Bending plexiglass for curved windshield

Charles King

Seaman Apprentice
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Nov 23, 2009
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37
Can anyone offer tips for converting an electric stove oven to bend 3/16" plexiglas panels 24" by 48"? Need to bend approx 90 degrees with a 12" radius. I have been told to heat plexiglass to approx 300-350 degrees, and form over a felt padded form until cool. Any tips on supporting in oven, moving to form, etc will be appreciated.
 

Allbutwet

Petty Officer 1st Class
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May 23, 2010
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Re: Bending plexiglass for curved windshield

I would not attempt to use an oven for this. With 3/16 you will need to get a cardboard tube with a 12" diameter. And secure it at the edge of a work bench. Lay your plexiglass with the paper covering still attached over the tube where you want it to bend. Put something on the end on the bench to help hold it down. Use a heat gun which you can get inexspensive at Harbor Freight. Heat not just the area you want to bend but about four to six inches beyond. Use the weight of the plexi glass to bend it. Once it starts to bend you can assit it with slight pressure. Just keep the heat even and wide on the area you are bending. And try not to stay in one spot to long or it will melt.And most important patience. I have bent numureous 1/4 inch pieces 4' wide at 90 degrees and 45 degrees this way. Should be no reason it would not work for a round bend. You will not burn the protctive cover doing it this way. If you do your getting it to hot. Good Luck:)
 

Charles King

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Nov 23, 2009
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Re: Bending plexiglass for curved windshield

Thanks for the suggestion. Any Idea of the degrees heat per square foot a heat gun puts out in this system of bending?
Thanks
 

Allbutwet

Petty Officer 1st Class
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Re: Bending plexiglass for curved windshield

Not sure. I assume you are bending the narrow section? It will be hot enough to burn you. If you heat it evenly and apply slight pressure you will know you are getting hot enough. You will most likely feel it before you really see it move. once it starts just stay steady with both the pressure and heat. Keeping the heat in the area you are bending. If the plexi wasn't wasn't so exspensive I'd tell you to cut a small peice and exsperiment first.
 

rivermouse

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Jun 16, 2011
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661
Re: Bending plexiglass for curved windshield

You may try using an outdoor bbq grill but why do you have to use plexiglass.? If the windshield has a frame why not use lexan. It is thinner but you can bend it with no heat and much easier to cut . It worked for me after I ruined and cracked the plexiglass I was trying to make work.
 
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CaptainKickback

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Re: Bending plexiglass for curved windshield

There are a bunch of videos on you tube where people do this. I watched them last week, then tried it. It worked. Biggest thing, as someone already said, is be patient. Also, if you push on the material to help it bend, try to make that pressure even over the entire bend.

Good luck.
 

Charles King

Seaman Apprentice
Joined
Nov 23, 2009
Messages
37
Re: Bending plexiglass for curved windshield

Restoring a 1965 Sportcraft Safari. It has Coke Green Plexiglass Windshield, original by Water Bonnet.
Thanks for your suggestion.
 

Last Mohican

Chief Petty Officer
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Aug 27, 2010
Messages
573
Re: Bending plexiglass for curved windshield

I built a couple windshields for jet boats last summer. I used one of those disk heaters that clamps on a propane bottle. Worked like a champ. You can read more about it here if you want. The info on how I made it actually starts about page 9.
http://www.texashotboats.com/forums/index.php?topic=11452.0

I used a heater like this:
http://www.homedepot.com/h_d1/N-5yc...angId=-1&keyword=propane heater&storeId=10051

Here is the finished product:
View attachment 132102
 

CaptainKickback

Lieutenant Junior Grade
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Messages
1,060
Re: Bending plexiglass for curved windshield

Awesome LM.

Now you've got me thinking I can make a windshield and not juxt my salon entry hatch. I don't have access to the CNC system, but I figure I could make a mold, cover it with felt, and let the plexiglass form around it.
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,924
Re: Bending plexiglass for curved windshield

I found this and thought you might be interested...

Make Your Own Curved Windshield for $100
I have a 1993 Mariah Diablo that had a broken windshield when I bought it. I could have had an original glass replacement for a mere $3885. A plastic's company could have provided one if I sent them the window frame and 8 weeks later and around $6-700.

