Plexiglass door Stc

[Dan Mahalak]

Looking for paperwork to put in at least one, Port side full plexiglass door.
Anyone with info on plexi thickness, do and dont's...and opinion from those with such door(s) already?

Thanks
Danno

[Len Petterson]

Re: Plexiglass door Stc

I am also interested in "glass in " doors.
Len Petterson

[TimHicks]

Re: Plexiglass door Stc

My hangarmate has clear doors. I'll try to post a picture here. WHen he refurbished the airplane, he debated whether to reuse Plexiglas (which had cracks at every attach hole), or change to Lexan (which doesn't crack but may impede escape in the event of a crash).

This picture was taken a couple of years ago on the Chandeleur Islands, a great place to land a taildragger and some specks and reds. I'm not sure that the Chandeleur Islands exist anymore since Hurricane Katrina.

[mulwyk]

Re: Plexiglass door Stc

Tim:
Wow. That looks just great!

Did he go with plexiglass or Lexan? And how has that worked out?

And did he go with an STC or a 337 or experimental or just-do-it-and-hope-noone-notices?

Bob Gustafson

[jgerard]

Re: Plexiglass door Stc

Rumor has it that depending on how your examiner interprets the regs and since a "Door" is non structural (auxiliary item#601 for model bc12-d1 "ACE") and therefore modifying it would be a minor alteration and only require a log book entry. 337 for is used with a major alteration.

And since the definition of minor alteration is "other than major alteration" Part of the definition of Major alteration is " That, if IMPROPERLY done, MIGHT appreciably affect weight, balance, structural strength, performance, power-plant operation, flight characteristics, or other qualities affecting airworthiness"

Since the "door" is not listed in appendix A to part 43 one could argue that it is not structure and should qualify as a minor alteration. Use AC43-13 as a guide to "properly" install the additional plexiglas and modify the inner door skin. If you can do that without "appreciably" affecting weight or strength you've got it made. Also since the F21 series aircraft came with an observer door I bet that could be used as approved data to modify a BC12D door. Forrest may have to chime in with info on how that was done.

[TimHicks]

Re: Plexiglass door Stc

I knew that you would ask me the Lexan or Plexiglas question before I could find out for sure. I haven't been able to reach my buddy yet. So I don't know for sure which material he used. I think that it's Lexan. And it was about 1/8" thick. But I'll find out specifics.

He bought the airplane with these "observation-type" doors already on it (with Plexiglas). But I'll check on what paperwork he has to go with the doors. The frames of the doors are very lightweight welded steel construction (thinwall square tubing).

When he took the old Plexiglas off and installed the new plastic, he drilled the oversize holes in the plastic very carefully and used rubber washers on either side of the plastic at each attach point.

[Dick Smith]

Re: SeeThrough Safety Door

The door cutout is quite common here in Alaska. I did it under a 337 a number of years ago, rather than an STC...I've never seen an STC for it as such. I used 1/8 " Lexan as the glazing material, rather than Plexiglas, although either will work. The Lexan is tougher, and seems to be less prone to crack, but it is clouded by contact with gasoline. I used pop rivets from the outside in, with very thin alum. washers on the inside of the Lexan sheet. Filled the rivet snapoff holes with appliance touchup...will paint someday!! Some use screws with washers and nuts, but I didn't like the rough surface created by the nuts. The alum. washer with the swelled head of the poprivet(used shortest rivet that would do a proper job), presents a much less ragged "sawblade", in the event of a crash. Be sure and allow for holes in the Lexan or Plexiglas that are large enough to permit expansion and contraction around the rivets, otherwise you will have cracking occur. It doesn't take much, but if you don't allow for it...you will get cracks. Practice drilling holes on scrap...buy some extra or save your trimmings. When it's twenty-five below Zero (Fahrenheit) I know my Lexan has really contracted, but the larger holes seem to compensate. Make up a scrap piece with your chosen hole/screw or rivet combo...put in deepfreeze to chill...take it out...bang/twist/try to get it to crack. Another thing...when you start fastening the poprivets or screws, if that's what you use, have the door in place and and closed, so the door has the plastic sheet oriented with the "twist" or "set" of the door when it is closed. You don't want to get the plastic fastened on and find that the door is "wracked" out of alignment by the trussing effect. After you get some rivets in place at the corners and a couple along each side, you can work with it off the plane. I also try to avoid getting gas on the lower part of the door, as it will get cloudy, but I like the strength of Lexan. I use Plexiglas on the upper window. If the Lexan on the lower cutout section gets cloudy and I get tired of looking through it, I can replace it, but the toughness seems to stand up well to the closing/flexing of the door. I've been told by the guys that sell the Lexan that some of it has been treated so as to not absorb gasoline, but that cutting it exposes an untreated edge that can absorb gas. I figure that the cut edge is on the inside of the door, so hopefully it won't be a problem. Hope this helps. By the way, I'm planning on replacing my Lexan skylight with plexiglas, as refueling in high winds has proven that gasoline will cause crazing/cloudiness of Lexan. It is very tough, but it will craze. DickSmith N5207M TF#159

[N96337]

Re: Plexiglass door Stc

Dick, do you find yourself looking through the lower section of your doors often? I always wondered if it was worth it. I flew a 1929 Fairchild that had a plex panel down between your feet and it was sorta neet to look through in the air... always thought that might be used more than the lower doors.
John H.

[Vasey fan]

Re: Plexiglass door Stc

Dick, I'm actually more interested in those big rear windows. How are they framed in?

[Dick Smith]

Re: Plexiglas/Lexan mods

John, of all three mods: door, sidewindow and skylight...I would rank the skylight first, sidewindows, second and door cut outs 3rd. I use the door cutout especially when I'm alone and looking to the right. This pix shows the view of the ski standard looking through the door cutout. I really like the skylight, because I can clear the area above and see over the top of the wing in a fairly steep bank. I think the skylight is a major addition to safety. The net effect of all the mods makes the plane feel a lot more roomy and the lighting levels are much better. Up here light goes a long ways toward making life enjoyable. One negative is that you lose a lot of heat through the glazing, but there isn't much to begin with! Dick

[Dick Smith]

Re: sidewindows

T.J., I did the windows on a 337...there are small metal tabs welded on at the proper location to carry a wood frame, utilizing light alum. "zee's", which were bent on a brake, to capture the plexi...with another "zee"-shaped piece holding the plexi against the outside edge of the first zee...clear as mud?? I used a Unibit to drill the holes. I love Unibits!
I will try to do a sketch using Paint and send it to you. (Can someone tell me how to utilize attachments in the email and private message features on the forum?) Dick

[Vasey fan]

Re: Plexiglass door Stc

OK, thanks. I've got a rough idea of what you mean.

[Jim Hartley]

Re: Plexiglass door Stc

I have been told by a friend who is a "seasoned", IA that when drilling plexi-glass or polycarbonate use what is referred to as a uni-bit or step drill,as it does not have the twist that can stress and twist the fibers in the plastic and set it up for cracking...?!

Jim

[mulwyk]

Re: Plexiglass door Stc

Dick :

It would be great if you could post your sketch on the forum for all to see. I'm also interested in the rear windows.

Bob Gustafson

[barnstmr]

Re: Plexiglass door Stc

On plexiglass installation... lets hear from some mechanics out there. I cant claim to be an expert, but have a little experience here.
Jim's right, cracks usually propagate from the rough finish left behind by drilling. The doors see a lot of vibration so that makes it more apt to crack. But another big problem is that most folks don't take time to do fasteners correctly. Its not like screwing sheet metal panels down.

Drill holes oversize and make bushings to tighten screw against. Use a large head screw. Use a bushing sized about .010 to .015 thicker than the plexiglass, OD slightly smaller than hole, and ID to fit screw shank. And use nylon washers approx .015 thick and with ID to fit over bushing. The idea is to have the nylon hold light pressure against the plexiglass. With multiple attach points like this, its not necessary to torque screws hard.

Also. take some time with some means to lightly polish the ID of holes drilled in plexiglass with crocus or sandpaper and a tiny rat-tail file. I recommend making a practice panel of plexiglass and work with it some before tackling your installation. Just some tips from a Jack of all, master of none.