Fixing 2m Tonna Dipole with Polymorph

What is Polymorph? Polymorph’s full name is Polycaprolactone which is basically a mouldable plastic when heated, normally in warm water.

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The problem I had, which seems to be a common one, is the threads for the thumb-screw which holds the driven element to the boom on the 2m 17 element Tonna used by G3PYE/P had all but gone meaning the driven was getting held in place with cable ties meaning it could be misaligned with the other elements reducing performance.

Polymorph came to the rescue by being moulded to creating a new threaded section, but there was a little preparatory work needing done first. The original hole the thumb-screw went into was not going to be big enough to add polymorph with sufficient quantity to create a strong bond and thread.

As shown in the image below, the the original hole was made bigger with and side channels created at 45 degrees to better hold the Polymorph in place.

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While the Polymorph was still hot and pliable I inserted (by screwing and NOT just pushing in) the original thumb screw so the thread would be set into the Polymorph once it hardened.

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Any excess Polymorph was cut away and filed flat so the driven element plastic mounting would sit flush to the boom.

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This is the final result.  The driven is now held in place without issue on the boom, you could of course just go out and buy a new driven element, but that’s not HAM RADIO!

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