If you want to go down that rabbit hole feel free, but its a fact I know to be true from 1st hand experience.
Acrylic can also be buffed out, where that really does not seem to work with polycarb.
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If you want to go down that rabbit hole feel free, but its a fact I know to be true from 1st hand experience.
Acrylic can also be buffed out, where that really does not seem to work with polycarb.
Old Koreelah
Active Member
Bob it’s even further from Oz, so I too would love to see some video.
My own attempts at compound-forming acrylic (for motorcycle screens and aircraft canopy) have taught me quite a bit of respect for those who know their stuff.
Regarding polycarbonate, I prefer to have it in front of me to take impacts from birds, etc. It does scratch and craze too easily, so it gets replaced every couple of years; the price has more than halved since I built my plane, thanks to Chinese manufacturing.
I still prefer to have acrylic over my head so that I can break my way out if I happen to prang it.
I’ve not tried it, but some automotive ads push a liquid restorer that is supposed to clear clouded Polycarbonate headlight covers with just a wipe. Has anyone tried this?
Like this, for example:
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The wife was a materials engineer last several years of her career for an automotive lighting company... she has had plenty to say about crazed lenses and polishing them out. Yeah, they sure look better, but they do not do any better at getting light where it is supposed to be. And polishing the coating from the lens allows it to craze over again much faster than the first time.
Billski
I can confirm this. A metal-polishing paste works for me. It fades again soon enough. I tried clear-coating it after polishing it clear the next time. Didn't seem to improve the result over time.
But, one can polish up nicely in preparation for sale, if required. Which reminds me, I'm selling the current vehicle in about 8 weeks, so I guess I'll be doing this again.
rdj
Well-Known Member
I used this last year to clear up the headlights on my 13 year old Honda Fit, and it worked well. The lenses are still clear, although I would take the '3X more light' and '140% more down the road visibility' claims with a grain of salt. It appears to work by finely and evenly scratching the surface with the polishing paste, and then as a final step flooding it with clear coat of the same general index of refraction. With nothing to lose but $20 I was pleased with the results on the Fit, but I'd want some of you guinea pigs to go first before I tried using it on an aircraft canopy 
https://www.autozone.com/wash-clean...ation-kit-with-uv-block-clear-coat/272381_0_0
BTW, when are we going to hear more about this HP-26?
https://www.autozone.com/wash-clean...ation-kit-with-uv-block-clear-coat/272381_0_0
BTW, when are we going to hear more about this HP-26?
TFF
Well-Known Member
I think it depends on the pocket book. Are the covers $50 or $500? What is the vehicle worth? If you can get five to ten more years out of a set of covers, it’s probably worth it. I tend to use up my stuff. Pretty dead at the end. If the vehicle is worth something, replacing them is the better way to hold the value up.
TFF
Well-Known Member
With the canopy molding, I was hoping to hear everyone who participated got to pull a conehead hat.
Anybody looked at "Vivak" PETG, the strong, tough, impact-resistant clear plastic, ubiquitous in soda pop and water bottles, such as 2 liter Coke? Reportedly, that is what Frenchman M. Columban used in his Luciole aircraft. This stuff is said to be almost as tough as polycarbonate, but less expensive and workable like acrylic:
See also: where in comments below the author says he used PETG sheet sourced in Australia, where prices are typically higher.
Vivak is sold at Home Depot and Lowe's here in USA, as I recall.
Thoughts?
See also: where in comments below the author says he used PETG sheet sourced in Australia, where prices are typically higher.
Vivak is sold at Home Depot and Lowe's here in USA, as I recall.
Thoughts?
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It does look like it has its uses. The regular Vivak doesn't hold up to UV, but UV resistant Vivak would be okay in the sun for awhile. It scratches more easily than acrylic.
Looked at a range of transparent plastics with my second project, and found pro's and con's to each of them.
Acrylic; reasonable mouldability, good scratch resistance, polishable, reasonably fuel proof, mid range expense, good optics.
Polycarb; harder to mould well, poor scratch resistance, not polishable, fuel DESTROYS it, expensive, questionable optics.
PETG; moulds well, poor scratch resistance, not polishable, totally fuel proof, cheaper, questionable optics.
PVC; moulds easily, poor scratch resistance, not sure about polishing, doesn't like fuel, dirt cheap, crap optics and crazes in sun quickly.
Sorry if this doesn't really help for choice, just my observations.
Acrylic; reasonable mouldability, good scratch resistance, polishable, reasonably fuel proof, mid range expense, good optics.
Polycarb; harder to mould well, poor scratch resistance, not polishable, fuel DESTROYS it, expensive, questionable optics.
PETG; moulds well, poor scratch resistance, not polishable, totally fuel proof, cheaper, questionable optics.
PVC; moulds easily, poor scratch resistance, not sure about polishing, doesn't like fuel, dirt cheap, crap optics and crazes in sun quickly.
Sorry if this doesn't really help for choice, just my observations.
Please also consider your potential to escape from, or be rescued from, the aircraft in an emergency.
Some plastics can be broken through, others can not. A related factor is the ability to jettison the canopy. If relying on that option, be sure to evaluate the ability for a rescuer to release the canopy from the outside, and the effectiveness of attempting to jettison the canopy while inverted on the ground.
BJC
Bille Floyd
Well-Known Member
- Joined
- Sep 26, 2019
- Messages
- 689
Is one Acrylic , better for building a canopy , than another ; or
are they all the same ? You probably already researched that ;
so that's why i asked.
Bille
Hephaestus
Well-Known Member
PETG can be polished... But there's an extra step. You can absolutely do it the normal ways out to 6000+ grit, but it'll remain cloudy until you hit it with flame/heat.
In one of his early presentations on the Sparrowhawk, Greg Cole said he was going to make his transparencies out of PETG for all of the reasons listed above. When I actually saw a Sparrowhawk canopy, the transparency was made out of acrylic. I asked him about the PETG and he just rolled his eyes and changed the subject.
Hephaestus
Well-Known Member
It's probably a fairly different process than we're used to. Check out the pop bottle blanks for blowing on amazon.
I know it was freaking annoying to vacuform when lexan was hard to come by early covid.
When I mentioned acrylic, think 'perspex', 'plexiglass', etc although these are trade names.
The only differences in acrylics are as mentioned earlier, whether using extruded or cast, cast having the better optical qualities and being accordingly more expensive.
MadRocketScientist
Well-Known Member
Some types of acrylics can be toughened or have coatings applied for even better scratch resistance. There are a lot of products out there these days!
davidjgall
Well-Known Member
Any update on when this might take place? I'm still interested in attending.
