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Cracked Canopy
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n4546v(at)mindspring.com
Guest

Posted: Thu Dec 29, 2011 11:21 am Post subject: Cracked Canopy

do not archive

  	  Quote: 	
		      In reality it is just as easy, maybe easier, to hack away at Lexan    as Plexiglass.



Best regards,



Paul

Camas, WA

    

   



I don't agree with that.  Here's    some more purely generic info.

    

   Regards,

    

   Randy, Las vegas

    

          

Discover the expert in you.

   What Is Lexan Made Out    Of?By Neal Litherland, eHow    Contributor    

Lexan is a commonly used replacement for    glass and even Plexiglas in a variety of areas. Stronger and more resilient,    but still providing many benefits of glass, Lexan is used in industry, in    communication, and even signage. But the process used to make this material,    as well as the definition of what Lexan is and isn't, can sometimes get a    little complicated.             Lexan                                 

Lexan is a name for a sheet of polycarbonate resin that is generally        considered to be a shatterproof material. Though still technically a        plastic, Lexan is stronger and more durable than either traditional glass        or the plastic Plexiglas, and it is used in situations where extra        survivability of the material is considered worth the extra cost, such as        "bulletproof" windows in police stations or armored        vehicles.



     Process                                 

Lexan is made through a patented chemical process. By reacting a        chemical compound called Bisphenol A with carbonyl chloride (also known as        phosgene), the base resin that makes up Lexan is produced. While sheets of        this resin material can be cut into a variety of lengths, only those which        are between .03 inches (or 0.75 mm.) and .48 inches (or 12 mm.) are ever        referred to as actually being Lexan.



     Development                                 

Lexan was first developed in the 1950s by General Electric Plastics.        Dr. Daniel Fox was attempting to create a new, more durable plastic to be        used as a wire coating when he made the discovery in the GE labs. This        exact same breakthrough had happened independently in Germany, where a Dr.        Herman Schnell of Bayer was equally impressed by the extreme toughness of        the new resin material. Though a scramble for patents ensued, GE Plastics        became the main manufacturer and distributor of      Lexan.



     Properties                                 

Though it is a great deal tougher, Lexan bears a very strong        resemblance to Plexiglas, also known as Lucite or Perspex. Lexan often has        a shiny, acrylic look though it is a great deal tougher than any acrylic.        Lexan will scratch in a manner similar to Plexiglas, however. Throughout a        variety of tests, Lexan has been shown to be nearly shatterproof, and to        even withstand bullets depending on the size of the weapon and distance        the shot was fired from. One of the other properties of Lexan, and one        which can be a major health risk, is that the resin may leach bisphenol A.        This chemical, which is used in Lexan's manufacturing process, has been        linked to cancer by several studies.



     Uses                                 

Given its durability, Lexan has been used in a huge variety of products        and industries. Lexan is a favorite of the aerospace industry for making        cockpits and windscreens that are used in a variety of aircraft. More        commonplace items, such as the original Apple Ipod (which had a white        plastic body made of Lexan) also use this shatterproof plastic.        Additionally, Lexan is popular in racing, being used for both helmets and        windshields to reduce the weight that is active in the vehicle. Also,        whether or not fans of the show are aware of it, Lexan is often used on        shows such as "Myth Busters" and "Deadliest Warrior," where the clear,        protective sheets are used to keep the hosts safe from explosions and        flying debris.

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Scotsman

Joined: 27 Aug 2007
Posts: 89
Location: Johannesburg, South Africa

Posted: Thu Dec 29, 2011 10:32 pm Post subject: Re: Cracked Canopy

How have you guys dealt with riveting on the canopy?  The sides of the front and rear canopy would need to be riveted but after my past experiences cracking the canopy I am really reluctant to do anything.



Now having learnt from the thread I will use the recommended drill bit and techniques but I am still worried that the pressure generated by the rivet on the canopy will cause the canopy to crack.



Any recommendations and practical experience would be gratefully received.



Cheers

James

_________________
Cell +27 83 675 0815

psm(at)att.net
Guest

Posted: Fri Dec 30, 2011 2:45 am Post subject: Cracked Canopy

I didn't do any riveting on the canopy.  All of the points where the 

canopy gets fasteners I used screws with tinnerman washers.



Paul

Camas, WA



On 12/29/2011 10:32 PM, Scotsman wrote:

 	  Quote: 	
		   



 How have you guys dealt with riveting on the canopy?  The sides of the front and rear canopy would need to be riveted but after my past experiences cracking the canopy I am really reluctant to do anything.



 Now having learnt from the thread I will use the recommended drill bit and techniques but I am still worried that the pressure generated by the rivet on the canopy will cause the canopy to crack.



 Any recommendations and practical experience would be gratefully received.



 Cheers

 James



 --------

 Cell   +27 83 675 0815





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=361971#361971

Scotsman

Joined: 27 Aug 2007
Posts: 89
Location: Johannesburg, South Africa

Posted: Fri Dec 30, 2011 3:01 am Post subject: Re: Cracked Canopy

Thanks Paul, and in the places where you have to go first through an aluminum piece and then into the canopy did you just make a large size hole in both the canopy material and the aluminum skin with the washer seated over the top of the two?



J

_________________
Cell +27 83 675 0815

psm(at)att.net
Guest

Posted: Fri Dec 30, 2011 4:07 am Post subject: Cracked Canopy

I hate to admit I just don't remember the answer to that question.  I 

looked at a photo I have on my computer and it seems like I made similar 

sized holes in the aluminum and plastic and seated the tinnerman washer 

on the outside of the aluminum.  On the other hand, I just can't remember.



I'll take a look next time I am at the airport.



Paul



On 12/30/2011 3:01 AM, Scotsman wrote:

 	  Quote: 	
		   



 Thanks Paul, and in the places where you have to go first through an aluminum piece and then into the canopy did you just make a large size hole in both the canopy material and the aluminum skin with the washer seated over the top of the two?



 J



 --------

 Cell   +27 83 675 0815





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=361980#361980

Scotsman

Joined: 27 Aug 2007
Posts: 89
Location: Johannesburg, South Africa

Posted: Fri Dec 30, 2011 7:22 am Post subject: Re: Cracked Canopy

Are you taunting me on purpose...."I'll take a look next time I am at the airport"    I can only go as far as looking next time that I am passing through my garage!

_________________
Cell +27 83 675 0815

steve.freeman(at)syntaxds
Guest

Posted: Fri Dec 30, 2011 7:29 am Post subject: Cracked Canopy

<< made similar sized holes in the aluminum and plastic and seated the

tinnerman washer on the outside of the aluminum.  >>



And what did you use for a fastener in locations like this? 



For instance - on the 650 B - there is a side flashing then the canopy

bubble.  If tinnerman washer is used in this location, what is used to

fasten the screw?  I was planning on riveting in these locations with my

hand riveter so I could control the force of the pull a little better.



Steve



--

psm(at)att.net
Guest

Posted: Fri Dec 30, 2011 8:25 am Post subject: Cracked Canopy

No, I'm not taunting you.  I just have a bad memory.  I did the canopy 3 

or 4 years ago.



You may not know - I had to ground my plane for a couple of years just 

as it was ready for inspection.  That was when the NTSB and FAA joined 

forces and asked all owners to ground XLs.  Then, I installed the 

upgrade in the hangar at the airport.  It would have been a lot easier 

to do if I could use my shop but I didn't want to haul the plane back to 

the shop.



I'm just nearing the end of flight test now.  The plane was first flown 

in July.



The good news - I have not had any problems with the canopy.  That is, 

the canopy has stayed in place with no cracks.  I did manage to scratch 

it - probably while installing the engine cowl.  I bought a polishing 

kit and will probably fix the scratches next Spring.  They are not deep 

and they are in a location I don't use to see where I am going.



You'll get there.  Just keep working . . .



Paul



On 12/30/2011 7:22 AM, Scotsman wrote:

 	  Quote: 	
		   



 Are you taunting me on purpose...."I'll take a look next time I am at the airport" [Laughing]  [Laughing] I can only go as far as looking next time that I am passing through my garage!  [Crying or Very sad]



 --------

 Cell   +27 83 675 0815





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=361996#361996

psm(at)att.net
Guest

Posted: Fri Dec 30, 2011 8:30 am Post subject: Cracked Canopy

Hi Steve,



I used the same screws and tinnerman washers at all locations where a 

fastener goes through the plastic canopy.  I'm afraid riveting through 

the plastic will surely cause cracks.



Again I must claim lack of clear memory of exactly what the screws 

attached to.   The way the screws work they have a tinnerman washer on 

the outside and a solid piece of metal (either aluminum or steel) on the 

inside with the plastic canopy captured in the middle.  I think the self 

tapping screws easily go into either steel or aluminum when you have a 

proper sized pilot hole in the metal.



I'm not sure, but I think some of the screws go into the thin wall 

square tubing that makes up the basic structure of the canopy base.



Paul



On 12/30/2011 7:27 AM, Steve Freeman wrote:

[quote] 



 <<  made similar sized holes in the aluminum and plastic and seated the

 tinnerman washer on the outside of the aluminum.>>



 And what did you use for a fastener in locations like this?



 For instance - on the 650 B - there is a side flashing then the canopy

 bubble.  If tinnerman washer is used in this location, what is used to

 fasten the screw?  I was planning on riveting in these locations with my

 hand riveter so I could control the force of the pull a little better.



 Steve



 --

steve.freeman(at)syntaxds
Guest

Posted: Sat Dec 31, 2011 7:15 am Post subject: Cracked Canopy

HI Paul,



I appreciate what you are saying but unless some type of rivnut is epoxied

to the inside of the canopy it would be virtually impossible to install a

screw (even loosely) in the rear canopy.  While it would not be impossible

it would be incredibly difficult (and I can't think of a way right now) to

get a tool to hold a nut while the screw were tightened.



