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Parapente Mag
February 2004
Pages 19 to 24

Translation from French to English by Christiane "CC" Moisan
 
Special thanks to Mario Mohl, who helped with some technical terms.

 

The screw-type carabineers or the automatic ones?
Steel or aluminum?
Are they unbreakable?
How are they fabricated?
  Which one to choose?
 

A carabineer has a lever and a spring, thus ensuring an automatic lock.  A link will close only with a nut that you must screw.  Most carabineers are made of Zicral (aluminum alloy) while the links used for paragliding are made of galvanized steel or better yet, stainless steel.  Zicral is lighter than steel but steel has the propriety of being extendable which permits deformation before it breaks.  Once it reaches maximum charge Zicral will break.

The stainless steel link has a very high security level as long you don’t forget to screw the nut.  It is a little heavier but its mechanical properties permit the use of inferior diameter threads (6mm in stainless steel is the equivalent of 12mm with Zicral).  With comparable resistance, a stainless steel link weighs 40 grams, a Zicral carabineer weighs between 70 and 90 grams (Austrialpin, conscious into reassuring their customers, has just introduced a stainless steel carabineer, very resistant but heavy:  138 grams).

The advantage of the automatic carabineer is the elimination of the risk in forgetting to screw the nut on the link style and it is easier to use.  But in 2002, twice, a Zicral carabineer from Austria broke.  In both cases the pilot did not see that the riser got stuck in the opening, thus preventing the lever to close and lock properly.  In one of the two cases, the pilot was engaged into very pronounced 360s, putting extreme pressure on the carabineers.  There are no other known incidences of this type in paragliding history.  With stainless steel carabineers there are no known breakages.

Due to these two incidences, which had no consequences, many manufacturers proceeded into more in-depth resistance testing of their products.  During those tests, carabineers that were closed properly never broke until their predicted rupture point (approximately 2 tons).  On the other hand, an open carabineer (simulated in case a pilot inadvertently does not insert the risers correctly and thus preventing the lever from closing), these same carabineers all ruptured between 400 and 700 kilograms, which still leaves a good security margin for a pilot flying solo and level.

But imagine our pilot being slightly overweight and feels like doing some acrobatics!  Imagine an extreme case where all the centrifugal force relies on, even for just one second, on one of the carabineers linking the wing to the harness.  With a centrifugal force of 3G (the maximum imaginable) the carabineer will instantly sustain 3 times the pilot’s weight (100 x 3 = 300 kg).  And if this same pilot does some acrobatics on a tandem the pressure could go to 200 x 3 = 600kg.  It is the extreme but possible.  With 600kg of pressure, the Zicral carabineer improperly closed, has all the chances of breaking.  It is interesting to note that in the same situation, a stainless steel carabineer with a comparable resistance, not closed, would resist better.  It would get deformed but would not break. 

The only positive consequence of this story is that we have to check our carabineers or links to be correctly closed!   With this condition in mind of checking our material properly, the metallic carabineers (or links) linking our wing to our harness are totally secure.  Only a big manipulation mistake (forgetting to screw on the nut on a link or automatic closure of an automatic carabineer being obstructed with a riser) can generate an incident risk.

Their limits

For the longest time, paragliding relied on the big square or triangular stainless steel carabineers (6mm in diameter).  They are the ones mostly seen on tandem rigs or for securing a reserve.  Pilots into mountain flying use, to gain some weight, carabineers clearly smaller (delta 5 type), which are more than enough to sustain, with a lot of margin, all the possible constraints of this type of flying. 

A delta 5 has a normal charge of 325kg and a rupture charge of 1625kg.  What does this mean?  The normal charge is the charge that the carabineer can sustain without any deformation.  The manufacturer guarantees that no breakage is possible if the charge is under, at least, 5 x higher than the normal charge.  This is the rupture charge.  This tells us that we must apply at least 1625kg of traction in order to have a delta 5 break!  Tests have demonstrated that they resist frequently above the guaranteed threshold.  When we know that when flying level the main carabineer must take charge of half the total weight (50kg for a 100kg pilot), we note that the over sizing is huge, even if this pilot does acrobatics and takes in 3Gs.  The Péguet manufacturer confirms that a small carabineer of 3.5mm in diameter would still suffice to support a main link to the wing (wing to harness) in a linear flight with no acrobatics.  But if the pilot forgets to screw in the nut, this link would probably be insufficient in supporting a riser.

The shape of a link or carabineer has an obvious incidence on its resistance.  The ideal form is oval.  In reality, whatever form they have, in the end what counts are the numbers of the normal charge and the rupture charge.  However, one must know that a link or carabineer, not well positioned, will lose some of its resistance.  For example, if link or carabineer positions itself sideways and that the riser gets positioned on the nut (for the link) or on the lever (for the carabineer), the total resistance is considerably lessened.  But rest assured, this resistance is still very sufficient, especially if what you are using is stainless steel.

Nonetheless, if you realize, during flight, that either a link or carabineer is not closed, don’t panic, but avoid all additional pressure (no hard banking) and carefully land.

Always make sure that links or carabineers are properly closed

 3 questions directed at Fabien Encelle, Commercial Manager for Péguet:

 Why do we use such big links in paragliding?

