TEXTILES.ORG
By Dan Dunstan
Q: What do tent rental companies need to
understand regarding the effect of wind on the safe operation of tenting equipment?
A: Every year, people are killed or injured by the unsafe use of tents in severe weather conditions. Aside from the devastating personal tragedy and negative business consequences, these events bring a higher level of scrutiny, oversight and bureaucracy to the entire tenting industry. With knowledge and safe practices, nearly all such incidents can be avoided.
If the wind gets nasty, GET OUT! The most important rule of safe tenting is that tents are not safe shelters in high wind conditions. If there is any doubt, move the party to a safer location.
Know your tent’s engineering stats. Any reputable tent manufacturer should be able to provide engineering stats for your tent. (Or tell you that your tent is not engineered.) Study this document and ask questions so you understand what wind speed your tent can withstand and how to correctly anchor your tent. These can vary significantly depending on the structural components used by the manufacturer and the tent’s size, shape and style.
Be good at driving and pulling stakes. Proper anchoring of engineered tents is the best defense against violent weather. Rather than skimping on the labor-intensive activity of driving and pulling stakes, embrace it as a necessary part of doing business and find ways to get good at it. Train and encourage your install crews to stake and give them the tools to do it safely and efficiently. The capital costs associated with mechanical stake drivers and mechanical stake pullers are easily offset by the daily labor savings for tent crews and the reduced risk that results from consistently installing strong, safe tents.
Use industry guides. The Tent Rental Division (TRD) of the Industrial Fabrics Association International (IFAI) has published a tent staking guide. This pamphlet describes the holding power of stakes under various conditions, and it should be referred to for every tent installation. TRD has also recently published an online tool for calculating safe tent ballasting requirements for when staking is not an option.
Understand the relationship between wind speed and force. Determining the exact force the wind is exerting on a tent involves several factors, but the most important variable is the wind speed itself. The key thing to know is that wind pressure increases exponentially with speed. A doubling of the wind speed increases the pressure by a factor of four. A tripling of the wind speed increases the pressure by a factor of nine.
Don’t be fooled by the “zone of complacency.” A common misconception occurs when installed tents appear to be safe and stable because the fabric is held in shape under light wind conditions. But when the wind suddenly gusts from 10 mph to 40 mph, the anchoring of the tent is suddenly required to resist 1,600 percent more force. The transition from the “zone of complacency” to the “zone of terror” can occur alarmingly fast.
Watch the weather, have a plan. Anchor tents appropriate to the weather conditions—with a safety factor—and follow the manufacturer’s instructions. Have a plan with your customer to move the party elsewhere if necessary. Many dealers include an extreme weather evacuation plan in the rental contract, identifying customer contacts and designating the person who monitors the weather and makes the call to evacuate the tent.
Tents usually blow UP, not DOWN. In high wind conditions, tents can often act like a wing, creating lift on the back/leeward side of the tent that is greater than the forces on the side facing into the wind. If not anchored correctly, tent stakes can be pulled from the ground, or on pole tents, side poles can begin to move causing the out-guys to fail. Extra care and anchoring should be applied on this leeward side in windy conditions.
Factor in tent-site exposure. Tent exposure is a term used by engineers and code officials to indicate how exposed the tent site is to windy conditions. Exposure conditions range from “A” (the most protected, but now virtually unused) to “B” and “C” (the most common) and finally “D” (the most exposed). These exposures are defined in the building code based on the distance of the tent location to various natural or man-made structures in the vicinity of the tent. This concept is important for tent engineering (most engineered tents are designed to meet C exposures) and site-specific tent permitting. From a practical standpoint, it is also important to evaluate your tent site for the same general considerations.