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-   -   Best Stopper Knots for Team Supplied Knots (http://www.chiefdelphi.com/forums/showthread.php?t=153779)

Cothron Theiss 16-01-2017 19:47

Best Stopper Knots for Team Supplied Knots
 
I wanted to make this thread to collect and disseminate information on the stopper knots that teams use to hold their ropes on the field. Inspection of these ropes will be a tumultuous undertaking, and I want to make sure as few teams as possible show up to competition with faulty stopper knots. I've already seen some poor suggestions made on these fora and in team meetings on which stopper knots to use, so I'd like to show some good knots that can fit a variety of situations.
I'd also like to hear what other people are planning to use!

My first suggestion for a stopper knot would be the Ashley Stopper knot. It's easy to tie, easy to inspect and can handle odd shapes in the rope. Also, when tied correctly, the load-bearing face of this knot is symmetrical which should reduce the chances of shifting or swinging when load is applied.

If for some reason you cannot tie the Ashley Stopper knot, another excellent alternative is the Stevedore knot. This is another knot that's easy to inspect and easy to tie, and it holds very well even during cyclic loading. Astute observers will notice that it is very similar to the figure-eight knot, but the Stevedore knot is superior because the shape of the knot is not affected by loading as much as the figure-eight.

If your team is using flat webbing or very slick material, you may have some issues getting the above knots to hold. If that's the case, you can try a Double Overhand knot. Knots based on the overhand knot are considered to be superior for webbing, but that's a point of contention among knot and climbing experts.

The above are my three suggestions for stopper knots. Below I have my suggestions for loops either at the end of the rope for easy grabbing or loops along the length for some other type of climbing.

The most versatile loop (and my personal favorite knot) is the Alpine Butterfly. It is strong, easy to tie, takes up relatively little rope length, and is symmetrical. It can be loaded from either end or the loop, or any combination of the three. It can also be tied in the bight or on the end of a rope. It's also easier to adjust the placement or size of the loop if you need to change your loops in between matches. However, if you need a loop to go on the very end of your rope, a different loop may be necessary.

A great end-rope knot is the Bowline. It has a relatively small profile and is very secure. However, the knot can become loose over time if it's not under load. Also, the tail of the knot runs inside the loop itself. This might cause problems if a team's climbing mechanism grabs onto the tail instead of the knot itself. A way to make the knot more secure and direct the tail out of the way is to use a Yosemite finish on the Bowline. However, make sure you know how to correctly tie and inspect the knot if you use a Yosemite bowline. It's one of those that can really go wrong if tied incorrectly.

If your team is using extremely slick or thin rope and/or webbing, you might need to use an Angler's loop. This end-rope loop can be very difficult to untie after loading, but it's one of the very few knots that can hold reliably in bungee cord or an elastic material.


Sorry for the huge dump of information! I just think that, while in the team's shop and under close observation, a team might climb perfectly every time. But in the heat of competition, when things are getting hectic and every last point is vital, I'd hate for a team to lose because of a faulty knot. I'm sure many teams already have resident knot experts, but for the teams that are planning to just use overhand knots for everything, here's some more detailed information.

EDIT - The monkey's fist was purposefully omitted from the list of stopper knots.

JPBlacksmiths 16-01-2017 19:58

Re: Best Stopper Knots for Team Supplied Knots
 
I'm going to take a guess here and assume that many of you don't know how to tie these knots so I figured I would share with you all a link to a website that has very easy, step-by-step instructions for tying all kinds of knots. It is called Knots by Grogg, and I hope it helps:
http://www.animatedknots.com/

Also, I might be a bit biased becuase of the fact that I sail, but I do think that the bowline and the figure eight knots are superior. Both are good becuase if you should need to retie them or change the location of the knot, they are very easy to untie, but also hold exceptionally well. Additionally, they are fairly easy to learn as compared to some of the other mentioned knots.

Cothron Theiss 16-01-2017 20:20

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by JPBlacksmiths (Post 1632093)
I'm going to take a guess here and assume that many of you don't know how to tie these knots so I figured I would share with you all a link to a website that has very easy, step-by-step instructions for tying all kinds of knots. It is called Knots by Grogg, and I hope it helps:
http://www.animatedknots.com/

Also, I might be a bit biased, but being that I sail I do think that the bowline and the figure eight knots are superior. Both are good becuase if you should need to retie them or change the location of the knot, they are very easy to untie, but also hold exceptionally well. Additionally, they are fairly easy to learn as compared to some of the other mentioned knots.

I probably should have linked to Knots by Grogg, so thank you! The website doesn't actually work that well for me using Chrome, so I haven't used it in a while and forgot about it.

