RE: [ATM] RE: RTV Silicone question

["mbyorick" <mbyorick@starband.net>]

Mike Lockwood noted:

>Art suggested first sanding the PVC, then coating it with a thin 
>layer of epoxy.  The epoxy can adhere to the PVC.  Then, we glued the 
>secondary to the epoxy layer (rather than the PVC), to which the 
>silicone can adhere.  

I'd add that Devcon "Plastic Welder" (sold at Wal-Mart), adheres
extremely well to PVC, has a tensile strength of 3500 psi, and is cheap.
When I was testing various epoxies (on aluminum), I 'plastic-welded' a
piece of (not-sanded) PVC pipe to the END a 1" x 1/4" piece of aluminum
- to my surprise, the (1/4 square inch) joint is practically
indestructible...

BTW, (contrary to what was indicated in someone's previous post)
"Silicone II" (a GE brand-name product) is <not> acrylic latex-based,
but is rather 100% silicone.  My 16" mirror is presently glued (quite
firmly) to its cell with 18 blobs of the stuff.  I even stow the scope
with the mirror facing slightly downward (takes up less space in my
obs.).  I'll report back every 12 months or so to inform interested
parties whether the mirror is still in place!

Mike Byorick
SW New Mexico

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