[UK-CONTEST] Fibreglass Mast

[Peter Hobbs]

I would never use self-tappers in fibreglass - they loosen quite quickly 
under stress and they chew up the material.  Rivets apply compression to 
the joint and leave the drilled hole smooth.  They also need to be 
fitted at least a mast diameter away from the main stress point, which 
is the top of the lower section you're joining.  A lightweight stainless 
jubilee clip is fitted here to prevent the top of the lower section 
splitting.  This system has been used by the military for at least the 
last 25 years.

73, Peter G3LET

David Gould wrote:

>I have read this thread with interest..  I have always used tape and 
>never had a failure yet..  But have had the mast coating come off 
>when the tape is removed.
>
>I have also had a Cobwebb antenna with the fibreglass spreader tube 
>sections joined together with self-tapping screws, and all 8 joints 
>have cracked round the screws, I am currently home-brewing a more 
>structurally sound version.
>
>However...  I recently happened to watch a TV program about building 
>a kit helicopter.. and the fibreglass sections were held together 
>with a device that required three holes to be drilled quite close 
>together in the fibreglass,  the outer two holes were for rivets 
>which held the fixing in place, and the centre part of the fixing was 
>a threaded nut which went through the centre hole and into which a 
>threaded screw could be used to hold a second panel onto the one to 
>which the fixing was attached.    If I remember rightly there were 
>over 200 of these in the helicopter..  Presumably there must be a 
>reason why cracking is not a risk in this usage, I can't imagine it 
>being allowed if it were a risk??
>
>73,
>Dave, G3UEG
>
>
>
>
>
>
>At 14:35 02/05/2011, Paul_group wrote:
>  
>
>>On 02/05/2011 09:03, Dave Lawley wrote:
>>
>>    
>>
>>>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.
>>>      
>>>
>>Bond - NEVER screw or rivet structural fiberglass.
>>    
>>
>
>
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>  
>


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