Lexan capping

I have a bid request right now. Funny you should ask...

My project windows will require 1 4x8 sheet of 1/4" each. 14 in total. I found a source for abrasion resistant and "extra" UV protected polycarbonate. (Poly is "Lexan" as opposed to acrylic "Plexi". ) I got a price of $245/sheet for the plastic, and I'm going to use a PVC "lumber" for the retainer stop. The plastics company does not reccomend screwing the sheet plastic in place, as it will expand/contract and pull the screws loose or break the plastic. The source for the 1x4 PVC runs $2.05/ ft, and I'm going to rip it down to 1x2, making the stop cost about a $1/foot.

I haven't figured the labor and scaffold rental yet. Plus the windows have a bunch of work to do on them.

Still working on the rest of the bid....

What reasons would there be for using Lexan as opposed to glass?

Jack

VANDALISM...plain and simple.

Lexan is practically bullet proof, cuts with a saw, and lighter than glass to transport and work with. It's the material of choice for outdoor protection and capping of SG.

-- JK Sinrod

www.MyConeyIslandMemories

Do you figure these jobs by the sq. ft., or how?

Leave out the "practically" given certain thickness with certain ammo. I got paid to shoot a bunch of it up back about '94 or so. 1/4" won't stop much, but

3/8" will stop your typical .38 round easy enough. Sure wish now I'd written down which thicknesses stopped which rounds. Velocity mattered more than overall energy though. 1/4" will certainly stop rocks, BBs, pellets and non-firearm type projectiles.

That's why I was asking for opinions from youze guys. I gave up formula pricing 20 years ago. I go by "perceived value" pricing. If I can do a job for $1500 and it looks like its worth $10,000, that's what the estimate will be. My reputaion usually gets me the job, not price. Bargain hunters are welcome to go elsewhere. With retail disappearing, I need to rely on these big hits several times a year to make it all work.

-- JK Sinrod

www.MyConeyIslandMemories

Give me a

Here is a reasonable and reliable source and price list from Florida.

are also fabricators, so you are definitely not locked into the 4x8 sheet mode.

Obviously shipping would increase the price and preference to local shopping might be considered. Just thought I would bring them to your attention.

Semi OT...I can't imagine anything EVER replacing the awesome beauty of glass, but I absolutely marvel at the advancement in plastic technologies. Poly casting in the early 70's was pretty lame and IMHO generally looked like a Girl Scout troop's craft project of hardened gelatinous goop. Now, the clarity is amazing and it can reflect any number of textures including a highly polished pseudo-glass. Great for those bulletproof service windows that are so ubiquitous in southern CA. Used for evil by those mass-marketing Chinese who have figured out that there is a huge market of Americans yearning to buy cheap plastic knock-offs of glass art and jewelry. Anyway...

Lori

Those are comparable prices to what I have locally. Going into a church in the 'hood, so bullet proof might be a "good" thing, eh?

Not really. Laminated glass is the first choice. Lexan WILL yellow and turn opaque in 15 years or so. Lami is just as strong and will look good forever.

Lexan expands and contracts 1/16" per linear foot. So you need to estimate where the Lexan is at the temperature you are instilling in., and figure out how deep the molding bite needs to be. A 4' span will move 1/4". I've actually seen Lexan installed in cold weather pop off the building in summer.

Lexan expands and contracts 1/16" per linear foot. So you need to estimate where the Lexan is at the temperature you are instilling in., and figure out how deep the molding bite needs to be. A 4' span will move 1/4". I've actually seen Lexan installed in cold weather pop off the building in summer.

Will lami stand up to rocks and the occasional stray bullet?

The church I'm bidding right now is, well, uh....right in the middle of da 'hood. Projects are right down the street, and the existing church windows have rock holes and BB/pellet holes. In order for the church to maintain their insurance coverage, the ins. company is requiring them to add safety glazing.

Safety glazing can mean laminated or tempered glass. You should ask the insurance agent what they really want.

Vic....what is your experience with lami or tempered when hit with rocks, pellets, BB's, etc.? Aren't we looking at breakage where the Lexan wouldn't break? I'm not so sure that the non-yellowing aspects of the glass safety glazing is all that valuable when compared with the vandal resistance of the plastic?

I'm really interested in your take on all this. Thanks.

For Vic and Steve. I'm not sure that the stuff you're referring too is the same as what they're selling today. Correct me if I'm wrong, but the material you tested in the early 90's, and the yellowing nature of plexi, are not the same as todays Lexan products. Someone can google the product stat sheets on all this. I'm pretty sure that reasonable bulletproofing and non yellowing are properties of todays Lexan.

Lami and tempured are designed to fracture & shatter before anything penetrates it, but most blunt projectiles will bounce off Lexan, and even if it's a high powered anti-terrorist shell, it'll just make a hole, and the entire thing won't need to be replaced like the other 2. In "the hood" Moon, most of the problem is rocks, sticks, and balls. Lexan is the way to go.

-- JK Sinrod

www.MyConeyIslandMemories

What I tested was the lexan specifically used in making canopies for naval aircraft; FA-18s among others.

Backstory: On a precision vertical planetary grinder, a machinist had spun a grinding wheel rated for 20,000 rpm up to 50,000 rpm. It blew apart and the guy was injured severely enough that he was out on workman's comp for years. The point was to make a shield such that any future "explosions" would be contained, yet still allow visibility of the workpiece. The engineer working with me on this calculated velocity and energy, and compared to a variety of ammo rounds. I think he was under the impression that energy would be the key parameter in penetration, but it turned out that a .22LR penetrated the same lexan that stopped a .38.

So, "reasonable bulletproofing" depends on your definition of "reasonable," "bulletproofing," the distance fired from, and the angle of impact.

Personally, from my limited experience with lexan, I would consider 1/4" to be fairly vandal resistant, but wouldn't even think about using the term bullet resistant until you get into 3/8" range.

I have no knowledge of any yellowing problems with aircraft canopies. Maybe they were automatically changed out every ten years, or maybe that particular grade of lexan just didn't yellow.

Give me a

J.K.S.:

I think your real problem with laminated glass will be the cost. Some of the helicopters in the Soviet Hind series had canopies with, IIRC, 600 laminations of glass which were evidently proof against most small arms fire. One would not think those units were cheap.

Another problem I've seen with Lexan is that it can burn when doused with a flaming 'hood cocktail, though whether this is something your client anticpates is another thing.

Regards,

Edward Hennessey