Plexiglass windshield
 

Hi,

My brother-in-law and I are refurbishing an old Sunray 14' boat. It's in
very good condition except for the windshield which has to be replaced. We
want to do it ourselves but need a little advice on how to proceed. Molding
it with plexiglass is definitely one option we're looking at. Does anyone
have a good site to propose where we could find complete and thorough
information on the technique to use? I have done some research and found a
few sites but they were not specific enough.

Thanks in advance to all!


Marcel

On Sun, 21 Nov 2004 21:37:04 -0500, "Linemar2002"
wrote:

Hi,

My brother-in-law and I are refurbishing an old Sunray 14' boat. It's in
very good condition except for the windshield which has to be replaced. We
want to do it ourselves but need a little advice on how to proceed. Molding
it with plexiglass is definitely one option we're looking at. Does anyone
have a good site to propose where we could find complete and thorough
information on the technique to use? I have done some research and found a
few sites but they were not specific enough.

Thanks in advance to all!


Marcel


1) Make a slim box with a heater you can control with e.g a dimmer
switch.
2) Heat a sheet until it is floppy.
3) Drape over a form covered with smooth felt, optionally greased
while it cools.

Repeat steps 2) and 3) once or twice until you get it right.

Brian Whatcott Altus OK

Brian Whatcott a écrit dans le message :
...
On Sun, 21 Nov 2004 21:37:04 -0500, "Linemar2002"
wrote:



1) Make a slim box with a heater you can control with e.g a dimmer
switch.
2) Heat a sheet until it is floppy.
3) Drape over a form covered with smooth felt, optionally greased
while it cools.

Repeat steps 2) and 3) once or twice until you get it right.

Brian Whatcott Altus OK

Thanks for the advice! English is not my native language and I am not sure
if I understand correctly: if I make a mold from plaster it would have to be
covered with felt that would have been greased prior to melting the
plexiglass? What kind of grease should I use? I have read somewhere that
bubbles could form in the plexiglass, what would cause this and how do we
avoid this? How thick should the plexiglass be?

Thanks again!

Marcel Trudel
Montreal, Canada

On Mon, 22 Nov 2004 23:01:15 -0500, "Linemar2002"
wrote:


Brian Whatcott a écrit dans le message :
...
On Sun, 21 Nov 2004 21:37:04 -0500, "Linemar2002"
wrote:



1) Make a slim box with a heater you can control with e.g a dimmer
switch.
2) Heat a sheet until it is floppy.
3) Drape over a form covered with smooth felt, optionally greased
while it cools.

Repeat steps 2) and 3) once or twice until you get it right.

Brian Whatcott Altus OK

Thanks for the advice! English is not my native language and I am not sure
if I understand correctly: if I make a mold from plaster it would have to be
covered with felt that would have been greased prior to melting the
plexiglass? What kind of grease should I use? I have read somewhere that
bubbles could form in the plexiglass, what would cause this and how do we
avoid this? How thick should the plexiglass be?

Thanks again!

Marcel Trudel
Montreal, Canada


I am concerned not to tell you more than I know. A felt covered form
is a standard recipe among homebuilders who embark on making an
aircraft windshield. They urge the importance of uniform heating, but
not over-heating. Bubbles are not the usual hazard one is warned
against. Cracking and waves are. People use various sizes - 3/16
in, 1/4 in etc ( That's 4.75 mm to 6.5 mm) Your supplier will
probably advise you..... Any grease would be as good as another, I
expect.

