Glad to hear it went to a contributing member of this community, Richard. Flourish has wonderful products and I see there were storms this past weekend in Omaha that brought down the tents:
I look at the photos posted to see who/what was still standing. When it comes to weights, mass is important but is placement to gain the best effect. That's the engineering side of my brain working.
Connie Mettler > Richard L. ShererJune 11, 2018 at 9:40pm
No weights will stop a really bad storm. if at all possible do a weather check before you close you booth for the night so you can be prepared. Button up, zip up, pack up, tie up, lower the canopy and hunker down. This really bad booth destruction is a light weight tent, so not surprised to see it destroyed. You can see the larger tent on its left standing well.
This show is three days long, so the setup should take that into account. Prepare for multiple days. The longer the show, the more we would add weight, bungee things together, and prepare for any eventuality. A one day show might bring out the easy up, but we'd still weight it, maybe bungee the heavy bins to the legs.
I never understood cement filled pvc hanging from a bungee.
Yes, it's a hard sell to artists that placement is just as important as mass. How many vertical elements do you see in a steel bridge?????
Reid Watts > Richard L. ShererJune 16, 2018 at 1:05pm
Richard: Your post made me think about weight placement. I’m not sure what you mean about vertical and horizontal components and how bridges relate to canopies. But here are some of my thoughts about canopy weights:
Weights do not prevent a booth from being moved by wind. If weight alone was able to keep an object stationary, a 10,000 pound sailboats with about the same sail area as my booth would not be able to sail at 7 knots in a 15 mph wind.
No mariner, not even a supertanker captain, relies on weight to keep their ship stationary. Instead, they rely on friction devices such as anchors, or tethering to stationary objects such as pilings.
Ditto for campers, mountain climbers, etc. Only art show artists, crafters, and show promoters think that weights are a good idea for keeping large canvasses from being blown away by the wind.
There appears to be a trend for show promoters to ban friction enhancing devices (stakes, screws), requiring the substitution of weights instead, under the theory that sufficient weights are equally effective in preventing wind damage.
Weights can help to keep a canopy from toppling (similar to the use of weight by sailors to keep their boats from capsizing), since in order to topple two of the legs need to be lifted off of the ground. But to move a canopy and blow it into other canopies, shelves, art and people, it only needs to move sideways. Without any stakes, the only thing preventing it from moving sideways is the friction between the little 4” square metal plates at the bottom of our poles, and the ground.
Inertia is increased with additional weight, and inertia will delay the moment at which the wind will begin to move a canopy. Inertia is initially our friend, until the canopy starts moving. Then it is our enemy, since a heavy canopy will do much more damage than a light one will. It may take a long time for a strong wind to move a supertanker, but once it starts to move, it can do a lot of damage. So relying on inertia to control wind damage is foolhardy, and artists and show promoters may be the only people who do.
Race car designers do not rely on weight either to keep their cars from slipping off of the track. In fact, they do the reverse: they cut as much weight as possible. Instead, they maximize the friction with the ground, choosing huge tires made of sticky rubber with a maximum “contact area”. But most of our canopies have almost no contact area with the ground, and what we have is a slippery metal plate, while our weights are suspended from our frames!
As an engineer, Richard, what do you think about the above analysis?
I believe some of the terminology is not being assigned correctly.
If we were to use them more accurately, weight would have nothing to do with it for weight is merely a relational measurement dependent upon our gravity.
Perhaps we should be using "mass"?
An example being your last scenario with the Race car.
They do rely on weight.
How? you ask... I knew you would :-)
They do not increase the mass of the car. However by designing the aerodynamics of the vehicle, including the scoops and spoiler, it causes far greater downward pressure on the vehicle. Akin to what would happen with greater mass. or what is aforementioned as weight. It is this far greater "weight" that allows the tires to generate greater friction with the track.
In this way, greater mass hanging from our tents, results in greater weight. results in greater friction. Results in less movement both horizontal and vertical.
What is the coefficient of friction to sideways force?
