[UK-CONTEST] High Winds...Rope ?

Fri Jan 12 06:17:45 EST 2007

Clive and everyone,

I should have corrected that in my post. The rope I use is made by Marlow
ropes specifically to replace the steel rope used to guy masts. It is 8
plait limited stretch (pre-stretched) stuff, and VERY UV tolerant. Mine had
been up over ten years at the previous QTH with no visible degradation.

See http://www.marlowropes.com/public/pageManager.cfm?page_id=199

73

Don, G3BJ

----- Original Message ----- 
From: "Clive Whelan" <clive.whelan at btinternet.com>
To: "Bob Henderson" <bob at 5b4agn.net>; "Adrian Rees" <rees.a at btconnect.com>;
<uk-contest at contesting.com>
Sent: Friday, January 12, 2007 11:09 AM
Subject: Re: [UK-CONTEST] High Winds...Rope ?

> Gentlemen
>
> I would humbly suggest you do not use polypropylene rope for
> guying. Its only advantage is that it is cheap, but its UV
> resistance is poor and its abrasion resistance rather  poor
> also.
>
> I'm puzzled that Bob finds it stretches as this is not a
> known property of the material.  Polypropylene is rigid and
> strong and is a good material for rods, bars and insulators
> ( although its RF properties are debatable), but not guys,
> except in non demanding applications ( e.g. tents). Nylon
> ( polyamide) also has poor UV resistance and high elasticity
> making it quite unsuitable for guys, although possibly
> beneficial for halyards; in fact I have used polester ( see
> below) for everything where financially viable. You might
> have to pay as much per metre as you do for RG213 :-((
>
> The generic material ( non metallic) for guys is polyester,
> and this is the most expensive commonly available rope, as
> may be seen by a trip to B&Q. There are then many types of
> polyester formulated specifically for various purposes, and
> Phillystran is  well known in the U.S. as a very good guy
> material in respect of strength, U.V resistance etc. That
> reputation is based largely on guyed freestanding towers,
> which is a very demanding application. I have used "garden
> variety" polyester rope for guying of masts over many years
> with no difficulties and no need to replace ( caveat British
> levels of U.V.!), and would suggest that it is also quite
> suitable for restraining guys on crank up towers.
>
> I am not an engineer , but I believe the strength will vary
> as the square of the diameter, such that 8mm dia is four
> times as strong as 4mm, but if I'm wrong somebody will no
> doubt correct me.
>
>
> 73
>
>
> Clive
> GW3NJW
> -----Original Message-----
> From: uk-contest-bounces at contesting.com
> [mailto:uk-contest-bounces at contesting.com]On Behalf Of Bob
> Henderson
> Sent: 12 January 2007 10:20
> To: Adrian Rees; uk-contest at contesting.com
> Subject: Re: [UK-CONTEST] High Winds...Rope ?
>
>
> Hi Adrian
>
> You say your biggest problem will be getting your towers up
> or down in high
> winds.  I assume you are talking about crank-up towers in
> that case?
>
> The first part of the above problem is easy to answer.  You
> never attempt to
> crank a tower up in high winds!  The answer to the second
> part of this, is
> that when you have crank-up towers you need to take steps to
> be aware when
> high winds are likely.  You then crank down your towers in
> advance.  If you
> get caught out and your towers are up while high winds are
> developing and
> the sections become locked together due to wind pressure
> then you will need
> the assistance of a second person if you are to stand a
> chance of retracting
> the towers.
>
> Now to the issue of guying.
>
> You should understand that crank-up towers are mostly NOT
> designed to be
> guyed in the way a fixed tower would be.  The accumulated
> tensions in the
> guy system translate into a downward force on the tower
> itself for which it
> is not designed.  Ignorring wind, this force is a dead
> weight headload, all
> of which would have to be supported on your tower cables.
> This is not a
> great idea, as it substantially reduces the usable headload
> of the tower.
> That said, the attachment of low tension guys for the
> purposes of
> stabilisation in modest wind conditions is of benefit and
> this for two
> reasons.
>
> 1. These will stop your towers from leaning uncomfortably
> and looking untidy
> in modest winds.
>
> 2. They provide a means by which a second person can assist
> you in
> retracting a jammed tower before the winds get high enough
> to cause serious
> damage.
>
> I have used the same P80HD for 12 years now and it has
> always been heavily
> (over)loaded.  Currently it supports a F12 C31XR, a
> Cushcraft XM240, a 5 ele
> 6m yagi  and an 80m delta loop, all on a very heavy 20ft
> chrome molly mast.
> All the above apart from the delta loop are rotated by an M2
> Orion rotator.
> I use 10mm polypropelene rope to add stability to the
> system, providing the
> benefits detailed in 1 & 2 above.  If it looks like it's
> going to be
> dangerously windy I retract the tower to about 45-50ft.
>
> Yes the poly rope stretches.  That's ok for this purpose.
> It's also not UV
> stable over long periods.  I have to change mine every two
> years here but we
> see more sun than you do.
>
> I hope this helps you with your planning.
>
> 73
>
> Bob, 5B4AGN
>
>
> ----- Original Message -----
> From: "Adrian Rees" <rees.a at btconnect.com>
> To: <uk-contest at contesting.com>
> Sent: Friday, January 12, 2007 9:48 AM
> Subject: [UK-CONTEST] High Winds...Rope ?
>
>
>> Hi all
>> Well with the high winds we've been experiencing (my home
> WX Station tells
>> me gusts up to 91MPH) I've been thinking about what type
> of rope I'll need
>> to use to guy my towers.
>> Steel or Stainless Steel would (I guess) be the strongest,
> but that has
>> the problem of Resonance (unless of course you break up
> the lengths with
>> insulators).
>>
>> Anyway, what suggestions does the list have for guy rope ?
>>
>> I have been looking at Phillystran, but wonder if a
> cheaper-just-as-good
>> version exists in the UK ? If so who supplies it ?
>>
>> As my QTH is on an exposed hill, its been pointed out that
> my biggest
>> problem will not be when the Towers are up or down. The
> problem will be
>> getting them up or down in high winds.
>>
>> Adrian MW1LCR
>>
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