what rope to use for aerial stay?

[VK4WTN]

Just a quick question I put up my new 7el yagi today and it has a bit of sag in the boom so I am going to fit a rope stay on the boom.What rope is the best to use? I want something that is resistant to the sun.I have some 400Kg mono longline fishing line but I think that it will stretch in the sun.Any ideas on the best rope would be appreciated.
73 Wayne

[VK4ADC]

Wayne

If you really want to use rope, look for some extra-good-quality marine stuff.

A better idea (for longetivity) is to use multistrand galvanised or stainless steel wire and turnbuckles. You can buy S/S wire at Bunnings (in the rope section) and they used to have galv wire in electrical where the TV antennas are. You need to buy some small wire grip clamps to fix either one off, preferably 2 on each fold-back - one right near the turnbuckle and one further back along about 300mm or so ( so a total of 4 for each turnbuckle, 2 each side). There is a right way and a wrong way to put those wire grips on the 'pair of wires' too.

Using a turnbuckle on each side allows you to independently adjust the 'lift' on either side of the mounting point to eliminate the boom sag - both front and back.

You can see how I did my anti-sags at http://www.vk4adc.com/50mhz_yagi.php

[VK4WTN]

Thanks for the reply Doug,stainless wire would certainly work the best out in the elements,I take it that using stainless wire for stays won't effect the performance of the beam at all?

[VK4ADC]

Wayne

There won't be any significant interaction because the anti-sag wire is perpendicular to the active elements - the same as the boom is. Many commercial long-boom yagis use the same concept without any concerns.

[VK4WDM]

"There is a right way and a wrong way to put those wire grips on the pair of wires too."

Can somebody give us the correct way please?

73

Wayne VK4WDM

[VK2HRX]

Stainless sounds good. I replaced some gal wire with dacron cord about 2 years ago an a set of Maspro beams. The dacron worked fine. Another option maybe??

[VK4ADC]

Wayne

The right and wrong way for the cable grips :

The U of the grip body must be on the incoming wire side - ie the tensioned side from the tower, boom etc - there are usually some small grooves or an intentional roughness to the cast surface.
The small U-bolt goes on the outgoing side - ie the one without tension - the cutoff section.

The concept behind all this is that the grip body must firmly 'grip' to the tensioned wire to prevent slipping & hence loosening the wire termination, particularly if not fully/properly tightened. It also allows the final 'wire' lengths to be adjusted more easily as the wire that is pulled through the grip on the u-bolt side is not running against the rough casting.

[VK4WTN]

thanks for the information Doug,I had a look at your site, there is some great info on it.I ended up using speargun shooting line which is 400kg breaking strain and sun resitance, but does have a small amount of stretch, hope it works ok otherwise I will replace with stainless steel. 73 Wayne

[VK4WDM]

Hi Doug (or anybody else)

Any chance of a picture or diagram on the correct way for the grips? This is very important info that I, and everyone else, needs to have correct!

Cheers

Wayne VK4WDM

[ZL1RS]

Maybe Doug can confirm that the top example in the image below is the correct way ...

[VK2FIL]

Another type of rope which can be used is the blue and yellow rope available from electrical wholesalers (TWS, AUSELEC, etc). It is often called "Parramatta rope" (from the color). It is used extensively by Telstra and other authorities for pulling cables through ducts. It is also used as a draw rope and left in duct sysetems and does not rot. I am not sure of the breaking limit.

It is available in 400m rolls for about $80. It is resistant to UV and the weather and has very little stretch, best of all it is cheap. I have used it for many years for staying masts, back stays, as halyard line to wire aerials and many other applications. Compared to other ropes available it probably is the best, next to marine types of ropes.

Hope that helps

Phil VK2FIL

[VK6OX]

Maybe Doug can confirm that the top example in the image below is the correct way ...

The top image IS correct Bob.

A rigger friend of mine came up with a neat little adage to remind me...."Never saddle a dead horse". To translate, never put the cable grip saddle on the tag (loose or "dead") end.