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steve.freeman(at)syntaxds
Guest

Posted: Sun Dec 25, 2011 1:52 pm Post subject: Cracked Canopy

Hi Guys,

 

We have all heard this story before…While installing the rear canopy on my 650 I got about a 3” crack.  I stop drilled it and I am trying to decide if I can live with this or not.  Roughly $650 to get a new canopy seems like a lot of money and I might wind up with the same thing again.  Honestly, I am not sure how this happened.  I was being super careful and I was not drilling in a location where there seemed to be any pressure.  Well…it happened…It sucks but I have to move on.

 

Can any of you guys make recommendations for the best practice to repair the crack?  I know it will never be perfect but I have heard some people have had a lot of luck.  There are no spider web cracks.  Just the one, it is clean and like I said I stop drilled it at the end.  I have found a couple of products on AC Spruce, in particular INSTA-WELD but it says to clamp the parts together…this is not possible.  Also, if I use some type of adhesive that will wick in to the crack, do I then use some type of epoxy to fill the stop drill hole?

 

Any help is always appreciated…

 

I hope everyone is having a great Christmas!

 

Steve

0235 Mounted will start wiring soon.

Moving along with fuselage..

  [quote][b]

Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Sun Dec 25, 2011 5:53 pm Post subject: Re: Cracked Canopy

Hey Steve,



Bryan Martin had that happen to his also and he used methyl Ethel, something or other, to repair the crack after stop drilling.



He monitors this list, perhaps he will reply.  Otherwise, just look up his posts and you just might find how he did it.

_________________
Ron Lendon
WW Corvair with Roy's Garage 5th bearing
CH 601 XLB
N601LT - Flying
http://www.mykitlog.com/rlendon
Corvair Engine Prints:
https://sites.google.com/site/corvairenginedata/

davgray(at)sbcglobal.net
Guest

Posted: Sun Dec 25, 2011 8:17 pm Post subject: Cracked Canopy

This might be a good thread to pursue as it seems to happen too  often.

 I would like to hear from others that cracked a canopy.  Details of  drill type and size, temperature at time of drilling, and hole-to-edge  distance.

 Also, from those that did not have this problem..

 I used a step drill, warmed the canopy over a warm air register, let the  bit generate a little heat from friction as it cut, kept the drill perpendicular  to the surface,

 and did not accept the 7 mm edge distance that would have occurred on a few  of my holes if I stuck entirely with the plans.

 My closest edge distance is 27 mm after a small modification.  Five  years plus without any cracks.  

  

 Gary Ray  

 Zenith 601XL-B, William Wynne Corvair 0.060 over, Roy's 5th bearing,

 Mark's Falcon Heads, Marvel Schebler MA3-SPA Carburetor, 175 Hrs TT

    

  

  From: Steve Freeman (steve.freeman(at)syntaxds.com) 

 Sent: Sunday, December 25, 2011 4:49 PM

 To: zenith-list(at)matronics.com (zenith-list(at)matronics.com) 

 Subject: Cracked Canopy

  



   

Hi Guys, 

  

We have all heard this story beforeâ€¦While installing the rear  canopy on my 650 I got about a 3â€ crack.  I stop drilled it and I am trying  to decide if I can live with this or not.  Roughly $650 to get a new canopy  seems like a lot of money and I might wind up with the same thing again.   Honestly, I am not sure how this happened.  I was being super careful and I  was not drilling in a location where there seemed to be any pressure.   Wellâ€¦it happenedâ€¦It sucks but I have to move on. 

  

Can any of you guys make recommendations for the best  practice to repair the crack?  I know it will never be perfect but I have  heard some people have had a lot of luck.  There are no spider web  cracks.  Just the one, it is clean and like I said I stop drilled it at the  end.  I have found a couple of products on AC Spruce, in particular  INSTA-WELD but it says to clamp the parts togetherâ€¦this is not possible.   Also, if I use some type of adhesive that will wick in to the crack, do I then  use some type of epoxy to fill the stop drill hole? 

