Re: [TCML] Preparing acrylic coil form

[David Dean <deano@xxxxxxxxxxxxxxxx>]

On Friday 02 May 2008 01:20:00 am Mark Lock wrote:
> Hi all.
> I've been slowly building my first TC for a while now and I've recently
> acquired my coil form, a nice piece of acrylic. My question is what do I
> need to do to prepare it for winding? I've read that it should be cleaned
> with a solvent, sanded, dried and varnished among others, but is that all
> necessary?
> My transformer is 12KV 30mA if that's any indication of how much insulation
> is required.

Hi Mark

The "cleaned with a solvent, sanded, dried and varnished" is fine for the more 
commonly used coil form material PVC, but should be unnecessary  for acrylic. 
Just a removal of grease and fingerprints with isopropyl alcohol, Windex, or 
just some water with a bit of dishwashing liquid. Be carefull of using any 
solvent around acrylic. Acetone will cause crazing, cracking, and the form 
will fall apart. Methyl alcohol (strong concentrations anyway) will dull the 
finish. Coating the form prior to winding is not necessary for sealing 
perposes but _may_ help with winding by giving the wire some traction. I have 
wound three secondaries on acrylic over the years and never used a coating 
before winding. Have never had any problems.

I have used Krylon clear acrylic spray coating over the windings to 
protect/hold them in place after winding. Once when Krylon was not available 
here, I used a clear coat I found in the decoupage area at Hobby Lobby. It 
was fine, and worked just like the Krylon. There is another product that may 
actually be better for the application though I have not tried it myself, it 
is 'Carlon multi-purpose weather gard (tm) spray on rubber coating'. The can 
I have is part number VC9WG5. A 4oz can. Larger can will have a similar but 
different part number. This stuff dries clear like the spray on acrylic, but 
remains flexable when dry. Should be available from Lowes or Home Depot, for 
sure can be found at an electrical supply house where electricians buy their 
wire, conduit, etc. I use it as a substitute for conformal coating on pc 
boards. I have tested it on a scrap of acrylic and it does appear safe, but 
as with any solvent or coating, it is best to try on a scrap first to see how 
it works out before using on the expensive acrylic coil form.

later
deano 
I have found clear acrylic spray coating works well for a topcoat to keep 
windings in place after winding. 
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