I should also mention that my experience with knots comes from Boy Scouts and several years of rock climbing and caving, so I have my own biases. I agree that the Bowline is a reliable and commonly known knot. But I listed the Alpine Butterfly above it for a couple reasons. First off, all these knots are easy to learn, and the Alpine Butterfly is easier to inspect and dress with a glance than the Bowline. I find the Alpine Butterfly to be more consistent and reliable over time, and it takes a smaller profile.
I left the Figure Eight loop out for a reason. It's reliable for end loops and is one of the most commonly known knots, but I think it falls short for these purposes for a couple reasons:
  • If teams are using some sort of winch, the loop won't lie flat or conform to the winch as easily as other loops and may cause issues.
  • If teams are using webbing or any other rope profile that isn't circular, the loop won't dress as easily and becomes much more difficult to inspect, adjust, or untie after loading.
  • I find it an extremely time consuming loop to adjust, especially if you only have a few inches of rope on either end to work with.
  • This loop does very strange and sometimes unpredictable things when load is applied to both ends and not the loop or when load is applied on the knot itself and not from the loop. It also can do odd things when load is applied in opposite directions from inside the loop.
  • It can jam and become difficult to untie even when loaded solely from the loop.

messer5740 16-01-2017 20:25

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by JPBlacksmiths (Post 1632093)
Also, I might be a bit biased becuase of the fact that I sail, but I do think that the bowline and the figure eight knots are superior. Both are good becuase if you should need to retie them or change the location of the knot, they are very easy to untie, but also hold exceptionally well. Additionally, they are fairly easy to learn as compared to some of the other mentioned knots.

I concur with JPB, the figure eight knot is very good at creating a large stop knot (I rock climb), and stays together well. They look similar to the Stevedore Knot, but I'm not sure how much larger the figure-eight knot is compared to it. Guess that's a good place to start.

EDIT: OH! You were talking about knots for the robot to interface with. Our team is using a double overhand for it fits in our hook system.

Cothron Theiss 16-01-2017 20:35

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by messer5740 (Post 1632104)
I concur with JPB, the figure eight knot is very good at creating a large stop knot (I rock climb), and stays together well. They look similar to the Stevedore Knot, but I'm not sure how much larger the figure-eight knot is compared to it. Guess that's a good place to start.

EDIT: OH! You were talking about knots for the robot to interface with. Our team is using a double overhand for it fits in our hook system.

While I think John was referring to the Figure Eight loop and not the Figure Eight knot, I'm curious as to why you think the Figure Eight is a better stopper knot than the Stevedore. A Stevedore knot is a Figure Eight knot with an extra turn around the standing end before the working end passes back through. Also, the load bearing face of a Figure Eight can be very asymmetrical, and since the DAVITs will only be supporting the stopper knots on 2-3 sides of the knot at any time, I think symmetrical knots are better for this application.

messer5740 16-01-2017 20:40

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Cothron Theiss (Post 1632110)
While I think John was referring to the Figure Eight loop and not the Figure Eight knot, I'm curious as to why you think the Figure Eight is a better stopper knot than the Stevedore. A Stevedore knot is a Figure Eight knot with an extra turn around the standing end before the working end passes back through. Also, the load bearing face of a Figure Eight can be very asymmetrical, and since the DAVITs will only be supporting the stopper knots on 2-3 sides of the knot at any time, I think symmetrical knots are better for this application.

True, but I have yet to test either knots. I will try both, and if one works better than the other, than thats the one I will use. Never used a knot like that before, so it will be interesting to see what happens. Perhaps a good idea would be to use multiple knots in very close proximity, or use one knot within another to get the best hold.

JPBlacksmiths 16-01-2017 21:21

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Cothron Theiss (Post 1632103)
I listed the Alpine Butterfly above it for a couple reasons. First off, all these knots are easy to learn, and the Alpine Butterfly is easier to inspect and dress with a glance than the Bowline.
I left the Figure Eight loop out for a reason. It's reliable for end loops and is one of the most commonly known knots.

I agree that they are all relatively easy to tie, however I think the alpine butterfly is one one the harder ones mentioned. I don't agree with the inspection point you made because bowlines are extreamly easy to inspect. They all make a uniform shape and it is always clear whether or not it is tied correctly. Also, you said that the figure eight is reliable for end loops, so wouldn't that make it better for this situation? How would someone utilize the sideways loop created by the alpine loop at a point other than the bottom of the rope?

Quote:

Originally Posted by Cothron Theiss (Post 1632110)
While I think John was referring to the Figure Eight loop and not the Figure Eight knot, I'm curious as to why you think the Figure Eight is a better stopper knot than the Stevedore.

Actually I was referring to the figure eight stopper knot. To be completely honest I have never actually used a stevedore knot. I like the figure eight stopper becuase it holds well, but even after pressure has been applied it is still easy to untie. Granted, in the context of this game I don't think people are going to have to untie their stopper knots, but as I mentioned before I am biased, and the ability to untie knots is essential when sailing.

Ether 16-01-2017 21:46

Re: Best Stopper Knots for Team Supplied Knots
 

I ran some somewhat-less-than-scientific tests several years ago to find the best knot for tying two pieces of same-size string together.

What would you recommend? Sole criterion is breaking strength.



cadandcookies 16-01-2017 21:49

Re: Best Stopper Knots for Team Supplied Knots
 
JPBlacksmiths, the reason your quote is failing is because you're missing a ] on the first quote block.

