[UK-CONTEST] Fibreglass Mast

[Paul_group]

On 02/05/2011 18:16, Stewart Rolfe wrote:
>
> Folks,
>
> Spiderbeam are very clear about how their jubilee clips should be used to prevent slippage,

All this talk of military masts, Spider beam poles and helicopters is 
very interesting but none of it relates to G4BUO's poles which he bought 
off ebay. The construction is described as thin and flimsy that suggests 
they are fishing rod blanks or roach poles.

They only remains strong if they are kept in tact and are jointed by 
spreading the load over the entire joint.

The long term effects of joining structural fiberglass and rp composites 
isn’t really fully understood yet however there are of course experts / 
engineers who do know enough to design fasteners  that are safe and sound.

This fishing rod mast really only needs two considerations. Do we need 
to disassemble or not and do we care (risk to life or property) if it fails.

Taped solutions are at best temporary, maybe a few years and that’s 
probably enough for an amateur mast but in theory can be taken apart and 
re made many times. If it fails its probably an inconvenience rather 
than life or death.

G4BUO said he didn't care if he couldn't take the joint apart so a 
bonded solution is best.

A bonded joint done properly doesn’t suffer from deterioration any 
faster than the original construction material – it will be stronger 
than the original material and it will not place stress at a single 
point or edge. A fishing rod  joint roughened with 80grit paper to cut 
the Gel coat and resin bond, preferably a uv cure variety will not break 
or collapse. Over expansion of the two sections is not necessary using 
this technique.

Jubilee clips damage the fiberglass even when done up finger tight and 
create an edge – nothing else considered that is where the joint will 
fracture.

Rivets place stress at a single point and will be the point that splits 
occur.

Self tapping screws are the same but  worse as they open and damage the 
fibers.

If the construction material is stronger or even just a bigger section 
such as the arms of a StepIr or these Spider poles then the design 
margin is greater  and careful use of clamps and tape will probably be 
ok… but in these cases we are sacrificing strength for convenience.




-- 
73 de Paul GW8IZR IO73TI
http://www.gw8izr.com