cable size for over the street banner?

[Big House Signs]

We are doing an over the street banner for the 25th anniversary of our Boys and Girls Clubs. It is 3ft high x 24ft wide, using 16 oz banner with webbing, d-rings on each corner and grommets every 2 ft to use snap hooks to cable. I have googled and googled to find exactly what the correct hardware to use. I have found lots of city ordinances of what they require. One suggested 3/8" cable. Is that correct?
Any direction or information is greatly appreciated.
Thanks,
Paula

 

[OldPaint]

3/8" steel cable???? or 3/8 rope?
i can tell ya real quick the steel cable that size is what is on most truck wenchs)))))
I have 2 steel cables holding up my 8' X 24' loft in my garage. each 1/4" cable is rated at 2000 pounds.
http://www.engineeringtoolbox.com/wire-rope-strength-d_1518.html
wind load is what is gona be your concern. ill put it this way, 3/8" steel cable would be able to hold up to a cat 3 hurricane)))))

 

[Desert_Signs]

How long does the cable need to be? What are the attachment points? If it's light poles, make sure they're rated for the additional sideload. I passed on a job like this due to the light poles not being designed for additional sideload. Another shop took it on. Both poles bent over 3" just during the installation trying to make the cable taut. They had to give up and pay to repair the poles.

At any rate, if your span is reasonable (30-40'), 3/16" cable should be fine. You coud get away with 1/8", but you're going to have some sag.

 

[Big House Signs]

3/8" steel cable???? or 3/8 rope?
i can tell ya real quick the steel cable that size is what is on most truck wenchs)))))
I have 2 steel cables holding up my 8' X 24' loft in my garage. each 1/4" cable is rated at 2000 pounds.
http://www.engineeringtoolbox.com/wire-rope-strength-d_1518.html
wind load is what is gona be your concern. ill put it this way, 3/8" steel cable would be able to hold up to a cat 3 hurricane)))))

Yea...I thought that was mighty big!

 

[Mosh]

Does your City know you are doing this? Are the pole strong enough if there are high winds? I would just hand them the banner and tell them to install. Way too much liability here. Happened here in our town, we had a wind storm come in and it damaged one of the poles/lights. Thankfully the city crew did the install, or my goose would have been cooked.

 

[Billct2]

This is not something I would want to be responsible for.
Either the city provides the specs and assumes responsibility in writing (even with that you'd be named in the lawsuit) or I'd pass.
I'd probably pass anyhow.

 

[CanuckSigns]

Our city has specs that have been stamped by a engineer that all banners must be made to. The banners are installed by city crews for liability reasons. I would check with the city about exactly what they want.

i've attached our city's specs to give you an idea

 

[Big House Signs]

The city told the Boys and Girls Clubs they could put it up. Infact the sign says the City congratulates them on 25 years. But Comcast is actually doing the install. I just need to come up with the banner and all the right hardware. I dont even think the city has specs for over the street banners.. It is very Mayberry RFD here. Thanks for everyone's help!
Paula

 

[Bretbyron]

In our City you have to talk to the "City" first, they contact CalTrans and clear it with them then the city hangs them. CalTrans is the one that has the banner hanging requirements and codes.

 

[Rocco G]

The city told the Boys and Girls Clubs they could put it up. Infact the sign says the City congratulates them on 25 years. But Comcast is actually doing the install. I just need to come up with the banner and all the right hardware. I dont even think the city has specs for over the street banners.. It is very Mayberry RFD here. Thanks for everyone's help!
Paula

Engineers tend to overbuild. One recently asked us to install some channel letters with 1/2" SS threaded rod, four per letter then backed up with 2" x 2" x 1/4" steel angle each spanning two studs. This was for 24" letters INSIDE a mall with no wind load, eight feet above the floor. That city spec stating 3/8" cable was prob done by an engineer. The lifting cable on my crane is 3/8" IIRC.

HOWEVER, if the city has a spec that calls for 3/8" cable, then you should spec 3/8" cable. Or call an engineer and get stamped plans. I would also specify that the cables be attached to a building, not poles. In reality 3/16" should be fine, but better safe than sorry.

And no, you cannot get it completely tight and straight. It will sag no matter what. Pull it too tight and it will either snap or start pulling over what it's attached to.