You should have:
Code:

[quote=Cothron Theiss;1632103]
vBulletin really doesn't like missing brackets.

Cothron Theiss 16-01-2017 23:17

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Ether (Post 1632153)

I ran some somewhat-less-than-scientific tests several years ago to find the best knot for tying two pieces of same-size string together.

What would you recommend? Sole criterion is breaking strength.



Off the top of my head, I'd say blood knot or Ashley bend. But a Figure Eight bend is also a good candidate.

In theory, the strongest knot would be the the knot that has enough internal friction that the rope breaks before it slips but reduces the rope's breaking strength by the least amount. And in general, the tighter the turn a rope has to make in a knot, the more strength lost. So following that line of reasoning, the strongest knot is to just wrap the two ropes around each other for a long enough stretch of rope that the friction holding them together is stronger than the rope. Now, this is obviously ridiculous in practice, but I wonder if the concept can be applied to making a 'long' knot. something like a repeated Carrick bend maybe? A single Carrick bend itself is good for wet ropes, but is considered to be a weaker bend. However, the turns in a Carrick bend have relatively large radii and can be repeated until you have enough friction. But I've no idea if this is actually practical.

EDIT - Also, I just noticed the title of the thread. Dang it.

Cothron Theiss 16-01-2017 23:35

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by JPBlacksmiths (Post 1632140)
I agree that they are all relatively easy to tie, however I think the alpine butterfly is one one the harder ones mentioned. I don't agree with the inspection point you made because bowlines are extreamly easy to inspect. They all make a uniform shape and it is always clear whether or not it is tied correctly.



My concern with the inspection of the bowline comes down to this subtlety. Even people born with ropes in their hands can miss this difference if they don't check closely. In a perfect world, it wouldn't really be an issue, but competitions are not perfect worlds.

Quote:

Also, you said that the figure eight is reliable for end loops, so wouldn't that make it better for this situation? How would someone utilize the sideways loop created by the alpine loop at a point other than the bottom of the rope?
If you only consider which knot is stronger and more convenient to use as an end-loop, then yes, the figure eight loop is better. But the Alpine Butterfly has a smaller profile and I think would lie flat on a winch barrel better than the figure eight loop. As for the perpendicular nature of the loop coming off of an Alpine Butterfly, I honestly don't know if it's an issue or not. That's something to be decided in prototyping, I guess.

GeeTwo 17-01-2017 00:42

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Cothron Theiss (Post 1632087)
EDIT - The monkey's fist was purposefully omitted from the list of stopper knots.

Why? While it was not invented as a stopper knot (more of a starter knot), and uses a lot of line, it's not terribly difficult to tie; I learned it in an hour or so. If you use a single overhand knot as the core, you can nest them, beginning with a "two loop" for the first layer and adding about two loops per layer. For use in the davit fingers with smaller lines, tt also distributes the force of the support quite well.

Quote:

Originally Posted by Ether (Post 1632153)
I ran some somewhat-less-than-scientific tests several years ago to find the best knot for tying two pieces of same-size string together.

What would you recommend? Sole criterion is breaking strength.

Quote:

Originally Posted by Cothron Theiss (Post 1632195)
...

In theory, the strongest knot would be the the knot that has enough internal friction that the rope breaks before it slips but reduces the rope's breaking strength by the least amount. And in general, the tighter the turn a rope has to make in a knot, the more strength lost. ...

I agree with this completely. Among the really small knots, the surgeon's knot would be good, presuming the line isn't too slippery for that to hold. If you're willing to use a lot of line, I suggest braiding the lines to each other, which would result in a section which is actually stronger than either line. A bit of web searching turned up the blood knot, which seems to do a great job of relieving the stress in each line before it is doubled over.

BeardyMentor 17-01-2017 07:47

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Ether (Post 1632153)

I ran some somewhat-less-than-scientific tests several years ago to find the best knot for tying two pieces of same-size string together.

What would you recommend? Sole criterion is breaking strength.




I would go for an alpine hitch or a carrick bend.

JesseK 17-01-2017 09:08

Re: Best Stopper Knots for Team Supplied Knots
 
Inventing and understanding knots is right up there in the mix of skillsets that are impossible to automate. These days it's like finding the name of a new planet, star or asteroid - just go ask the expert.

My team doesn't plan to use any knots in the rope for climbing. However, given the ~6mm rope we're testing now we'll need a good DAVIT knot. Are there tricks to making any of the listed knots bigger?

JCharlton 17-01-2017 09:31

Re: Best Stopper Knots for Team Supplied Knots
 
The 'Ultimate Encylopedia of Knots and Ropework' warns that Figure of Eight and Stevedore knots can both pull through a hole similar in diameter to that of the rope. With the large opening in the Davit, while they may be satisfactory for pulling your robot, may fail with smaller ropes. Figure Eight knots can also travel down a rope.

Suggested instead is the Ashley stopper knot, but if your rope is significantly smaller than the opening in the davit you may need a Monkey Fist to make a large enough ball.