Visually it’s reassuring.  But we could, without any trouble, trust links with much smaller diameters.  Stainless steel is an infallible material within the resistance limits indicated.  It is the existing material most reassuring. 

Any incidences ever?

With stainless steel, never.  The only known incidence was with a paraglider that took off with one of his links completely open (nut was not screwed in), so very highly loaded.  The link got deformed while opening, but the riser got caught in the nut thus preventing an accident.

Any projects?

We are currently working on a carabineer with composite materials, but this project is still at the conception level.

Sup’Air carabineers:  (from left to right), the old (aluminum 72g, resistance: 1,8 tons), and the 2 new models (stainless steel in the center and aluminum on the right).  Stainless steel:  130 g, resistance:  2.6 tons.  Aluminum:  66 g, resistance:  2 tons.

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The lightest in the world!  Bertrand Maddalena (Rip’Air) invented and perfected this soft connector, made of braided Vectran, which weighs a mere 6 gr!  It resists up to 2.8 tons (more then the stainless ones).  Commercialized by Sup’Air.

****************** 

Scorpio:  traditional automatic carabineer made of Zicral.  Weight:  60g.  Resistance:  2.2 tons. 

Camp:  Automatic carabineer made of Zicral.  Weight:  68g.  Resistance:  2 tons.

AustriAlpin:  the new automatic carabineer, Powerfly, made of steel.  Resistance of 2.6 tones but is on the heavy side, weighing twice the weight of its counterpart made of zicral (139g)

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Normal Péguet link:  those models were often used at the beginning of paragliding.  The smallest ones are still used for speed systems.

Delta link from Péguet:  3 or 3.5mm, it is currently used to link risers to wing.  The 5mm (here under to the left) can be used to link harness to risers for paragliders (weight:  24g, resistance:  1 ton 625).

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Péguet Trapèze

6mm (right) is the main link used for harness to risers.  Weight:  45g, resistance 2 tons 250.

Péguet Carré

7mm, is often used to link a reserve.  Weight 64 g, resistance, 3 tons 125.

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Resistance tests

Sup’Air proceeded to do a series of resistance tests for its Zicral carabineers.  15 carabineers, randomly selected, sustained a charge equivalent to the rupture charge (1500kg).  None broke, not even the old carabineers (5 year old).  The same test was conducted keeping the lever in the open position.  In this configuration all of them broke between 400 and 700 kg of charge.  Logical conclusion:  closed carabineer, no problem.  Open carabineer:  danger ! 

Security margin

Even with heavy weight pilots, even doing acrobatics, it is difficult to imagine that a link or a carabineer sustains more than 300 kg of charge (600 kg for tandem).  A small stainless steel link with a 3.5mm diameter has a rupture charge of 750kg and a simple Delta 5 has 1625 kg !

7 points to remember

Personal:  A link or carabineer is personal.  If you find one, do not use it.  You don’t know its “history”.  It might have been used to tow a car !

Warning:  Don’t forget that a link not completely screwed in or a carabineer not properly closed, loses a lot if its resistance.

Riser position:  Don’t forget that a riser not well positioned (the link or carabineer has gotten sideways and the riser pulls on the lever) has also less resistance. 

Forgetting:  A link of reasonable dimension which was not well screwed has a risk of getting deformed, but it will not break and will easily resist to the weight of a man (even overweight), so don’t panic if this should happen to you someday.  Just avoid wingovers. 

Mechanism:  A link or carabineer which does not work perfectly well (screw and unscrewing of the nut without effort for links, closure of the lever without any gaps for the carabineer) must be thrown away.

Tightening (for a link):  not too much, but not too loose either.  Tightening by hand is enough.  None of the threads must be showing or apparent except for the stopper which is slightly thicker than the threads. 

Beware of copies:  All Péguet links are engraved with “Maillon Rapide” (Quick Link) as well as many numbers.  Normal charge and rupture charge are also engraved (the smaller links necessitate a magnifying glass). 

First page text boxes 

With comparable resistance, a stainless steel link weighs 40g, a Zicral carabineer between 70 and 90g. 

Where are they being manufactured? 

Many companies manufacture automatic carabineers for paragliding.  The most known models are the AustriAlpin, Camp, Scorpio, Stubai and Sup’Air.  In France, they are generally manufactured by Alu Design, Simon or Conta.  All are made of Zicral, except for two models in steel by AustriAlpine and Sup’Air.  Their average weight (Zicral) is 80 grams.  For most cases, each carabineer is individually controlled on a machine which inflicts a 1 ton traction (rupture charge being situated generally around 1.5 tons). 

Only one company, in Europe, manufactures stainless steel links:  Péguet, in Annemasse, specializing in this product line since 1941.  The company (60 employees) uses machines conceived and fabricated on-site.  Its principal market is paragliding, skydiving, mountaineering and marine. 

The steel rod arrives as either straight lengths or in a roll.  It is first cut into the rod size necessary for future maillon, then die stamped and finally threaded.

The nut is then threaded and installed.  The link is then folded into the desired form.  Then they affine the nut and threading perfectly.  At Péguet, the notion of security is almost an obsession.  Péguet manufactures galvanized steel links or stainless steel:  no hesitation, for paragliding, take the best, stainless steel!

The Original French article: