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General Aircraft: Tips & Techniques
Discussions on specific A/C building techniques.
Canopy Trouble...
Merlin
Staff MemberSenior Editor
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#017
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United Kingdom
Joined: June 11, 2003
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Posted: Thursday, November 19, 2009 - 07:57 AM UTC
Hi there

Ever come across a problem like this?:



The vacuformed canopy in my Planet Models Flitzer has yellowed while it's been in the stash. I've just checked the pic in my 2005 Review and it was fine then. The canopy has been wrapped in tissue and kept out of direct sunlight, so that can't be the culprit.

As you can see, the yellowing is worst on the spare plastic around the canopy - it gets less apparent as the plastic gets thinner - but, does anyone know of a fix? Bleaching somehow?

All the best

Rowan
Siderius
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Tennessee, United States
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Posted: Thursday, November 19, 2009 - 08:49 AM UTC
Have you thought Rowan of placing the canopy in direct sunlight. Like a decal sheet. Might the Ultra Violet radiation help things out. I'm just guessing. Russell
Merlin
Staff MemberSenior Editor
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#017
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Posted: Thursday, November 19, 2009 - 09:00 AM UTC
Hi Russell

I was wondering about that, but was scared of making it even worse. Of course, I could always try with one of the cut-offs.

Trouble is - England in November... how long will I have to leave it on the window sill to get sufficient sunlight?!

All the best

Rowan
alpha_tango
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Germany
Joined: September 07, 2005
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Posted: Thursday, November 19, 2009 - 09:07 AM UTC
Hi Rowan

already posted several times in diff. forum: no cure, make new one

Depends on the material used. Forgot which. i have one that is brown .... (Karo As Vaku)

all the best

Steffen
Merlin
Staff MemberSenior Editor
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#017
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Posted: Thursday, November 19, 2009 - 09:15 AM UTC
Cheers Steffen

Well - I guess i can always put it down to the quality of Luft '46 perspex suffering a bit due to poor materials.

I did spot similar yellowing on a short-run vacuform kit when I was packing the Stash this year. I can't remember which, but it was probably 20+ years old. I'm surprised (or should that be "worried") to see it on a 4-year old kit...

All the best

Rowan
Siderius
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Tennessee, United States
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Posted: Thursday, November 19, 2009 - 09:38 AM UTC
Rowan, if natural UV light isn't available what about finding a source for artificial UV light and bathing the canopy in that? Might that work? Russell
LuckyBlunder
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Kansas, United States
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Posted: Thursday, November 19, 2009 - 08:35 PM UTC
Hi Rowan -

You mention that the canopy was wrapped in tissue paper. As an old coin colector I know that silver coins placed in those little paper "collector" books will, over time, obtain a golden color called a patina. This might be the cause of the yellowing. It is caused by sulphuric acid used in the manufacture of paper.

I'd try a tthorough wash and polish with baking soda. Of course, I may be totally off base.

Steve

alpha_tango
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Posted: Thursday, November 19, 2009 - 08:45 PM UTC
mornin all

strange why nobody believes me, but then, what do i know...

Rowan, have a look at HS Plane talking its been a few weeks since this has been asked and someone made a longish chemical post what material will yellow and that it is the material that goes bad over time.
(maybe it was this thread: Age Related Vacuform Canopy Yellowing Problems.... Any Solutions?)

Especially since yours is such a young kit I am pretty convinced that nothing will cure the problem but you might destroy your only master in trying. Make at least a plaster copy before you try to use aqua regis to "clean" it ...

all the best

Steffen
Merlin
Staff MemberSenior Editor
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#017
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United Kingdom
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Posted: Thursday, November 19, 2009 - 09:29 PM UTC
Cheers everyone

I will try cleaning the cut-offs, but I doubt it'll do anything - the fact that the thicker the plastic, the darker the yellow, convinces me it isn't a surface effect.

I will definitely make a mould as Steffen suggests - even if I do use the original for now, I've a nasty feeling the yellowing will just get worse with age, to the point where the canopy is almost opaque (I've just remembered that I threw away a JGMT Caudron C.714, because the canopy had turned dark brown in the 15 years it'd sat at the back of the shelf).

All the best

Rowan