I'm going to replace the 5/16" Dacron lines that hold up my main antenna. They've been up for two years and have withstood some phenomenal weather, particularly because they are just thrown over some 70ft tall pine trees with no pulleys or anything. So they are getting replaced as preventive maintenance.

I was thinking it would be easy (and expensive, but still easy) to find some Kevlar or Spectra line to replace them with and make the entire mess ridiculously strong, but my Google Fu is weak on this one and I can't seem to find anything appropriate. Does anyone have suggestions for something better than the usual UV-resistant Dacron?

Let me get this straight...

Your dacron which has been badass needs replacing and you want to put up something that might not be badass?

I don't actually know what I'm talking about here, so feel free to ignore me, but...

I'm wondering whether Kevlar would be too stiff and not stretchy enough - wouldn't you want to have some 'give' in the line that supports a wire antenna?


I'd also wonder about abrasion resistance of Kevlar.

But then I haven't been on a sailboat now for probably 10 years and I'm too lazy to do a google search to see if they use Kevlar for mooring lines where stretchiness can be a plus, or only for halyards and sheets and the like on a boat, where both strength and lack of stretch are needed.

I'm not sure I understand what you are trying to say?

The Dacron has either been lucky, or bad-ass, or both. In either case, it is now also OLD, and probably bears replacing.

I want to put up something that is more abrasion resistant and that has greater strength than the 5/16" Dacron. If I can't identify something with those properties in an appropriate diameter, then I will simply replace Dacron with Dacron. But since I want to (probably have to) go through the replacement exercise it is worth considering other, potentially superior, options.

I'm simply pointing out that the solution you have has worked well by your own admission.  Why not just replicate it?  Buy the same, or thicker, dacron, and systematically drop each line and re-tie with new dacron.

DX Engineering sells Mastrant synthetic rope that works well for antennas. Mastrant rope.
I personally used 3/16 Phyllystran Aramid fiber guy rope to support the beam on my Mosley Yagi. The Phylistran has a 4000 lbs break strength ans is flexible and non-conductive. Link to Phyllystran.

@stimpsonjcat--good point, and that was my original plan, but as my fingers reached towards the keyboard to do that I got the idea that maybe it was worth seeing if I could do better. As it turns out, thanks to @Gyprat, I can!

BREAK

@Gyprat--I was not looking at the Phyllistran, thinking that was too expensive (and it is!) However I had not, surprisingly, heard of the Mastrant brand. Mastrant offers both double-braided poly jacket/core and the same with an Dyneema aramid core. The Dyneema cored product is just what I'm looking for, but blows the budget at three times the price of normal polyester (Dacron) . More interestingly, their poly-only product claims half again the breaking strength of the "normal" 5/16" Dacron offerings.

Knowing that most rope comes from very few mills, and that "Band-Aids" cost more than "adhesive bandages", I looked for other sources of the Mastrant poly rope with the higher breaking strength. Pricing did not change by very much, but KF7P has what appears to be the same stuff as Mastrant and without the stupid blue stripe. I think that is what I'm going to go with, thanks!

SAMSON ROPE
AmSteel®-Blue Single Braid, 5/16" Diameter, Green 13,700lb breaking strength
$1.88/ft
That should be strong enough!

https://www.westmarine.com/buy/samson-rope--amsteel-blue-single-braid-5-16-diameter-green--6331011

7/64" $.31/ft   1600lb breaking strength

FWIW I use 550 paracord. I may be doing it all wrong but thats what I use. Anyone got a better idea I am ALL ears.

That being said, Kevlar and Spectra have NO stretch and do NOT handle chafe worth a fiddler's fuck.

You WANT both the ability to handle chafe and you need stretch. You need stretch of some sort because SOMETHING'S gotta give on windy days.

Been using bank line. Its shown no degradation.

@JBT ...but too expensive. Nice stuff, though!

@piccolo -- I used to use 550 cord, but it did not prove strong enough to deal with the swaying of the big pine trees. Hence the transition to 5/16" Dacron two years ago.

Amsteel is big in the hammock world. It is used for super lightweight but strong endless loops.

Damned little is going to hold up to the swaying of big pines in a spring or fall bluster.

I tie one end to the antenna and the other end to a counterweight and use that as a shock absorber.

I also put a pulley with a counterweight on one side of a wire antenna if the antenna is tied to trees. Currently I only have several dipoles (in Inverted V configuration) with the center feedpoint tied to my tower at about 60 ft. level. The ends of the dipoles are tied to the bottom half of the trees. I simply leave some slack on both ends to allow for slight tree trunk movements. All dipoles were hung with 3/16 black antenna rope from HRO.
I also used a pulley and a long rope for the center of each dipole. This way I can raise and lower the antennas without having to climb the tower.

The picture below shows the 7 ft long arm, 15 ft below the Yagi. The arm has pulleys on both ends. There is only one dipole on the picture. I added more later.

My installation has held up in many storms over the last two years, including several with 50KN gusts. Just lucky, I guess...

If you just have rope thrown over trees with no pulleys then this will cause the tree to saw right through the rope where it goes over the top. Learned that lesson the hard way. No pulleys = no counterweight approach. Things must stay reasonably taught and un-moving. I do leave a few feet of slack (sag) in the antenna between trees. Combined with the inherent stretch of the Dacron this seems to work OK. No stretch in the 13AWG copperweld between the Dacron, though

Just started using Mastrant over Dacron, so far so good. By all accounts should hold up well.

For my heavy duty support through trees for my low band Inverted L's I had to go to 3/16" 7x19, Vinyl Coated Galvanized Cable as even the heavy Dacron would not hold up. I bought mine at http://www.e-rigging.com/  from their Bargain Bin as I did not care about the vinyl color. Has made a huge difference.

Fantastic idea, @6290LE! Thank you! 4000+ lbs breaking strength, and cheaper than Mastrant. I think that's what I'm going to use.

I got tired quickly of the tree branches destroying even the Kevlar Dacron, so galvy steel rope was inexpensive and handled well. If that breaks I have a lot more issues!

Now I am only using this for the length that goes up the tree and over, then Dacron/Mastrand from there to the ends of the Inverted L.

What he said. I've been using the same paracord going on 7 years. I've had tree branches fall on my antenna, and the copperweld wire snapped while the paracord remained intact. It does have a little spring to it, and hold up well in the elements. Some folks poo poo it, but I have yet to figure out why.