I removed the left front window as they are the same size. I placed double sided tape on the windshield, applied construction paper and traced around the outside edge. I removed the construction paper and cut around the edges including the pencil line. I now had a template for my new window....figure 1.

Next I took small pieces of duct tape and placed them on the inside/outside edge of the left front window. I then took 1x8 boards and cut them to align with the curvature of the window. I numbered these 1, 2, 3, & 4. You also have to measure how far apart each board is from the one next to it. Beings you are constructing the opposite sided window...when you go to construct this form, the one on the top is now the one on the bottom as you will be flipping this form over. This took me about 3 hours to measure.....trim...and construct. It helps to have spare pices of lumber and an air nailer. Figure 2.

I then placed my paper template on the form and traced around the outside edge, so I'd know where the edges should line up when they are heated. Figure 3.

I contacted a glass company and they cut out my template using marine grade plexiglas (1/4 inch thick) for $60. I then used spring clamps and attached the glass to the flat edge of the form. I'd bought a heat gun and started heating away. Do NOT buy the cheapest Heat Gun. After 2-3 hours, I'd returned mine and bought a better gun (Wagner) for $40 dollars. This time I placed the glass in my mold at the curved edge. I'd clamped it with a 1x2 and started to heat away. You have to heat with the curve, going top to bottom.
Plexiglas melts at 250 degrees. My heat gun has a digital readout and I had it way above that. Go back and forth about an inch from the glass. If you nick the glass with the gun it will leave a scar, it will buff out later. The weight of the other end is all it takes for the glass to lay down as it heats up. Don't bother trying to clamp it, if it is not bent all the way..clamping will not bend it further. You may want to clamp it when you are done so it keeps its shape as it cools. You may hear a slight cracking sound as it heats and that is normal. It takes patience and 3 hours to complete this step.
If I had to do it again....I would have gotten some aluminum sheeting used for ductwork and made a mold using that. Put it in the frame and solder the mold in place. The window did need a minor adjustment with the very back upward corner. It is in the boat. Last figure.

The glass was $60, heatgun $40, 1 x 8 lumber $10. Probably 12 hours labor. Saving thousands or hundreds of dollars.....worth it. If you have questions, hit me up.

Bend1.jpg


bend2.jpg


bend3.jpg


bend4.jpg
 

CaptainKickback

Lieutenant Junior Grade
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Re: Bending plexiglass for curved windshield

Wood, definitely of interest. Thanks.
 

Last Mohican

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Messages
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Re: Bending plexiglass for curved windshield

Nice find WOG. Good info in that post.

CaptKick. Not sure I would use felt. The only thing I used the CNC router table for was to cut the piece. You could just as easily use a jig saw especially for a one off piece. I had the tool at my disposal so it did make it easier. :)
 

CaptainKickback

Lieutenant Junior Grade
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Re: Bending plexiglass for curved windshield

Thanks LM. The reason i said felt is because many of the videos I watched used it. They say in the videos that the hot plexi doesn't stick to the felt, as it would with most other materials.
 

Last Mohican

Chief Petty Officer
Joined
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Messages
573
Re: Bending plexiglass for curved windshield

Thanks LM. The reason i said felt is because many of the videos I watched used it. They say in the videos that the hot plexi doesn't stick to the felt, as it would with most other materials.

Interesting. I never would have thought that. I would be worried about the felt leaving an texture on the soft heated material. Learn something new every day.
 

CaptainKickback

Lieutenant Junior Grade
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1,060
Re: Bending plexiglass for curved windshield

LM, I'll definitely try a test bend first. It will be a while before I get to that part of the project.
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Bending plexiglass for curved windshield

Nice post woodonglass...I have tried searching for marine grade plexi glass in a green tint...Cant find a thing any ideals out there..
 

Charles King

Seaman Apprentice
Joined
Nov 23, 2009
Messages
37
Re: Bending plexiglass for curved windshield

Marine Glass Specialties stocks Color # 2111,"coke green". Google them.
 
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