I am thinking of lining the inside 20mm edge of the rear canopy with the

Slap Stix product Jerry Latimer recommended after pre-drilling for a rivet.

Then I will carefully pull the rivets by hand. 



Anyone else have any ideas?



Steve



--

psm(at)att.net
Guest

Posted: Sat Dec 31, 2011 8:25 am Post subject: Cracked Canopy

Hi Steve,



Yes, the rear end of the canopy is a different issue from the portion 

that meets the metal mechanism and flashing.



In the rear, I just installed some rubber seal material.  I also trimmed 

the plastic so it fits the metal curve of the rear fuselage top.  I 

don't think this makes a completely perfect seal, but I don't think that 

matters either.



At first I planned to stick some rubber sealing material between the 

canopy and the fuselage side edges.  After seeing another XL at the Sun 

n Fun auction last year I decided to try just leaving the 1/4 inch or so 

open to the air.  All of this seems to work just fine.  There might be a 

little air noise in flight at 120 kts, but I use noise cancelling (Bose) 

headphones anyway.  I would guess the actual airflow through the canopy 

seal gaps is very small - perhaps similar to the flow into the cabin 

from the cabin heater and two air vents.



Paul



On 12/31/2011 7:10 AM, Steve Freeman wrote:

[quote] 



 HI Paul,



 I appreciate what you are saying but unless some type of rivnut is epoxied

 to the inside of the canopy it would be virtually impossible to install a

 screw (even loosely) in the rear canopy.  While it would not be impossible

 it would be incredibly difficult (and I can't think of a way right now) to

 get a tool to hold a nut while the screw were tightened.



 I am thinking of lining the inside 20mm edge of the rear canopy with the

 Slap Stix product Jerry Latimer recommended after pre-drilling for a rivet.

 Then I will carefully pull the rivets by hand.



 Anyone else have any ideas?



 Steve



 --

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Sat Dec 31, 2011 12:22 pm Post subject: Cracked Canopy

I'm  not familiar with the two-piece canopy but I would not recommend installing rivets into acrylic. I would think you would want to use a flashing strip to attach the rear canopy. Then glue the acrylic to the flashing. The flashing would be riveted to the fuselage.



3M double sided molding tape also works very well for attaching flashing to acrylic. The vinyl foam tape seals the gap and holds the pieces together. I used this tape on the front flashing on my 601XL, I've had no problem with it. I used it to attach the fog lights to the bumper of my old ford pickup and they never came loose in the 4 years I owned it.

On Dec 31, 2011, at 10:10 AM, Steve Freeman wrote:



 	  Quote: 	
		   

 

 HI Paul,

 

 I appreciate what you are saying but unless some type of rivnut is epoxied

 to the inside of the canopy it would be virtually impossible to install a

 screw (even loosely) in the rear canopy.  While it would not be impossible

 it would be incredibly difficult (and I can't think of a way right now) to

 get a tool to hold a nut while the screw were tightened.

 

 I am thinking of lining the inside 20mm edge of the rear canopy with the

 Slap Stix product Jerry Latimer recommended after pre-drilling for a rivet.

 Then I will carefully pull the rivets by hand. 

 

 Anyone else have any ideas?


	


-- 

Bryan Martin

N61BM, CH 601 XL, 

RAM Subaru, Stratus re-drive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Sat Dec 31, 2011 1:00 pm Post subject: Re: Cracked Canopy

I ended up using large  headed [1/2 long  x 1/8Dia]  self taping screws on the bottom steel RHS tubes.On the hinge cover panel I put in anchor nuts .I also cut the sides of the canopy less, so that they extend past the fuselage [by 1/8"]  for weather proofing,and a very soft rubber seal under the steel  RHS tubes so that the canopy locks down with only a little downward pressure.I also drilled a 3/8" hole on each side [on the inside] so you can see the locking mechanism [spring tang] engage properly and positively [put a bit of red paint on the tangs]. All holes drilled either 1/4" or bigger thru the plastic canopy [Todds canopy]using a step drill with NO cracking so far. Cheers Alan

Last edited by Thruster87 on Sat Dec 31, 2011 8:56 pm; edited 1 time in total

Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Sat Dec 31, 2011 8:52 pm Post subject: Re: Cracked Canopy

 	  Thruster87 wrote: 	
		  I ended up using large  headed [1/2 long  x 1/8Dia]  self taping screws on the bottom steel RHS tubes.On the hinge cover panel I put in anchor nuts .I also cut the sides of the canopy less, so that they extend past the fuselage [by 1/8"]  for weather proofing,and a very soft rubber seal under the steel  RHS tubes so that the canopy locks down with only a little downward pressure.I also drilled a 3/8" hole on each side [on the inside] so you can see the locking mechanism [spring tang] engage properly and positively [put a bit of red paint on the tangs]. All holes drilled either 1/4" or bigger thru the plastic canopy [Todds canopy]using a step drill with NO cracking so far. Cheers Alan

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