Removing paint and gunge from inside OTA

[pmrid (Peter)]

One of my lingering projects is restoring an 8" Celestron Newt that has good optics but a dreadful tube. In a past life someone has first tried to paint the inside of it and embed sand in the paint. That didn't work because the sand (or whatever it was) turned out to be very reflective. So they flocked it but of course, the adhesive didn't take too well to the rough sand subsurface and soon enough, it becan to buckle and pull away. That's when I bought it (for good money but ignorant of this little piece of it's history that the IIS seller chose not to share).

So now I have a problem - how to take the tube back to metal so I can start again.

ANy ideas?

Peter

[DavidU (Dave)]

It depends on what the tube is made of. Aluminium requires Aircraft paint stripper, standard paint stripper is ok for steel.
I can't see any other way around it.

[bmitchell82 (Brendan)]

sand blasting always makes short work of anything !

[ZeroID (Brent)]

Bit of extremely hot air appplied to the outside might blister the worst off. One of those hot air paint stripper guns long as you can remove all other attachments. Don't think I'd use a flame as it might get too hot and melt especially aluminium.

[cristian abarca]

I'd use auto paint stripper. Available from auto paint shops. A litre should do it. It's stronger and quicker. Just don't let it dry.I'd also use this type of scraper http://cgi.ebay.com.au/PAINT-BRUSH-B...item43a118b3f5 available from bunnings. Follow the instructions in the can. Don't use hot water to clean the paint stripper of the tube only cold water. Wear protective gear, glasses,gloves etc.

Cristian

[pmrid (Peter)]

All good ideas and many thanks.
I was in the local hardware this morning and had a rush oif blood to the head when I spotted some of the new types of sanding discs for angle grinders.
I bought 2 types - one was a disc with a whole heap of small overlapping sheets of sandpaper arranged around the circumference like the inlet fans on a jet engine. The other was a disc with a thick brillo-pad sort of thing, a hard blue scouring pad sort of material. Becasue I'm working on the inside of an 8" tube, these both looked promising. Having now done the job, I can vouch for both but strongly recommend the scourer-pad type. As the pad wore down at the edges, it conformed more and more to the inside shape/profile of the tube and became more effective as more of the pad came into contact at any given time. It really ripped the dickens out of the gunge in there and brought it back to nice clean and shiny steel in no time.

Peter.

[astronut (John)]

After all your hard work, I would recommend that you take it to a Powder Coater and have the tube professionally finished.
PC is a very durable finish (will literally last forever) and you can choose the external colour. They will also finish the interior as well.
A friend had their 12" (Grey) GSO tube PC white for $45.

[DavidTrap (David)]

I agree with powdercoating the exterior, but glossy black powdercoating on the inside might cause a few reflections. Are you planning to "flock" the interior Peter?

DT

[pmrid (Peter)]

Originally Posted by DavidTrap

... Are you planning to "flock" the interior Peter?

I was. I've so far been to 3 Spotlight stores looking for some black felt with an adhesive backing but they all seem to be out of it. Any ideas for alternate sources of decent flocking material (short of importing some from Protostar or some such).
Peter.

[peter_4059 (Peter)]

Spotlight in Everton Park had it just before Astrofest.

[bert (Brett)]

Instead of using adhesive backed material, you could use contact adhesive.

I sewed up a shroud for my vc200 truss recently and used a tracksuit type material, its a little shiney on the outside and a black hole on the inside.

Brett