[UK-CONTEST] Fibreglass Mast

[CHRIS COLCLOUGH]

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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