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Flocking a newt - help

Astronut

By Astronut
in DIY Astronomer

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Astronut

Astronut

Posted
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I'm at the planning stage. I have enough of the extremely black ("how much more black could it be?" Answer: "none! none more black!" Spinal Tap :( ) self-adhesive material from Scopestuff to do the whole tube (2 rolls of 2ftx47" and 1 roll of 1ftx47") but I'm undecided on the application method. The instructions recommend cutting the material into 3" wide strips and applying each strip longitudinally along the tube as expansion and contraction of the tube and changes in humidity could possibly cause the material to wrinkle if it's applied as one piece right around the tube.

Before it arrived, I was planning to peel the backing off the material on one edge and apply this edge longitudinally along the tube seam (for alignment) and slowly work around the circumference peeling the backing off bit by bit and pressing the material to the tube until I meet the first edge with an overlap of about half an inch. I've made a template of the circumference with 4 sheets of A4 paper taped end to end and then running this long sheet of paper around the inside of the tube circumference, marking the overlap and trimming the paper to the correct length ie. the circumference - this measures as 43".5. As the material roll is 47" long this gives me plenty of extra length for overlapping the edge (or edges if I apply it in 8 strips of roughly 6" width which I think would be more do-able than 15 or 16 strips of 3") but....

...how much of a problem is contraction and expansion of the tube going to be? Has anyone who's done the whole tube and used the 'scope a few times since noticed any wrinkling or peeling?

It seems to me it might be easier to apply it as one piece rather than cutting it into strips because with strips I'd have to make sure that each strip was cut accurately (I have no straight-edge or set-square but I'm prepared to get these if necessary) and if the overlaps of each strip were slightly misaligned along the length as I worked around the tube then the final overlap could be way out. Seems like alot of extra room for error to me and then there's the other rolls to do overlapping the first bit to consider - arrrrgh! I see this is going to take some time to do it right.

Help :? .... what would you recommend? I know someone recently applied their flocking material to a piece of pre-measured and cut card first and then fitted the flocked card to the tube (ie. a tube within a tube). Seems like a straightforward and elegant solution (especially with a smaller aperture tube with little room to work inside) but I'd rather apply the material permanently to the tube as I think a piece of backing card might get damp with dew over time.

Decisions, decisions ;)

Ian

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philsail1

philsail1

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Hello Ian,

Yes, I flocked my 8" Newt by sticking the flocking materiel to two pieces of pre-measured card, then sliding the two pieces inside the tube - one from the main mirror end and the other from the open end. I've had no trouble with damp or wrinkling.

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However, I have noticed recently that a tiny bit of flocking has curled away from the edge of the card. I will simply remove the "spider" and then slide out the flocked card, to glue the bit down.

I lost my nerve when I thought of trying to stick the flocking to the inside of the tube. (there just did not seem to be enough room to manouvre ones hands inside the tube - and see what you are doing at the same time!).

However, if Andrew has done it in one piece, then it can be done!

Best wishes with whatever method you choose!

philsail1

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Astronut

Astronut

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Thanks Phil and Andrew. Phil - I don't think I read through your original thread properly because I didn't realise you'd used 2 half-tubes. I don't suppose you're bothered about the visible ring where the 2 tubes meet in the middle but it would bother me. It's difficult to tell from your photo if one tube overlaps the other in the middle or if the two ends butt together. With the 3 rolls I've got there's going to be some overlapping involved anyway so I'll pass on the card tube method if you don't mind. It's a great idea though especially for owners of smaller diameter tubes where there's no room to work.

I've had a bit of a rethink tonight while distracting myself and taking a trip over to my Mum's house to set up her new TV and I've had a flash of inspiration - I'll use some string for a guide (see later).

I've been experimenting with overlapping edges with the sample rectangular pieces supplied with each roll (the overlapping edges stick really well - much better than expected) and have decided that the strip method might be a better idea after all. It may take a little longer but I think strips may be easier to manage. I did a trial run (leaving the backing on) spreading the whole roll around the tube and it's quite tricky to handle such a large piece in a confined space - kudos to those that have done it in one. This material doesn't have any discernable give or stretch to it (unlike felt) and I'm beginning to feel that following the manufacturer's recommendations may be the wise thing to do but I'll compromise and use 6" strips instead of 3".

I've found a suitable metal straight edge (an old carpet door brass strip) and I know I have a protractor lying around somewhere so it shouldn't be too difficult to cut reasonably consistent 6" wide strips with the straight edge and a stanley knife. As I'll be overlapping each edge by a quarter or half an inch (instead of butting two edges together) then the edge cutting won't need to be too critical - reasonably straight should be OK. This is the inspiration bit :) - I'm going to use a piece of thin string and tie it from one end of the tube to the other along the inside (starting with the tube seam) to use as a guide when laying each strip. I'll move each end of the string around the circumference 5".5 (for a half inch overlap) for each successive strip. Obviously, the final strip on each of the 3 trips (one for each roll) around the tube will be less than 6" wide so a quick remeasure and trim with the knife will be required. I'll start at the business end and use the smaller 1ft roll at the mirror end. Should be plenty of material left over too for the secondary edge. I think I may very carefully blacken the bevelled edge of the primary too with a permanent marker pen because I can see it as a ring of refracted scattered light when looking down the tube through the small removable cap hole of the tube dust cover with the focuser cap on (closed tube) and backlighting the primary. I may do this at a later date though and just concentrate on the tube for now.

Hey, it's a plan and it may work well :(

Mission for tomorrow - strip cutting and if I'm up early enough and I get no distractions I may motivate myself to knuckle down, strip the tube bare of all its bits and bobs and complete the job. ;)

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Andrew*

Andrew*

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Astronut,

you're probably wise not to use my method with your material. The fact that felt is stretchy somewhat facilitated getting it all flush and straight. Also, it took quite some time to do, and two people were required.

Best of luck on the job - and you be careful with that pen :shock: . Rather you than me!

Andrew

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philsail1

philsail1

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That's OK "Astronut." The exposed edge didn't bother me (until you mentioned it!!) No, seriously though, I will remove one of the tubes and stick a narrow strip to overlap the other when I sllide it back in.

You go ahead and proceed with the method of flocking that you feel comfortable with. It's the end result that counts, and as long as it darkens the inside of the tube it doesn't matter how you do it.

"Blinky." I can't say whether I've noticed any real difference since flocking my 8" Newt. (I don't think I can remember what it was like before!). I think it might be psychological - "the tube looks nice and dark, so it must do some good!"

Regards,

philsail1

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Astronut

Astronut

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I know some people only flock the area underneath the secondary - might be worth doing initially to see if it does make a difference?

From what I've read, flocking just that area has the most effect but with me, as always in all things, it's 'all or nothing' - 'in for a penny, in for a pound' as they say. ;)

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Astronut

Astronut

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No Problems "Astronut." Thanks for your eyepiece info!

Hope the "flocking" is going OK for you.

REgards,

philsail1

I haven't started yet. I was going to cut the strips yesterday but something came up and even though I'm off work for the next 2 days my cousins from Canada are arriving for a weeks stay later today so it's all on hold for now. I bought some Isopropylene Alcohol in a 400ml spray can from Maplins yesterday for cleaning the inside of the tube before applying the strips. The labelling on the can doesn't state the purity so I'm not going to be tempted to use if for cleaning any optical surfaces but it should be just the job for getting rid of any grease spots on the inner tube surface. Preparation is everything ;)

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