  

Any help is always appreciatedâ€¦ 

  

I hope everyone is having a great Christmas! 

  

Steve 

0235 Mounted will start wiring soon. 

Moving along with fuselage..

[quote]



href="http://www.aeroelectric.com">www.aeroelectric.com

href="http://www.buildersbooks.com">www.buildersbooks.com

href="http://www.homebuilthelp.com">www.homebuilthelp.com

href="http://www.matronics.com/contribution">http://www.matronics.com/chref="http://www.matronics.com/Navigator?Zenith-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/c

[b]

jaybannist(at)cs.com
Guest

Posted: Mon Dec 26, 2011 7:28 am Post subject: Cracked Canopy

I did my canopy fabrication in the Summer (on purpose).  Cold plastic is anxious to crack.  I drilled the pilot holes for clecoes with a new drill bit that had about a 45 deg angle on the tip.  I used that bit to drill right through the plastic into the bow.  When I drilled the pilot holes out with a step drill bit for the washers,  I got no cracking.  I drilled one pilot hole way too close to the cut-out for the latch handle.  I made a note to myself oi not use this hole.  A year later when I went to fasten the bubble to the frame, I completely forgot that note and put a cleco in that hole.  CRACK !!  I quickly stop drilled the crack, but it kept running.  I stop drilled again and it kept running.  I finally stop drilled about a half inch beyond the end of the crack and that stopped it.  In the end, I was able to cut the crack out to install a plastic air vent; so I never attempted to repair the crack.  I did use one or two washers between the plastic and the bow at a couple of holes near the ends of the rear bow to insure that the screws didn't stress the plastic. 

 

 Jay

   

  

     

  

     

  

    --

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Mon Dec 26, 2011 7:55 am Post subject: Cracked Canopy

I had some small cracks from my drilling. I applied some methylene chloride with an insulin syringe. It wicked into the cracks and sealed them. I made sure to wipe off the excess immediately. The stuff works by dissolving the edges of the crack and fusing them together as it evaporates.



The water thin adhesive from ACS should work as well, it's probably the same ingredient. I didn't worry about the stop holes because they are hidden by the lower flashing. A little dab of Shoe-Goo or something similar might plug the hole.



On Dec 25, 2011, at 4:49 PM, Steve Freeman wrote:



 	  Quote: 	
		    

 Can any of you guys make recommendations for the best practice to repair the crack?  I know it will never be perfect but I have heard some people have had a lot of luck.  There are no spider web cracks.  Just the one, it is clean and like I said I stop drilled it at the end.  I have found a couple of products on AC Spruce, in particular INSTA-WELD but it says to clamp the parts together…this is not possible.  Also, if I use some type of adhesive that will wick in to the crack, do I then use some type of epoxy to fill the stop drill hole?


	


-- 

Bryan Martin

N61BM, CH 601 XL, 

RAM Subaru, Stratus re-drive.

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

jlatimer1(at)cox.net
Guest

Posted: Mon Dec 26, 2011 5:15 pm Post subject: Cracked Canopy

Steve,

 Sounds like you are making steady progress.  Still  plan on a trip to DVT to see your project.

  

 I have a crack in my HDS canopy.  It is more than  3inches long.  I stopped drilled then applied a strip of "Slap Stix".   Glide pilots have used it for years.  It works fine.  The plane has  130 hours on it and no problem.

  

 Here is a link to where I ordered  it.

  

 http://www.skysailing.com/pages/slapstix.htm

  

 Jerry

 Flying and having a great time.



   From: owner-zenith-list-server(at)matronics.com  [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Steve  Freeman

Sent: Sunday, December 25, 2011 2:49 PM

To:  zenith-list(at)matronics.com

Subject: Cracked  Canopy

 

  

Hi Guys, 

  

We have all heard this story before…While installing the rear  canopy on my 650 I got about a 3” crack.  I stop drilled it and I am trying  to decide if I can live with this or not.  Roughly $650 to get a new canopy  seems like a lot of money and I might wind up with the same thing again.   Honestly, I am not sure how this happened.  I was being super careful and I  was not drilling in a location where there seemed to be any pressure.   Well…it happened…It sucks but I have to move on. 

