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Discussion in 'Scratch Built' started by neil_w, Oct 31, 2019.
Every time I read the title of this rocket, I can't help but think of the Premium dancer:
Hey this is cool:
Cut by my co-worker on his bandsaw, 3/32" polycarbonate. These still have the protective film on (I guess you keep it on as long as possible). In hindsight I'm pretty sure 1/16" would have been sufficient, but these will do nicely. I got extras in case I mess any up. There is a fair bit of clean-up sanding to do here, and we'll finish up by flaming the exterior edges (that would seem to be the time to rmove the film).
Still haven't gotten my parts orders in... trying to resolve some nose cone uncertainty.
sport scale Super Deluxe #2 Skywriter XL Premium Pro Max......
Very limited. I heard they only made one, and even then I don't know if it was ever finished
"Very limited. I heard they only made one, and even then I don't know if it was ever finished"
I read somewhere the manufacturer had trouble procuring the parts needed to build the prototype.
I sanded the three best-looking fins, and got the edges looking pretty good:
Pretty good is not good enough, though, so we'll be flame-polishing these guys in the near future. Knowing that was to happen, it seemed a good time to remove the protective film and see what they look like:
One thing I learned: it's pretty darn easy to scratch polycarbonate. I have some polishing ahead of me.
This suggests that in the real world, these guys are gonna get scratched up. But they sure ain't gonna break.
Would it make any kind of sense to clear-coat the finished fins for scratch protection?
Unless you accidentally sit on 'em.
Don't know, interesting idea!
If you broke it, it's probably not polycarbonate.
If you look at the edge it should be bluish. If it looks white or yellow it's definitely not polycarbonate or Lexan as the trade name. If you look at the pics of Neils fins edge on you'll see the bluish tinge. Look at them flat on you'll see a dark edge. Definately polycarmonate. In your pic Kurifin the fins have a clear/ white outline. Probably not polycarbonate.
Polycarbonate is very easy to scratch. Incredibly tough, but not strong. So it will bend but not break.
If you vacuum form it you should preheat in a low oven to drive off moisture. It absorbs moisture which if you don't get rid of will give you bubbles if vac formed.
For polishing ( if you can't flame polish) work up to 2000 grit wet and dry then polish with toothpaste. Works a treat and gives them a nice minty smell. If you flame polish you'll likely get bubbles on the flame polished edge due to the moisture retention.
I don’t know that normal clear coat is particularly scratch resistant. I wonder what the coating used for eyeglasses is.
Think I could take these to the eyeglass shop and get a Crizal coating put on them? Answer is most certainly "no", but it's fun to think about.
Aren't there eyeglass lenses made of polycarbonate? I would think you could get it Crizal coated. Worth inquiring into anyway.
I really don't think that's possible. Other ideas:
1) apply smartphone screen protectors to each side. Downsides: weight, hard to cut exactly, possibility of edges lifting
2) Apply Rain-X. Doesn't harden the surface, but lubricates it so that contaminates will slide off rather than dig in
As far as I can tell there isn't really any good DIY chemical scratch protection process.
Hindsight: there are scratch-resistant polycarbonates out there, although I don't know how hard it would be to a acquire a small piece. I will make do with what I have.
I'm not sure it would adhere well, or finish smoothly, but what about clear nail polish? I've used that before when I needed a hard and durable finish. But I've never tried to cover a large area such as the side of a fin.
Free sample here:https://www.weetect.com/scratch-resistant-polycarbonate-sheet/
There are also coatings that can be applied, but not for the DIYer, since they must be applied and cured with special equipment.
Probably cost prohibitive.
I sent them an email. Doubt small quantities will be cost-efficient to obtain here, but who knows.
You should ask Corning for some gorilla glass samples. Might be hard to cut
The retail eyeglass shops get their lenses from an outside lab, so as you say "most certainly 'no'". On the other hand, they might tell you who said lab is and how to contact them, and asking the the lab if they'd be willing couldn't hurt. You want these invisible, so get both the scratch resistant and antireflective coatings.
