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Thread: Lexan vs Acrylic for a PA-12 door.??

  1. #1
    Alex Clark's Avatar
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    Lexan vs Acrylic for a PA-12 door.??

    My PA-12's clear swing up door is all sorts of messed up. I can buy acrylic or Lexan The Lexan sheets are twice as expensive.
    Which one is less likely to crack around the screw holes??? I have have to bend it in the middle.
    Float and Tailwheel CFI,
    Dragonfly Aero
    Homer, Alaska
    dragonfly@alaska.net

    http://www.floatplanealaska.com

    or http://www.dragonflyaero.net

  2. #2
    cubdriver2's Avatar
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    Lexan is strong as hell, good at holding up, bad if you need to punch your way out.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  3. #3
    Alex Clark's Avatar
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    Pros of Acrylic:

    Shinier
    Less expensive than polycarbonate
    High level of impact resistance (17 times the impact resistance of glass)
    Greater resistance than polycarbonate against evenly distributed loads
    Greater resistance than polycarbonate against scratching
    Greater UV resistance than polycarbonate
    Easier to cut than polycarbonate
    Can be polished smooth if necessary
    Provides cleaner glue joint compared to polycarbonate
    Does not yellow over time
    Greater clarity, clarity can be restored through polishing
    Available in a wider variety of colors than polycarbonate
    Float and Tailwheel CFI,
    Dragonfly Aero
    Homer, Alaska
    dragonfly@alaska.net

    http://www.floatplanealaska.com

    or http://www.dragonflyaero.net

  4. #4
    Alex Clark's Avatar
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    Cons of Acrylic:

    Very rigid
    Cracks more easily than polycarbonate
    Can crack easily during drilling
    More likely to chip than polycarbonate
    Softens at 195 degrees Fahrenheit compared to polycarbonate’s 240
    Float and Tailwheel CFI,
    Dragonfly Aero
    Homer, Alaska
    dragonfly@alaska.net

    http://www.floatplanealaska.com

    or http://www.dragonflyaero.net

  5. #5
    Alex Clark's Avatar
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    Pros of Lexan:

    Higher level of impact resistance (250 times the impact resistance of glass)
    Less rigidity than acrylic and can be bought in flexible grades
    Can handle temperatures up to 240 degrees Fahrenheit
    Highly resistant to acids and other chemicals such as gasoline
    Can be drilled without worry of cracking
    Can be cold formed or bent without heating
    Low level of flammability
    Float and Tailwheel CFI,
    Dragonfly Aero
    Homer, Alaska
    dragonfly@alaska.net

    http://www.floatplanealaska.com

    or http://www.dragonflyaero.net

  6. #6
    Alex Clark's Avatar
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    Cons of Lexan:

    Easier to scratch
    More expensive in comparison to acrylic
    Poorer clarity, cannot be polished to restore clarity
    Can be yellowed over time by UV rays
    Low level of resistance to abrasive cleaners and surfaces
    Can be dented easily
    Float and Tailwheel CFI,
    Dragonfly Aero
    Homer, Alaska
    dragonfly@alaska.net

    http://www.floatplanealaska.com

    or http://www.dragonflyaero.net
    Thanks OzAK, Delta Cub thanked for this post

  7. #7
    skywagon8a's Avatar
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    Bending Acrylic:
    https://www.briskheat.com/how-to-mak...acrylic-sheets
    https://www.tapplastics.com/product/...er_element/169
    Be certain the edges at the ends of the bend are absolutely smooth before bending. If not the acrylic can and will crack. A fine file, sandpaper or a razorblade dragged along the edges all work for smoothing edges.
    Use gloves when handling the hot acrylic.

    Drilling Acrylic:
    Use a Unibit as it makes nice smooth clean holes. Drill the hole oversized to allow for expansion and contraction of the acrylic with temperature changes and flexibility in opening and closing the door. When the screws are tightened, back them off 1/2 turn so they don't initiate cracks around the edge of the hole.
    The screws want to be smaller than the hole so that they do not apply any pressure on the acrylic. Check the accuracy of the hole locations so that when installed the screws do not apply pressure against the acrylic. If one of the screws creates tight pressure against the side of the hole, increase the size of the hole or using a small round file elongate the hole.