  

Can any of you guys make recommendations for the best  practice to repair the crack?  I know it will never be perfect but I have  heard some people have had a lot of luck.  There are no spider web  cracks.  Just the one, it is clean and like I said I stop drilled it at the  end.  I have found a couple of products on AC Spruce, in particular  INSTA-WELD but it says to clamp the parts together…this is not possible.   Also, if I use some type of adhesive that will wick in to the crack, do I then  use some type of epoxy to fill the stop drill hole? 

  

Any help is always appreciated… 

  

I hope everyone is having a great Christmas! 

  

Steve 

0235 Mounted will start wiring soon. 

Moving along with  fuselage..

   [quote][b]

Afterfxllc(at)aol.com
Guest

Posted: Tue Dec 27, 2011 5:10 am Post subject: Cracked Canopy

Guys 

  

 I found the reason for all this cracking canopy phenomenon. What I  found was Zenith says to drill  do a specific size (which I don't know off  the top of my head) but what I found was it wasn't big enough for the counter  sunk washer so when pressure is applied it exerts force around the hole thus a  crack. The fix is simple (and I have never cracked a canopy) is..... Use a step  bit to drill the canopy because it can't grab like a regular bit WILL. Then make  the holes big enough that the counter sunk washer is loose that way the washer  will rest on the rails and not be exerting outward pressure on the hole which  WILL crack the canopy eventually.

  

 Happy building 

 Jeff

  

  In a message dated 12/25/2011 11:18:16 P.M. Eastern Standard Time,  davgray(at)sbcglobal.net writes:

  	  Quote: 	
		           This might be a good thread to pursue as it seems to happen too    often.

   I would like to hear from others that cracked a canopy.  Details of    drill type and size, temperature at time of drilling, and hole-to-edge    distance.

   Also, from those that did not have this problem..

   I used a step drill, warmed the canopy over a warm air register, let the    bit generate a little heat from friction as it cut, kept the drill    perpendicular to the surface,

   and did not accept the 7 mm edge distance that would have occurred on a    few of my holes if I stuck entirely with the plans.

   My closest edge distance is 27 mm after a small modification.  Five    years plus without any cracks.  

    

   Gary Ray  

   Zenith 601XL-B, William Wynne Corvair 0.060 over, Roy's 5th  bearing,

   Mark's Falcon Heads, Marvel Schebler MA3-SPA Carburetor, 175 Hrs TT

          

    

      From: Steve Freeman (steve.freeman(at)syntaxds.com) 

   Sent: Sunday, December 25, 2011 4:49 PM

   To: zenith-list(at)matronics.com (zenith-list(at)matronics.com) 

   Subject: Cracked Canopy

    



         

Hi Guys,   

    

We have all heard this story beforeâ€¦While installing the    rear canopy on my 650 I got about a 3â€ crack.  I stop drilled it and I am    trying to decide if I can live with this or not.  Roughly $650 to get a    new canopy seems like a lot of money and I might wind up with the same thing    again.  Honestly, I am not sure how this happened.  I was being    super careful and I was not drilling in a location where there seemed to be    any pressure.  Wellâ€¦it happenedâ€¦It sucks but I have to move    on.   

    

Can any of you guys make recommendations for the best    practice to repair the crack?  I know it will never be perfect but I have    heard some people have had a lot of luck.  There are no spider web    cracks.  Just the one, it is clean and like I said I stop drilled it at    the end.  I have found a couple of products on AC Spruce, in particular    INSTA-WELD but it says to clamp the parts togetherâ€¦this is not possible.     Also, if I use some type of adhesive that will wick in to the crack, do I then    use some type of epoxy to fill the stop drill hole?   

