# A Quonset-style PVC Tunnel



## Revenant (Mar 17, 2007)

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.


----------



## Revenant (Mar 17, 2007)

Monkey Hut II: The Assembly

I'm not building a full tunnel in these pictures, just using what pipe I have on hand to demonstrate the technique.

As with any building, you lay the foundation first. Lay your ground rails where you want them, spaced parallel about 10 feet apart. Then slip your tee-footings onto both rails, and slide them so they're spaced equally on both rails. Put your rope loops on the tees, and stake them to the ground. 

http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun03layout.jpg

Now lay out the ribs: For each rib, lay two full lengths of 1" PVC end-to-end. Take a foot-long tube of 1-1/4" PVC and slip both ends of the 1" pipe into it so they meet in the center of the tube (you remembered to mark the 1" pipe, right? Sharpie is Your Friend). Wrap a little duct tape around each end of the tube so it's firmly stuck to the 1" pipe and doesn't slide. 
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun04ribconnect.jpg
Slip the end of each rib into one of the footings (feeting?) on one of the rails, and just let it lie across the opposite rail. Each tee/footing on that "empty" rail should be positioned so that the "open" tube is pointing up, ready to accept the other end of the rib.
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun05ribonrail.jpg
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun06getready.jpg

If you have a cassette or CD with a drumroll on it, now's the time to play it:

Go to the free end of a rib, face the rail, and pick up the rib like you were carrying a flagpole in a parade; one hand leading to stabilize the high part, the lower hand behind you bearing the weight. The rib will bow upwards. And just walk forward. That's all there is to it. The other end is anchored by the footing on the opposite rail, and it will smoothly rotate into the up position as the rib bows. 
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun07bend.jpg
When you reach the rail with the empty footing, slip the end of the rib into the 1-1/4" tube on the tee and make sure it goes all the way in (This is the part when a helper is nice to have, in case the tee has fallen over and needs to be rotated upright again. You can finagle it yourself, but its slightly awkward). 
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun08footit.jpg
Let go, step back, and admire your work. The stakes will keep the tees from pushing apart, the tees and rails will prevent the arch from falling over forward or back, and the tension in the arch will keep it from shearing to either side. As long as those stakes are holding the tees in place, it's all self-supporting. Now repeat for the other ribs.
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun09ribs.jpg

Looks kinda like a tunnel now, dunnit? Or at least the ribcage of one. Stand inside and you'll feel sort of like Jonah (or Pinnochio, if you're not into scripture). At this point you'll have a full sense of the area and volume of the tunnel. The one in the pictures is 11' wide at the base and about 7-1/2 feet tall.
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun10armsout.jpg
If you want it a little wider, the rails can be spaced out a bit at the expense of height. If you want it taller, however, bringing the rails in tighter than 10 feet is not recommended because it stresses the PVC. Adding a section of 1" pipe to each end would be a preferred way to add height (joined the same way as at the center, with a stick of 1-1/4"). The ribs can be re-spaced or added to easily since they slide along the rails. Now's a good time to decide if you want to do that, because you'll want to put a spine in and fix the ribs into place. This keeps all the ribs spaced from each other, stabilizing the structure. You can save money and use smaller pipe, because it doesn't have the structural load on it that the ribs have. At the top/center of the tunnel, affix a length of ¾" PVC along the axis, using duct tape to secure it to each rib. On the outside or inside of the tunnel doesn't really matter; but outside makes it easier to conceal if you're going to surface/decorate the inside of your tunnel. 
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun11spine.jpg
Side rails aren't essential, but they do add stability and help keep your fabric/plastic from pooching down into the tunnel. 
http://i36.photobucket.com/albums/e31/pjhawke/revenant/Tun12archconn.jpg


