Bending Plexiglass

[Tony Condon[_2_]]

I need to make a new section of the canopy on the Cherokee. Its a pretty
simple bend, not really a compound curve or anything. But I dont know
anything about how to do it. I suspect that I need to heat the plexi up
and then weight it to bend, repeat as necessary? Im sure that several of
us have been there done that. Looking forward to ideas. Thanks!
-Tony Condon
Cherokee II N373Y

[Brad[_2_]]

On Mar 23, 4:30*pm, Tony Condon >
wrote:
> I need to make a new section of the canopy on the Cherokee. *Its a pretty
> simple bend, not really a compound curve or anything. *But I dont know
> anything about how to do it. *I suspect that I need to heat the plexi up
> and then weight it to bend, repeat as necessary? *Im sure that several of
> us have been there done that. *Looking forward to ideas. *Thanks!
> -Tony Condon
> Cherokee II N373Y

Hi Tony,

Quite a coincidence that you would post this today. I just finished
installing the slider window and rails in my HP-24 canopy today. It
fit well but the window is slightly curved too much and one corner did
not seat well.

What I did was fire up my propane heater and put some gloves on, then
held the window close enough to get it pliable, then held it in place
to get an idea of the proper fit, then over bent it a bit. When it
cooled it snapped almost perfectly in place.

This might work for you!

Cheers,
Brad

[Wayne Paul]

Brad,

Here is another approach to constructing a canopy window.
http://www.soaridaho.com/Schreder/Construction/Canopy/slidingwindow.html



"Brad" > wrote in message
...
On Mar 23, 4:30 pm, Tony Condon >
wrote:
> I need to make a new section of the canopy on the Cherokee. Its a pretty
> simple bend, not really a compound curve or anything. But I dont know
> anything about how to do it. I suspect that I need to heat the plexi up
> and then weight it to bend, repeat as necessary? Im sure that several of
> us have been there done that. Looking forward to ideas. Thanks!
> -Tony Condon
> Cherokee II N373Y

Hi Tony,

Quite a coincidence that you would post this today. I just finished
installing the slider window and rails in my HP-24 canopy today. It
fit well but the window is slightly curved too much and one corner did
not seat well.

What I did was fire up my propane heater and put some gloves on, then
held the window close enough to get it pliable, then held it in place
to get an idea of the proper fit, then over bent it a bit. When it
cooled it snapped almost perfectly in place.

This might work for you!

Cheers,
Brad

[Brad[_2_]]

On Mar 23, 6:10*pm, "Wayne Paul" > wrote:
> Brad,
>
> Here is another approach to constructing a canopy window.http://www.soaridaho.com/Schreder/Construction/Canopy/slidingwindow.html
>
> "Brad" > wrote in message
>
> ...
> On Mar 23, 4:30 pm, Tony Condon >
> wrote:
>
> > I need to make a new section of the canopy on the Cherokee. Its a pretty
> > simple bend, not really a compound curve or anything. But I dont know
> > anything about how to do it. I suspect that I need to heat the plexi up
> > and then weight it to bend, repeat as necessary? Im sure that several of
> > us have been there done that. Looking forward to ideas. Thanks!
> > -Tony Condon
> > Cherokee II N373Y
>
> Hi Tony,
>
> Quite a coincidence that you would post this today. I just finished
> installing the slider window and rails in my HP-24 canopy today. It
> fit well but the window is slightly curved too much and one corner did
> not seat well.
>
> What I did was fire up my propane heater and put some gloves on, then
> held the window close enough to get it pliable, then held it in place
> to get an idea of the proper fit, then over bent it a bit. When it
> cooled it snapped almost perfectly in place.
>
> This might work for you!
>
> Cheers,
> Brad

Wayne,

that's excellent! thank you for posting this!

Brad

[Tony Condon[_2_]]

neato, maybe ill have to think about putting a side window in. right now
my ventilation is a big hole in the nose with a tube running up to the
panel.
-Tony Condon
Cherokee II N373Y

[[email protected]]

If you can get away with just a flat bend, I would use a piece of
polycarbonate (lexan or many other trademarks). Just bend it. No
heat necessary and it won't crack. Ever. If you are looking pretty
much straight through the glass - the glass is more or less parallel
to your face, you can use PETG which is a lot cheaper. It is what is
used to make pop bottles and that diabolical plastic packaging that
you can't get open. PETG is typically run through the machines faster
and usually has a lot of waviness. If it is thin (.060") and it is
not at a sharp angle to your line of sight, they won't affect the
optics enough to worry about.

With polycarbonate or PETG, you can also use a thin piece as it is
something like 16 times as strong as acrylic. Of course, if you use a
thinner piece of acrylic, it is also less likely to crack too.

Mount the glass with double sided trim tape from the auto parts store
- just be sure it is the heavy duty stuff.

