Air travel in the jet stream; why your specs can't be glued

Hey Matt:
I got my tickets yesterday to fly from Los Angeles to São Paulo, Brazil, at the end of the year. On my way to Brazil it will take 10 hours, 45 minutes on my Korean Air Boeing 777. On the way back it will take 13 hours and 20 minutes on the same plane. Both flights are non-stop. Is there a hill the plane has to climb coming back? Are the pilots turning on the “super turbo blaster” on the way there? What gives?
— Paulo Da Silva

I’m thinking back to eighth-grade meteorology class and how the teacher let us go outside to look at the sky and any visibile airborne phenomena at the altitudes where planes fly. Though we couldn’t behave ourselves in the fresh air and lost the privilege of going outside, I remember distinctly that there were no hills up in the sky, just lots of clouds. I might add that it’s one of nature’s greatest crimes that clouds are just cold, wet, dirty air, and not the fluffy sky-pillows that children’s TV shows always showed. I also remember learning about the jet stream.

Jet streams are narrow bands of rapidly moving air that cut distinct swaths across the sky. Partly caused by the Earth’s rotation, the jet streams affect airline travel dramatically because they can move along at upwards of 100 miles/hour and they’re positioned at the altitude of commercial aviation. It’s the jet stream, specifically the northern sub-tropical jet stream, that’s messing with your flight times to and from Brazil. Being unsure of the present location of that air current (they can move around a little bit, depending on the time of year and other meteorological factors) I checked with JetBlue airlines. Sure enough, the subtropical jet stream has lately cut across L.A. before heading south toward Brazil. It blows in an easterly direction, so planes get a big tailwind for about half the journey to São Paolo and they either have to fly against it or take the long way back on the way to L.A. to avoid the high-altitude wind. Jet streams in the northern hemisphere flow west to east. In the southern hemisphere, the flow is reversed. Almost every flight that travels longitudinally has to deal with a jet stream in some manner, although it’s fair to say that every flight against the wind has a corresponding flight with the wind at your back. Like so many things in life, you give and you get.

Heymatt:
What are eyeglass frames made of? I broke mine and every glue I have tried — even two-part epoxy and super glue — won’t bond the pieces together.
— Jerry

I count near-perfect vision among my virtues, so this problem is one that’s never beset me in the past. Whenever cheap sunglasses (the only kind there are, if the ZZ Top song is right) break around the Alice Research Facility they’re given summary disposal and swift replacement. But I’m not totally insensitive to the plight of glasses wearers and I’ve seen many a friend mourn the unplanned destruction of a favorite pair of spectacles. Lots of glasses are made of cellulose acetate, an industrial fiber that sets up as a low-strength plastic when combined with the right resin. It’s used for purposes as diverse as playing cards and satin fabric, too. There’s no reason you shouldn’t be able to glue it, materially speaking. In theory, if you had the mold for your glasses frames you could melt them down and start from scratch. Great way to get a third-degree burn. It’s not exactly aerospace-grade carbon fiber, which is set with epoxies that bond together at the molecular level. High-tech materials like that can’t easily be repaired because the structures are a lot more complex than simple plastics, and the material’s strength is built in during the curing process, which can’t be replicated because the epoxy’s change of state is irreversible.

Looking further afield for the answer to this one, I ended up talking to Bill at Hot Shots Eyewear Repair in Carlsbad, and he confirmed my suspicions that others suffer greatly in this regard. Over the past 18 years, they’ve fixed about 60 pairs of glasses a day, lots of them broken plastic frames that can’t seem to be glued. The problem, Bill said, is in the surface area of the break. Glue is only as strong as the surfaces it bonds, and eyeglasses are of such slight dimensions that there just isn’t enough material for good adherence. Take a couple 2x2 inch squares of the same material that your glasses are made out of and they’ll glue together no problem; slender little frames are another thing entirely. Bill’s solution is to implant metal rods into the material, which adds stability and a surface for the glue to grab. Metal frames don’t glue up, but they can be welded or soldered. We can only imagine that Bill has a small army of elves at his disposal for such painstaking work. Perhaps he has a few graduates of the Alice Research Facility plying a new trade, industriously welding Prada eyewear with nimble fingers and the kind of know-how that comes from years of rifling through the labyrinthine Alice filing systems.