Now, as long as the stakes are there we know it won't fall down, but if there's a chance for strong wind we may not be out of the woods yet. According to some law of physics (Bernoulli's I think), when air blows across a curved surface it lowers the air pressure, meaning it creates lift. That's great for an airplane that you want to go airborne, but sucks for a structure that's supposed to stay on the ground. If the wind blows across the top of the tunnel hard enough it could feasibly pull the ribs out of the footing tees and then all bets are off. Some people drill holes through the tees (and the ends of the ribs in them) to put stout wire through there, or bolts or cotter pins. But frankly, a lot of people have built these things at Burning Man securing the ends of the ribs down with just duct tape and they've survived some hellacious windstorms, a lot worse than what you can expect in your neighborhood. Of course, going with cotter pins or such like does eliminate some of the nasty cutting and peeling off of duct tape during breakdown, and the stickiness left behind by it. Your call. If you drill, just make sure you use a jig so the holes going through the footings and the ends of the rib struts are all uniform, otherwise you'll have to match which rib goes into which footing next time you set it up (at which point I guarantee you'll just say the hell with it and use duct tape). I've been told that WD-40 will take the gummy duct-tape residue off; I haven't tried it, but I know WD-40 is some magic stuff. It may be worth looking into. Besides&#8230; it just ain't a proper haunt if something isn't taped together with duct tape.

Well that's the basics of a monkeyhut. I think curved tunnels are cool&#8230; gives a different feeling than walking through an upright room or tent. You can spraypaint the inside to look like stone walls or intestines or cave rock&#8230; if you were really ambitious you could glue in pieces of soft cushion foam and paint it to look like stone masonry; I know Lilly's made some awesome looking stonework out of cushion foam. If you don't want a full tunnel, you could make just a section like in my pictures to use as an archway covering an entrance. If anyone tries this, please post pictures somewhere!


----------



## Fright Zone (Sep 28, 2006)

It needs to be called the Terror Hut ; )

I like the detailed instructions and supporting photos. That's not always easy to don.

When it's finished is that how deep it's going to be? Or would you make it deeper so it's more of a tunnel instead of an archway?

I'd be a little bit worried about ToT's inadvertantly stepping on, kicking or tripping over the horizontal peices on the ground. Maybe a rubber strip or something like what they use to cover up wires across floors in office buildings something along those lines(?)


----------



## Zombie-F (Apr 12, 2004)

Fantastic instructions! I may have to try something like this someday.


----------



## Vlad (Aug 2, 2005)

I couldn't tell in the last pics whether or not the horizontal ground pieces were still in place? When I made this type tunnel in the past, I drove 
1 1/2' lengths of pipe, larger in diameter than the rib pieces, into the ground, and merely inserted the rib sections into them. It eliminates the need for staking, and keeps the frame from spreading at the same time. 
I used self tapping, hex head screws in each joint to hold it all together. With a drill powered nut driver, it's a quick, sure, attachment with no cleanup needed.
It is a great, easy way to make a tunnel, cave, or room though. Thanks for the pics Revenant!!


----------



## Revenant (Mar 17, 2007)

Thanx guys!

I know I'm not going to be building at my place this year, so I don't know if I'll be making a tunnel... I just did this little demo with pieces of pipe I happen to have left over from 2 previous projects. I've never made a full length tunnel, I've made shorter arches and awnings over doorways; I've seen a few nurseries make temporary greenhouses this way. These are just fun to make. PVC is like big Legos (I love Legos). The beauty of this design is you can make it longer by just adding to the ground rails and adding more tee footings & ribs... (insert dreamy Bob Ross voice here)... You can make it as long as you want... because it's _your_ tunnel... it's a happy tunnel...

Um, where was I? Oh yeah, ground rails. Yes, they're there in the picture, my grass just needed cutting  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.

Vlad, the reason I went with stakes-and-rail rather than your post method of securing the ribs was purely for ease (easier to drive in a narrow stake) and smaller holes in the ground (a section of pipe can pull up a pretty big divot. That's kinda the principle sod pluggers work on LOL). I got the ground rails idea from one I saw at a nursery where the hut was built on a parking lot; they weighted the rail down with concrete blocks). You're right on the money when it comes to those self-tapping screws; those things are awesome. Perfect for drilling into PVC; they tap right in, and the plastic has enough flex that it doesn't need a pilot hole. I just use tape because I re-use pipe and fittings a lot so if I can get by without drilling or tapping them that's what I'll do.

