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-   -   Warped 'fibreboard' (?) on Avominor (https://www.vintage-radio.net/forum/showthread.php?t=178584)

The Philpott 5th Apr 2021 8:51 pm

Warped 'fibreboard' (?) on Avominor
 
2 Attachment(s)
Question: Can this be straightened out?

The rear covers on universal avominors are made out of this very tough pressed sort of fibreboard, it's either black, dark red or grey. I am at a loss to know how to straighten it without damage, although i do have a broken one which i could experiment on if anyone has ideas. I doubt very much that the material is significantly porous. I would like to be able to use it as the (riveted on) bakelite battery holder and terminals are very good. De-riveting these items from the board is not viable- they don't take well to being separated.

Thanks
Dave

jonnybear 6th Apr 2021 12:38 pm

Re: Warped 'fibreboard' (?) on Avominor
 
It has obviously warped with damp, I think I would have a go at soaking in hot water then clamping between two pieces of wood, years ago the old cobblers would always have a bucket of water with leather soaking in it to make it pliable.
John

pmmunro 6th Apr 2021 3:32 pm

Re: Warped 'fibreboard' (?) on Avominor
 
Dave,

I don't know if is of any help to suggest that this material may be a grade of Presspahn. (https://www.presspahn.com/product-so...ial-solutions/ ). It might be worth a look at their web-site to see if any information there is useful to you.

Do you think that steam (actually mist in scientific terms) from a kettle or similar would soften the sheet to allow it to be flattened by clamping?

PMM

G6Tanuki 6th Apr 2021 4:52 pm

Re: Warped 'fibreboard' (?) on Avominor
 
In the past I've used a steam-iron on such fibreboard radio card-backs: give the part a good steaming - both sides - then when it's steamy and still too-hot-to-touch put it flat under a foot or so of heavy books to press it down.

Leave for a few weeks!

The Philpott 6th Apr 2021 9:29 pm

Re: Warped 'fibreboard' (?) on Avominor
 
Thankyou all. I am going to steam it over my spare mini-kettle (which conveniently, does not have a switch, so it can produce steam as long as i need it to. Knew i'd find a use for it eventually)

I will mount the fibreboard vertically in a workmate with some spreader boards, with the boiling kettle immediately below, then take up any slack by feel. If this works i can then clamp it between sheets of kitchen roll as it dries.

Dave

The Philpott 9th Apr 2021 7:46 pm

Re: Warped 'fibreboard' (?) on Avominor
 
-Just held it over the boiling kettle with soft-jawed grips and turned a few times. 75% success with the first steaming and clamping, interesting to see a memory effect when the second steaming went on too long. Hurriedly clamped it up and there was a further improvement. Minor dry tweaks to the shape after a day out of the clamp were successful- i THINK that i detected improved malleability when doing these final tweaks, but this could have been a bit of retained moisture. Against my initial instinct, the material IS rather porous! Thanks for your advice. Will leave it a few more days to check stability.

Dave

G6Tanuki 10th Apr 2021 1:33 pm

Re: Warped 'fibreboard' (?) on Avominor
 
Good to hear your steaming is having the desired effect; it's amazing what warmth, moisture and physical restraint can achieve.

[A friend used to make guitars: I once went round to his house only to find his kitchen with a 'cloud layer' extending several feet down from the ceiling, with the aforementioned Alex hunched over a wood-forming contraption made from sections of floor-joist and G-clamps, with _four_ electric kettles on the go to provide the steam...]


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