You might be surprised what LensCrafters or some other shops might do for you, if you agree to put a LensCrafters decal for advertising on the opposite side from your planned decals.
“LensCrafters: We Aim for Sharp Clear Vision”
Shazam, you are a professional sponsored Rocketeer!
Fin on the right was sanded up to 1500 grit, fin on the left was flame-polished. Significant improvement when viewed from this angle, a little less dramatic from other angles but still noticeable. Flaming requires a light touch; too much heat and the polycarbonate can bubble. Ruined one fin that way; fortunately I made extras.
3/32" is definitely thicker than necessary; 1/16" would have been fine. No matter.
Did you find it better to hold the edge near the side of the flame, over the flame, or running the flame over the piece swiftly?
Yes, I'm curious about your technique, that really helped. Also, what kind of flame (candle, butane torch)?
Um, uh, er... well I didn't actually do the torching myself, just relaying what I was told. I know it was a torch, not a candle. I'll try to get some more details and report back. I'm *sure* this is the sort of thing that you get the hang of after a bit of practice with a piece of scrap.
One thing I was not sure of was how smooth I should try to get them before torching. And the answer turned out to be "as smooth as possible". There were a couple of telltale grooves in one of the edges, and the attempt to polish those out is what caused excess heat and bubbling and the ruination of one fin. So the smoother it starts, the less flaming needed. There's still a trace of haze here and there on the edges post-flaming, but I'd rather live with that than risk destruction.
I've also been experimenting with some plastic polish to clean up the surface scratches, with mixed results. Might need to attempt it with toothpaste technique next. Clearly (ahem) these fins are going to get scratched up, but I'm going to expend some effort to keep that to a minimum. I also still don't know what the rocket is going to look like with these things sticking out. Still not sure if I made a mistake putting the fins where I did. Oh well!
I wonder if jewelers polish and a buffing wheel would work.
Next time I get new eyeglass lenses and they ask if I want to have the edges polished ($$$$$) I can just say "No thanks. I have a pencil torch at home!"
BTW currently working on a Boyce 1/100 Merc. Atlas with clear fins.
They say you can either permanently glue them on OR friction fit with a strip of masking tape.
Don't know if I want to risk a fin popping out in flight.
Those things are worse than camo paint to locate on the ground.
Heh heh, I get it, "pencil" torch.
Thanks. I didn’t!
Good looking! If you have any of the paint left over paint some cardstock or a piece of body tube and after it has fully dried shoot it with some clear coat to see what happens.
1) My big parts order to BMS is due here next week, and then I'll have the parts I need to commence the rest of the build. I ordered an extra nose cone because there is a darn good chance I'm going to mess one up. I continue to plan out how I'm going to do it, and continue to be nervous about my ability to get the result I'm hoping for. Unfortunately I won't know the answer to that for quite a while, as I can't really do much with the nose until the body is finished.
2) I tried some polishing the surface of the worst-scratched fin, to no effect. Man, I scratched that thing pretty badly, despite the fact that all I did was dry it with a paper towel. Lesson learned. Only hope for that one is to try to sand it out, maybe starting at 400 and going up to 3000 grit, and *then* polishing. I will only try that after I get my two new replacement fins, to be sure I have an extra, in case it doesn't work out. Those two replacements are awaiting flame-polishing, I should have them back soon.
3) I'm considering trying 1/64" plywood skin instead of the 1/32" balsa I've been planning on. The balsa works great, but a slight reduction in overall size would make the body match the ferrule slightly better (I should have made the ferrule a bit bigger, oh well). Apart from the difficulty of finding a clean sheet of 1/64" plywood at HL, are there any special considerations on working with it? I'm only guessing that it will work well as a skin, will need to experiment a bit to get confident with it. It seems like it doesn't need papering, and a coat of filler/primer should be enough to smooth it out.
I haven't tried working with 1/64" plywood, so I can't offer any observations. I wonder how the area density compares between 1/64" plywood and 1/32" balsa, does it change the weight or CG of the rocket much?
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