Foolproof Oplux Autoblock / Friction Rappel Config

[trailblazer75]

I don't have it tied currently, but a distel with 7mm sterling cord on 9mm htp (and a distel with whatever cord aerohunter provided with the kestrel and predator) in my tether testing, could be set up such that they would grip, but release when squeezed, even loaded. Note: these were close to the edge (embarrassingly, i had my wife test sit and the knot promptly slid down the rope until she was sitting on the floor, as she didn't trust the knot and eased into it slowly with tension on the tail) so test thoroughly. An autoblock would likely perform similarly. My inclination would be to upsize the hitch cord and explore different combos, if I were working to set up such a config.

This seems a bit counter productive to me. It’s difficult to justify tying a hitch that barely holds you when you can tie one that you KNOW will hold you. I see the merit of not needing to unclip in order to put the 8 in your system but I’d rather (personally) be in danger for that short bit of time than be in danger of not being held the entire time I’m at hunting height. You’d be hard pressed to get your friction hitch into your figure 8, at least the way I set it up.


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[mattsteg]

This seems a bit counter productive to me. It’s difficult to justify tying a hitch that barely holds you when you can tie one that you KNOW will hold you. I see the merit of not needing to unclip in order to put the 8 in your system but I’d rather (personally) be in danger for that short bit of time than be in danger of not being held the entire time I’m at hunting height. You’d be hard pressed to get your friction hitch into your figure 8, at least the way I set it up.


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Sure - and to clarify when it's dialed it will absolutely hold you (and will grab if loaded with any urgency). It's more of a reminder that, when testing hitches, load them every which way - slow, fast, free tag, tensioned tag, wet rope, etc. and always have a stopper knot (or even better clip the tag to your saddle). Personally I could never get that knot to slip the way my (much lighter) wife did the first time she tried it.

 

[trailblazer75]

Sure - and to clarify when it's dialed it will absolutely hold you (and will grab if loaded with any urgency). It's more of a reminder that, when testing hitches, load them every which way - slow, fast, free tag, tensioned tag, wet rope, etc. and always have a stopper knot (or even better clip the tag to your saddle). Personally I could never get that knot to slip the way my (much lighter) wife did the first time she tried it.

I think what really pops out as more counter productive (and less unsafe) in my mind is the fact that your weight is on the hitch and not the figure 8. At that point you’re basically rappelling on the hitch and may as well simply leave the figure 8 at home. The point of the figure 8 in sequence with the hitch is to bear the brunt of your weight and provide friction while the hitch gives you the ability to stop. In the configuration you described, the hitch bears the weight and this descent device does what?


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[CharlieTN]

Another consideration when using any sort of friction hitch in conjunction with a belay/rappel device is the problem with friction and heat built up on the friction hitch rope itself as it is essentially slid down the rappel rope. Although we are just rappelling a short distance, check that device you’re using to rappel and you’ll be surprised how much heat is generated, especially if you like to rappel quickly.

Be sure, if you’re going to use a friction hitch as a backup on a rappel, to check that hitch rope often to make sure it is not being damaged by the friction and heat. Rope is cheap and easy to replace. Your life and limbs are not.

I’ll be honest, my plan with my whole rappel rope setup is to replace it every 2 years. I will switch ends of my rappel rope after the first year, then retire after the second. I’m using the Sterling HTP so $40 every two years is nothing. From there I’ll just use it for other uses around the house.

 

[trailblazer75]

Another consideration when using any sort of friction hitch in conjunction with a belay/rappel device is the problem with friction and heat built up on the friction hitch rope itself as it is essentially slid down the rappel rope. Although we are just rappelling a short distance, check that device you’re using to rappel and you’ll be surprised how much heat is generated, especially if you like to rappel quickly.

Be sure, if you’re going to use a friction hitch as a backup on a rappel, to check that hitch rope often to make sure it is not being damaged by the friction and heat. Rope is cheap and easy to replace. Your life and limbs are not.

I’ll be honest, my plan with my whole rappel rope setup is to replace it every 2 years. I will switch ends of my rappel rope after the first year, then retire after the second. I’m using the Sterling HTP so $40 every two years is nothing. From there I’ll just use it for other uses around the house.

The beauty of my setup is that once I rappel I have to remove the hitch to pull my rope down and retie the hitch. So that cord gets checked each and every rappel.


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[loujo61]

If yoU match the rope/cord/ hitch well it'll work fine

Yup, my old 10mm tether worked great as a 4 wrap Klemheist around 11mm semi-static rope, it didn't bind up and held well. With my new 10mm static rope I slid right by my stick/platform (bad brakes) on the way down, I had to climb back up to retrieve it... I'm learning that there is a fine line between these hitches and ropes.

 

[loujo61]

I think what really pops out as more counter productive (and less unsafe) in my mind is the fact that your weight is on the hitch and not the figure 8. At that point you’re basically rappelling on the hitch and may as well simply leave the figure 8 at home. The point of the figure 8 in sequence with the hitch is to bear the brunt of your weight and provide friction while the hitch gives you the ability to stop. In the configuration you described, the hitch bears the weight and this descent device does what?


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Yes but once you get it moving the bite in the figure 8 takes a lot of weight off of the hitch.

 

[CharlieTN]

Yup, my old 10mm tether worked great as a 4 wrap Klemheist around 11mm semi-static rope, it didn't bind up and held well. With my new 10mm static rope I slid right by my stick/platform (bad brakes) on the way down, I had to climb back up to retrieve it... I'm learning that there is a fine line between these hitches and ropes.

As a rule of thumb your friction hitch rope should be 2mm smaller than the rope it’s wrapped around. If you stick with this, then generally you won’t have problems with the hitch holding. Of course, the type of rope makes a difference as well. Some are stiffer or have a slicker outer sheath causing issues with the hitch holding.

That is one of the reasons why I went with the 9mm Sterling HTP over the more popular 8mm ropes. There just aren’t that many 6mm ropes that fall within the strength rating I am comfortable with but 7mm has a substantial jump in strength.

Another issue that happens, depending on the hitch, is that when the running end from the actual knot down to your carabiner is excessively long it can cause the hitch to elongate, therefore not grabbing as well either. I find this mostly with knots such as the VT, Distel, Schwabisch, and other similarly constructed friction hitches. With the tails shortened the hitch seems to grab much quicker but still allow it to loosen up to move. That is at least my experience and I’ve tried many of the mainstream hitches out there.