Portlight Glass

[skottc]

Hey guys, I work in the plastic industry. My company makes thousands of windows for boats, buses, trains, planes and race cars every month. Maybe I can clear some of this up.

Acrylic vs. Polycarbonate
Though Polycarbonate is stronger and more impact resistant, Acrylic is the better choice for many reasons. Acrylic is cheaper and looks better. Acrylic is optically clearer. Polycarbonate is softer, so it scratches easier. Good quality Acrylic that's properly cared for will last you many, many years.

Crazing, cracking and fogging.
The number one reasion for this is chemical cleaners. Do not use Windex or other chemicals or cleaning products on Acrylic. You may have used a cleaner on Acrylic before and it did not appear to damage it, it did. Cleaners attack the Acrylic and cause microscopic cracking, this is often not immediately apparent. Over time the cracks get bigger and bigger. Always use a soft clean rag or towel when cleaning. Otherwise you create very fine scratches, over time all those scratches create fogging. Edge polishing(flame polishing or buffing) can also create crazing over time.

Tinted material vs. film
Go with tinted material. The problems with film stated in this thread are correct. Bubbling, blisters and tears are very common.

A newer trend is to have a double layer window. You have your primary window with whatever tints and coatings you want protected by a thin(1/8"), cheap replaceable outer window.

[roverhi]

Before the link got removed, noticed you have corrugated plastic sheet. I've been thinking of making a light wind sensing vane for my self steering. Believe it needs to be 1/4 inch material. It has to be lighter weight than the plywood of the standard vane or the counterweight wouldn't be able to center it making for erratic steering. From memory, the vane would probably have to be 4' long by 2' wide. Is there a plastic corrugated material available that is light and has enough stiffness to fit the bill??

The vane now is just not large enough to be responsive in light wind. The vane will steer if it gets the input from the windsensing vane. The windvane just isn't large enough to overcome the inertia, friction of the vane mechanism and stands vertical not reacting to light winds. Also needed for downwind where relative wind becomes a problem.

You can email me off list. roverhiatyahoodotcom

[Stillraining]

How about light sheet aluminum?

[skottc]

Corrugated Polycarbonate. It usually comes in 3/8" or 1/2". There's also a corrugated polypropylene but it is not as rigid.

[captden]

Crazing, cracking and fogging.
The number one reasion for this is chemical cleaners. Do not use Windex or other chemicals or cleaning products on Acrylic. You may have used a cleaner on Acrylic before and it did not appear to damage it, it did. Cleaners attack the Acrylic and cause microscopic cracking, this is often not immediately apparent. Over time the cracks get bigger and bigger. Always use a soft clean rag or towel when cleaning. Otherwise you create very fine scratches, over time all those scratches create fogging. Edge polishing(flame polishing or buffing) can also create crazing over time.



[/QUOTE]

So you are saying just use a soft cloth and just water?

[skottc]

That's what most manufacturers recommend. There are cleaners for acrylic out there that are safe. We use Brillianize.

[Extemporaneous]

Originally Posted by skottc

A newer trend is to have a double layer window. You have your primary window with whatever tints and coatings you want protected by a thin(1/8"), cheap replaceable outer window.

How is this done?
Is a space left in between?
Laminated on somehow?
How do you clean in between?
How do you get them apart?

I guess I have more than one question.

Thanks,
Extemp.

[mikereed100]

Originally Posted by skottc

Edge polishing(flame polishing or buffing) can also create crazing over time.

Hi scotte,

Are you sure about this? Another professional explained in detail on another forum that the "microcracks" caused by cutting could, in time, cause crazing and that it could be eliminated by flaming the edges. My confusion knows no bounds.

Mike

[skottc]

Originally Posted by mikereed100

Hi scotte,

Are you sure about this? Another professional explained in detail on another forum that the "microcracks" caused by cutting could, in time, cause crazing and that it could be eliminated by flaming the edges. My confusion knows no bounds.

Mike

10-4. You can flame an edge and never have a problem. Wipe the wrong type of chemical on it.... The crazing is caused by "stressing" the the acrylic. Flame polishing(rapid heating and cooling) and cleaners stress the material. Again, you do not see this immediately. That's why you never flame an edge then bond it. A simple test is to flame an edge, let it cool and wipe it with isopropyl alcohol. The alcohol gets in the cracks and expands, many times you can see it immeadiatly. Try it on an edge that's not flamed. When I made my original post I had added in a link to a bunch of manuals from different acrylic manufacturers. I think some of them covered a little about this.

Now, I could see if you did some really bad cutting(melting, chipping), that flaming the edge could help heal it. However over time you have problems. Honestly, we cut(saw and cnc) and fabricate thousands of acrylic parts everyday and never have a crazing issue with an untreated edge(with the exception of extruded acrylic tubing, it's totally stressed to start with). However, we are using first rate equipment and tooling so our cutting process is not stressing the acrylic.

The other question about the two layered windows, I can't really answer. We make the windows but that's as far as I see it. I do know they are not laminated together.

[mikereed100]

Thanks Scott, I wish I had been fast enough to catch your links. What is your method for sawing acrylic?

Mike

[skottc]

For saw cutting we're using computerized panel saws that are made specifically for plastic. With those we can control almost every aspect(rpm, feedrate, blade projection, clamping pressure, hold down pressure, blade cooling...). Of course the tooling is another huge factor, it takes the whole package. We pride ourselves on our cutting.
For people who want to do it themselves, the best method is usually a table router. I actually have a how-to blog and videos on this. We are trying to educate and clear up common misconceptions(like the one about cutting acrylic with the blade on backwards, wholly #*@~!). I'm not going to put the links here because it would be considered commercial links. The forum mod was gracious not to ban me for doing that before(sorry again).

[bg9208]

I would have thought that Makralon or a similar polycarbonate would be as tough as if not tougher than either laminated or tempered glass and possibly cheaper and definitely easier to cut to shape.

[cantxsailor]

Here are my ports before and after. You can see the delamination of the glass.and the new acrylic after. Cut on a band saw and finshed to shape on a belt sander. Sealed with 3M 101. 2 1/2yrs and still no leaks.Polished on a fine wire wheel.........m

[Epicurean]

Can laminated glass take a small bend? (curved cabin top)

[bobconnie]

When I bilt my Colvin schooner, I added a semi pilot house 3 sided windshild with a folding sunbrella top. I used windshild glass from a earley chysler 300 almost 3/8 thick and DARK tinted, lasted till the day we sold her over 20 yrs ! still clear and easy on your eyes! had removeable storm covers when needed but only used them a couple of times !!I just made the windows the size I needed to cut them from windshilds with as little waste as possible! Im sure theres a windshild out there that will be useable in most all pilot house windows ! just a thought from a cost watchin oldie