    

Any help is always appreciatedâ€¦   

    

I hope everyone is having a great Christmas!   

    

Steve   

0235 Mounted will start wiring soon.   

Moving along with fuselage..

 	  Quote: 	
		  



href="http://www.aeroelectric.com">www.aeroelectric.com

href="http://www.buildersbooks.com">www.buildersbooks.com

href="http://www.homebuilthelp.com">www.homebuilthelp.com

href="http://www.matronics.com/contribution">http://www.matronics.com/chref="http://www.matronics.com/Navigator?Zenith-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/c





tp://www.aeroelectric.com/">www.aeroelectric.com

/ href="http://www.buildersbooks.com/">www.buildersbooks.com

http://www.homebuilthelp.com/">www.homebuilthelp.com

p://www.matronics.com/contribution">http://www.matronics.com/contribution

ef="http://www.matronics.com/Navigator?Zenith-List">http://www.matronics.com/Navigator?Zenith-List

s.matronics.com/">http://forums.matronics.com

p://www.matronics.com/contribution">http://www.matronics.com/contribution



	
	


 [quote][b]

foxatgibsons(at)gmail.com
Guest

Posted: Tue Dec 27, 2011 10:39 am Post subject: Cracked Canopy

hello  builders



take a really {40-100x} close look at any hole drilled in any lexan /poly

sheet and if one used a regular or even a ultra sharp bit  you should see a

dozen or so very tiny cracks that appear at the boundary area  {clear to

opaque} i believe to avoid this propagating in to a crack later

you must

1. drill in steps

2 ream or melt to the proper size

3 inspect  to see if the cracks are gone

4 slightly break the edges

5 make sure the fastener does not contact the sheet plastic on the inside

of the hole{ allow for the  thermal and vibration stress }



take a really close look at any hole you drill in plastic sheets and what

appears to be perfect

still has the cracks

it has to be viewed with a loupe at least 40 power and they are on the

bottom only

cheers Peter

 Fox

On Tue, Dec 27, 2011 at 5:08 AM, <Afterfxllc(at)aol.com> wrote:



[quote] **

 Guys



 I found the reason for all this cracking canopy phenomenon. What I found

 was Zenith says to drill  do a specific size (which I don't know off the

 top of my head) but what I found was it wasn't big enough for the counter

 sunk washer so when pressure is applied it exerts force around the hole

 thus a crack. The fix is simple (and I have never cracked a canopy) is....

 Use a step bit to drill the canopy because it can't grab like a regular bit

 WILL. Then make the holes big enough that the counter sunk washer is loose

 that way the washer will rest on the rails and not be exerting outward

 pressure on the hole which WILL crack the canopy eventually.



 Happy building

 Jeff



  In a message dated 12/25/2011 11:18:16 P.M. Eastern Standard Time,

 davgray(at)sbcglobal.net writes:



  This might be a good thread to pursue as it seems to happen too often.

 I would like to hear from others that cracked a canopy.  Details of drill

 type and size, temperature at time of drilling, and hole-to-edge distance

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Wed Dec 28, 2011 1:00 pm Post subject: Cracked Canopy

The canopy is made of acrylic (Plexiglas), It must be handled with extreme care, it is very easy to crack. 



Polycarbonate (Lexan) is very forgiving. You can treat it like plywood as far as cutting and drilling are concerned. It's almost impossible to crack.



Lexan is much more expensive than Plexiglas, which is one reason it's not used in the canopy.

On Dec 27, 2011, at 1:37 PM, Peter Fox wrote:



 	  Quote: 	
		   hello  builders 

 

 take a really {40-100x} close look at any hole drilled in any lexan /poly sheet and if one used a regular or even a ultra sharp bit  you should see a dozen or so very tiny cracks that appear at the boundary area  {clear to opaque} i believe to avoid this propagating in to a crack later

 you must 

 1. drill in steps 

 2 ream or melt to the proper size 

 3 inspect  to see if the cracks are gone 

 4 slightly break the edges 

 5 make sure the fastener does not contact the sheet plastic on the inside of the hole{ allow for the  thermal and vibration stress }


	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus re-drive.

do not archive.