Good luck and have fun.
Doug


On Mar 24, 12:30*am, Tony Condon >
wrote:
> I need to make a new section of the canopy on the Cherokee. *Its a pretty
> simple bend, not really a compound curve or anything. *But I dont know
> anything about how to do it. *I suspect that I need to heat the plexi up
> and then weight it to bend, repeat as necessary? *Im sure that several of
> us have been there done that. *Looking forward to ideas. *Thanks!
> -Tony Condon
> Cherokee II N373Y

[[email protected]]

On Mar 24, 3:31*am, wrote:
> If you can get away with just a flat bend, I would use a piece of
> polycarbonate (lexan or many other trademarks). *Just bend it. *No
> heat necessary and it won't crack. *Ever. *If you are looking pretty
> much straight through the glass - the glass is more or less parallel
> to your face, you can use PETG which is a lot cheaper. *It is what is
> used to make pop bottles and that diabolical plastic packaging that
> you can't get open. *PETG is typically run through the machines faster
> and usually has a lot of waviness. *If it is thin (.060") and it is
> not at a sharp angle to your line of sight, they won't affect the
> optics enough to worry about.
>
> With polycarbonate or PETG, you can also use a thin piece as it is
> something like 16 times as strong as acrylic. *Of course, if you use a
> thinner piece of acrylic, it is also less likely to crack too.
>
> Mount the glass with double sided trim tape from the auto parts store
> - just be sure it is the heavy duty stuff.
>
> Good luck and have fun.
> Doug
>
> On Mar 24, 12:30*am, Tony Condon >
> wrote:
>
>
>
> > I need to make a new section of the canopy on the Cherokee. *Its a pretty
> > simple bend, not really a compound curve or anything. *But I dont know
> > anything about how to do it. *I suspect that I need to heat the plexi up
> > and then weight it to bend, repeat as necessary? *Im sure that several of
> > us have been there done that. *Looking forward to ideas. *Thanks!
> > -Tony Condon
> > Cherokee II N373Y- Hide quoted text -
>
> - Show quoted text -

Polycarbonate is an excellent choice for a simple bend as described.
It will also tolerate drilling and countersinking for fasteners if
needed.
PETG will not hold up very well in sunlight from my experience.
As described, skip the heat and cold bend.
Good Luck
UH

[Tony Condon[_2_]]

Interesting. I was worried about the possibility of crazing from a cold
bend due to surface tension. apparently thats not an issue? Im going to
try to run to the local plastic shop today and see what they can do for
me.
-Tony Condon
Cherokee II N373Y

[Tony Condon[_2_]]

Alright well I bought a sheet of polycarbonate (Lexan) tonight and got it
cut to fit the canopy. Next trick is to get it glued in place. The
canopy frame is a steel tube wrapped in fabric and coated with something
that turns it brown. the fabric is still for the most part intact, a few
bits here and there were sacrificed during plexiglass removal. Any
recommendations on glue?
-Tony Condon
Cherokee II N373Y

[[email protected]]

As mentioned in my previous post, the heavy duty, double sided trim
tape works quite well. It is available at most auto parts stores. I
am sorry I can't remember the exact number. Most of what you find is
made by 3M. There are different grades and you want the one that is
used for holding moldings to the outside of the car. Should say heavy
duty or Very High Bond, etc. It is usually gray foam about .060"
thick, but sometimes is black. (3M does make a VHB tape that has
white foam and is strong, but needs a special primer and is not as
easy to work with - not to mention, it is more expensive) All of the
heavy duty stuff I have seen has a reddish-orange (or, orangish-red?)
backing tape.

Clean the canopy frame well. The tape will conform pretty well, but
if there are any sharper bumps, you might want to sand them down a
little. Stick the tape down and rub it on really well. I have a hard
rubber wheel that I screwed onto a scrap of wood for a handle and roll
it. Pressure is key to getting a good bond. Peel back a little of
the protective film from around the edge of the glass and lightly
scuff the glass with fine Scotch-brite in the area where it bonds. If
possible, try to leave the rest of the protective film on until you
are finished. I have seen some Lexan with a paper covering, which you
might want to peel back a little around the edge so you can see how
you are doing when you stick the glass to the tape. You should be
able to just blow the dust off, but if you feel the need to clean it,
just use soap and water. Different manufacturers claim different
resistance to various solvents like alcohol. There are too many
different formulations, so in the absence of actual information from
the manufacturer, I would avoid using any hydrocarbon solvents. (An
earlier post mentioned using alcohol to clean acrylic, which is
usually a bad idea as it will craze and crack many acrylics. Some are
resistant to ethyl alcohol, but most of the alcohol used for cleaning
(denatured alcohol) has some methanol in it which is really bad for
acrylic.)

