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Why knots? A science and engineering reply.

knots stem why ask why

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#1 qwazse

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Posted 13 April 2017 - 11:35 AM

For those scouts for whom "Because, the bad day, when winds exceed 50mph ..." just isn't enough  ...

 

http://rspa.royalsoc...3/2200/20160770

 

My apologies to anyone who can't bring up the article in all of its glory. In summary:

 

The controlled experiments showed that increasing inertial effects of the swinging laces leads to increased rate of knot untying, that the directions of the impact and swing influence the rate of failure, and that the knot structure has a profound influence on a knot's tendency to untie under cyclic impact loading.

 


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#2 Chisos

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Posted 13 April 2017 - 12:31 PM

They are most certainly aiming for an Ig Nobel Prize.


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#3 SSScout

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Posted 13 April 2017 - 12:44 PM

Somebody has way too much time available....  Only fair results.  

 

Maybe in my short perusal I missed these, but Did They Consider....  

** Tightness of knot? 

** Skill of knot tier?  (self actuated indeed...) Who pulled it how tight? 

**   Material used?  Cotton stays tied better than synthetics.  Roughness of surface, etc.  Every sailor and "pioneer" knows a sisal or manila rope will hold a knot better than a nylon cord.  

**   While laces are snug around a foot at rest, the lace will stretch a mite and the foot will shrink a mite as it exercises and the fluid/blood  collected in the foot at rest gets pumped out . Hence, a loose lace will untie easier than a tight lace. Because...

** A properly tied , snug SQUARE bow will stay tied.  A GRANNY bow will loosen by dint  of it's own construction.  Pulling on a Granny will untie it.

** One of the reasons for the flat lace is it jams more effectively than the round kind.   Which did they use?  

**   Can this be replicated with other cordage?   Bet they lost their grant on this and couldn't continue....


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#4 qwazse

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Posted 14 April 2017 - 08:31 AM

@SSScout, in words:

 

Templates were used to manage knot geometry (size of free ends and loops) and tightening of the knots. For the latter, knot tightening was standardized by hanging weights from knot loops. Initially, the knots were tied so that the loops and the free ends were of equal length (8.26 cm). The free-end length was defined as the distance of the lace end relative to the knot centre and the loop length was defined as the distance of the middle of the outstretched loop (i.e. half of its arc length/chord length) relative to the knot centre (cf. appendix A (figure 14j)). All knots studied were tied with identical store-bought black (unwaxed) dress laces with a cross-sectional diameter of 2 mm. An attempt was made to characterize the bending stiffness of the laces, but values determined via an optical and force-based method were on the order of the error of the method (10−6 Nm2). The exceptionally small value of the bending stiffness led us to conclude that it is of negligible importance relative to frictional terms.

But, Doesn't anybody look at pictures of anything but kittens anymore?

F6.large.jpg?width=800&height=600&carous

 

You can get the datasets, and some videos here: https://dash.berkele...:10.6078/D15K5K.

 

But, for all that is right and holy, don't have your STEM award oriented scouts go over this pre-collected data to settle any arguments. Use it to inspire them to build their own knot testing stand (possibly from re-purposed trailer parts and stationary bikes). Or maybe two stands designed to test scout knots. Each patrol ties a designated knot on the other's human-powered shaker, then on the start signal, see whose knot can survive the machinations of the other patrol.


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#5 TAHAWK

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Posted 14 April 2017 - 05:33 PM

Somebody has way too much time available....  Only fair results.  

 

Maybe in my short perusal I missed these, but Did They Consider....  

** Tightness of knot? 

** Skill of knot tier?  (self actuated indeed...) Who pulled it how tight? 

**   Material used?  Cotton stays tied better than synthetics.  Roughness of surface, etc.  Every sailor and "pioneer" knows a sisal or manila rope will hold a knot better than a nylon cord.  

**   While laces are snug around a foot at rest, the lace will stretch a mite and the foot will shrink a mite as it exercises and the fluid/blood  collected in the foot at rest gets pumped out . Hence, a loose lace will untie easier than a tight lace. Because...

** A properly tied , snug SQUARE bow will stay tied.  A GRANNY bow will loosen by dint  of it's own construction.  Pulling on a Granny will untie it.

** One of the reasons for the flat lace is it jams more effectively than the round kind.   Which did they use?  

**   Can this be replicated with other cordage?   Bet they lost their grant on this and couldn't continue....

STOP BEING REALISTIC!   :p


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#6 eagle90

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Posted 15 April 2017 - 08:14 AM

Let's get our scouts out into the woods camping and hiking instead of wasting their time on crap like this!

 

Dale


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#7 qwazse

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Posted 17 April 2017 - 07:40 AM

Let's get our scouts out into the woods camping and hiking instead of wasting their time on crap like this! ...

This is not an "either or" proposition.

 

Perhaps you have been able to retain youth by brushing them off with "Why ask why?" replies to the hundreds of questions that come up about their world when hiking and camping.  I've found that to be a good way to stifle scouts' leadership ability and, with regard to advancement, make them merit-badge-mill dependent.


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#8 Stosh

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Posted 17 April 2017 - 07:44 AM

I wear loafers (at my age, tying knots takes too much time)..... but when I wear boots, I tie a double knot.  :)


Edited by Stosh, 17 April 2017 - 07:44 AM.

