Since the birth of paragliding the cloth has always been a major issue when it comes to paragliding design and manufacture
I think we are all fully aware of this
Paragliders are made from cloth and I guess it will continue to be in this way for a long while – unless there is some major development of which I am not aware, so it makes sense to stop for a minute to take a closer look, trying to understand the issue.
Let’s explain things in simple terms.
The cloth used by industry is widely referred to as paragliding ripstop material – usually nylon with typical ripstop square pattern.
Sometimes, manufacturers like to present the issue as very complicated high-tech stuff.
Heated debates always in the air – all interested parties blowing smoke, praising their cloth and creating confusion
Here I would like to make some order and set things straight, so you all can understand what it is about – because in the end it is simple and uncomplicated matter – easy to understand if the smoke is cleared.
Let’s set things straight and look at several parameters required from the cloth to be worthy of paragliding manufacture
Everybody wants to have their
wings light, especially lighter than their neighbors. Obviously the lighter the cloth, the lighter the wing, and the general belief is that it is good- less volume, less bulk, less weight, more passive safety and so on ……
So let’s see what it takes to make the cloth lighter and if it is indeed so crucial.
All, but all paragliders are made from cloth of similar construction.
Basically all woven from the same nylon filament (thread) – which is 30 Denier filament of high tenacity nylon, known as Nylon 6.6
(30 Denier designates the weight of the filament for a fixed length – the lower the Denier number, the lighter, thinner and weaker the thread)
All paragliders are made from cloth woven from the same 30 Denier filament in typical ripstop pattern (in general it is believed that ripstop construction is something needed to prevent runs (small tears), but this is not necessarily the case and there is no problem making gliders from plain weave cloth and it will even have some advantages – I will attempt to prove this later on)
In anycase, as a first parameter, weight of the cloth will depend on how tight is the weave. You can build the cloth (which can be imagined as a net) very tightly, placing each filament side by side with next filament, or making a loose net with big holes
Industry reference is that good quality cloth should have at least what is called 100T count, meaning you have 50 threads weft and 50 threads warp constructed tightly per cm. sq. of cloth (or more threads)
Now – If you wish to produce lighter cloth it is easy – just reduce the count to 40 x 40 thread construction per cm. (usually referred to as ends and peaks) and you will have it lighter by 20% in no time.
You can go further and reduce count even more to 35 x 35 ends and peaks (some do). Obviously the lower the count, the lighter the cloth and by the way, it will also be cheaper to produce – less filament, faster to weave etc. Looks like the stairway to heaven – lighter cloth, lower costs, higher price tag on sale = better profits
Now – If you wish to produce lighter cloth it is easy – just reduce the count to 40 x 40 thread construction per cm. (usually referred to as ends and peaks) and you will have it lighter by 20% in no time.
You can go further and reduce count even more to 35 x 35 ends and peaks (some do). Obviously the lower the count, the lighter the cloth and by the way, it will also be cheaper to produce – less filament, faster to weave etc. Looks like the stairway to heaven – lighter cloth, lower costs, higher price tag on sale = better profits
But, there is a side effect to this – unfortunately the cloth will also be weaker and insuring its air permeability will be a more difficult task.
(it is clear – there are no free lunches)
So next time you buy a wing from lighter cloth, be aware that its tensile strength and aging deterioration is in direct correlation to the thread count and do not get confused by guys claiming it is High-tech blah, blah and it is lighter, but stronger and more expensive – I guess it is never true (all but the price tag).!!!
And please correct me if I am wrong
(Except when cloth is made from even lower number denier – there is 20 Denier Nylon 6.6 existing, recently developed, but it is practically not used for mass produced standard paragliding wings)
Reinforcement tapes provide critical structure to parachutes, cargo decelerators, and inflatables, especially during high-speed deployments and high-load transitions.
These tapes are:
Proper design and placement directly impact opening performance and structural longevity.
Mission-Driven Material Selection
From high-speed UAV recoveries and VTOL inflatables to low-altitude cargo drops and ram-air parachutes, every textile component we use is chosen for performance under pressure. With over 50 years of experience, Apco builds systems that combine low volume, minimal weight, and battlefield reliability – ensuring success where it matters most.
“Sexy” light cloth will have very thin layer of coating – polymer has a certain weight and cost, the less applied – the lighter and thinner / cheaper the cloth
On the other hand, you have much better chance to have the cloth with zero porosity (airtight) for a long time, if instead of one layer of coating, two layers are applied. Three or even four layers preferable and it is better if each coated layer is thicker – obviously each layer of coating is a time consuming process and costs more, which has to be paid by you at the end
In this way heavier, more expensive cloth is produced, but it will have no signs of deterioration in its performance over longer period of time.
A number of different approaches have been taken on this subject in an effort to work out the magic formula – less weight (cost) in, more price (profit) out
Today, no paragliding cloth manufacturer offers cloth with one layer of coating – most make with two layers of coating, but here the opinions are split. Some apply two layers of coating to the same surface of the cloth, others apply one layer of coating to each surface. Applying two coated layers to one side is less expensive and faster than applying one layer to each surface, I guess the more expensive alternative is also the better one
There is one manufacturer who used to go even further, they constructed the cloth from minimum 50×50 thread count and then coated 4 times – two coats of PU polymer one to each surface and then again two coats of silicon one on each surface which are to protect the PU surface, providing the ultimate in paragliding cloth performance. They are known for the legendary durability of their cloth, but for a price and extra weight.
