Wind force on a tent

Wind force on a tent

Wind is a mass of air that moves in a mostly horizontal direction from an area of high pressure to an area with low pressure. High winds can be very destructive because they generate pressure against the surface of a structure (your tent). The intensity of this pressure is the wind load. The effect of the wind is dependent upon the size and shape of the structure.

Wind load pushing against your tent in a wind of 40kph.

Example Regal tent:
Tent length=6m
Side-wall height=1.7m
Roof-length=7m (L side-wall to R side wall over the top)
If assuming that the wind is directly from the side (argument sake).

The area exposed to the wind (ignoring the 45degree roof pitch for now): 
LxWxH
=6x1.7x3.5=35.7m2   (note 3.5m is the windward side of the tent)

Pressure applied by the wind force on an area is measured in Newton Meter (Nm) 1Nm=9.80665Kg

Wind speed (velocity) kph to meter per second(Ms) 
1kph=0.277778ms
So, 40kphx0.277778ms=11.1111ms

Using the Wind Velocity to Wind Load table below 11ms=73Nm
73Nm2x35.7m2 =2606N 

Ignoring the air density and the roof-pitch, the total pressure applied to a 36m2 piece of canvas during a 40kph wind is 2606N!! 

Wind Velocity (m/s)	Wind Load1) (N/m2)
1	0.6
2	2.4
3	5.4
4	9.6
5	15
6	22
7	29
8	38
9	49
10	60
11	73
12	86
13	101
14	118
15	135
16	154
17	173
18	194
19	217
20	240
21	265
22	290
23	317
24	346
25	375
26	406
27	437
28	470
29	505
30	540
31	577
32	614
33	653
34	694
35	735
36	778
37	821
38	866
39	913
40	960
41	1009
42	1058
43	1109
44	1162
45	1215
46	1270
47	1325
48	1382
49	1441
50	1500

So what is supporting your tent from being blowing away?

A frame constructed from 22mm tubing with a 1.4mm wall thickness, attached to the ground. This is the reason having additional vertical poles placed next to the existing main poles supporting and counteracting the downward force of the storm-straps. The poles must be adjustable and just clicks over the horizontal roof sections.

I also lace down the vertical poles inside my tent to prevent them from actually lifting up during storm conditions due to different pressure gradients in and outside the tent.

Roof support poles

Characteristics of a good storm-strap?

• Strong
• Ideal with 90mm
• Adjustable with Nylon ropes and aluminum rope sliders (plastic slips)
• Light weight allowing wind and air to pass through, solid webbing types flap in the wind driving you crazy.

Adjustable storm-strap

Anchoring the storm-strap either side of your tent

The storm strap should be leaving the roof section of your tent at an angel of 450  and pegged directly to ground, anchor-peg thickness 10mm minimum. The anchor-pegs should be driven in all the way until the rope attachment section touches the ground.

Note the storm-strap angel of 450°

Installing the storm-strap over your tent roof veranda is useless as you will not be able to tie it down firmly without damaging your tent. An easy way to fix this is to have slits made on both sides of your tent roof were the awning is attached to the roof passing through the storm-strap and pegging it down. (Why the tent manufactures aren't doing it at the factory is unknown)

How many storm straps do you need? One at every vertical upright pole-remember you will need additional supporting poles as well.

What the best storm wind protector, storm-straps or cargo net?

Both got their pros and cons; for me three well placed storm straps kept my tent standing during a 78kph SW gale at Buffalo bay.

EasyGrip Clips

EasyGrip Clips now also available in Cape town

EasyGrip clips with hundreds of camping uses; tying down protection sheet, stiffening that section on your tent were rain water is accumulating, preventing tent windows from ripping apart during storm conditions, add extra support to you tent during storm conditions this all without any alterations or damages to your tent.

Tips on tent maintenance

The most frequent cause of cloth breakdown is due to mildew called diamond spot. These are small black spots that multiply with the presence of a combination of moisture, heat and organic substances. After the first outing or after a longish period of storage, there may be a tendency for the canvas to show signs of leakage. This is due to the fibers losing bulk through dehydration. On damping, the fibers will swell and reseal again. This however is not enough. Sufficient resealing and anti-fungicidal compound treatment must be present as well. The efficiency of the resealing compound is directly dependent on the condition of the canvas being treated. By applying the following hints and tips, the life span of your tent will be prolonged:

1. Never store a wet tent. If unavoidable, only slightly bundle together. That limits the build up of heat during temporary storage.

2. Never store a wet or dry tent in a plastic bag.

3. Do not wash the tent with soap or any solvent.

4. Only use a soft household broom to wipe off loose dust and dirt.

5. Soil marks must only be removed with clean water.

6. Avoid the scrubbing down of canvas. Only use a sponge or cloth to remove heavily stained marks. This will prolong the lifespan of your tent.

7. Wash plastic windows with clean water, and use a Chamois to dry.

8. Wash zips with clean water, and use e.g. an old tooth brush to remove accumulated dirt. Avoid using soap or candle wax to ease operation.

9. Tree gum, fruit bats and Mopanie worm droppings, berries and some bird droppings cause permanent stains. Learn to identify your South-African trees; this can save you a lot of money. A light shade net (40%) can reduce these damages.

10. Store tent in a cool dry area, and not directly on cement floor.

11. Air the tent every four to six months, by pitching or spreading over garden chairs in sun light and not on grass.

12. Do not store mothballs directly on canvas; first roll it in an old hanky or cloth.

13. Never attempt to reseal a dirty tent, the sealant and the dirt will be baked into the pores of the material resulting in a permanently stained tent.

14. The GOLDEN motto on tent maintenance - - - - Prevention is better than cure.

Enjoy your holiday and arrive safely.

Hugo's Tent Cleaning Services

For the CLEANING and RESEALING of all canvastents. Specializing in the cleaning and resealing of Caravan tents, Add-A-Room, Multi Rooms, Canopies and tent extensions.