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Wind forces and your awning

By Bill Hendrix, F761S

We all know of accidents in which an awning came unrolled while traveling. It usually happens in windy conditions, and can be both startling and costly, especially if a large patio awning is involved.

The real culprit in these instances is wind velocity. Whether the motorhome is parked or moving, an awning can withstand only so much wind before something  gives. The wind is a mighty force, as evidenced by the damage it inflicts during storms, hurricanes and tornadoes. Given enough velocity, the wind can destroy even a brick home.

Two styles of RV awnings are offered today: those that can be rolled up into a container or housing and usually are referred to as box awnings, and conventional awnings, which leave the fabric and roller tube assembly exposed. Conventional awnings are the most popular -- mostly because they are less expensive -- and will be the focus of this article, as they relate to wind forces.

Wind forces
When the wind is calm and you are driving at highway speeds, the wind basically is flowing parallel to the awning and not exerting much energy on your motorhome. Add a strong quartering headwind, however, and the picture starts to change. Windy conditions usually are accompanied by gusts, which can move your vehicle around and require you to work the steering wheels to stay in your lane. These wind forces also are acting on your awning.

In these conditions, the latching mechanism on the awning will be tested. If you start hearing unusual noises coming from the direction of the awning, this would be a good time to slow down or find a stopping spot to wait for calmer weather.

Conventional RV awnings do not fit airtight against the motorhome's sidewall. From the center of the roller tube to the sidewall is a narrow opening where the wind can exert energy that pushes upward, then outward, on the awning. This opening allows wind to get under the awning and exert energy on several square inches of the canopy.

Window awnings usually do not have a locking mechanism, because the wind exposure area is very small and they fit fairly tight against the coach. They depend upon the strength of the roll-up spring to resist the wind.

The smaller window awnings usually don't pose a problem in windy travel. However, if the window awning is large, the area exposed to the wind is also larger and could become a concern. Some awning manufacturers offer supplemental restraints for their window awnings.

For the patio awning, the area exposed to the wind force is significant. If there were 4 inches  from the center of the roller tube to the sidewall of the coach, on a 15-foot awning, this area would be 5 square feet. Traveling at 65 mph with a quartering headwind of 25 mph gusting to 40 mph would produce a vectored effect of around 80 to 90 mph of wind energy acting upon these 5 square feet of awning.

The awning may be able to tolerate this amount of energy -- for a while -- but if there is slack in the roll-up spring or some play in the locking mechanism, the wind will tug relentlessly at the awning. If this movement is developed to the extent where more of the canopy is exposed, the energy exerted will likewise be increased. You are now in a catch-22, and the wind is in control.

If you're driving with a strong wind quartering on the patio awning side, it would be prudent to reduce your speed or park the motorhome for the day and take in some of the local attractions.

The role of locks
All roller tube-locking mechanisms are friction devices. They have a reversible ratchet, teeth and pawl, and a rolling lobe, and they depend on friction to secure the roller tube. Engineers have a saying: "Force always wins over friction." This is true because friction is a constant and force is a variable. When the force exceeds the holding power of friction, the lock fails.

Some folks may believe that improper torquing of the roll-up springs is the reason for an awning unrolling. On the patio awning, the springs contribute very little holding power once the lock has failed.

No awning locking mechanism will withstand an unlimited velocity of wind. At some point, failure is inevitable. Many people put additional securing straps around the awning arms to reinforce the standard latches. This may offer a degree of security, but it will not keep the canopy from bellowing out if the roller tube lock fails.

Once the canopy starts to unravel, the area available to the wind increases dramatically, and the situation now becomes a safety issue. The awning has now become a sail, and a large awning could provide enough energy to make you loose control of the vehicle.

If it is windy, stop often and check the awning to make sure it is snug against its upper brackets or upper mounts. If the awning is several years old, it's possible that the locking mechanism has worn to a degree, and it may be more likely to fail than a newer awning.

After unrolling...
Once the awning has started to unroll, this huge "sail" creates a tremendous amount of stress on the fabric, the arms, and the mounts. Unless, you're lucky enough to get the vehicle stopped quickly, the awning usually tears away. It appears that the awnings with a metal weather shield are better at resisting the initial forces of the wind, because the metal is more rigid than the fabric.

An unrolled awning must be made secure before you resume your travels -- at a slower pace. To do this, you somehow need to get the coach turned away from the wind. You risk serious injury trying to do this with the full effect of the wind still present. Do not climb on the roof of the motorhome, and do not try to physically hold the awning down. Get some help.

If the hardware is still attached to the coach, push the roller tube back against the coach and tie it there. Then move the coach to a protected area for further securing. If the awning fabric is torn, it must be replaced eventually, so if it becomes part of the problem, cut it away and secure what is left.

Most awning suppliers will not cover this type of damage under warranty unless you can prove that  a defective part failed under normal operating conditions. However, your motorhome insurance might apply if the damage falls under "windstorm" or another provision of your coverage.

Precautions
You can do a few things to reduce the possibility of wind failure. For one, make sure the locking mechanism is functioning properly. If you have to fiddle with it to get it to engage and disengage, something is wrong and you should have it fixed. The lock is the awning's primary protection against unrolling. Also, be sure to engage the travel latches or straps that secure the inner arm (rafter) to the main arm.

Here's a little trick to fitting the awning tightly against the motorhome. This will work on any awning that has a ratchet-type lock and can be put in a patio position. With the awning rolled up in the travel position, unlatch the right awning main arm from the lower mounting bracket. Be prepared to support the weight of the awning for a few moments. Pull the bottom of the awning arm away from the coach approximately one foot or until the ratchet lock clicks. Then put the awning arm back into the lower mounting bracket. As you do this, the roller tube is fixed to the arm and will rotate slightly with the arm as you move the arm back to the coach. This tightens the fabric and roller tube against the side of the coach. The next time you pull the awning out, the lock will be rather firm. If it is very stubborn, reverse the process to get the lock to release.

Special features
Some awnings have special features to help the awning withstand windy conditions. Zip Dee uses a hook-and-eye lock operated by the awning wand. This latch can be used with any window or patio awning provided the awning has a metal weather shield.

The Dometic Corporation offers and A&E awning kit that is primarily designed for slideout awnings, but it will work on any window awning with a 2-inch diameter roller tube. If you're careful, it can be fitted onto a 2-1/2-inch tube.

A& E's window awning has a short arm that is attached to the roller tube. The arm is designed to engage the awning rail or a provided retainer plate during the first inches of wind-induced opening.

Carefree of Colorado utilizes a wind baffle designed to obstruct the path of the wind under the roller tube.

If you're concerned about wind damage, find out more about these and other products for added protection. Search FMCA.com's Business Directory for companies that produce and/or supply awning products.

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