Your opinion on large banners

[Flame]

Alright, so here's a topic for discussion. I have a 20' banner stretching across a busy street, only going to be up for a couple weeks... and I'm trying to make a decision here. I'm normally against wind slits, as they look cruddy and not sure if they do much.

HOWEVER... do they do much? Or not? Good idea or bad?

Customer is paranoid about this falling, and unfortunately due to time restrictions, all I can get is 13oz material, no 18. So sorta stuck and trying to make the judgement call. Cut the wind slits... or no?

Your thoughts?

 

[BigfishDM]

Man thats a tough one, how is the wind in your neck of the woods? Would you client let you print mesh instead of banner? Wind slits to be safe, on the other hand alot of people say wind slits compromise the strength of your banner.

 

[32bantum]

cut the slits!! You'd be amazed at how much drag it cuts down. It is also required by code in some munincipalites if it is hung above a street. JMO

 

[Gino]

For what it's worth... I would never use less than 19-oz or 21-oz for a banner spanning across a street.

You should have cables stretching across the street both top and bottom and attach the banner to that. We've always used slits or mesh banners.

If you're stuck using 13-oz, I would think either the slits will tear out or the ends where you tie off will give way at this time of year.


I would think very hard about passing on the order if all you can offer is 13-oz

 

[Flame]

For what it's worth... I would never use less than 19-oz or 21-oz for a banner spanning across a street.

You should have cables stretching across the street both top and bottom and attach the banner to that. We've always used slits or mesh banners.

If you're stuck using 13-oz, I would think either the slits will tear out or the ends where you tie off will give way at this time of year.


I would think very hard about passing on the order if all you can offer is 13-oz

Eh, I was nice and said I'd donate a banner for a gig. Next day client comes in and lets me know it needs to be done NOW or not at all... and it's going above a road!!! So got myself a little stuck.

Thinking of using the fold over re-enforcements on all of the grommets, then cutting small 3" wind slits rather than the huge ones, and double hemming the edges.. then hoping for the best cuz it only has to last 2 weeks.

 

[hydo1]

Eh, I was nice and said I'd donate a banner for a gig. Next day client comes in and lets me know it needs to be done NOW or not at all... and it's going above a road!!! So got myself a little stuck.

Thinking of using the fold over re-enforcements on all of the grommets, then cutting small 3" wind slits rather than the huge ones, and double hemming the edges.. then hoping for the best cuz it only has to last 2 weeks.

Honestly, I would pass on this job. They gave you all this additional information LAST MINUTE that is required to obtain the correct materials for this type of job. I am not sure about your area, but we need permission from the city to do a job like this. Did they get that? Probably not. Can you imagine how bad it would look for you if the banner you donated fell into the street and caused an accident?

 

[Letterbox Mike]

I'd pass on it if all you have is 13oz, but if you insist on doing it, double-stitch the hems, sew nylon webbing in them, and add extra reinforcement in the corners. It's a tossup if it'll hold up or not, windslits will only introduce a bunch of weak points. A decent wind will rip the banner to shreds. Unless you have so many holes in the banner that the surface area is reduced by 50%, they cause the banner to fail, but they don't relieve a tremendous amount of pressure on the banner. I guess a ripped up banner is better than broken telephone poles or cables, but I dunno...

 

[Pat Whatley]

Don't tie rope from your grommets to the poles. Tie the rope (or better use cable) across the road then tie the banner to that through grommets placed every two feet. It will spread the windload across the banner instead of putting it all on the corners.

Don't do the windslits. They're just a place for the banner to start tearing.

 

[Mosh]

Pass on the job. I made a banner for a local group, not knowing they planned on hanging it over the street. They used cables and it looked great, until that night, a storm blew in and knocked one of the poles down. The City tried to get me to pay for it, but I got out of it cause the City was the ones that installed it in the first place.

Not worth the trouble, especialy for a donation.

 

[royster13]

And of course you carry "liability" insurance......

 

[Flame]

Written permission by city hall and the local PUD is doing the install. Customer is signing a waiver releasing us from any possible damages, and that we are not responsible for possible damages.

I'm gonna take a whack at it with no wind slits and let you guys know how it goes.

 

[Mosh]

Get a pic!

 

[kazoosigns]

I'm looking for it, because our company had done some extensive tests on the use/need of wind slits, and have some lit on it. Basically, it really doesn't do anything as a benefit, but can actually rip out and ruin your banner quicker than a really strong wind will.

Edit: Found the part of our lit referring to wind slits

We are often asked for our recommendation on the topic of wind holes or slits in banners that are meant to allow wind to pass through banners therebyto, hopefully, reduce total banner wind load. In both of our full-size wind tunnel tests, in 1984 and 2002, we tested banner with wind holes on our BannerFlex hardware as well as non-vented banners. In both cases, it was visually obvious that these wind holes became, in fact, detrimental to the banners due to vibration and fabric stress within the banner and they tended to increase the wind load rather than reduce it.

How can they increase load? The holes allowed the fabric to ripple and catch more wind which increases the drag factor. The fiberglass arms deflected more rather than less indicating more force on the system with the holes than without. Also, again, the banners vibrated considerably more at 60 mph to 100mph with the holes than without the vents.

Also, the typical hole pattern that we are asked by unknowing customers to cut into the banners and which we see on many non-KBW banners do not allow enough wind relief to make a difference regardless of the rippling effect. For example if 3 –6”diameter “half-moons” are cut into a 30” x 94” banner those holes only represent 1.5% of the surface area. Even twice that number of holes, which is more than normally seen, is only 3% of the surface area.

 

[J Hill Designs]

hem the rope in with the banner