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

Scotsman

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

Posted: Thu Dec 29, 2011 5:14 am Post subject: Re: Cracked Canopy

hi guys, I had received advice to blunt the drill bit so that it grinds as opposed to bites into the material. Some of the local guys referred me to this US video on the subject.



http://www.eaavideo.org/video.aspx?v=1200008869001



I have not tried it yet but believe that it may be correct as my second crack in the canopy occurred with almost no pressure and a brand new unused high quality drill bit. 



I would be interested to hear your thoughts on it.



Cheers

James

_________________
Cell +27 83 675 0815

jaybannist(at)cs.com
Guest

Posted: Thu Dec 29, 2011 5:43 am Post subject: Cracked Canopy

James,

 

 I used a very sharp pointed drill bit to drill pilot holes.   This bit was recommended for drilling acrylic plastic and it worked well for me.  Others have recommended a really flat point drill bit.  That tells me that either pointed or flat is OK, but not in between, ie "normal" bits.  I was  able to drill right through the plastic and into the aluminum tube,  which you probably couldn't do with the flat pointed bit.  

 

 Jay

    

  

     

  

     

  

    --

psm(at)att.net
Guest

Posted: Thu Dec 29, 2011 6:13 am Post subject: Cracked Canopy

Hi Guys,

     

     The classic trick for drilling acrylic is to reduce the "Rake" on     the drill bits used.  This means the bit cannot bite into the     plastic but rather takes either a very shallow chip or just melts     through the plastic.

     

     I hand grind my own drill points, so it is easy for me to reduce the     rake to zero on drills for acrylic.  I'm not sure that is what I     did.  Instead, What I tend to do is to use a very slow speed on my     battery powered drill and also I tend to use step drills for this     kind of drilling.  Step drilling can be done either by using a store     bought step drill (looks like a Christmas tree) or buy using steps     of drill size so you are only taking a small bite out of the     existing hole to enlarge it a little bit.  

     

     The reduced rake trick can be simulated by running the drill     backwards.  This ensures you don't take any bite at all out of the     plastic but melt your way through.  It is an extreme approach, but     works just fine.

     

     Paul

     Camas, WA

     

     On 12/29/2011 5:40 AM, Jay Bannister wrote:     [quote]James,

           

           I used a very sharp pointed drill bit to drill pilot holes.             This bit was recommended for drilling acrylic plastic and it           worked well for me.  Others have recommended a really flat           point drill bit.  That tells me that either pointed or flat is           OK, but not in between, ie "normal" bits.  I           was able to drill right through the plastic and into the           aluminum tube, which you probably couldn't do with the flat           pointed bit.  

         

           Jay

            

           

            

           

            

           

           -----Original             Message-----

             From: Scotsman <james.Roberts(at)standardbank.co.za> (james.Roberts(at)standardbank.co.za)

             To: zenith-list <zenith-list(at)matronics.com> (zenith-list(at)matronics.com)

             Sent: Thu, Dec 29, 2011 7:20 am

             Subject: Re: Cracked Canopy

             

                             	  Quote: 	
		  --> Zenith-List message posted by: "Scotsman" <james.Roberts(at)standardbank.co.za (james.Roberts(at)standardbank.co.za)>



hi guys, I had received advice to blunt the drill bit so that it grinds as 

opposed to bites into the material. Some of the local guys referred me to this 

US video on the subject.



http://www.eaavideo.org/video.aspx?v=1200008869001



I have not tried it yet but believe that it may be correct as my second crack in 

the canopy occurred with almost no pressure and a brand new unused high quality 

drill bit. 



I would be interested to hear your thoughts on it.