Brian W

You can build a form for most windshield shapes by bending thin sheets of
plywood over frames cut to shape. Use single sheets of plywood because
joints will show in the finished piece. Use enough frames to prevent the
plywood from sagging between them. Cover the form with felt. Pool table
felt works better than fabric store felt. No grease. Borrow a couple of
propane radiant heaters and mount them about 250mm above the form so that
they can be moved back and forth. Cut the acrylic roughly to shape, a
little longer than finished size so you can clamp it, remove the protective
paper and lay it on the form. Fo not try to clamp it yet. Starting either
side of the high point heat the sheet until the ends start to drop and
slowly move the heaters towards the ends. As you get close to shape the
suspended areas will not be heavy enough to pull down so use some spring
clamps and a strip of wood to bring the ends to the form evenly. Press it
down very gently. Don't force it or you will get an uneven bend. Once
clamped keep the heat going all over the form for a few more minutes to
insure that the acrylic sets to the form but don't let it get so hot that it
flows.

You can do this with acrylic (Plexiglass) but not with polycarbonate
(Lexan). Lexan absorbs water and will form bubbles unless it is carefully
baked for a long time at lower than softening temps to drive off the
moisture.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Linemar2002" wrote in message
. ..

Brian Whatcott a écrit dans le message :
...
On Sun, 21 Nov 2004 21:37:04 -0500, "Linemar2002"
wrote:



1) Make a slim box with a heater you can control with e.g a dimmer
switch.
2) Heat a sheet until it is floppy.
3) Drape over a form covered with smooth felt, optionally greased
while it cools.

Repeat steps 2) and 3) once or twice until you get it right.

Brian Whatcott Altus OK

Thanks for the advice! English is not my native language and I am not
sure
if I understand correctly: if I make a mold from plaster it would have to
be
covered with felt that would have been greased prior to melting the
plexiglass? What kind of grease should I use? I have read somewhere that
bubbles could form in the plexiglass, what would cause this and how do we
avoid this? How thick should the plexiglass be?

Thanks again!

Marcel Trudel
Montreal, Canada

This thread is really useful to me as I wish to make a windshield for my 14' speedboat. It sounds like Plexiglass is the thing to use. What is the recommended thickness and what are the techniques for cutting and finishing the edges?

Thanks
Richard

How thick should the Plexiglas be?

That is actually a tough question to answer. Certainly no less than 1/4".
It depends on the shape and if it is framed or unframed. Unframed, if there
is a fairly constant curve over a relatively short distance 1/4" will do.
If there is a flat area in the middle you need a frame or go up to 3/8".
The main danger is someone grabbing the top and pulling on it as they stand
up. That is a natural action and hard to prevent.

I have had good luck trimming to shape with a sharp new fine toothed
sabersaw blade. Cut a little outside the final size and sand down with 80
grit on a ROS. Move the sander quickly to prevent melting. Work up to 240
with the ROS and shift to 600 up to 1200 on a sanding block. Finish up with
a plastic polish on a small buffing wheel. A quicker alternative method
would be flame polishing but that takes a lot of practice and an artist's
touch to avoid bubbles. I would not risk ruining the project that way
unless you are really good at it.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Wed, 8 Dec 2004 08:03:11 -0500, "Glenn Ashmore"
wrote:

How thick should the Plexiglas be?

That is actually a tough question to answer. Certainly no less than 1/4".
It depends on the shape and if it is framed or unframed. Unframed, if there
is a fairly constant curve over a relatively short distance 1/4" will do.
If there is a flat area in the middle you need a frame or go up to 3/8".
The main danger is someone grabbing the top and pulling on it as they stand
up. That is a natural action and hard to prevent.

I have had good luck trimming to shape with a sharp new fine toothed
sabersaw blade. Cut a little outside the final size and sand down with 80
grit on a ROS. Move the sander quickly to prevent melting. Work up to 240
with the ROS and shift to 600 up to 1200 on a sanding block. Finish up with
a plastic polish on a small buffing wheel. A quicker alternative method
would be flame polishing but that takes a lot of practice and an artist's
touch to avoid bubbles. I would not risk ruining the project that way
unless you are really good at it.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com


I've had good luck trimming to final size using a wood plane and
spokeshave

I've had good luck trimming to final size using a wood plane and
spokeshave

That works even better but I just don't have the patience. :-)

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com


I've had good luck trimming to final size using a wood plane and
spokeshave

good finish whit router

stef