[TowerTalk] Need a Knot Expert

[Gedas]

GM Wes and happy thanksgiving !

Surprisingly when the rope (knot portion with antenna) is hoisted up and 
the antenna pulled tight that still tightens up those vertical ropes. Do 
you remember that problem we were all given in college to calculate the 
tension in a rope if you pulled on it in the middle perpendicular to 
that rope? Even though that perpendicular pull is WAY WAY off on one end 
it still seems to pull it out and away from the tower almost a foot 
stretching the entire vertical ropes.

Probably did a poor job explaining that but in the end the tension in 
those vertical ropes does increase when the "dipole" is made nice and 
tight and 30 or so pounds of tension is applied. Add to that some wind 
or 1/2" of ice and that 30 pounds seems to turn into several hundred 
pounds of tangential pull.

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 11/28/2019 8:06 AM, Wes wrote:
> Hi Gedas,
>
> Originally you used the flag on a flagpole as an analogy. Absent the 
> flag, I see little need for a lot of tension in the loop. Then if the 
> flag is hoisted by that portion of the loop located above the joining 
> knot then the knot still sees very little stress; it's just along for 
> the ride. Remove the flag and attach the antenna.  Nothing changes.
>
> Wes  N7WS
>
>
> On 11/27/2019 2:50 PM, Gedas wrote:
>> Hi Wes and TU. I am not sure I am positive what you mean by only a 
>> load on the upper side of the knot.
>>
>> I am going to have two pulleys, one at the top of the tower and one 
>> at the bottom. I am going to have a single long rope threaded around 
>> both pulleys and I am going to use a fisherman's knot or similar to 
>> tie the two together nice and tight. Not going to be much tension in 
>> the rope at this point, maybe 10 pounds just to keep both sides of 
>> the line nice and tight with no slop.
>>
>> Now, I was hoping for a single knot that not only joined the two ends 
>> of the rope together but that also left me with an open loop so I 
>> could easily slip in something like a temporary chain link etc and 
>> then attach one end of a dipole etc to that link.
>>
>> This way from the ground I would be able to hoist up or down that end 
>> of the dipole as I pleased. Now, when the end of the dipole gets 
>> attached to the other end of that temporary chain link etc and the 
>> dipole is up in the air stretched tight there may be 30-40 pounds of 
>> tension pulling on that line. Since the two pulleys are fixed that 
>> tension from the dipole will get translated to my ropes going up and 
>> down the tower between the pulleys.
>>
>> I have been doing this type of arrangement for 20 years but only with 
>> a pulley at the top of the tower. Up until now I just had the long 
>> single rope looped around a round aluminum cross member of my free 
>> standing tower.
>>
>> There was some friction with the rope looping around the 3/8" dia 
>> round & smooth diagonal but I never had a failure. This season I 
>> installed a meaty pipe across the tower at about the 5' level and 
>> attached a pulley at each end (I am going to have several ropes going 
>> up and down so I can support and mess with more then 1 antenna).
>>
>> I hope that paints a more clear picture. So far I have had a lot of 
>> great ideas and the only issue is me understanding their words and 
>> making my fingers tie the knots the way I'm supposed to hi-hi.
>>
>> Gedas, W8BYA
>>
>> Gallery at http://w8bya.com
>> Light travels faster than sound....
>> This is why some people appear bright until you hear them speak.
>>
>> On 11/27/2019 4:25 PM, Wes wrote:
>>> I'm with the other Wes on this one. If I understand correctly you 
>>> only have a load on the upper side of the knot. I would join the 
>>> ends with any old knot and tie a alpine butterfly loop on the upper 
>>> side of the knot: 
>>> https://www.animatedknots.com/alpine-butterfly-loop-knot or one I 
>>> find easier to tie, a bowline on a bight: 
>>> https://www.animatedknots.com/bowline-on-a-bight-knot
>>>
>>> Wes  N7WS 
>
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