When you are ready to stick the glass to the frame, test fit it and
make some index marks - I make a mark on a couple of the pieces of
masking tape that I use to hold it while fitting it. Then just cut
that piece of tape rather than peeling it off. You have to be pretty
accurate. Peel a short piece of the backing away from the tape in a
few key places. It is a good idea to start in the middle of the bend
and work out from there, but you also need a few spots to stick
initially all around the perimeter. Lightly put the glass in place.
As long as you don't press it much, you can reposition it. Once it is
in place, you can start pulling the tape backing out from under the
glass and sticking it down.

A couple of cautions: If this is for a removable canopy, do this on
the glider as you can distort the shape a lot. Don't start in one
corner and work your way around as you will wind up putting a twist in
the frame and glass. Work, more or less, from the middle of each side
toward the corners. Do a few inches in each direction, and then go do
the same on the opposite side. It is kind of like torqueing down a
cylinder head.

Once you have it all stuck down, go around with a roller (or you can
just use you finger and press as hard as you can) to really stick it.

The acrylic adhesive on the tape is supposed to be very resistant to
UV - and even get stronger with continued exposure - so you can just
leave it like that, or you can put a strip of tape of whatever color
you prefer around it. It might look nicer that way too.

If you have any more questions, feel free to email me.

Doug



On Mar 25, 5:00*am, Tony Condon >
wrote:
> Alright well I bought a sheet of polycarbonate (Lexan) tonight and got it
> cut to fit the canopy. *Next trick is to get it glued in place. *The
> canopy frame is a steel tube wrapped in fabric and coated with something
> that turns it brown. *the fabric is still for the most part intact, a few
> bits here and there were sacrificed during plexiglass removal. *Any
> recommendations on glue?
> -Tony Condon
> Cherokee II N373Y

[[email protected]]

On Mar 25, 5:14*am, wrote:
> As mentioned in my previous post, the heavy duty, double sided trim
> tape works quite well. *It is available at most auto parts stores. *I
> am sorry I can't remember the exact number. *Most of what you find is
> made by 3M. *There are different grades and you want the one that is
> used for holding moldings to the outside of the car. *Should say heavy
> duty or Very High Bond, etc. *It is usually gray foam about .060"
> thick, but sometimes is black. *(3M does make a VHB tape that has
> white foam and is strong, but needs a special primer and is not as
> easy to work with - not to mention, it is more expensive) * All of the
> heavy duty stuff I have seen has a reddish-orange (or, orangish-red?)
> backing tape.
>
> Clean the canopy frame well. *The tape will conform pretty well, but
> if there are any sharper bumps, you might want to sand them down a
> little. *Stick the tape down and rub it on really well. *I have a hard
> rubber wheel that I screwed onto a scrap of wood for a handle and roll
> it. *Pressure is key to getting a good bond. *Peel back a little of
> the protective film from around the edge of the glass and lightly
> scuff the glass with fine Scotch-brite in the area where it bonds. *If
> possible, try to leave the rest of the protective film on until you
> are finished. *I have seen some Lexan with a paper covering, which you
> might want to peel back a little around the edge so you can see how
> you are doing when you stick the glass to the tape. *You should be
> able to just blow the dust off, but if you feel the need to clean it,
> just use soap and water. *Different manufacturers claim different
> resistance to various solvents like alcohol. *There are too many
> different formulations, so in the absence of actual information from
> the manufacturer, I would avoid using any hydrocarbon solvents. *(An
> earlier post mentioned using alcohol to clean acrylic, which is
> usually a bad idea as it will craze and crack many acrylics. *Some are
> resistant to ethyl alcohol, but most of the alcohol used for cleaning
> (denatured alcohol) has some methanol in it which is really bad for
> acrylic.)
>
> When you are ready to stick the glass to the frame, test fit it and
> make some index marks - I make a mark on a couple of the pieces of
> masking tape that I use to hold it while fitting it. *Then just cut
> that piece of tape rather than peeling it off. *You have to be pretty
> accurate. *Peel a short piece of the backing away from the tape in a
> few key places. *It is a good idea to start in the middle of the bend
> and work out from there, but you also need a few spots to stick
> initially all around the perimeter. *Lightly put the glass in place.
> As long as you don't press it much, you can reposition it. *Once it is
> in place, you can start pulling the tape backing out from under the
> glass and sticking it down.
>
> A couple of cautions: If this is for a removable canopy, do this on
> the glider as you can distort the shape a lot. *Don't start in one
> corner and work your way around as you will wind up putting a twist in
> the frame and glass. *Work, more or less, from the middle of each side
> toward the corners. *Do a few inches in each direction, and then go do
> the same on the opposite side. *It is kind of like torqueing down a
> cylinder head.
>
> Once you have it all stuck down, go around with a roller (or you can
> just use you finger and press as hard as you can) to really stick it.
>
> The acrylic adhesive on the tape is supposed to be very resistant to
> UV - and even get stronger with continued exposure - so you can just
> leave it like that, or you can put a strip of tape of whatever color
> you prefer around it. *It might look nicer that way too.
>
> If you have any more questions, feel free to email me.
>
> Doug
>
> On Mar 25, 5:00*am, Tony Condon >
> wrote:
>
>
>
> > Alright well I bought a sheet of polycarbonate (Lexan) tonight and got it
> > cut to fit the canopy. *Next trick is to get it glued in place. *The
> > canopy frame is a steel tube wrapped in fabric and coated with something
> > that turns it brown. *the fabric is still for the most part intact, a few
> > bits here and there were sacrificed during plexiglass removal. *Any
> > recommendations on glue?
> > -Tony Condon
> > Cherokee II N373Y- Hide quoted text -
>
> - Show quoted text -