Cheers

James



--------

Cell   +27 83 675 0815





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=361886#361886



_blank">www.aeroelectric.com

" target="_blank">www.buildersbooks.com

="_blank">www.homebuilthelp.com

_blank">http://www.matronics.com/contribution

arget="_blank">http://www.matronics.com/Navigator?Zenith-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	
             

                        

                 	  Quote: 	
		  

	
     [b]

steve.freeman(at)syntaxds
Guest

Posted: Thu Dec 29, 2011 6:39 am Post subject: Cracked Canopy

Hi Guys,

 

I have seen many notes on this topic suggesting “step drills” (are we talking about a Uni-Bit) but I have never seen a step drill small enough for the holes required for the canopy.  Can anyone provide a link to where I can find a small hole step drill?

 

When my canopy cracked I don’t think it had anything to do with the bit I was using.  What I “think” happened is a small piece of debris got trapped between the glass and the rear canopy flashing which caused a pressure point.  As I drilled this caused a small lever point and the canopy cracked at that point.  I suspect this is the case because when I examined the location a small bead of plastic (but big enough to do the job) fell from the space between the canopy and the flashing.  Until that point and at all points after the drilling was not an issue but I will admit I am nervous about enlarging the holes to accept the hardware.

 

Steve

 

From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Paul Mulwitz

Sent: Thursday, December 29, 2011 7:11 AM

To: zenith-list(at)matronics.com

Subject: Re: Re: Cracked Canopy

 

Hi Guys,



The classic trick for drilling acrylic is to reduce the "Rake" on the drill bits used.  This means the bit cannot bite into the plastic but rather takes either a very shallow chip or just melts through the plastic.



I hand grind my own drill points, so it is easy for me to reduce the rake to zero on drills for acrylic.  I'm not sure that is what I did.  Instead, What I tend to do is to use a very slow speed on my battery powered drill and also I tend to use step drills for this kind of drilling.  Step drilling can be done either by using a store bought step drill (looks like a Christmas tree) or buy using steps of drill size so you are only taking a small bite out of the existing hole to enlarge it a little bit.  



The reduced rake trick can be simulated by running the drill backwards.  This ensures you don't take any bite at all out of the plastic but melt your way through.  It is an extreme approach, but works just fine.



Paul

Camas, WA



On 12/29/2011 5:40 AM, Jay Bannister wrote: 

James,



I used a very sharp pointed drill bit to drill pilot holes.   This bit was recommended for drilling acrylic plastic and it worked well for me.  Others have recommended a really flat point drill bit.  That tells me that either pointed or flat is OK, but not in between, ie "normal" bits.  I was able to drill right through the plastic and into the aluminum tube, which you probably couldn't do with the flat pointed bit.  



Jay

 



 



 



--

larrycmcfarland(at)gmail.
Guest

Posted: Thu Dec 29, 2011 7:02 am Post subject: Cracked Canopy

Paul,

You can find a small Uni-Bit drill at Harbor Freight.  See link.

These work very well in canopy plastics.

http://www.harborfreight.com/catalogsearch/result?keyword=unibit

 

Larry McFarland  601HDS at www.macsmachine.com

 

From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Steve Freeman

Sent: Thursday, December 29, 2011 8:37 AM

To: zenith-list(at)matronics.com

Subject: RE: Re: Cracked Canopy

 

Hi Guys,

 

I have seen many notes on this topic suggesting “step drills” (are we talking about a Uni-Bit) but I have never seen a step drill small enough for the holes required for the canopy.  Can anyone provide a link to where I can find a small hole step drill?

 

When my canopy cracked I don’t think it had anything to do with the bit I was using.  What I “think” happened is a small piece of debris got trapped between the glass and the rear canopy flashing which caused a pressure point.  As I drilled this caused a small lever point and the canopy cracked at that point.  I suspect this is the case because when I examined the location a small bead of plastic (but big enough to do the job) fell from the space between the canopy and the flashing.  Until that point and at all points after the drilling was not an issue but I will admit I am nervous about enlarging the holes to accept the hardware.

