Posted by Frank Murch | May 22, 2013 5:09:00 PM
Dealing with the wind There are a number of issues with banners and the wind.
First it is not really the average wind speed that is the issue it is about gusts of wind. It is these gusts that pull a banner apart. Most banners use grommets in the corners and edged to attach to the anchor points.
If wind is expected to be an issue taking the stress over as large an area as possible will increase the banner’s durability. Banners have hems and these run the length of the banner. Placing a cord in the hem gives the maximum area for the stress to be absorbed. A grommets attach is great for lower stress but a hem cord is preferred for the wind
The next step is to resist the wind or pass it through. There are 3 methods:
- Often there are “Air Relief” holes. These are half circle holes in the banner. The idea is wind will push these open and flow through reducing the resistance on the banner. In some cities these are actually in the signage codes. This works but it has limitations. The edges of a banner are reinforced with a hem but the air relief slits are not. Ripping and stretching at the end of the cut can shred a banner. There is also considerable debate about gusts – a constant wind will open up the flaps but a gusts may not. It is generally the gusts that destroy banners.
- Open mesh materials are also common. Like having are relief slits an open mesh allows wind to go through the banner. The advantage is the holes are very small and not cut they have a higher resistance to tearing and sheading. The disadvantage is ink flows through these holes and makes a double sided banner impossible. Placing two banners back to back can work but light also comes through and with it an image breed from the opposite side. A center layer (liner) can be added but this generally negates the open mesh. So for single sided prints an open mesh may be the answer
- Use a heavier material. Many banners are made from 12 or 13 oz. material. Using an 18 ounce vinyl or heavy poly cotton increases the banners ability to resist wind more than the 150% increase in thickness.
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