Popular Mechanics HQ was predictably spellbound yesterday when news reports trickled out concerning a protester who glued himself to the top of a British Airways plane at London City Airport.
On top of that, the protester, identified as a man named James Brown, is a partially visually impaired former Paralympic runner and cyclist. Meet your new Most Interesting Man in the World.
While we’d like to reach out to Brown to ask him some questions—actually, all the questions—what’s complicating matters is the small fact that he may or may not be in jail at the moment. Brown was acting on behalf of Extinction Rebellion, a London-based environmental group known for theatrical gestures of protest, when he bought a ticket for a flight, went through security, proceeded up the steps of the BA Embraer 190 jet, and propelled himself on top, according to The Sun.
“Here I am on top of a f****** aeroplane at City Airport,” Brown said in a video he posted online during the stunt. “I hate heights, I’m s******* myself, I managed to get on the roof. I am so shaky.”
Security soon approached Brown, and not a moment too soon. “Oh good,” Brown said after a few impassioned rally cries against government inaction on climate change, “security are coming. I hope they don’t take too long, because this is f****** scary.”
Brown was eventually removed, and we await more information about his status.
There’s lots to unpack here, like, say, how exactly a partially visually impaired man was able to climb on top of a twin-engine jet airliner. Seems pretty hard! But we were mostly curious about how you’d go about gluing yourself to a plane. Since airport security was pulled Brown off the jet with relative ease, he honestly couldn’t have tried very hard.
So. Let’s say you actually wanted to do this thing the right way. We won’t ask why. But you’re dead-set on sticking to a plane, dammit, and that’s all that matters. Where do you start?
Master the Physics
“The first order of business,” says Giles Dillingham, Ph.D., the CEO and chief scientist at BTG Labs, a materials science company that performs research in surface science, surface treatments, and adhesion, “is to determine the load we are asking the bond to withstand.”
In this scenario, imagine you’re 170 pounds. This is your load. If you try to stick yourself to the bottom of a plane, you’ll put the adhesive bond (the glue) into too much tension, and the forces will probably fail it, Dillingham says. But go to the top of the plane and your weight will compress the bond instead. In that case, the only thing that could fail the bond is the shear stress that results from the drag of the airflow on your body.
Your bond will have to resist the force of wind, says Dillingham, so you’ll need an estimate of that force. “A skydiver who is facing straight down has a terminal velocity of about 200 mph,” he says. “At that speed, the force of gravity pulling the body down is just equal to the force of the wind on the body.” Let’s assume, then, that your bond has to survive a speed of 200 mph and withstand a 170-pound load.
You’ll want to maximize the entire bonded area, of course. If you only glue your hand to the plane, your entire load—your weight, plus the drag from the airflow—must be supported by the spot on your skin that’s actually bonded. Bond a large area, however, and the force per unit area will be low, Dillingham says.
In other words, spread that glue all over your body, and leave no patch of skin unturned.
Nail the Chemistry
Now it’s time to select your glue. Adhesives are rated by shear strength, which is the force per unit area that just causes the adhesive to fail. Your typical glue—say, a nice, classic Elmer’s—has a sheer strength over 1000 psi. That means a joint that has a bonded area of 1 square inch can support at least 100 pounds of weight.
But ah, it isn’t as simple as slathering on a few square inches of glue and jumping on a plane. Because it turns out an adhesive blond contains multitudes—i.e., five components: You have a substrate, the adhesive, another substrate, and two interfaces established between the adhesive and substrate, says Dillingham.
Bonds fail 99 percent of the time because the interface between the adhesive and at least one of the substrates can’t carry the load imposed by the application, Dillingham says. “This is why a glue that’s tremendous for attaching wood to leather would result in a rapid detachment of a human body from an airplane.”
That would suck. To avoid disaster, you’ll need to brush up on some chemistry.
The interface in question is a region that’s only two to five molecules thick, says Dillingham; the layer of salts and fatty acids left behind by a fingerprint, by comparison, is around 10,000 molecules thick. When the molecules in the adhesive react with the molecules on the surface to form the interface, that’s adhesion. And it’s beautiful. But if the chemistry isn’t right, the glue won’t stick.
Even the tiniest layer of contamination on the surface can screw up the chemistry. “It can be way too thin to see or feel,” Dillingham says, “but it basically prevents the glue from ever touching the substrate. We have to prepare the substrates so that the adhesive can actually touch and react with the substrate on a molecular level.”
Here’s where you’ll have to do some dirty work. If the plane you want to stick to is made from aluminum, it needs to be insanely clean. We’re talking no deicing fluids. No engine oil. No bird shit. “And it shouldn’t have a thick oxide from months or years of exposure to rain, sun, and corrosive atmospheric pollutants,” says Dillingham.
That means you need to clean the airplane bond area to remove all contaminants and abrade it with a fine sandpaper to remove any thick oxide. (Steer clear of anti-loading stearate additives.) In addition to scrubbing the plane, you’ll also have to scrub yourself: No lotion. No hair conditioner, which contains silicones.
But in lieu of being in the buff, “it would be much better to wear an appropriate high-strength jumpsuit and depend on the adhesion of the fabric to the adhesive,” says Dillingham. That means cotton over polypropylene, nylon, polyester, and Kevlar, all of which are chemically dull and really, really hard to bond.
Pick the Right Sticky Stuff
After you’ve put in all that prep, it’s finally time to select the glue. Obviously, you want an adhesive that jibes with both aluminum and skin or a cotton fabric. While you can choose from a couple, you’ll have to think practically. Airport security will inevitably interfere, so you’re basically left with cyanoacrylates—a.k.a. superglues.
Here’s the thing about superglues: They’re not actually that super, at least in terms of strength. But they cure really quickly and stick well to aluminum, skin, and natural fabrics like cotton, Dillingham says.
The catch? “Cyanoacrylates need a small amount of hydroxyl groups on the surface to cure, and freshly abraded aluminum needs to be exposed to humidity for a few hours to develop enough hydroxyl groups on the surface to effectively stick to cyanoacrylates.”
That means you should probably set aside an afternoon to prepare the aluminum surface of the plane ahead of time. Shouldn’t be too hard.
But hey, it’s finally gluing time! So how much of the stuff do you need? A typical bondline of a superglue joint is around 0.003 inches thick, or about 80 microns. You’re going to bond about 1 square foot, so you’ll need about 7 milliliters of adhesive.
And that’s it. When you think about it, really, the whole process of cleaning a plane and gluing yourself to it and sticking there for a prolonged period of time, at least until armed security steps in, is actually pretty simple. Just remember: When you want to remove the glue, use lots of warm water and peel, not pull.
You Might Also Like