 

Steve

 

From: owner-zenith-list-server(at)matronics.com (owner-zenith-list-server(at)matronics.com) [mailto:owner-zenith-list-server(at)matronics.com] ([email][mailto:owner-zenith-list-server(at)matronics.com][/email]) On Behalf Of Paul Mulwitz

Sent: Thursday, December 29, 2011 7:11 AM

To: zenith-list(at)matronics.com (zenith-list(at)matronics.com)

Subject: Re: Re: Cracked Canopy

 

Hi Guys,



The classic trick for drilling acrylic is to reduce the "Rake" on the drill bits used.  This means the bit cannot bite into the plastic but rather takes either a very shallow chip or just melts through the plastic.



I hand grind my own drill points, so it is easy for me to reduce the rake to zero on drills for acrylic.  I'm not sure that is what I did.  Instead, What I tend to do is to use a very slow speed on my battery powered drill and also I tend to use step drills for this kind of drilling.  Step drilling can be done either by using a store bought step drill (looks like a Christmas tree) or buy using steps of drill size so you are only taking a small bite out of the existing hole to enlarge it a little bit.  



The reduced rake trick can be simulated by running the drill backwards.  This ensures you don't take any bite at all out of the plastic but melt your way through.  It is an extreme approach, but works just fine.



Paul

Camas, WA



On 12/29/2011 5:40 AM, Jay Bannister wrote: 

James,



I used a very sharp pointed drill bit to drill pilot holes.   This bit was recommended for drilling acrylic plastic and it worked well for me.  Others have recommended a really flat point drill bit.  That tells me that either pointed or flat is OK, but not in between, ie "normal" bits.  I was able to drill right through the plastic and into the aluminum tube, which you probably couldn't do with the flat pointed bit.  



Jay

 



 



 



--

jlatimer1(at)cox.net
Guest

Posted: Thu Dec 29, 2011 7:38 am Post subject: Cracked Canopy

Steve,



I used a small regular well used dull bit (#20 I think) to drill the pilot holes and then a Uni Bit to enlarge the holes for the mounting hardware.



Jerry

psm(at)att.net
Guest

Posted: Thu Dec 29, 2011 8:24 am Post subject: Cracked Canopy

Steve,

     

     The final size of the holes in the plastic canopy is around 3/8     inch.  This allows the tinnerman washers to rest on the flat flange     to hold the canopy in place.  The angled (cone) shape of the     tinnerman washer holds the canopy approximately in place while     allowing a little movement as temperature changes create different     expansion in the plastic and metal parts.

     

     I've never seen a step drill that was so large it couldn't enlarge a     hole from #40 to 3/8 inch.  I tend to use ones from Harbor Freight     because I'm too cheap to buy the expensive Unibits.

     

     Paul

     Camas, WA

     

     On 12/29/2011 6:37 AM, Steve Freeman wrote:     [quote]       

       

I           have seen many notes on this topic suggesting “step drills”           (are we talking about a Uni-Bit) but I have never seen a step           drill small enough for the holes required for the canopy.  Can           anyone provide a link to where I can find a small hole step           drill?     [b]

n4546v(at)mindspring.com
Guest

Posted: Thu Dec 29, 2011 9:54 am Post subject: Cracked Canopy

do not archive

  

 Hello Listers:

  

 Attached is the drill geometry LP Plastics,  the people who make the windows, suggest.

  

 The important part is the "dubbing" of the cutting  lip rake angle.  An off the shelf drill has a positive cutting lip angle  which will "dig" into soft materials like brass, AL, or plexi.  By dubbing  the rake angle to "0" or a slightly negative angle, the cutting edge "scrapes"  the material in front of it rather than digging in which is what cracks  plexi.  Since this scraping action does not result in the drill self  feeding or pulling itsself into the material, it only cuts by you applying  pressure.  Dub the cutting edge, apply pressure judiciously, and always  back up the work with a piece of wood so the drill doesn't burst through upon  penetration.

