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=35.7m2Â Â (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!!
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=35.7m2Â Â (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.
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 450Â 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.
The storm strap should be leaving the roof section of your tent at an angel of 450Â 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.
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.
