Bending Plexiglass

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

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

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