  

 The drill still "drills" the hole by removing  meteral, it doesn't burn through it.  To see many other diagrams to  clarify, Google search "drill dubbing", lots comes up.

  

 RE Lexan:  Arn't there two very good reasons  Lexan isn't used for aircraft cabin windows?

  

 1.  It scratches much easier than  plexi.

  

 2.  And more importantly, it's what is used  for bullet proof and shatter proof glass, so in a crash, rescuers can't break  through to get occupants out, that's especially bad if there's a  fire!

  

 Regards,

  

 Randy, Las Vegas

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psm(at)att.net
Guest

Posted: Thu Dec 29, 2011 10:26 am Post subject: Cracked Canopy

Hi Randy,

     

     Mostly the reason for not using Lexan (polycarbonate) on home built     airplanes is the expense.

     

     You are correct that it is soft and scratches easily.  For that     reason it is necessary to "Hard Coat" it with polyurethane in any     normal application.  This solves the scratch problem but adds cost.      You can get an idea of the cost increment if you go to your local     eyeglasses store.  They charge a significant increment price for     polycarbonate lenses over standard (mostly acrylic) lenses.  Even in     small quantities this is often a $50 increment.

     

     I don't understand the issue of being "Bullet Proof".  In reality it     is just as easy, maybe easier, to hack away at Lexan as Plexiglass.

     

     Best regards,

     

     Paul

     Camas, WA

     

     On 12/29/2011 9:48 AM, Randy L. Thwing wrote:     [quote]       RE Lexan:  Arn't there two very           good reasons Lexan isn't used for aircraft cabin windows?

        

       1.  It scratches much easier than           plexi.

        

       2.  And more importantly, it's           what is used for bullet proof and shatter proof glass, so in a           crash, rescuers can't break through to get occupants out,           that's especially bad if there's a fire!

        

     [b]

wjones(at)brazoriainet.co
Guest

Posted: Thu Dec 29, 2011 10:36 am Post subject: Cracked Canopy

A 1/4" thickness will stop a 38 caliber ,sounds  bullet proof to me . Wade

 [quote]   ---

steve.freeman(at)syntaxds
Guest

Posted: Thu Dec 29, 2011 10:58 am Post subject: Cracked Canopy

Hi Paul,

 

Thanks for the input.  I was thinking of the original pilot hole not the finished hole size.  Thanks for clarifying.

 

Steve

 

From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Paul Mulwitz

Sent: Thursday, December 29, 2011 9:21 AM

To: zenith-list(at)matronics.com

Subject: Re: Re: Cracked Canopy

 

Steve,



The final size of the holes in the plastic canopy is around 3/8 inch.  This allows the tinnerman washers to rest on the flat flange to hold the canopy in place.  The angled (cone) shape of the tinnerman washer holds the canopy approximately in place while allowing a little movement as temperature changes create different expansion in the plastic and metal parts.



I've never seen a step drill that was so large it couldn't enlarge a hole from #40 to 3/8 inch.  I tend to use ones from Harbor Freight because I'm too cheap to buy the expensive Unibits.



Paul

Camas, WA



On 12/29/2011 6:37 AM, Steve Freeman wrote: 

I have seen many notes on this topic suggesting “step drills” (are we talking about a Uni-Bit) but I have never seen a step drill small enough for the holes required for the canopy.  Can anyone provide a link to where I can find a small hole step drill? 	  Quote: 	
		   </     -- Please Support Your Lists This Month nbsp;    (And Get Some AWESOME FREE    November is the Annual List Fund Raiser.  Click below to find out more Free Incentive Gifts AeroElectric www.aeroelectric.com<www.buildersbooks.comwww.homebuilthelp.comhttp://www.matron===================http://forums.matronics.com[/url]         - List Contribution Web generous nbsp;                        --> http://www.matronics.com/c=[/b] 	


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