Banner Tower - Need Help

[pepster]

I have been asked to build a support system for a sign banner that will be used as the starting and finish line for a bicycle race. The banner is approximately 36 ft. long and 4 ft. wide. It is made of vinyl and is supported by 1/4 inch aircraft cable. The bottom of the banner needs to be higher than the tallest rider. I would assume that 7 ft. would be adequate. The banner itself weighs approximately 30 lbs. The only stipulations are the support must be simple enough and light enough for two people to set up quickly. Storage is not a problem. The attached rough sketch shows what I am thinking of. The base will be made out of steel and the support legs can fold up for storage. The main tower is aluminum tubing which has a pulley mechanism for the top cable and attachment points for the guy wires.
At this point I am completely open to suggestion. Any and all thoughts on this project would be appreciated. I am especially anxious to hear from you engineers out there. These towers will be set up in Florida during the month of June. Sudden rainstorms with occasional strong winds are not uncommon at that time of the year.
Thanks for your help,
Pepster

[Wheat]

Looks like it will work fine. The only trick I can help ypu with is some banners have "half moon" holes manufactured in them so the banner does not act like a "sail" Start your project maybe Lance will show up for the race....Good luck...

[RST200]

I am guessing this is for a road race? 7 feet might be a tad low. When you consider the height of the rider with their arms raised on a road bike as the winner is crossing the line.
just a thought...

[FullMetal]

If I were you... I'd have them supply a certified engineered drawing. Your dealing with dynamic pressures. Static or dead load of 30 lb is not the issue it's Wind Load. Even with vents sewn in your looking at numbers in 1000 lb range at min. (slight breeze) with the potential loads up to 5700+. These are number are at a width of 36' actual most likely will be greater. The high up it's placed off grade the greater the wind pressure will be. 10 ft min to bottom is standard for safety. It all seems easy... It's only a banner. But if it should fail who do you think they'd look at... Nowadays they put everyone in a bucket shank and see what falls out. With a engineer's drawing that gives you a bit shield from liability.

[RST200]

I should have looked at the diagram of the stand before I posted my last message.. Depending how the stand is secured, I may not be comfortable with that stand. Imagine the banner tipping over from the wind or the rider catching the banner with his/her hands. First rider falls with the banner accross the finish line...next group of riders sprinting to the finish at 30 miles plus per hour...60 or more riders crashing through the banner into a huge pile up. Not a pretty scene. Most banners that I have seen that size use scafolding on both sides of the street. Or the tie off to a larger structure...as a tree or big post.

[pepster]

Thanks for the response. The race is really more of a ride. A fund raiser. No mad dash to the finish line if you know what I mean. Also, I was kind of volunteered to make the supports for the banner. No money, no liability. As long as a tower doesn't come down on somebody's head I think we'll be OK. I'm mainly concerned about the wind load if the weather gets bad. If the guy wires are properly placed and secured it should tolerate a modest wind. Nothing will stand up to a strong wind, even scaffolding. By the way, scaffolds were used last year and it took two people six hours to set them up.
Thanks again,
Pepster

[Rhett]

Thanks for the response. The race is really more of a ride. A fund raiser. No mad dash to the finish line if you know what I mean. Also, I was kind of volunteered to make the supports for the banner. No money, no liability. As long as a tower doesn't come down on somebody's head I think we'll be OK. I'm mainly concerned about the wind load if the weather gets bad. If the guy wires are properly placed and secured it should tolerate a modest wind. Nothing will stand up to a strong wind, even scaffolding. By the way, scaffolds were used last year and it took two people six hours to set them up.
Thanks again,
Pepster

I am a physician by trade, not an attorney, but I think several of the above concerns are very significant. The "no money, no liability" statement may or may not be true in this scenario, but ethics dictate that your work be reasonably expected not to fail and there are significant forces placed on it here. Just be sure you take all of the above warnings seriously.

[storts]

I am a physician by trade, not an attorney, but I think several of the above concerns are very significant. The "no money, no liability" statement may or may not be true in this scenario, but ethics dictate that your work be reasonably expected not to fail and there are significant forces placed on it here. Just be sure you take all of the above warnings seriously.

The world is sue happy, and the winds in fla can pick up withins a mins notice, thats one big sail!!! How Boute if they sank some pipe or tubing in the ground,thats flush,and a plastic caps, that king supply sells, so next year its not full of hurrican goop? Just a thought, or guide wires into the ground and flagged and baracated,Like a tent ?Jack