Geekster, can you explain the roof better?
Why is a flat roof bad?
How do you keep the dust out of your tent?
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geekster
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Imagine you have two carports side by side but they are covered with shade cloth rather than tarp. Now, remove the "outside" row of support poles on both of the frames and allow the outsides to drop to the ground. You now have something very close to what we use. The angle is going to be such that the two now meet at something of a down angle. Looking at it endwise, there will be a "double peak" albeit at only a slight angle but just enough of an angle.
A flat roof (and even a "low pitch" as on our old "hospitality" space) has been "bad" in our experience because it tends to lift in high winds. The roof basically acts as an airfoil and the low pressure caused by the fast wind blowing across the roof causes either a flat out lifting (if the roof tarp is very tight) or at the least, constant flapping of the material (if it isn't so tight) which causes the life of the material, the grommets, bungees, and whatever else is involved (including the patience of the occupants) to be considerably shortened when you get hours and hours and hours of that going on.
The "gull wing" roof and sloping sides causes some interesting things to happen. First of all, the slope of the "long" side causes some downward pressure (rather than "inward" pressure if the wall was 90-degrees to the playa and acting like a "scoop") and sheds the wind load better. The wind rides up along the slope. When it gets to the first peak, there is some outward pull on the first downslope of the gull wing but when the wind hits the upslope headed for the second peak, again, it causes some downward pressure on the structure. Basically, we get more force holding the thing down to the ground than trying to pull it up into the air.
Last year we had the two halves separated with a flat tarp between the two. On the day of the double rainbow when the wind came up, that tarp pulled out its grommets and when we lost that, the "downwind" half of the structure acted like a scoop and that shade cloth also blew out its grommets and we lost that half for a while. The "upwind" side stayed firm to the playa. This year we simply did away with the flat section and connected the two halves directly and it worked like a charm in all the wind we had. Nothing moved and the tents inside had no problems at all.
It is hard to describe without drawing it, I hope I did well enough for you to get the idea.
A flat roof (and even a "low pitch" as on our old "hospitality" space) has been "bad" in our experience because it tends to lift in high winds. The roof basically acts as an airfoil and the low pressure caused by the fast wind blowing across the roof causes either a flat out lifting (if the roof tarp is very tight) or at the least, constant flapping of the material (if it isn't so tight) which causes the life of the material, the grommets, bungees, and whatever else is involved (including the patience of the occupants) to be considerably shortened when you get hours and hours and hours of that going on.
The "gull wing" roof and sloping sides causes some interesting things to happen. First of all, the slope of the "long" side causes some downward pressure (rather than "inward" pressure if the wall was 90-degrees to the playa and acting like a "scoop") and sheds the wind load better. The wind rides up along the slope. When it gets to the first peak, there is some outward pull on the first downslope of the gull wing but when the wind hits the upslope headed for the second peak, again, it causes some downward pressure on the structure. Basically, we get more force holding the thing down to the ground than trying to pull it up into the air.
Last year we had the two halves separated with a flat tarp between the two. On the day of the double rainbow when the wind came up, that tarp pulled out its grommets and when we lost that, the "downwind" half of the structure acted like a scoop and that shade cloth also blew out its grommets and we lost that half for a while. The "upwind" side stayed firm to the playa. This year we simply did away with the flat section and connected the two halves directly and it worked like a charm in all the wind we had. Nothing moved and the tents inside had no problems at all.
It is hard to describe without drawing it, I hope I did well enough for you to get the idea.
Pabst Blue Ribbon - The beer that made Gerlach famous.
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geekster
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Look at it another way. We are talking about something that is roughly 30 or more feet wide and about 40 feet long. When you have a flat roof or a low pitch there is a lot of force pulling up on the thing. Rebar only needs to move a tiny bit or guys stretch a little to allow wind to get under the sides of the thing and once that happens, you start to get religion. Sides being 90-degrees to the playa make it worse because the windward side wants to push in at the same time weight is being removed from the legs from the lifting action of the roof. The center of our old space would sometimes lift more than a foot and last year I had to drive rebar in a hurry right through a carpet inside and guy the center ridge pole to it to keep the thing down on the ground. With a sloping sides design, the wind tends to push it down more than pull it up and there is less chance of the wind getting under the thing.
Oh, and we also do other things for strength, too, like weld gussets into the curved part of the canopy fittings. That made a huge difference. We have been making our own shade since '05 and it can be a pain in the ass unless you have a people who don't mind doing a lot of repetitive tasks.
Oh, and we also do other things for strength, too, like weld gussets into the curved part of the canopy fittings. That made a huge difference. We have been making our own shade since '05 and it can be a pain in the ass unless you have a people who don't mind doing a lot of repetitive tasks.
Pabst Blue Ribbon - The beer that made Gerlach famous.
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geekster
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Dont think of an arc. Imagine a building with a roof that has a double peak. And now imagine that the side walls slope. So imagine the sides of the roof continue their slope all the way to the ground but there is a double peak. The wall slopes up, comes to a peak, slopes down a bit, then back up to another peak and then back down to the ground. Take the letter M here and bend out out the uprights so they are at about the same angle as the "v" in the middle.
Yeah, the sharp angle in the center creates a lot of turbulence. Anyway, it isn't like we did a lot of wind tunnel testing at Ames or anything, we just discovered that it works great. It would suck in rain though because that center would catch water.