    The acrylic likes to relax in it's installation. Any nicks along the edges can initiate cracks.
    It is best to work the acrylic when in a warm environment.
    Last edited by skywagon8a; 05-29-2021 at 07:56 AM.
    N1PA

  8. #8

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    Polycarbonate is not gas resistant. I built a kit that used polycarbonate for glazing. I would replace the windshield every year because the gas cap was at the base of the windshield. Even covering with a blanket before refueling couldn't keep the poly from crazing crazily. I replaced the backlight because I touched it an hour after I got gas on my hands. Etched fingerprints and poly can't be polished. The kit manufacturer switched to wing tanks.
    My current ride is all poly, but with wing tanks and a wized up owner. I use mogas.
    What's a go-around?

  9. #9
    cubdriver2's Avatar
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    I used .060 lexan on my homemade seaplane doors 15 years ago and they are still in decent condition. I just pop riveted it to the door frame. A few cracks developed after about 10 years. They take a beating because I fly with them open most times.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  10. #10
    courierguy's Avatar
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    We S-7 pilots have long used Plexi for the windshield, and lexan e erywhere else, with good results.

    If the price difference is a concern, a deciding factor, you are in the wrong sport/activaty, or a heck of a comedian!
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  11. #11
    Dave Calkins's Avatar
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    I always oversize the screw holes and margins/edges of Plexiglass/Acrylic. I always install with a foam/rubber layer between it and the structure. I always smooth the edges with sandpaper to at least 180 grit.

    I only use Lexan/Polycarbonate when I need a coldformed product that is easy to replace in about 4 years.

    Otherwise, plexi/acrylic for good clarity for many years amd good chemical/fuel resistance.

    Thanks Brian, for your thorough descriptions of the 2 materials.

  12. #12

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    Hello Dave, a generic question to you and all that have been there done this....
    What is your go-to thickness of acrylic that holds up yet isn’t too thick to keep the weight in check? I get it if it’s not a one thickness fits all situations. Expound as needed.
    Thanks!

    Mike

  13. #13

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    .090 acrylic is what my windows and skylights are made of. Screw holes are melted using a piece of copper tube the the tip sharpened on a bench grinder. Slag pops off easily when warm. I got a few short cracks in a couple of places. Stop holes were melted with the chuck end of a very small drill bit. Mike likes using a steel tube with a castle cut tip for melting holes. I struggled with it because the slotted tip cools faster. It leaves less slag, though.

    The only Lexan product I use for applications where you look through it is mar-guard Lexan. Pretty much scratch proof. Nearly impossible the break. Much more expensive. Not necessary on an airplane.
    Last edited by stewartb; 06-01-2021 at 08:35 AM.
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  14. #14
    Dave Calkins's Avatar
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    .090” is most often used. I have gone thinner by mistake, and also as planned, and found flutter/flapping/drumming/rattling/shattering and gnashing of teeth!!! (at different times, on different Cubs, Beavers, and 185’s). But chosen wisely, for the application, thinner than .090” can be utilized

    I drill and debur the holes with modified twist drills. A Unibit stepdrill works also, but both should be tested on scrap acrylic. obtaining a smooth cutting action is not always easy.

    MarGuard is the best Polycarbonate. but it will craze much sooner than Acrylic. and is relatively much more expensive.
    Thanks Just call me Al thanked for this post

  15. #15

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    Thanks guys, just what I was looking for. I like a tip I picked up on here some time back that MCS Mike posted, utilizing the end of an acid brush to put holes in the plastic with. Inexpensive, easy to find, very thin wall, just heat it up,with a propane torch. It’s even slightly adjustable for hole size because the metal is rolled on itself and you can roll it smaller by squeezing it or expand it with some snap ring pliers. Works slick. No cracks.

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