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Stosh

 

There's a reason why I don't always answer the phone, doorbell or comments on forums.  :)


#9 perdidochas

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Posted 17 April 2017 - 08:34 AM

For those scouts for whom "Because, the bad day, when winds exceed 50mph ..." just isn't enough  ...

 

http://rspa.royalsoc...3/2200/20160770

 

My apologies to anyone who can't bring up the article in all of its glory. In summary:

I read an article on that. Basically the conclusion I took from it is that a shoelace knot is best when it's a double-slipped square knot versus a double-slipped granny knot.  It's easy to tell the difference on a tied shoe. If a proper square knot is the basis of it, the loops lie parallel to the strands  of the knot. If a granny knot is the basis of it, the loops are perpendicular. I tend to tie a granny on my left shoe, and a square on my right shoe.  The best solution to a shoelace knot not coming undone, of course, is the double knot. 


Edited by perdidochas, 17 April 2017 - 08:34 AM.

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#10 TAHAWK

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Posted 17 April 2017 - 08:59 AM

That low-growing plant covered with bright yellow flowers growing along the side of the road in front of the church?  What if I were to tell you it comes from the area where Asia and Europe meet?  How do you suppose it got all the way to Ohio?

 

That raucous call that sounds like it came from a movie about the jungle?  See that smallish bird climbing up the trunk of the old maple in short bursts? You're right; it's making that big sound.   What sort of bird do you think it is?

 

A lot of "nature" can be observed in the semi-urban, and even fully-urban, areas.

 

weed_zpsayxjssqb.png

 

Kestrel_zpsuebvgl3l.png

 

coyote_zps05nvmwpq.png

 

Owl%20city_zpsycnulqbr.png


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#11 Tampa Turtle

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Posted 17 April 2017 - 12:42 PM

While some view knots as vestiges of an old technology (Sailors needed to know a LOT of knots in the Age of Sail) I believe they are still a very relevant and overlooked tool for combining, attaching, and holding things in this age of DNA strands and molecular strings. Perhaps a scout will grow into the scientist who will use the best knot for some advanced nano-technology.


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#12 NJCubScouter

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Posted 17 April 2017 - 02:20 PM

A lot of "nature" can be observed in the semi-urban, and even fully-urban, areas.

 

Good photos, I particularly like the one of the owl trying to blend in with the sky.  If it were a cloudier day...


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#13 Ankylus

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Posted 18 April 2017 - 09:16 AM

Actually, knots are highly significant in some areas of science and technology.

 

For example, "knot theory" is an important field in mathematics. Some studies indicate that the universe may actually be a large woven "mat" and that knot theory may be a key to unlocking further understanding of the structure of the universe:

 

http://discovermagaz...loopsofspace199

 

One aspect of knot theory is how stresses are transmitted and held in a "knot" or structure including knots, including the filaments of the knot or structure.

 

And, nanotubes and some other emerging technologies are making new structures possible in which knot theory and this kind of study will be crucial from an engineering standpoint.

 

So, the study is more important than might seem at first blush.


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#14 SSScout

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Posted 18 April 2017 - 09:27 AM

"You can observe a lot just by watching."     = Yogi Berra =

 

 

After a semi successful session teaching the Bowline to Cub Scouts,  one smiling Cub holds up a tangle batch of cord and asks me, "What knot is THIS ?"

 

"What's your name, Scout?"

 

"Jesse! "

 

"Well, I think that's a 'Jesse Knot' !   "


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#15 TAHAWK

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Posted 18 April 2017 - 09:46 AM

Probably the favorite Scout knot - the Severe Tangle and Half Hitch


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#16 Eagle94-A1

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Posted 18 April 2017 - 10:20 AM

For anyone who thinks knots and lashings are not relevant Checkout then Lt.Col. Scarfoss's story.

 

https://books.google...shuttle&f=false


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"Train 'em. Trust 'em. LET THEM LEAD!" William "Green Bar Bill" Hillcourt


#17 TAHAWK

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Posted 18 April 2017 - 11:31 AM

They can be relevant - if the patrol and troop program allow them to be relevant.  

 

One might start by removing the "sliders" from all the tent ropes.  

 

Erect a flag pole at each patrol or troop campsite using lashings.  

 

Tug-of-war after safe rope is assembled using appropriate knots.

 

 "Knot Club" with beads on a thong for accomplishing designated levels of understanding, with beads forfeited if the bearer can't tie the knot on demand after it has been originally earned.

 

If it's actually useful or a game . . . .


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#18 Eagle94-A1

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Posted 18 April 2017 - 08:54 PM

They can be relevant - if the patrol and troop program allow them to be relevant.  

 

One might start by removing the "sliders" from all the tent ropes. 

 

If I told this story before, bear with me. One of my Eagles told me that during his first deployment to Iraq, they were living in tent. One of the sliders broke, so he used a tauntline hitch to fix the problem. His gunny sees him doing this, and tells him he needs to teach the rest of his platoon so that when the rest of the sliders break, they can fix them. Yep, more broke, and the Marines had the situation well in hand.


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"Train 'em. Trust 'em. LET THEM LEAD!" William "Green Bar Bill" Hillcourt






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