A solo negative rigging workflow

[joshuarov]

Nice smooth system, that was sweet! Resulting from lack of available help in my region, I've spent the last decade solo rigging a fair amount. I do have a steady groundie now, but I definitely agree - nothing like the peace and acute focus of solo tree work.

I just recently added the downrigger to our systems and have enjoyed exploring different configurations with it. Just curious what your thoughts are about Rock Exotica listing the Downrigger as not applicable for negative rigging? I haven't seen anything specifically stating that the Morganblock is not suitable for negative rigging. Obviously with the pieces being double whipped, and the block only taking about half the load is a whole different scenario than single line work. Definitely interested in your thoughts. Even having a full time groundie these days, I'm still trying to improve climber controlled lowering systems to free them up to maneuver pieces onto the ground and increase overall efficiency.

We've primarily relied on the triple thimble for climber control on negative rigging, but have found it to be somewhat fickle and inconsistent. Had it lock off completely part way through lowering a spar chunk onto a high line. There was just enough rope against trunk friction as the thimble pressed into the spar as it came under load. Seemed like a good slowed down example of what might happen in during typical negative rig scenarios in the past when the thimble seemed jerky and resistant to run the piece. Not exactly and earth shattering realisation, others may have had similar observations.

Thank you for taking the time to share your work, very much appreciated.

Re the downrigger/morgan: First and foremost, it's currently my favorite AFD for light rigging by a decent margin. Primarily because it works quite well at such a large range of loads. I concur regarding the safeblock, it has inconsistent friction (due to the rope path being outside the device) and is honestly way overbuilt for the majority of what I want areal friction for anyway. The rigging wrench has a much narrower band of loads that work well, and those loads are actually quite high (as far as light rigging is concerned).

Why is it listed as not appropriate for negative rigging as per the literature? My assumption is that this device is lumped into the came category (no negative rigging printed on the tin) as the omni blocks, as their closure mechanism/built in swivel is nowhere near as robust as a classic ISC or similar. But that's just speculation on my part. (And the reason the morgan doesn't have that language is just that it was made in a garage and there weren't as many lawyers involved, it's functionally identical from what I understand.)

In other words, if there is an argument to not use it for negative rigging, it'd be more of a robustness one than a strength one. More or less, the way I see it is that it's important to set it up so that it doesn't side load itself into a stub or something like that to mitigate this risk, but I should be doing that anyway, regardless of rigging type.

Re strength: I believe the weakest component of this rigging system is 1/2" rigging rope (which I honestly tend to steer clear of for negative rigging for the most part in conventional crew scenarios). It's got an MBS of 46kN and with any reasonable de-rate for a knot + wear and tear that will put it will below the 30kN of the Morgan. Or, if we look at the peak load in the rope at the ring in this setup, where there'd be no reason de rate for a knot, it could arguably be double what is seen at the friction device (testing would need to be done to prove that conclusively as it's a fairly complex problem). Whatever the case, by time we're down to SWL, the difference will be greater still (the rope being lower than the device, that is).

From my perspective: If I'm working within the limitations of the rope, I'll be well within the limitations of the device in question. Happy to hear if someone thinks I'm wrong or sees a fail case I'm missing

 

[Lviv79]

Re the downrigger/morgan: First and foremost, it's currently my favorite AFD for light rigging by a decent margin. Primarily because it works quite well at such a large range of loads. I concur regarding the safeblock, it has inconsistent friction and is honestly way overbuilt for the majority of what I want areal friction for anyway. The rigging wrench has a much narrower band of loads that work well, and those loads are actually quite high.

Why is it listed as not appropriate for negative rigging as per the literature? My assumption is that this device is lumped into the came category (no negative rigging printed on the tin) as the omni blocks, as their closure mechanism/built in swivel is nowhere near as robust as a classic ISC or similar. But that's just speculation on my part. (And the reason the morgan doesn't have that language is just that it was made in a garage and there weren't as many lawyers involved, it's functionally identical from what I understand.)

In other words, if there is an argument to not use it for negative rigging, it'd be more of a robustness one than a strength one. More or less, the way I see it is that it's important to set it up so that it doesn't side load itself into a stub or something like that to mitigate this risk, but I should be doing that anyway, regardless of rigging type.

Re strength: I believe the weakest part of the rigging system is 1/2" rigging rope (which I honestly tend to steer clear of for negative rigging for the most part in conventional crew scenarios). It's got an MBS of 46kN and with any reasonable de-rate for a knot that will put it will below the 30kN of the Morgan. Or, if we look at the peak load in the rope at the ring in this setup, where there'd be no reason de rate for a knot, it could arguably be double what is seen at the friction device (testing would need to be done to prove that conclusively as it's a fairly complex problem). Whatever the case, by time we're down to SWL, the difference will be greater still (the rope being lower than the device, that is).

From my perspective: If I'm working within the limitations of the rope, I'll be well within the limitations of the device in question. Happy to hear if someone thinks I'm wrong or sees a fail case I'm missing

I don't agree with you.Lets mbs for rope and blocк 30кN,only 60 кN in 2:1 setup broке the rope/.On mblocк we'll have 30++кN.Second broке little faster But for real life they both are equal combo Honestly,I thinк the weaкеr point is swiwel /if it has bearings.Rigging wwrench to weaк for neg rig

 

[joshuarov]

I don't agree with you.Lets mbs for rope and blocк 30кN,only 60 кN in 2:1 setup broке the rope/.On mblocк we'll have 30++кN.Second broке little faster But for real life they both are equal combo Honestly,I thinк the weaкеr point is swiwel /if it has bearings.Rigging wwrench to weaк for neg rig

I'm sorry to say, I don't quite follow...