If you're planning to use webbing or Velcro, well, that's a tricky one...

As for joining two similar sized ropes, it's difficult to define a 'best' knot as it depends on the rope material and use case. Many knots may snag or fail under particular or peculiar circumstances. For modern synthetic rope a Simple Simon Double would be worth a look, but I don't know if they'd be recommended for Dyneema or Vectran for example.

mrnoble 17-01-2017 09:59

Re: Best Stopper Knots for Team Supplied Knots
 
Major props to OP for creating this post. We all needed this.

Cothron Theiss 17-01-2017 18:33

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by GeeTwo (Post 1632231)
Why? While it was not invented as a stopper knot (more of a starter knot), and uses a lot of line, it's not terribly difficult to tie; I learned it in an hour or so. If you use a single overhand knot as the core, you can nest them, beginning with a "two loop" for the first layer and adding about two loops per layer. For use in the davit fingers with smaller lines, tt also distributes the force of the support quite well.

Quote:

Originally Posted by JesseK (Post 1632290)
My team doesn't plan to use any knots in the rope for climbing. However, given the ~6mm rope we're testing now we'll need a good DAVIT knot. Are there tricks to making any of the listed knots bigger?

I'll try and answer both of your questions at the same time, because they both concern the same knot.

The Monkey's Fist is often touted as the largest stopper knot, which may very well be true. But I really don't like using the Monkey's Fist without a solid core, like a marble or something. And using a small knot like an overhand or an Ashley Stopper as the core feels like a messy solution to me. But it may end up being the only feasible option for very small diameters of rope. If this ends up being the case, adjusting the knot will become a chore, but that may just be the way it is.


Stepping away from the solid ground of well known stopper knots, you may be able to use some sort of follow through looping stopper knot. Lots of end-loop are basically a stopper knot that has the tail following through the knot to form the loop. I know that's not a good explanation, so check out the Figure Eight follow through for a prime example of what I mean. I wonder if the same concept can be applied to stopper knots to create larger stopper knots. So what I'm thinking is that you'd create a loose Ashley stopper, then reroute the tail (NOT the standing end) through the knot so that the tail is coming out next to the standing end. You'd then have a loop coming out where the tail usually exits the knot. I've no idea if something like this would work or not. I don't have nay rope on hand at the moment, so I'm kind of flying blind if it comes to inventing a larger stopper knot.

Jonah303 17-01-2017 21:20

Re: Best Stopper Knots for Team Supplied Knots
 
My team is planning on using a monkey fist knot as the stopper on the end of our rope. If you use a monkey fist as the core of another monkey fist and tie it really tight, It is very strong.

Gary Bonner 17-01-2017 23:14

Re: Best Stopper Knots for Team Supplied Knots
 
I am not thrilled about the idea of suspending our robot by a stopper knot, especially with a 1" square retaining opening. There are much more secure ways of fixing a rope to the davit. The blue box 12" rule makes even things less secure, as larger line, with which you could tie larger knots, is more likely to fail the test. I doubt that the line in the field tour videos would pass the test.

Complaints aside, some other knots to consider are those used in soft shackles, such as the diamond knot and the button knot which can be seen here.

s_forbes 17-01-2017 23:22

Re: Best Stopper Knots for Team Supplied Knots
 
I wonder if this would be a good approach if you're using a really small diameter rope:


Cothron Theiss 17-01-2017 23:39

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Jonah303 (Post 1632706)
My team is planning on using a monkey fist knot as the stopper on the end of our rope. If you use a monkey fist as the core of another monkey fist and tie it really tight, It is very strong.

The more I think about it, the more I think that I may have to amend my earlier statements warning against monkey's fists. They may be the best, if not only way for teams using very small diameters of cord to get a stopper knot large enough. I imagine a team using standard solid core paracord will need to use several successive monkey's fists to get to the size they need. When I get a chance and get some rope, I'll try tying this and see what happens.

Quote:

Originally Posted by Gary Bonner (Post 1632756)
I am not thrilled about the idea of suspending our robot by a stopper knot, especially with a 1" square retaining opening. There are much more secure ways of fixing a rope to the davit. The blue box 12" rule makes even things less secure, as larger line, with which you could tie larger knots, is more likely to fail the test. I doubt that the line in the field tour videos would pass the test.

Complaints aside, some other knots to consider are those used in soft shackles, such as the diamond knot and the button knot which can be seen here.

I agree. Having a peg or hook for a loop to go onto would have been a MUCH more secure way to attach the Ropes.

I'd been avoiding all the knots and shackles used in splicing because I figure many teams won't be using a splicable rope, but if teams want to go down the splicing path, that does open up a lot of really great options. Do you know of a way to make single strand variants of the diamond and button knots?

