Best Stopper Knots for Team Supplied Knots

[Cothron Theiss]

Originally Posted by Jonah303

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.

Originally Posted by chrisrin

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.

Originally Posted by Mark McLeod

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]

Originally Posted by Cothron Theiss

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]

Originally Posted by Gary Bonner

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]

Q142 has been Answered now.

[GeeTwo]

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]

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]

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]

Originally Posted by chrisrin

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.

Originally Posted by Mentor_Rick

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.

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.

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.

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]

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]

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]

Originally Posted by Tom Line

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]

Originally Posted by Richard Wallace

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]

Originally Posted by Richard Wallace

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]

Originally Posted by Gary Bonner

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]

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.