advice on knots and ropes

[tommaso]

>Mark G
> in respect of the OP stated desire to find a solution to his issue

>roo
> I don't mean to divert this thread, but I hope you can give different approaches a fair shake (pun intended)


Well thank you, but feel free to debate, as I, anyway, as learner, do enjoy the discussion.

As someone approaching this world, it is quite interesting to see that each knot seems to have
his supporters, just like some sport team :-)

I have looked online for the clove hitch too, but it seems that the site "animatedknot" was
warning about it, stating some "dangers" (see: http://www.animatedknots.com/cloveend/)

Clearly, I understand that there could be no absolute winners, uniformly dominating under all
circummstances, but depending on the specific situation, surrounding conditions,
and the direction of applied forces any knot can possibly offer some value.

By the way, what are other candidates that are suggested for the 5 knots I currently have?

As to the gnat hitch I don't have much diversified experience to suggest anything on general performances.
One thing that I noted is that, although the knot seemed quite "simple", when I tried to replicate (as an exercise)
day after day, it without a visual guide, I had initially some difficulty and had to go look up  again.
Looks like this stuff needs anyway some daily practice to be remembered and permanently stored in the brain.

I think the top "overhand" knot is way too "ugly" (although possibly effective to simply create
the attachment loop) and should be changed with something else.

In my various explorations on the web, I have seen the so called "alpine butterfly", which at first look
seemed good looking. However, after playing with it for a few minutes, I realized that the 2 ends
of the rope come out of the knot one on top of the other (and not at the same precise height), and that
does not seem desirable in my case.

[agent_smith]

tommaso, I actually recommend that you use chain (stainless steel chain) instead of rope.

One of the reasons for this recommendation is that you avoid the issues with s-t-r-e-t-c-h... which might cause issues with gymnasts trying to hold on while there is rebound/elasticity.

To form links at each end termination, use 'maillon rapides' (sometimes known as quick-links). Maillons can be purchased in a variety of shapes and sizes (eg oval, delta, pear, semi-circle, etc).

Using chain will also eliminate knots - which can be a potential failure point.
Link: http://www.peguet.fr/self-certified-maillon-rapide-quick-links

EDIT NOTE: Webbing with sewn terminations would also work well!

Mark G

[Sweeney]

I have looked online for the clove hitch too, but it seems that the site "animatedknot" was
warning about it, stating some "dangers" (see: http://www.animatedknots.com/cloveend/)

Be careful with this warning - it applies to a clove hitch used as a terminal knot (as the Gnat Hitch is used) - if used in the middle of a sling it simply stops slippage or "see-sawing" of the loop but only useful if that is a problem. I support Mark's suggestion of using chain particularly for someone who is not confident about knots.

Sweeney

[tommaso]

Thank you for the advice and guidance.

For the upper part of the tool, chains can certainly be used.

For the lower part, I think we need a rope, and therefore we still need some knots.

Some pro and cons of using inox chains I can think of:

Pros:
 - possibly easier and more precise sizing (once one has decided the measures)
 - slow wear, duration
 - possibly a more professional "look"

Cons:
  - with chains making trials is more uncomfortable (ropes allow easy prototyping)
  - larger weight (ropes allow much better portability of the tool in a bag, lighter and
        avoid scratching other equipment)
  - difficult to cut and work with; costly to modify/replace.
  - noisy

At this prototypical stage and for greater portability at the moment I am using ropes. (Clearly, if one should create something to be possibly sold to public, I think that chains would probably be "mandatory". Not my case, anyway.)

Personally, I am not perceiving the knots as possible weak points. It seems to me that, once in tension, it's quite impossible for them to go anywhere. The general "feeling" is that even adding large weight it seems more likely the bar to bend and break than a knot of these to open. (Of course I may be wrong: this is just a personal feeling.)
 
Also, once in tension, the ropes do not seem to be much elastic. I have noted that especially the larger top white rope tends to stretch visibly when you apply weight initially, however, once it settles in tension, it does not seem to go far in an appreciable manner.

A more practical concern is instead the wear of the rope. I can see that the loop where the rope attaches to the carbine is changing color and probably in some (long) time it would wear too. However, the cost of the rope is quite negligible, so I guess one can change it easily every few months, after inspection, if necessary.
On the other hand, I guess that quick links may wear too due to friction (but much slower).

[roo]

Cons:
  - with chains making trials is more uncomfortable (ropes allow easy prototyping)
  - larger weight (ropes allow much better portability of the tool in a bag, lighter and
        avoid scratching other equipment)
  - difficult to cut and work with; costly to modify/replace.
  - noisy

I think non-metallic is the way to go.  The lighter the device, the better.  These athletes don't want heavy things slowing them down.   The noise of chains would be annoying with so much motion (as you note), and chains would be more likely to injure someone from an incidental hit or get tangled in long hair.

If this were to be sold commercially, sewn straps could be a good option if you don't want people messing around with the knots, although there are plenty of commercial items that do use knots in various forms.  People at this high of level might want to fine-tune their instrument anyway.

[agent_smith]

The noise of chains would be annoying with so much motion (as you note), and chains would be more likely to injure someone from an incidental hit or get tangled in long hair.

Obviously I am only talking about the upper connective section of the apparatus.

If additional connective material is required for the feet - then yes, sewn webbing with adjuster buckles would be ideal because obviously, every person is a different height and has different length limbs.

