Paraglider Porosity Check
Book an inspection for you own glider or any glider that you’re thinking of purchasing. You can freight the glider to us or drop it off.
Quick turn around. We will ship via TNT if you freight it to us and can also organise pick-up from you.
WHAT IS POROSITY
Porosity is the measurement of the amount of time it takes for a certain volume of air to pass through the paraglider canopy fabric. At High Adventure, we use the JDC MK 1 Porosimeter, which is the most used porosimeter in the paragliding industry.
It works with a 100 mm water column pressure (10 mb) and is an improved version of this device, characterised by a stronger magnet and better fitting, eliminating undesired air flow between cloth and device corpus.
The result is given in seconds needed for 0.25 litre of air to permeate through cloth of 38.5 cm2 area under 10 mb pressure. It is then recalculated into standard units and 20 mb pressure with the formula: permeability [l/m2/min] = 5400 / time of measurement
After the test is performed, we use an industry standard formula to derive a “score”.
Following table is used in interpreting the results:
0 – 20 – “as new” cloth condition
20 – 50 – excellent cloth condition
50 – 100 – good cloth condition
100 – 150 – satisfactory cloth condition
150 – 300 – well-used cloth, paraglider airworthy
300 and above – worn-out cloth, safety cannot be guaranteed
We consider a paraglider with porosity of less than 300 [l/m2/min] Airworthy.
HOW DOES THER POROSITY CHECK WORK
Porosity measures should be taken on at least three points of both the top and bottom surface. The first point should be placed 20-30 cm from leading edge in the middle of canopy. Second and third points are placed left and right from first measure point at 25% of the span. One additional measurement should be made on the top surface of the wing tip.
The device is mounted at midpoint on the wing chord. Before the measurement is taken, the glider needs to be checked over, as even the smallest tears can drastically alter the results. It is advised to look at the glider cloth against the light. If any of the results radically differ from the average, the site of measurement on the wing surface must be carefully checked again and possibly changed.
HOW DOES POROSITY AFFECT MY PARAGLIDER?
A new glider will have very little porosity (assuming it meets all specifications). Because paraglider’s are designed to maintain pressure between the top and bottom surfaces as they fly, the porosity of a glider can greatly affect its pressurisation. The characteristics and behaviour of a paraglider will change as the material becomes more porous and the porosity increases. These changes can affect the performance of the glider – such as glide ratio, speed, recovery from collapses, handling turns, resistance to collapse and surging.
If a glider is more porous, it also means the material has degraded and it is weaker than it was when you first bought it. The weaker the material, the easier its going o be to tear. Tears can when you are launching or landing near rocks or sticks.
HOW DO I SLOW DOWN POROSITY OF MY GLIDER?
The most common reason for raging glider material is repeated or extended UV exposure. Its important to always keep your glider out of UV sunlight when possible. Avoid the glider becoming moist or wet for any extended period of time. While any amount of water won’t immediately affect the glider, leaving it packed over night will not do it any favours. Always air you glider at room temperature if it has become damp or wet. Avoid exposing a wt glider to direct sunlight, this can also affect the materials such as the lines and stitching. If you have come into contact with salt water, we recommend hosing the glider down with some fresh water and let it dry throughly in the shade or preferably inside in an airy room.
We also recommend NOT storing your glider in the boot of you car. The heat within a car boot can quickly damage the glider material and protective coatings four on glider fabrics.
Price does not include freight