Cothron Theiss 18-01-2017 02:18

Re: Best Stopper Knots for Team Supplied Knots
 
Ok, so I took a shot at the double monkey fist. (Successive monkey fist? Fist in a fist? I'm not sure what to call this.) The cord is gutted 550 paracord, which is ~3mm in diameter. While I would never use this cord itself to hold anything of value, true 550 paracord could hold a robot. (The 550 comes from its static load rating, 550 lbs.) To make this knot, I put an Ashley Stopper at the end of the line, then tied a monkey fist around the Ashley Stopper. This first monkey fist had 3 wraps per side. Then, I tied a second monkey fist around the first one. The second monkey fist had 6 wraps per side.



I am pleasantly surprised with the result. I actually made a few small mistakes on the first monkey first, resulting in a less spherical knot than I would like. After tying the first monkey fist, I wasn't very pleased from how it was turning out. even aside from my errors, it wasn't looking good as a robust stopper knot. But after the second monkey fist, I felt much better about it. The amount of length taken up by this knot is astounding, but considering that the goal is a sphere at least 9 times the diameter of the rope making up the knot, it's not too surprising.

Tomorrow, I will try it again. I'll do a better job on the initial core (I might try a different knot for the initial core.), I'll make sure to rectify any errors on the first monkey fist, and I'll switch to only 5 wraps on the second monkey fist. Currently, it's quite loose around the corners and there's a bit of folding in the sides, which are both signs of there being one too many stands per side. Eventually I'd like to buy some real paracord and try out this knot on something that actually resembles the DAVIT, but until then, I can only recommend that teams consider this knot as a potential option and try it out themselves.

Jonah303 18-01-2017 07:04

Re: Best Stopper Knots for Team Supplied Knots
 
I've already done a triple layer monkeys fist. After that many layers and wraps, you can get a very substantial knot. What I've found, is that for each successive layer you need to add two more wraps. (Ex 3,5,7) That is so you won't have wraps overlapping each other. I've also trimmed and fused the two extra ropes that stick out when you finish each layer (that is not the first fist). I've e only kept the strand that sticks out when you finish the first monkey fist. If you do it like that, the rope that the robot will be pulling on is deep within the knot.

chrisrin 18-01-2017 09:01

Re: Best Stopper Knots for Team Supplied Knots
 
Is it viable to use a section of thick rope with an overhand knot at the top joined to a very thin rope (like 550 paracord) that hangs down to interface with the robot? Not joined by splice but using strong loop knots?

JesseK 18-01-2017 09:05

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by s_forbes (Post 1632757)
I wonder if this would be a good approach if you're using a really small diameter rope:

That is an excellent choice for any team called the Robocats.

GeeTwo 18-01-2017 09:26

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by chrisrin (Post 1632839)
Is it viable to use a section of thick rope with an overhand knot at the top joined to a very thin rope (like 550 paracord) that hangs down to interface with the robot? Not joined by splice but using strong loop knots?

Certainly seems legal now. (after Q22 and Q89)

Per IO4-F, there is a 29" minimum distance between the davit knot and the first knot in the rope, presumably to put it below the davit channel. This This means that your thin rope would have to begin several inches below the touchpad. Not a show stopper, but something you'd have to design for.

Gary Bonner 18-01-2017 13:11

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Cothron Theiss (Post 1632759)
Do you know of a way to make single strand variants of the diamond and button knots?

My initial thought was essentially to splice a loop and then cut the end of the loop, resulting in a "Y" at the end of the line. However, I'm not sure the splice bury would pass the 12" rule.

I'd be interested to hear how the monkey fists perform under a 150# load.

Daniel_LaFleur 18-01-2017 13:18

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Gary Bonner (Post 1632986)
My initial thought was essentially to splice a loop and then cut the end of the loop, resulting in a "Y" at the end of the line. However, I'm not sure the splice bury would pass the 12" rule.

I'd be interested to hear how the monkey fists perform under a 150# load.

I'm more interested in a much heavier load when the robot winch keeps turning after the robot has hit the davit ;)

JesseK 18-01-2017 13:19

Re: Best Stopper Knots for Team Supplied Knots
 
If we do exactly a 1" knot, is there anything in the DAVIT's construction to prevent the knot from off-centering and falling through? If knot, will thinner ropes need a knot of up to 2" in diameter?

Mark McLeod 18-01-2017 13:49

Re: Best Stopper Knots for Team Supplied Knots
 
1 Attachment(s)
From the field drawings (GE-17081) it appears that the slot holding the top knot is 1.125" wide and 1.675" tall (to center of holding pin, so a tiny bit less).
Our holding knot had better not be compressible to pull through that.

Cothron Theiss 18-01-2017 16:00

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Jonah303 (Post 1632805)
I've also trimmed and fused the two extra ropes that stick out when you finish each layer (that is not the first fist). I've e only kept the strand that sticks out when you finish the first monkey fist. If you do it like that, the rope that the robot will be pulling on is deep within the knot.

I tied mine out of a continuous piece of rope, so the standing end comes from the outside wraps. That's much more secure than pulling on the core of the knot itself.

Quote:

Originally Posted by chrisrin (Post 1632839)
Is it viable to use a section of thick rope with an overhand knot at the top joined to a very thin rope (like 550 paracord) that hangs down to interface with the robot? Not joined by splice but using strong loop knots?

