Bubble party--acrylic canopy transparencies

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

ToddK

Well-Known Member
HBA Supporter
Joined
Jan 13, 2016
Messages
512
Location
Shweaty Texas
Fact-Checking is a disease with me:
Polycarbonate sheet Hardness R 118
Tensile ultimate 9500 psi
Softening temp 152 degC

Acrylic sheet Hardness Rockwell M 93 (about the same as Rockwell R 118)
Tensile ultimate 10000-11700 psi
Softening 115 deg C


Cannot put my finger on the reason for scratch resistance differences?
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
Joined
Oct 4, 2013
Messages
27
Location
Australia
It's a long way from Florida but I'd love to see some video clips or pics with descriptions after the fact.
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.
 

bmcj

Well-Known Member
HBA Supporter
Joined
Apr 10, 2007
Messages
13,875
Location
Fresno, California
Acrylic can also be buffed out, where that really does not seem to work with polycarb.
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:
 
Last edited:

wsimpso1

Super Moderator
Staff member
Log Member
Joined
Oct 18, 2003
Messages
8,226
Location
Saline Michigan
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?
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
 

Voidhawk9

Well-Known Member
HBA Supporter
Joined
Mar 26, 2012
Messages
630
Location
Timaru, NZ
And polishing the coating from the lens allows it to craze over again much faster than the first time.
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
Joined
Sep 10, 2009
Messages
336
Location
Northern California
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-cleaners-and-exterior-care-products/headlight-lens-restorer/sylvania-headlight-restoration-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
Joined
Apr 28, 2010
Messages
15,435
Location
Memphis, TN
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.
 

Bart

Well-Known Member
Joined
Apr 13, 2007
Messages
309
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?
 
Last edited:

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,796
Location
US
Anybody looked at "Vivak" PETG, the strong, tough, impact-resistant clear plastic, ubiquitous in soda pop and water bottles, such as 2 liter Coke? ...
Vivak is sold at Home Depot and Lowe's here in USA, as I recall.

Thoughts?
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.
 

pylon500

Well-Known Member
Joined
Dec 26, 2003
Messages
395
Location
Taree Airport Australia
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.
 

BJC

Well-Known Member
HBA Supporter
Joined
Oct 7, 2013
Messages
13,594
Location
97FL, Florida, USA
Looked at a range of transparent plastics with my second project, and found pro's and con's to each of them.
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
516
... 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.
...
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
Joined
Jun 25, 2014
Messages
2,281
Location
YMM
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.
 

BoKu

Pundit
HBA Supporter
Joined
Aug 15, 2013
Messages
2,954
Location
Western US
Anybody looked at "Vivak" PETG, the strong, tough, impact-resistant clear plastic, ubiquitous in soda pop and water bottles, such as 2 liter Coke? ...
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
Joined
Jun 25, 2014
Messages
2,281
Location
YMM
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.
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.
 

pylon500

Well-Known Member
Joined
Dec 26, 2003
Messages
395
Location
Taree Airport Australia
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
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.
 
Top