[UK-CONTEST] Fibreglass Mast

[Paul Beecham]

Dave et all,
Slippage is a problem with these type of mast. I have 5 of them here 4
x 18m and 1 x 25m. All have suffered and I have tried different
methods to stop it.  Mechanical  methods at the joint, rivets, jubilee
clips, pins, nuts and bolts stop the slippage but have caused
premature failure at the joint when under load.
What has worked for me is a good quality PVC electrical insulation
tape wrapped carefully and stretched when applied for 4 inches on the
upper part of the joint.  I tapered the wrap away from the joint so
that the diameter of wrap is smaller at the joint and increases as it
moves away. It is important not to tape over both parts at this stage
when applying this wrap.  A good application of tape is necessary to
stop itself  slipping on the pole . I then tape over both parts of the
joint with a few turns and then finish off by covering all with a self
amalgamating tape to keep the elements out. When finishing  a
stretched tape wrap the last turn should be applied with out "stretch"
and cut cleanly with a knife or scissors, this stops unravelling.
Spiderbeam sell rubber sleeved jubilee clips but I have heard of
failures using this method due to over tightening, but have not tried
it my self.

73 Paul
G6PZ

On Mon, May 2, 2011 at 11:14 AM, CHRIS COLCLOUGH
<chrisg1vdp at btinternet.com> wrote:
> Just a word of warning on drilling fibreglass, it is not recommended because it
> can cause stress fractures. This is from experience where a short (4M) pole was
> used to extend a piece of aluminium tubing to make a 30M vertical, the
> fibreglass eventually split around the drilled hole for the screws used.
>
>
> Good luck.
>
>
> Chris Colclough
> G1VDP
> http://www.g1vdp.com
> http://www.mc0shl.com
>
> "If you ain't the lead dog, the scenery never changes"
>
> Tel: 024 7673 5940
> Mob: 07814 374921
> QTHR
>
>
>
>
> ________________________________
> From: Andy Cowley <andy.cowley at uwe.ac.uk>
> To: "uk-contest at contesting.com" <uk-contest at contesting.com>; dave at g4buo.com
> Sent: Monday, 2 May, 2011 11:05:39
> Subject: Re: [UK-CONTEST] Fibreglass Mast
>
>
>> Message: 6
>> Date: Mon, 02 May 2011 09:03:47 +0100
>> From: Dave Lawley<dave at g4buo.com>
>> Subject: [UK-CONTEST] Fibreglass Mast
>> To: UK Contest Reflector<uk-contest at contesting.com>
>> Message-ID:<4DBE6563.9000507 at g4buo.com>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> I'm currently using a mast of about 38ft to support a doublet. Most of
>> the mast is made of a telescopic fibreglass mast bought on eBay. I
>> removed the top two sections as they are very flimsy, and attached light
>> wires and 300ohm feeder to the top with cable ties, making a lightweight
>> structure.
>>
>> Each joint in the mast was pulled out to a tight fit, then taped and
>> finally a cable tie installed over the top. It is guyed at the top and
>> middle.
>>
>> However, in the strong winds of the weekend a couple of sections have
>> telescoped and I now only have a 30ft mast for entry in this evening's
>> 80m CC contest! This was mainly due I think to wind pressure on the
>> wires and guys applying a strong compressive force on the mast.
>>
>> My question to UK-contest is what is the best way of fixing the
>> sections? I'm not too bothered about being able to telescope the
>> sections again so I could glue it, what type do you recommend or
>> alternatively would it work to use rivets to fix the joints? Any other
>> suggestions gratefully received.
>>
>
> Fibre glass resin or Araldite - use the regular, not rapid, and
> apply it hot, when it is much less viscous. Get some inside the
> outer section and pull it nice and tight. Jubilee clips are fine
> for temporary stuff but a good glueing job will be much more
> robust for a permanent solution. Apply fibreglass tape and
> resin/araldite above and over the joint for a real bomb proof job.
>
> Warming the joint with a hair dryer/hot air gun before it sets
> will help with glue penetration and give a nice glossy surface.
>
> Getting Jubilee clips tight enough without over-stressing the tube
> or providing a sharp corner/stress point to encourage snapping under
> stress is very difficult. Good luck in the contest tonight.
>
> HTH
> 73
>
> Andy, M1EBV
>
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