It's legal. But you'll have to make sure the connection between the different ropes is strong. The bigger the difference in diameter, the more likely you'll run into issues with the bend. There are several knots that are well suited for tying together two ropes of dissimilar diameter though.

Quote:

Originally Posted by Mark McLeod (Post 1633024)
From the field drawings (GE-17081) it appears that the slot holding the top knot is 1.125" wide and 1.675" tall (to center of holding pin, so a tiny bit less).
Our holding knot had better not be compressible to pull through that.

Thanks so much for posting this picture. I had not seen the clevis pin before now. I wonder if someone could ask in the Q&A if teams are allowed to attach to the pin itself with a loop, and not rely on a stopper knot. That'd be far more secure for smaller diameters of ropes and straps of webbing.

Gary Bonner 18-01-2017 17:21

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Cothron Theiss (Post 1633113)
I wonder if someone could ask in the Q&A if teams are allowed to attach to the pin itself with a loop, and not rely on a stopper knot. That'd be far more secure for smaller diameters of ropes and straps of webbing.

Q142 asks a similar question, but is unanswered. The blue box after I04 says the rope's retaining feature must be greater than 1" in diameter, so you'd have to put a know at the end of the loop.

Cothron Theiss 18-01-2017 17:31

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Gary Bonner (Post 1633151)
Q142 asks a similar question, but is unanswered. The blue box after I04 says the rope's retaining feature must be greater than 1" in diameter, so you'd have to put a know at the end of the loop.

Ahh, ok thank you. I should, but frankly I haven't kept up much with the Q&A this year.

Mark McLeod 18-01-2017 18:02

Re: Best Stopper Knots for Team Supplied Knots
 
Q142 has been Answered now.

GeeTwo 19-01-2017 09:51

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Q142
Rope Retaining Featurecontinued from Q85 Larks Head Knot around steal ears?
Can the rope pass through the steal ears with a loop and wrap around the ears? The rope knot would look similar to a "Larks Head" Knot.

Answer

We cannot rule absolutely on hypothetical ROBOT or ROPE designs, and the final decision as to legality of a particular ROBOT or ROPE lies with the Lead ROBOT Inspector (LRI) at each event. Generally, loops which wrap around the DAVIT fingers would constitute engaging "securely with the FIELD" per I04-E provided that the ROPE still passes between the fingers (secured by the pin) to ensure that it does not slip off the fingers.

Please note that placing any knot used to form loops, as described above, below the DAVIT fingers would violate I04-F.

No knots below the DAVIT fingers.. you'd have to get those loops exactly the right size, and then the loops would be under high tension. Pass.

Edit - it could go just around one finger for the load, and the other to keep the knot rotated between the fingers. Not too bad.

chrisrin 19-01-2017 10:11

Re: Best Stopper Knots for Team Supplied Knots
 
Does anyone have a picture of the davit fingers? I saw a couple pictures from the unveiling of the game, but they weren't from a great angle.

Mentor_Rick 19-01-2017 10:18

Re: Best Stopper Knots for Team Supplied Knots
 
Oh man the Rock climber in me is cringing about some of the stuff I just read in this thread but there is some very good stuff in here.

A few points:

1, I saw spectra and Dyneema/ Vectra mentioned ( all just different names for uhmw-pe) Tying knots in these are very difficult and not recommended in the least as they dont hold knots. In climbing situations if you use these materials they are sewn together or if they do have knots you MUST have very long tails as they can capsize. ( There are other issues with these materials that I would love to talk about if your interested)

2, As for knot strength, the breaking strength of a knot is a function of the strength of the rope and the number and angle of the bend entering the knot, if you tie a knot and test to failure the cord almost always breaks at the knot. To this end the Figure 8 is the strongest knot you can use as it preserves the most amount of strength in the rope. If that is your concern this is your knot.

3. A very simple stopper knot widely used is the Barrel knot. Used widely to finish off rappel ropes to save climbers from rappelling off the ends of their ropes. Its very simple easy to tie and untie and expands the diameter of your knot. This knot will be limited by the size cord you choose to use.

4. When tying different ropes together very few methods beat a double fishermen in terms of strength but this works best with cord of a circular cross section. If using webbing you will want to use a water knot.

Cothron Theiss 19-01-2017 14:06

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by chrisrin (Post 1633418)
Does anyone have a picture of the davit fingers? I saw a couple pictures from the unveiling of the game, but they weren't from a great angle.

Check Mark McLeod's earlier post. He has a good picture attached.

Quote:

Originally Posted by Mentor_Rick (Post 1633422)
1, I saw spectra and Dyneema/ Vectra mentioned ( all just different names for uhmw-pe) Tying knots in these are very difficult and not recommended in the least as they dont hold knots. In climbing situations if you use these materials they are sewn together or if they do have knots you MUST have very long tails as they can capsize. ( There are other issues with these materials that I would love to talk about if your interested)

Yup. Frankly, I see no reason for teams to use Spectra, and a hwole lot of reasons not to.