Oh, BTW, I noticed some of you folk live in the Great White North or thereabouts, and sometimes have wicked cold Halloween weather. PVC is nice and flexible but will get brittle if it gets too cold. If you think the temperature is going to go below about 50F, Under stress like that it will probably start to lose impact resistance. Probably not an issue if it's not going to get whacked with something hard, but I thought I'd mention it. I don't think it would be in danger of snapping under the bend stress unless temperatures got well below freezing.


----------



## Fright Zone (Sep 28, 2006)

That's good clarification.


----------



## TwistedDementia (May 2, 2007)

Are intire Haunt was PVC at one time, PVC is one of a Haunters best friends. And we also used the sheet metal zip screws, they work great.


----------



## Sickie Ickie (Jun 20, 2006)

October is very cold here at times. 30's is not unusual, so I guess pvc arches may not work for me, but maybe pvc boxes...


----------



## Revenant (Mar 17, 2007)

Yeah, I'd think it would be kinda dicey in the 30's with all that strain. You're probably better off with straight poles. Of course, it can be pre-bent, but its hard to get it uniform.
Where in Illinois do you live? I'm in Missouri and 30's is crazy cold for October... you get the wind off Lake Michicgan?


----------



## Sickie Ickie (Jun 20, 2006)

Indirectly, but yes. I live about 30 miles south of Chicago....Brrrrr.....


----------



## Ghostess (Aug 21, 2005)

Those are excellent instructions... I may need to use that method when building my tents and such this year.


----------



## pyxl (Oct 17, 2005)

*additional idea...*

I thought this was awesome. As we do an outdoor party, I decided to add this to my yard. For the interior, I'm combining two things....

1. Scene setter roll of material called "spider frenzy" http://www.frightcatalog.com/Halloween-Props/Scene+Setters/Spider+Frenzy+Room+Roll-1022004/

2. some actual hanging "spider bags" based on a design shown in Martha Stewart's good/bad halloween issue this year. You take a foam egg shape, wrap in some batting and put it in a white stocking. Put plastic baby spiders inside between the batting and the stocking..then hot glue some bigger plastic spiders on the outside...looks just like the spider "bags" on the scene setter.

The scene setter is black light ready, so I'm going to put some black lights inside... and put the real "sacks" hanging from the top. I'll post pictures when it's up.

Great "cheap" spider cave!


----------



## jdubbya (Nov 6, 2005)

Hadn't seen this thread. Really neat idea and a lot less expensive than building/framing wall panels. I think the straight pieces would work for me; planning a 16 foot walk through tunnel/cave thingie.
So what would be a good way to skin this frame? tarps, black plastic?
I really like this.


----------



## pyxl (Oct 17, 2005)

I did black plastic. I used the 4 mil (which is thin, but should be fine for me).
It took two 10 x 25 foot sections (I did a 20ft. tunnel).


----------



## jdubbya (Nov 6, 2005)

pyxl said:


> I did black plastic. I used the 4 mil (which is thin, but should be fine for me).
> It took two 10 x 25 foot sections (I did a 20ft. tunnel).


What did you use to fasten it? Duct tape?


----------



## Toktorill (Sep 15, 2007)

Revenant said:


> Thanx guys!
> Oh, BTW, I noticed some of you folk live in the Great White North or thereabouts, and sometimes have wicked cold Halloween weather. PVC is nice and flexible but will get brittle if it gets too cold. If you think the temperature is going to go below about 50F, Under stress like that it will probably start to lose impact resistance. Probably not an issue if it's not going to get whacked with something hard, but I thought I'd mention it. I don't think it would be in danger of snapping under the bend stress unless temperatures got well below freezing.


Thanks for the nod.  A few years ago we had a halloween that hit around -25C (-13F). I noticed a few people were heating PVC with heat guns in their projects- would a little heat during assembly lessen the stress?


----------



## pyxl (Oct 17, 2005)

Yeah, duct tape is the haunters wd-40.


----------



## Haunter112 (Oct 4, 2009)

Sorry to resurect an old thread but...

Anyone interested in this type of structure should google HOOP HOUSE and/or HIGH TUNNEL.

My uncle has a 30' long greenhouse made this way and it's been standing for 4 years straight.

His green house is simply PVC hoops slid over rebar stakes, tied together with twine, then covered with clear poly.

It's lasted through 40 mph winds, temperatures in the teens, even a hail storm.


----------