Old conservative mechanical guy speakin' now. To be safe, I would add
a row of screws or rivets, at least along the sides, to handle most of
the peeling force that will remain after installation. If the plastic
were to be formed, this would not be an issue. Most simple way would
be Pop rivets with holes in plastic slightly bigger than rivet body.
About 4 inch spacing would be fine. If you put one in the center of
the top, forward and aft, this would give you a good way to position
and index the plastic on installation.
Rivets on your canopy frame might be a bit ugly, but not as ugly as
blown off canopy and doing it again.
Good Luck
UH

[bumper]

> wrote in message
...
On Mar 25, 5:14 am, wrote:
Old conservative mechanical guy speakin' now. To be safe, I would add
a row of screws or rivets, at least along the sides, to handle most of
the peeling force that will remain after installation. If the plastic
were to be formed, this would not be an issue. Most simple way would
be Pop rivets with holes in plastic slightly bigger than rivet body.
About 4 inch spacing would be fine. If you put one in the center of
the top, forward and aft, this would give you a good way to position
and index the plastic on installation.
Rivets on your canopy frame might be a bit ugly, but not as ugly as
blown off canopy and doing it again.
Good Luck
UH


Another old conservative mech guy:

I would not recommend using pop-rivets of any type on acrylic plastic
(Plexiglas). You may get away with it on polycarbonate (Lexan) or other
mechanically strong plastics, but it may crack Plexi.

Even if you over-drill the holes to help prevent cracking, the pop-rivet
itself is set by drawing in a metal bead at the end of the mandrel to expand
the rivet. This will apply pressure to the Plexi and may well cause stress
cracking. Note that you might get away with it if the "factory head" (the
original rivet head) is on the Plexi side and the "shop head" (the part that
expands) is on the poly side - - still, I wouldn't risk it. Safer to drill
(using plastic drill bits or drill bits ground to reduce relief angle -
again, to help prevent cracking the plastic) and then tap the plastic for
small machine screws (just like Mecaplex does).

bumper
maker of the world famous QV and MKIII
zz
Minden, NV

bumper

[[email protected]]

On Mar 25, 2:09*pm, "bumper" > wrote:
> > wrote in message
>
> ...
> On Mar 25, 5:14 am, wrote:
> Old conservative mechanical guy speakin' now. To be safe, I would add
> a row of screws or rivets, at least along the sides, to handle most of
> the peeling force that will remain after installation. If the plastic
> were to be formed, this would not be an issue. Most simple way would
> be Pop rivets with holes in plastic slightly bigger than rivet body.
> About 4 inch spacing would be fine. If you put one in the center of
> the top, forward and aft, this would give you a good way to position
> and index the plastic on installation.
> Rivets on your canopy frame might be a bit ugly, but not as ugly as
> blown off canopy and doing it again.
> Good Luck
> UH
>
> Another old conservative mech guy:
>
> I would not recommend using pop-rivets of any type on acrylic plastic
> (Plexiglas). You may get away with it on polycarbonate (Lexan) or other
> mechanically strong plastics, but it may crack Plexi.
>
> Even if you over-drill the holes to help prevent cracking, the pop-rivet
> itself is set by drawing in a metal bead at the end of the mandrel to expand
> the rivet. This will apply pressure to the Plexi and may well cause stress
> cracking. Note that you might get away with it if the "factory head" (the
> original rivet head) is on the Plexi side and the "shop head" (the part that
> expands) is on the poly side - - still, I wouldn't risk it. Safer to drill
> (using plastic drill bits or drill bits ground to reduce relief angle -
> again, to help prevent cracking the plastic) and then tap the plastic for
> small machine screws (just like Mecaplex does).
>
> bumper
> maker of the world famous QV and MKIII
> zz
> Minden, NV
>
> bumper

I agree. I was assuming he would be using polycarbonate and did
suggest oversize holes.
UH