Quote:

2, As for knot strength, the breaking strength of a knot is a function of the strength of the rope and the number and angle of the bend entering the knot, if you tie a knot and test to failure the cord almost always breaks at the knot. To this end the Figure 8 is the strongest knot you can use as it preserves the most amount of strength in the rope. If that is your concern this is your knot.
Yes, but in this case, I don't think we're worried about the rope breaking so much as we're worried about the stopper knot slipping through the DAVIT, and so I don't think the Figure Eight is the best stopper to use in this case.

Quote:

3. A very simple stopper knot widely used is the Barrel knot. Used widely to finish off rappel ropes to save climbers from rappelling off the ends of their ropes. Its very simple easy to tie and untie and expands the diameter of your knot. This knot will be limited by the size cord you choose to use.
I'm pretty sure I know what knot you're referring to, but can you provide an example of the barrel knot? I know several different knots that are all referred to as the barrel knot, and a Google search pulls up a whole host of knots all bearing that name.

Quote:

4. When tying different ropes together very few methods beat a double fishermen in terms of strength but this works best with cord of a circular cross section. If using webbing you will want to use a water knot.
Yup. Though I honestly hope for their sakes that there aren't teams planning to use multiple sections of webbing as their Rope. That just sounds like asking for trouble.

Mentor_Rick 19-01-2017 14:32

Re: Best Stopper Knots for Team Supplied Knots
 
Cothron sounds like we are on the same page!

A figure 8 used as a stopper with regard to the davit would probably not be the best choice unless your cord was really thick. I was mentioning that more in regards to some earlier comments on the strengths of knots.

The one I was referring to as a barrel knot is a knot of this type


This would not be ideal for teams looking at very small diameter cords but if your in the 8mm-12mm rang it could do the trick.

Tom Line 19-01-2017 15:51

Re: Best Stopper Knots for Team Supplied Knots
 
As a sailor knots are pretty much second nature. When looking at 'popular' knots folks need to understand that strength is usually not the only concern. In many cases knots like the bowline are used because it's possible to untie one even after it's spent a year or two exposed to the elements under load.

All that said, I haven't seen anyone talking about how to tie a suitable stopper knot in webbing or cargo strapping that a lot of teams are planning on using.

Ideas?

Richard Wallace 19-01-2017 16:19

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Tom Line (Post 1633604)
As a sailor knots are pretty much second nature. ...

I have very little sailing experience. In the 1980s, I did a lot of rock climbing as a trip leader with the outdoor rec group at Georgia Tech. Climbers work with dynamic kernmantel ropes, and webbing.

On the recommendation of a very experienced sailor, our team is now practicing climbing on Sta-Set, a popular double braid polyester cord that is used for several purposes on many boats. 3/8" diameter is rated 5100 lbf tensile. The price is not bad.

Any comments or concerns, Tom?

Gary Bonner 19-01-2017 20:55

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Richard Wallace (Post 1633613)
I have very little sailing experience. In the 1980s, I did a lot of rock climbing as a trip leader with the outdoor rec group at Georgia Tech. Climbers work with dynamic kernmantel ropes, and webbing.

On the recommendation of a very experienced sailor, our team is now practicing climbing on Sta-Set, a popular double braid polyester cord that is used for several purposes on many boats. 3/8" diameter is rated 5100 lbf tensile. The price is not bad.

Any comments or concerns, Tom?

I would never climb using a sailing rope. Sailing line is designed to minimize stretch. You don't want your sail shape to change as as the load varies. Sta-set, while polyester and stretchier than high tech lines like dyneema, etc. is still pretty static. You don't want to fall in a static line. The forces get big pretty quick, even in a short top-rope fall. The human body doesn't like sudden stops.

Tom Line 19-01-2017 21:01

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Richard Wallace (Post 1633613)
I have very little sailing experience. In the 1980s, I did a lot of rock climbing as a trip leader with the outdoor rec group at Georgia Tech. Climbers work with dynamic kernmantel ropes, and webbing.

On the recommendation of a very experienced sailor, our team is now practicing climbing on Sta-Set, a popular double braid polyester cord that is used for several purposes on many boats. 3/8" diameter is rated 5100 lbf tensile. The price is not bad.

Any comments or concerns, Tom?

Nope. That rope will work just fine. If you are using velcro, there are ropes made specifically to be soft on the hands. They have very fuzzy covers.

Trophy braid is usually considered the softest and will probably be the easiest for velcro to grab if you're just using straight rope:
http://www.apsltd.com/samson-ropes-t...raid-line.html

Generally we use these as stopper knots because they form a large knot, but even after being under tension they can be easily undone.

http://www.animatedknots.com/doubleo...om#ScrollPoint

There isn't really much mystery in rope.

Tom Line 19-01-2017 21:03

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Gary Bonner (Post 1633724)
I would never climb using a sailing rope. Sailing line is designed to minimize stretch. You don't want your sail shape to change as as the load varies. Sta-set, while polyester and stretchier than high tech lines like dyneema, etc. is still pretty static. You don't want to fall in a static line. The forces get big pretty quick, even in a short top-rope fall. The human body doesn't like sudden stops.

