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Flocking with velvet fabric

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#1 petrus45

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Posted 05 January 2013 - 10:09 PM

Has anyone flocked a reflector with velvet? I have heard velvet fabric is just about the most light absorbant material available, beating even specialty papers. Apparently you can just spray-glue it in to the OTA. However from what I've read so far the trick seems to be (a) thermal expansion post-install, which can cause the fabric to buckle or tear unpredictably post-installation unless you have properly placed some "expansion joints" in the fabric; and (b) the cut edges of the fabric have to be either hemmed or melted with a candle to prevent fraying.

I have my bolt of very very black velvet (it's like looking into space), and am wondering how to get this attached properly. Any advice?

Pete

#2 shawnhar

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Posted 05 January 2013 - 11:31 PM

Mine is flocked with velvet from Jo-Ann's crafts store.
I promise you no eye could tell the difference between that and the expensive astro flocking material.
Cut the fabric with a brand new blade using a carpet knife and straight edge, no fraying.
Mine is attached with gaffer's tape, double sided tape, been that way for a couple of years with no problem. I ran long strips length-wise down the tube and flattened it as I went around. I never saw any kind of buckling or tearing post installation, even in 100 degree weather.
You could try the spray on fabric glue from an auto-parts store, the kind for gluing a headliner maybe?
I don't know what kind of felt you got but the stuff my wife got me WILL NOT tear...it's like trying to rip a phone book, that stuff is tough!
Good luck!

#3 petrus45

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Posted 06 January 2013 - 12:21 AM

Shawnhar:

Thanks for the tip! Seems like the spray glue may be risky - it has occurred to me maybe the glue solvents somehow interact with the synthetic backing on the velvet.

The tape solutions sounds like it has worked for you, and is standing the test of time. I'm familiar with double sided tape, but what is gaffer's tape? Is there a brand of tape you used? Also, about how far apart are your lengthwise tape strips? Does the velvet lay smooth? Did you tape around the perimeter at the top and/or bottom of the tube?

Thanks,

Pete

#4 johnnyha

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Posted 06 January 2013 - 12:26 AM

The spray glue solvents can also deteriorate the coating on your mirror so be careful with anything like that. I'd stick to the double sided tape - or use flockboard instead of fabric.

#5 howard929

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Posted 06 January 2013 - 12:29 AM

I took a different approach. It cost a bit more but was so easy to do. On a tip from someone around here, I bought a couple of sheets of magnetic plastic and an equal amount of pressure sensitive flocking. Cutting the plastic to size was simple and after the flocking was attached, it went in easily.

#6 SteveTheSwede

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Posted 06 January 2013 - 08:05 AM

Great tip. But aren't velvet usually a bit shiny? Doesn't that imply it reflects light? I am hardly a fabric expert so I'm just asking.

Steve

#7 Tony Flanders

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Posted 06 January 2013 - 09:24 AM

The usual answer is ProtoStar flocking paper. I would worry about commercial velvets for the reasons mentioned by others.

#8 howard929

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Posted 06 January 2013 - 09:38 AM

That's where I bought pressure sensitive flocking, no shine to it at all.

#9 CharlesW

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Posted 06 January 2013 - 10:41 AM

If you can get in touch with a company that provides stage equipment, they have black material that is designed to absorb light. If you don't ask for too much, they might just give it to you.

#10 panhard

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Posted 06 January 2013 - 11:47 AM

I took a different approach. It cost a bit more but was so easy to do. On a tip from someone around here, I bought a couple of sheets of magnetic plastic and an equal amount of pressure sensitive flocking. Cutting the plastic to size was simple and after the flocking was attached, it went in easily.

That is a great idea. Thanks for sharing it. :bow:

#11 precaud

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Posted 06 January 2013 - 12:04 PM

Great tip. But aren't velvet usually a bit shiny? Doesn't that imply it reflects light?


The question needs to be more specific than that. Many materials are good absorbers when the light source is perpendicular to the material. But that's not what is happening in a dob OTA. What is needed is a material that has low reflectance at very low angles of incidence - almost parallel to the material. You can test this by placing the material in between you and a strong light source and move your head until the angle of reflection is very small... as I said, almost parallel to the material.

Generally speaking, the paper-backed materials do poorly on this test. I have a piece of black velvet from JoAnn's that does quite well, called "Royalty 3 Velvet - Black". It is 14.99 a yard.

#12 shawnhar

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Posted 06 January 2013 - 12:31 PM

Generally speaking, the paper-backed materials do poorly on this test. I have a piece of black velvet from JoAnn's that does quite well, called "Royalty 3 Velvet - Black". It is 14.99 a yard.

This is the exact material I used, looking into the tube is like looking into a black hole, my wife picked up a bunch of 9x11 squares on clearance for dirt cheap. It doesn't look like the "shiny velvet" people commonly think of, there is no shine to it at all.
Pete, Gaffer's tape is a little different from regular double sided tape at Wallyworld, it's a much better grade product used in the stage industry. I came across it back when I did roadie work for bands.
http://en.wikipedia....iki/Gaffer_tape I ran strips so that each 11" square had one in the middle and one at the edge. I just made sure the 1st square was perpendicular to the top of the tube and yes, I started with a circle of tape around the top and bottom of the tube. I removed the mirror, focuser and secondary, cutting holes in the fabric after instalation with an exacto, then replace the components. My scope is sonotube and it would be a nightmare to redo it, the tape would most certainly rip out the inside layer of the tube, it is stupid strong and sticky.