As far as I can tell, in this setup: the load is equivalent at the place where the fixed end of the rope is tied to the stem and at the morgan block (technically not exactly true as there is an additional force on the M-block equal to the amount of force my hand on the rope is generating, but that seems negligible for the purposes of this discussion).

 

[Flying~Squirrel]

Does a Morgan block produce enough friction that you could be anywhere near mbs when running it by hand? I haven't used one very much, but my assumption is that the hand is the weak point in the system.

 

[joshuarov]

Does a Morgan block produce enough friction that you could be anywhere near mbs when running it by hand? I haven't used one very much, but my assumption is that the hand is the weak point in the system.

You're very likely right, my main point above is that I believe that the rope is weaker than the M-Block, as a justification of why I'm not concerned about light negative rigging on the device (despite manufacturer advise).

That being said, there is so little rope out in the system though, so if we imagine the hypothetical that the hand can lock the device, the peak shock load would be a true worst case scenario... The device can create truly astonishing amounts of friction, particularly if the brake strand is preemptively held with a lot of force prior to the load being applied (I think because if the way the cam operates). I'm therefore pretty cautious and always want to be letting stuff run for both comfort and extra margin.

 

[BrianGehan]

Re the downrigger/morgan: First and foremost, it's currently my favorite AFD for light rigging by a decent margin. Primarily because it works quite well at such a large range of loads. I concur regarding the safeblock, it has inconsistent friction (due to the rope path being outside the device) and is honestly way overbuilt for the majority of what I want areal friction for anyway. The rigging wrench has a much narrower band of loads that work well, and those loads are actually quite high (as far as light rigging is concerned).

Why is it listed as not appropriate for negative rigging as per the literature? My assumption is that this device is lumped into the came category (no negative rigging printed on the tin) as the omni blocks, as their closure mechanism/built in swivel is nowhere near as robust as a classic ISC or similar. But that's just speculation on my part. (And the reason the morgan doesn't have that language is just that it was made in a garage and there weren't as many lawyers involved, it's functionally identical from what I understand.)

In other words, if there is an argument to not use it for negative rigging, it'd be more of a robustness one than a strength one. More or less, the way I see it is that it's important to set it up so that it doesn't side load itself into a stub or something like that to mitigate this risk, but I should be doing that anyway, regardless of rigging type.

Re strength: I believe the weakest component of this rigging system is 1/2" rigging rope (which I honestly tend to steer clear of for negative rigging for the most part in conventional crew scenarios). It's got an MBS of 46kN and with any reasonable de-rate for a knot + wear and tear that will put it will below the 30kN of the Morgan. Or, if we look at the peak load in the rope at the ring in this setup, where there'd be no reason de rate for a knot, it could arguably be double what is seen at the friction device (testing would need to be done to prove that conclusively as it's a fairly complex problem). Whatever the case, by time we're down to SWL, the difference will be greater still (the rope being lower than the device, that is).

From my perspective: If I'm working within the limitations of the rope, I'll be well within the limitations of the device in question. Happy to hear if someone thinks I'm wrong or sees a fail case I'm missing

You're very likely right, my main point above is that I believe that the rope is weaker than the M-Block, as a justification of why I'm not concerned about light negative rigging on the device (despite manufacturer advise).

That being said, there is so little rope out in the system though, so if we imagine the hypothetical that the hand can lock the device, the peak shock load would be a true worst case scenario... The device can create truly astonishing amounts of friction, particularly if the brake strand is preemptively held with a lot of force prior to the load being applied (I think because if the way the cam operates). I'm therefore pretty cautious and always want to be letting stuff run for both comfort and extra margin.

Thanks for the clear explanation of your thought process. Definitely impressed with how the downrigger performs compared to other AFDs, especially with regards to its ability to handle a much broader weight range of pieces. The midline attachability really increases its usefulness in more creative applications and is really nice when using a rope-snap termination for quick and/or remote tie offs.

 

[joshuarov]

Unbelievably psyched that someone was willing to try out my scheme, it appears to work with a safeblock as well:

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[JMerritt]

Nice smooth system, that was sweet! Resulting from lack of available help in my region, I've spent the last decade solo rigging a fair amount. I do have a steady groundie now, but I definitely agree - nothing like the peace and acute focus of solo tree work.

I just recently added the downrigger to our systems and have enjoyed exploring different configurations with it. Just curious what your thoughts are about Rock Exotica listing the Downrigger as not applicable for negative rigging? I haven't seen anything specifically stating that the Morganblock is not suitable for negative rigging. Obviously with the pieces being double whipped, and the block only taking about half the load is a whole different scenario than single line work. Definitely interested in your thoughts. Even having a full time groundie these days, I'm still trying to improve climber controlled lowering systems to free them up to maneuver pieces onto the ground and increase overall efficiency.

We've primarily relied on the triple thimble for climber control on negative rigging, but have found it to be somewhat fickle and inconsistent. Had it lock off completely part way through lowering a spar chunk onto a high line. There was just enough rope against trunk friction as the thimble pressed into the spar as it came under load. Seemed like a good slowed down example of what might happen in during typical negative rig scenarios in the past when the thimble seemed jerky and resistant to run the piece. Not exactly and earth shattering realisation, others may have had similar observations.

Thank you for taking the time to share your work, very much appreciated.

To answer your question about the prohibition on negative rigging with the DR, it is mainly due to the swivel and the button lock side plate both being potentially vulnerable to side loading. In a negative rigging situation it is much more difficult to control or prevent. This is the same reason the Omni blocks carry the same warning.
I’m excited to see people getting good use out of it! I’m really hoping that it catches on and becomes a piece of kit that adds value and versatility to the industry.