Also once the movement starts it does not continue. Law of physics states an object remains in a state of rest or unrest until acted upon by outside forces.
A) The tent is not in a vacuum.
B) There is gravity acting upon it.
C) There is friction acting upon it (even though movement has started, friction is still applied).
D) Air currents may not be in a single plane or path.
Hence, once it starts moving, the weight / mass will cause friction with the ground resisting the inertia, thereby reducing the effects.
Perpetual motion does not apply.
The comparisons to objects in water are good however different rules apply, due to the difference in properties of the two substances.
How much would the same sailboat move if placed upon dry land with the exact same sail area and weight?
A simple, non scientific test is this:
Setup your tent with no weights nor stakes.
Now push a corner post 12" in any direction parallel to the ground.
Now restore to original position and add 75 lbs to each corner (what I user at shows).
Now push the corner post as before. Hugh difference.
Ground stakes and plenty of weight, as well as wind pressure releases on the canopy will help.
Replies
Glad to hear it went to a contributing member of this community, Richard. Flourish has wonderful products and I see there were storms this past weekend in Omaha that brought down the tents:
http://www.ketv.com/article/overnight-storms-cause-damage-at-omaha-...
I look at the photos posted to see who/what was still standing. When it comes to weights, mass is important but is placement to gain the best effect. That's the engineering side of my brain working.
No weights will stop a really bad storm. if at all possible do a weather check before you close you booth for the night so you can be prepared. Button up, zip up, pack up, tie up, lower the canopy and hunker down. This really bad booth destruction is a light weight tent, so not surprised to see it destroyed. You can see the larger tent on its left standing well.
This show is three days long, so the setup should take that into account. Prepare for multiple days. The longer the show, the more we would add weight, bungee things together, and prepare for any eventuality. A one day show might bring out the easy up, but we'd still weight it, maybe bungee the heavy bins to the legs.
I never understood cement filled pvc hanging from a bungee.
Yes, it's a hard sell to artists that placement is just as important as mass. How many vertical elements do you see in a steel bridge?????
Richard: Your post made me think about weight placement. I’m not sure what you mean about vertical and horizontal components and how bridges relate to canopies. But here are some of my thoughts about canopy weights:
As an engineer, Richard, what do you think about the above analysis?
I believe some of the terminology is not being assigned correctly.
If we were to use them more accurately, weight would have nothing to do with it for weight is merely a relational measurement dependent upon our gravity.
Perhaps we should be using "mass"?
An example being your last scenario with the Race car.
They do rely on weight.
How? you ask... I knew you would :-)
They do not increase the mass of the car. However by designing the aerodynamics of the vehicle, including the scoops and spoiler, it causes far greater downward pressure on the vehicle. Akin to what would happen with greater mass. or what is aforementioned as weight. It is this far greater "weight" that allows the tires to generate greater friction with the track.
In this way, greater mass hanging from our tents, results in greater weight. results in greater friction. Results in less movement both horizontal and vertical.
What is the coefficient of friction to sideways force?
Also once the movement starts it does not continue. Law of physics states an object remains in a state of rest or unrest until acted upon by outside forces.
A) The tent is not in a vacuum.
B) There is gravity acting upon it.
C) There is friction acting upon it (even though movement has started, friction is still applied).
D) Air currents may not be in a single plane or path.
Hence, once it starts moving, the weight / mass will cause friction with the ground resisting the inertia, thereby reducing the effects.
Perpetual motion does not apply.
The comparisons to objects in water are good however different rules apply, due to the difference in properties of the two substances.
How much would the same sailboat move if placed upon dry land with the exact same sail area and weight?
A simple, non scientific test is this:
Setup your tent with no weights nor stakes.
Now push a corner post 12" in any direction parallel to the ground.
Now restore to original position and add 75 lbs to each corner (what I user at shows).
Now push the corner post as before. Hugh difference.
Ground stakes and plenty of weight, as well as wind pressure releases on the canopy will help.