piece of 1-1/4" pipe, 2 1-1/4" tees, about 20" of 1-1/4" pipe to finish the tees (two 2" pieces and one 6" piece for each), 2 loops of rope/webbing, and 2 tent stakes.
Finally, to brace the whole structure, you need at least a full-length spine at the top and (optional but preferable if there's wind) 2 side rails to attach to the ribs to keep them spaced and "solidify" the tunnel. You can use thinner pipe for that, ¾" would be plenty.
Decide how many ribs you'll want first. In a 10-foot tunnel, 5 ribs will give you about 2-1/2 feet of spacing between each; that's pretty sturdy unless you're using a very heavy cover and you need more strength. No problem; using the sliding "feet" on the ground rails, you can add as many ribs as you want and space them however you like. So, for a 10-foot tunnel with 5 ribs, we want:
(12) full lengths (10') of 1" pipe (2 ground rails, 5 ribs)
(10) 1-1/4" Tees
(1-1/3) lengths of 1-1/4" pipe (5 X 1 foot, 10 X 6", and 20 X 2")
(10) tent stakes
(10) rope loops
(3) full lengths ¾" pipe (spine, two side rails)
Grand total, not including some duct tape and whatever you're skinning it with, is about 50 to 55 bucks.
Next: The set-up.
The flexible nature of PVC pipe allows curved structures with their own internal tension, negating the need for outside bracing or guy lines. You can make a half-round tunnel roughly 10 feet wide by around 7 or 8 feet tall that can easily be set up by one person, absurdly easily with a helper. The materials you need are schedule 40 1" PVC pipe, 1-1/4"pipe and tees, some thin rope or strong webbing, and some tent stakes to anchor it into the ground (if building indoors or on concrete you'll need a different anchor system, I'll get to that later). And some duct tape, of course. Always duct tape. BTW, all these pics are linked to larger uncropped versions for a better look.
http://i36.photobucket.com/albums/e31/pjhawke/revenant/PVC1ingredients.jpg
The 1" pipe is the actual structural material of the frame. The 1-1/4" pipe is just used for connectors so you'll only need 1 or 2 lengths of it as you'll be cutting it into smaller pieces. With schedule 40 pipe, these 2 pipe sizes are unique in that they very neatly slide into one another; snug enough that there's no jiggle but loose enough to slide and rotate.
The 1-1/4" pipe serves as the sleeves that connect the 1" pipe sections, and as reducers in the openings of the tees. The pipe sections in the straight-through section of the tee can be small, say 2", since they're just acting as bushings. The piece in the 90-degree position should be longer, around 4-6".
This allows the tees to function as pivot joints or hinges on the lengths of 1" pipe that are your ground rails. The 90-degree section on each tee is the "foot" that joins your rib strut to the ground rail.
Each foot/tee needs to be anchored to the ground to keep the bowed ribs from pushing the base apart on the ground. Using some thin but strong rope or webbing, make loops big enough to connect around the tee as shown in the picture with enough loop left over to get a stake through. 20-22" should do it.
Each rib strut is composed of 2 10-foot lengths of 1' pipe, joined in the middle by a 1-foot section of 1-1/4" pipe. It's a good idea to mark the rib lengths at 6" from each end, so you know you have the connection properly centered in the tube.
Don't use actual 1" PVC couplings for this; since the pipe is flexible, the bending stress on the joint will pop the pipe out of the shallow sockets of the coupling unless it's cemented, which would give you 20-foot lengths of straight pipe to store. No thanks. Use the 1-1/4" pieces as connectors and just duct tape the ends to keep from sliding and you'll be in fine shape.
So, to recap: For each rib, you'll need 2 full lengths of 1" pipe, 1 1-foot piece of 1-1/4" pipe, 2 1-1/4" tees, about 20" of 1-1/4" pipe to finish the tees (two 2" pieces and one 6" piece for each), 2 loops of rope/webbing, and 2 tent stakes.
Finally, to brace the whole structure, you need at least a full-length spine at the top and (optional but preferable if there's wind) 2 side rails to attach to the ribs to keep them spaced and "solidify" the tunnel. You can use thinner pipe for that, ¾" would be plenty.
Decide how many ribs you'll want first. In a 10-foot tunnel, 5 ribs will give you about 2-1/2 feet of spacing between each; that's pretty sturdy unless you're using a very heavy cover and you need more strength. No problem; using the sliding "feet" on the ground rails, you can add as many ribs as you want and space them however you like. So, for a 10-foot tunnel with 5 ribs, we want:
(12) full lengths (10') of 1" pipe (2 ground rails, 5 ribs)
(10) 1-1/4" Tees
(1-1/3) lengths of 1-1/4" pipe (5 X 1 foot, 10 X 6", and 20 X 2")
(10) tent stakes
(10) rope loops
(3) full lengths ¾" pipe (spine, two side rails)
Grand total, not including some duct tape and whatever you're skinning it with, is about 50 to 55 bucks.
Next: The set-up.
They don't constitute a tripping hazard because they're along the long axis of the walkway, not across it (that yellow line across in the picture is my tape measure); the rails are the bottom edge of your walls when you put your plastic/fabric skin on the frame . People won't be going in that direction. And since the walls curve inward, even fairly short people's feet probably wont get within two feet of the sides. Unless you plan on intersecting tunnels (which would be way cool BTW) or have side entrances/exits off the main path. If you plan on people going through the side (guests or actors), I would suggest that there be no ground rail there. Since every footing is individually staked down, you can have a "between the ribs" segment of ground rail missing without compromising the structure (Note: If you do this, you're probably better off using elbows than tees for the footings at either side of the opening... that way you don't have that extra 2" piece of PVC there on the ground for someone to stumble on if they cut really close to the corner when they make the turn. Highly unlikely that they would, but I like to err on the side of parano-- eh, caution.) Like everything else, figure out what you want ahead of time, draw it out on some graph paper and cut your pieces accordingly.