However, the upper connective portion can be swaged wire or chain. This section would not need to be adjustable - its the lower section for the limbs (feet) that should be adjustable.
NOTE: Can also use rated webbing with sewn terminations (terminations that form a connective 'eye').

The comment re hair entanglement is unlikely - given that the chains or swaged wire exists above the horizontal pipe/bar which is gripped by the gymnasts hands. Also, the original OP has not given much detail as to precisely what the apparatus will be used for (or the manner in which it will be used). The original post was largely focused on the upper connective section with respect to the swivel. I would also comment that gymnast safety rules dictate that long hair must be tied back/secured. A gymnast would not be allowed on an apparatus with long hair freely waving/flapping about - further reducing the likelihood of hair entrapment.

S-t-r-e-t-c-h will be an issue with any synthetic connective materials in the upper section - due to the force induced by the included angle. Newtons laws of physics means that increasing included angles = higher forces. The 'included angle' is the internal angle created at the 'apex' point where the swivel connector is located. It is not difficult and inexpensive to get cable cut and swaged to measure. I originally suggested chain because it is easy to cut and has ready made links. Cable will require swaging - but this is inexpensive.

To be honest, I am not 100% clear as to precisely how the apparatus is intended to be used - so my recommendations are based on educated guesses. I would comment though that safety should be paramount - and hand tied knots should be avoided where practicable. The OP is not an engineer or a knot tying specialist so this is another complicating factor. Also, it is conceivable that children may be involved...and if this is true, if it were me, I would take every reasonable step to ensure that the apparatus is as safe as reasonably possible. Having said all this...if the apparatus is only intended for personal use in his own backyard - and not for use by gymnasts in a workplace environment - then the legal onus of 'fitness for intended purpose' is relaxed.

Legal disclaimer: Anything that is homebrew or home-made by definition may come without an inspection certificate or gymnastic association approval. Most western nations have a legal concept for products known as; 'Fit for its intended purpose'.
This takes on a particularly acute definition when children are involved. In many nations, a child (or 'minor') is a person who is under 18 years of age. Some States in the USA - eg Colorado + Mississippi, I think it is 21).

The comment re noise is also not relevant if only the upper connective section is metal - again, sewn webbing with adjuster buckles would work well for the lower section (feet).

Mark G
EDIT...Legal commentary added

[roo]

To be honest, I am not 100% clear as to precisely how the apparatus is intended to be used -

Did you see the youtube link the OP gave?:

https://www.youtube.com/watch?v=98sr7TO7t94

The wild breakdance moves could easily rattle chain above as things recoil and make noise.

Just standing up, one's head may be near the upper section, and so the little crevices where links meet could be an annoying long hair grabber as you reach up to connect or disconnect the system. 

Since the segments involved are so short on the upper section, I don't expect stretch to be a major issue. 

[agent_smith]

Did you see the youtube link the OP gave?:

Clearly Roo, you have a little difficulty understanding my words. I thought I was clear in that I stated that I was not 100% certain of how and the manner in which the apparatus would be used. I dont have access to youtube on my computer due to site blocking but I will try to use someone else's computer if I find time.

You seem fixated on pushing the hair entrapment issue...I wonder what the real source of your posts are (hmmmmmm). Maybe your various posts have some link to me not recommending your gnat hitches?
If you are intent and motivated on pushing this further, I would request that you show me the evidence you have gathered where the alleged gymnastic movements could get (hair) caught up in wire and chain above the horizontal bar. Have you personally experimented to model the hair entrapment issue? How do you reconcile a gymnast having long hair that is untied or unsecured - would that make sense when using the apparatus? I'd like to learn how you imagine a person would want to allow unrestrained/unsecured hair to deliberately flail about while using the apparatus.

As stated, the lower leg support section ought to be sewn webbing - preferably adjustable to allow the gymnast to achieve the perfect fit.

As for stretch, the greater the included angle, the greater the force - its simple physics. Wire or chain would work. And yes, to ease your mind - webbing straps with sewn terminations would also work.

I'll make my position crystal clear: I don't recommend the use of unsecured hitches in any apparatus that is used in a workplace or open public domain. Sewn terminations on webbing straps would be preferable to unsecured gnat hitches.

This is my last direct reply to Roo - as it is trending off-topic and because he appears (in my view) to have motivations that are not solely directed at assisting the OP.

[roo]

Did you see the youtube link the OP gave?:

Clearly Roo, you have a little difficulty understanding my words. I thought I was clear in that I stated that I was not 100% certain of how and the manner in which the apparatus would be used. I dont have access to youtube on my computer due to site blocking but I will try to use someone else's computer if I find time.

Thank you for letting me know.  That is why I asked. 

You seem fixated on pushing the hair entrapment issue...I wonder what the real source of your posts are (hmmmmmm).

I'm just following the flow of the thread.  People ask questions, respond, clarify, etc.  Try not to be so suspicious.

I'd like to learn how you imagine a person would want to allow unrestrained/unsecured hair to deliberately flail about while using the apparatus.

If you look again at my previous post, I mentioned a person's head being near that portion when you go to remove or install the device before or after use (not during).

I've had to help people with long hair get untangled from chain on more than one occasion.  It doesn't happen regularly, but when it occurs, it's a mild annoyance.