To conclude – more coating polymer and / or more layers of coating will end up with better cloth porosity (airtightness).
It will be more expensive to produce, also heavier and thicker
There are no magic tricks here either and no short cuts to lighter and better cloth
There is another way to reduce weight of the cloth (very bold way)
Just by declaring 40 gram on specs instead of 45 grams – the manufacturer reduces the weight of cloth by 12%. Since the cloth weight on specs always is declared with some tolerance, let’s say 45 gr. +/- 5gr. tolerance, you will find that most manufacturers will put 40gr. on cloth weighing 50gr. I suggest don’t take manufacturers declaration for granted and from time to time, check the weight
So next time your guy claims his cloth is lighter, thinner, better performing, but for a price – I guess you know by now that again this is blah, blah hype, designed to get an extra dollar from you
Welcome to correct me if I am wrong
Something more – if you watch your glider age and check your cloth porosity by old fashioned primitive method – squeezing moisture through the cloth by pressing wet finger to the cloth surface, you have probably noticed that moisture bubbles first on the cross section of thicker threads of ripstop construction. Rest of the surface is still airtight. It is because the thin layer of coating does not fully cover the thicker cross section of ripstop junctions and these points give in first
So maybe plain weave cloth with the same coating would give better porosity results for longer time – am I right?
Again correct me if I am wrong
So far we have discussed 2 parameters of cloth – weight and air permeability. There is something else which comes up when discussing paragliding cloth issue. It is about the cloth elasticity – its elongation under load in different directions and ability to recover to the original dimensions when load not applied
Again, there are a host of opinions regarding what is good and bad for paragliding cloth – should it be rigid? Or is better to allow some elasticity? Should it be crunchy, or smooth silky feel is preferable? Different hands manipulated the cloth and the subject – the answer depends on who you ask. Not to confuse you, let me tell you what we think
Again, it is simple.
Since all types of paragliding and parachute cloth are made from same nylon filament, the basic elasticity characteristics of the cloth before calendaring, coating and finishing will be quite similar
Woven cloth before being finished (grey goods) will have quite low elasticity and good recovery parameters on both warp and weft (along and across the cloth)
On the bias (diagonal 45 degree direction to warp or weft), the cloth is not as stable,
it is easy if applying tension on bias to change the dimensions of the cloth construction and then after load is released deformed cloth will not recover to its original shape
Here comes the coating to overcome this problem.
The layer of coating material bonding the threads together create a frozen like construction and could be imagined as a thin layer of ice frozen on netting. The ice will make the net rigid in all directions (including bias) as well as airtight
Properly made coating locks the thread construction in a way preventing the relative movement of thread in the woven cloth, making it more rigid in all directions, as well as airtight (same as the case of iced netting)
Let’s imagine that the cloth is coated with material like ice (rigid, but brittle) – when applying load in different direction, ice will crack contributing to deformation of cloth and increased air permeability.
So certain degree of elasticity in coating material is a desirable parameter in order to prevent cracking (known as White breaks – White lines appearing on the cloth marking the cracked edges of coating),
Ability of coating to stretch under load as little as possible without cracking and then regaining its original shape when the load is off – is a desirable feature. Proper blend of minimal elasticity and good recovery characteristics will guarantee long term performance of the fabrics
The quality of coating is paramount to insure performance of cloth over time
Bearing the above in mind, let’s now decide what is the best cloth for the wing.
It is generally accepted that medium-soft crunchy feel cloth with certain degree of elasticity and good recovery are best for external surfaces
For ribs- the opinions are split
There is one school of thought which believes that the cloth should be as rigid as possible – no stretch whatsoever
Other manufacturers use same cloth for ribs and external surfaces
So who is right?
Of course it seems logical and simple to understand the rigid cloth must be better for the ribs, because whatever shape is designed, cut and sewn into the profile it should remain the same as it is rigid
The problem is that all the different types of rigid cloth have quite bad recovery characteristics.
They tend to quickly distort under excessive load and do not regain their original shape
The process is accelerated because the cloth is crushed, crumbled, fluttered, shaken when glider is used, generating endless amount of little coating cracks and then wing flown on profile which is becoming more and more different from the designed profile.
Another argument against rigid cloth is that the designed rib profile is known/defined only in places rib is stitched in between the panels. Any other wing cross section will reveal profile quite different to profile projected, because it is a result of inflated surfaces with variable cross section across the span. So in every given cross section all over the wing span we will have different profiles or rib section and they definitely differ from the actual rib stitched in.
The designer has control only over the profile he stitches into the actual rib and the performance of the glider in general is the result of empiric trim performed by the design team (entirely trial and error evolution process) without any analytic base.
Under these circumstances it is more important to preserve and guarantee same optimal performance of the glider as trimmed during the lifespan of the wing than living under the illusion that using rigid cloth will bring closer the theoretic design and reality, not giving consideration to the accelerated aging of the cloth performance (rib and external surfaces)
So we vote against rigid cloth unless this cloth will remain rigid without plastic deformation as long as the glider is used
I would like to conclude that due to these considerations, the preferable cloth for rib construction is the cloth which has the best recovery characteristics and will not deteriorate / deform over the life-span of the product
I understand that some may not agree or dislike the above views laid out.
But you are welcome to correct me if wrong
Anatoly Cohn
So maybe plain weave cloth with the same coating would give better porosity results for longer time – am I right?
Again correct me if I am wrong