Exactly right. That's also why it is highly recommended to not use racing line as your dock lines. Dock lines should always have stretch, or you will shock load the cleats on your deck and develop cracks and leaks around them. Plus, when you're tied up at the dock sleeping it's a much gentler motion with a dock line that haves some give.

Gary Bonner 19-01-2017 22:24

Re: Best Stopper Knots for Team Supplied Knots
 
A busy week and couple of days away from the robot, and responses from climbers and sailers, and I lost context of the discussion.

I'd still be hesitant to use a stopper knot with 3/8" line on a opening that size. A loop around the fingers as described above would be a safer option.

s_forbes 19-01-2017 22:34

Re: Best Stopper Knots for Team Supplied Knots
 
I've been thinking about this rope that we might have to make, and I'm a little perplexed that FIRST decided to go with a stopper knot instead of a looped end for holding the rope. I feel like we'll see a few robots yanking their rope out of the airship during the season because the stopper knot slipped through.

Still have no idea how to make a good stopper knot with a thin line. Nothing I'd want to hang a robot from, anyway.

Oblarg 19-01-2017 22:37

Re: Best Stopper Knots for Team Supplied Knots
 
We're simply using webbing and a water knot.

Richard Wallace 19-01-2017 22:54

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Gary Bonner (Post 1633724)
I would never climb using a sailing rope.

Neither would I. The topic here is robots climbing, not humans.

When I said the team is practicing climbing, I meant getting the robot to attach to a ROPE (per the Game Manual) and ascend ~36".

Human climbers should be belayed with ropes that give, as you said.

myedinak 06-02-2017 15:49

Re: Best Stopper Knots for Team Supplied Knots
 
Is anyone considering using eye splices in the ends of the rope? Could an eye splice be used as the retention feature. It could go over the davet fingers and would not slip. I was also planning on putting an eye splice in the robot end of the rope since it would be the least amount of extra material and have the lowest profile when wrapping around the winch.

I am also perplexed why they chose to use a stopper know as the means of securing the line to the airship. These seam line the most likely to fail. Using a loop would be much more secure.

Cothron Theiss 06-02-2017 15:53

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by myedinak (Post 1641231)
Is anyone considering using eye splices in the ends of the rope? Could an eye splice be used as the retention feature. It could go over the davet fingers and would not slip. I was also planning on putting an eye splice in the robot end of the rope since it would be the least amount of extra material and have the lowest profile when wrapping around the winch.

I am also perplexed why they chose to use a stopper know as the means of securing the line to the airship. These seam line the most likely to fail. Using a loop would be much more secure.

Relevant Q&A response. Thankfully, this means that teams using very small diameters of rope can just completely ignore trying to use a stopper knot and just use a loop or a splice.

GeeTwo 06-02-2017 15:57

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Cothron Theiss (Post 1641236)
Relevant Q&A response. Thankfully, this means that teams using very small diameters of rope can just completely ignore trying to use a stopper knot and just use a loop or a splice.

Absolutely! We haven't stopped trying things, but we're currently looking at tying a bowline on a bight and passing one loop over each finger if we go with 3/8" round line. TBD if we do flat webbing.

Ether 06-02-2017 18:29

Re: Best Stopper Knots for Team Supplied Knots
 

Quote:

Q: Since the splice is not a knot, per Q57, and the splice itself meets the specifications of a rope, is it ok that part of the splice extends more than 2” below the davit fingers?

A: Yes, per I04, part E as updated in Team Update 05 any retaining feature may extend up to 2 in. below the DAVIT fingers.

Yes what?

Yes the splice itself meets the definition of a rope.. and therefore it's OK that part of the splice extends more than 2” below the davit fingers?

or

Yes the splice is a retaining feature... and therefore is not allowed to extend more than 2” below the davit fingers?




Cothron Theiss 06-02-2017 22:30

Re: Best Stopper Knots for Team Supplied Knots
 
Quote:

Originally Posted by Ether (Post 1641329)




Yes what?

Yes the splice itself meets the definition of a rope.. and therefore it's OK that part of the splice extends more than 2” below the davit fingers?

or

Yes the splice is a retaining feature... and therefore is not allowed to extend more than 2” below the davit fingers?




Hmm... the more I read that now, I think there was a mistake or a typo in the response to Q342. According to my interpretation of the rules and the updates and the relevant Q&A responses, since a splice is itself a rope from the definition of the rope, a splice can extend more than 2" from the bottom of the DAVITS fingers. However, as you noticed, the response states that:
Quote:

any retaining feature may extend up to 2 in. below the DAVIT fingers.
However, in that same sentence, they reference I04:
Quote:

be configured such that it engages securely with the FIELD. with a Retaining Feature (RF) that
does not extend more than 2 in. (~5 cm) below the DAVIT fingers.
Am I just misreading something, or is the response to Q342 contain a typo?

And thanks for pointing that out, Ether!


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