Yeah, the sharp angle in the center creates a lot of turbulence. Anyway, it isn't like we did a lot of wind tunnel testing at Ames or anything, we just discovered that it works great. It would suck in rain though because that center would catch water.
Pabst Blue Ribbon - The beer that made Gerlach famous.
Beware cheap tents...
I brought a $45 fiberglass-pole tent at a drug store... staked it to the ground with rebar in one corner and cheap 6" wire stakes in the other corners (I was going to go back and replace them with rebar later). Then the Monday dust storm came up, so I left it on the ground without even trying to put the poles in.
Came back that evening, and the tent was gone. There was 1 inch of corner fabric attached to the rebar stake *and* two of the wire stakes. Apparently, a dust devil had ripped the tent right off the ground... carried it over the entire city a few hundred feet in the air (we were at 5:45 and I) ... it even cleared the MOOP fence, and was never seen again.
Our other tent was still there, but had an inch of dust on the floor. It was still dust-storming, but less hard, so we put the poles in... then realized that it had a big mesh area at the top, and the wind was blowing dust right under the fly, up the sides, and into the tent.
Next year, I'm getting a well-made 4-season tent. Either that, or I'm building a custom-designed structure with a custom-fitted tarp.
Yes, things will get somewhat dusty no matter what you do. But there's a big difference between a little bit that drifts off your clothes, and a constant heavy rain of dust that makes you wear your dust mask inside your tent.
Came back that evening, and the tent was gone. There was 1 inch of corner fabric attached to the rebar stake *and* two of the wire stakes. Apparently, a dust devil had ripped the tent right off the ground... carried it over the entire city a few hundred feet in the air (we were at 5:45 and I) ... it even cleared the MOOP fence, and was never seen again.
Our other tent was still there, but had an inch of dust on the floor. It was still dust-storming, but less hard, so we put the poles in... then realized that it had a big mesh area at the top, and the wind was blowing dust right under the fly, up the sides, and into the tent.
Next year, I'm getting a well-made 4-season tent. Either that, or I'm building a custom-designed structure with a custom-fitted tarp.
Yes, things will get somewhat dusty no matter what you do. But there's a big difference between a little bit that drifts off your clothes, and a constant heavy rain of dust that makes you wear your dust mask inside your tent.
cphoenix at gmail dot com. Email for info on rebar removal, dyslexia correction, futurism...
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geekster
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No, not anywhere near the ground, it comes down to about 7 feet or so. Remember this is mainly designed to be a shade covering for our tents. The outside walls peak at about 10-12 feet, it drops down to about 7 feet and goes back up and then down to the ground. Anyway, the bottom line is that it was very stable, kept the tents cool, and really cut the wind through the tent area. It was plenty large enough for the job. We had a Springbar Vagabond 7 and a Vagabond 4 side by side, one under each half of the thing at one end and an assortment of other tents down a row on each side from there along with a seating area where we could sit and chill with our camp mates. It worked out well.
Pabst Blue Ribbon - The beer that made Gerlach famous.
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geekster
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It is in two halves and the two halves are basically lashed together with zipties. It is so stable that we didn't need anything else, even on Monday.
It came about from back in 05. I had a regular 10x20 carport that I brought out. My wife at the time was going to join me a few days later with our pop-up trailer but in the meantime I needed a tent and some shade. I started building the shade canopy, got the top section built, put the tarp on top, and lifted one side up with the poles and the wind was blowing a little. It was hard to lift up, the wind kept wanting to push it back down. Once I got one side up, I noticed that with the poles on only one side, it made a nifty little lean-to. I put my tent up under it, drove some rebar and guyed it down ... the long side was faced Southwest with the open side Northeast. It was stable has hell and this was the week before the event ... so we set up several chairs and a table under it and it became the daytime hangout area for our camp members who were on the playa working the week before the event for various departments.
I did it again in 06 and again it worked really well for my personal shade. My camp mate, Heidi, liked it so much that she "scaled it up" in 07, changed the tarp to shade cloth, and that is when we had that flat piece between the two halves that didn't work so well and we took that out in 08 and there you have it. It is the "accidental shade structure" sort of.
It came about from back in 05. I had a regular 10x20 carport that I brought out. My wife at the time was going to join me a few days later with our pop-up trailer but in the meantime I needed a tent and some shade. I started building the shade canopy, got the top section built, put the tarp on top, and lifted one side up with the poles and the wind was blowing a little. It was hard to lift up, the wind kept wanting to push it back down. Once I got one side up, I noticed that with the poles on only one side, it made a nifty little lean-to. I put my tent up under it, drove some rebar and guyed it down ... the long side was faced Southwest with the open side Northeast. It was stable has hell and this was the week before the event ... so we set up several chairs and a table under it and it became the daytime hangout area for our camp members who were on the playa working the week before the event for various departments.
I did it again in 06 and again it worked really well for my personal shade. My camp mate, Heidi, liked it so much that she "scaled it up" in 07, changed the tarp to shade cloth, and that is when we had that flat piece between the two halves that didn't work so well and we took that out in 08 and there you have it. It is the "accidental shade structure" sort of.
Pabst Blue Ribbon - The beer that made Gerlach famous.
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Elderberry
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