#13 enys

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Posted 06 January 2013 - 12:57 PM

i have no experience with a telescope since im here looking for advice on buying my first but ill tell you about spray type glues like 3m . Super strong and tacky and if you get a ripple your probably stuck with it. I build poker tables and glueing the foams to the wood is done this way . It has to be perfect or the table is toast . These glues mostly require each surface to be sprayed and allow a few minutes to get tacky and when you stick them together its an instant bond .....my 2 cents

#14 johnnyha

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Posted 06 January 2013 - 01:50 PM

Protostar flockboard is the best, a little pricey but re-usable. You just curl it up and stick it inside your tube. Also makes a great replacement for kydex in the UTA of a truss scope.

#15 petrus45

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Posted 06 January 2013 - 01:57 PM

There's a cloudynights article discussing testing done on various materials, and Jo Ann velvet apparently outpeformed the other flocking options, including specialty scope paper.Flocking Material Test

I can say anecdotally The stuff I bought from JoAnn is not shiny at all - it is basically like looking into total darkneess.

By the way, I am proud to say I ventured into Jo Ann Fabric all by myself, and looked at several other fabric options, including felt and some lower grade satin-like materials, but the best grade *velvet*(about $15 per yard, 42" wide) was visually the darkest in a side-by-side comparison. I think the sales person was a little taken aback I was shopping for telescope materials, but she was very helpful.

I bought spray glue initially, but based on good advice here :bow: I am going with some strategically placed high grade double sided tape. The sales person also noted the concern the spray glue solvent might degrade synthetic fabrics, so I'm not going to risk that.

Pete

#16 precaud

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Posted 06 January 2013 - 02:22 PM

JoAnn's has lots of great multi-use stuff. A couple years ago I was doing s roof repair and needed some polyester mesh to imbed into the emulsion. JoAnn's had it for 1/4 the cost of the home repair stores. And I didn't have to buy a whole roll of it - I could buy exactly as much as needed!

#17 mfromb

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Posted 06 January 2013 - 03:21 PM

On a tip from someone around here, I bought a couple of sheets of magnetic plastic


Do you have the source information for this material? I've found what I think is a viable product for this, but I'd like to sanity check vs. what you used. Or, if you don't have the info for where you obtained it, do you know the thickness of it?

Wondering if it is the same/similar to this?

http://www.magnetkin.../#regularmagnet

The idea of using a magnetic sheet, aside from the fact that it will add weight to the OTA, seems like an attractive non-permanent solution that can be more readily repaired, replaced, or removed. I'm wondering how thick the sheeting is, as that would no doubt have a significant impact on the added weight.

mark

#18 mfromb

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Posted 06 January 2013 - 03:31 PM

Hmm... anyone tried this?:

http://www.protostar.biz/tubeliner.htm

Would this not potentially share the ease of install/removal of the magnetic sheeting + flocking? And in an 'all-in-one' ready made product? I'll have to do some homework on this, perhaps in the reflector forum. Seems like a pretty compelling option.

mark

#19 mfromb

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Posted 06 January 2013 - 03:51 PM

found some links over in the reflector forum, and on other site forums as well. looks promising. A little more costly than a strictly DIY project, but for not alot of extra money it would seem to be a quick and easy solution vs. a more 'arts and crafts' approach. ;-)

On my wish list, but well behind my desire to get another EP or two.

#20 petrus45

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Posted 06 January 2013 - 04:45 PM

Precaud: What did you use to adhere the velvet?

#21 precaud

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Posted 06 January 2013 - 05:01 PM

I didn't... yet. But I plan on using the 3M #77 spray adhesive, and already have a can of it. I used that stuff for years in manufacturing a different sort of product and it's excellent stuff.

#22 petrus45

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Posted 06 January 2013 - 10:05 PM

You'll want to be careful with the spray glue method, because apparently the velvet material tends to contract and expand somewhat, either due to moisture or temperature.
See: Thread

#23 precaud

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Posted 06 January 2013 - 11:08 PM

That seems rather odd to me, the #77 is a contact adhesive, and needs to be sprayed onto both surfaces to be mated. The bond is quite aggressive... one wonders if that poster used it correctly.

#24 Allan...

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Posted 06 January 2013 - 11:16 PM

Can someone please explain to me why Flocking is so necessary (I'm afraid to try it) and if it IS, then why are the manufacturers not doing it that way from the factory? thanks, Clare

#25 petrus45

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Posted 06 January 2013 - 11:42 PM

Seems like 3M 77 should be the right product.
This to That Website
I am not sure why it failed in the previously-linked example, but maybe you are right it was not applied properly. If you use it, let me know how it goes.






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