Friday Weird Science repost: The physics of the strapless evening gown

Aug 23 2013 Published by under Friday Weird Science

NOTE: Sci's got some major stuff going on now professionally which requires her full attention. But as I would hate for you all to be stuck without your Friday weird science (who could IMAGINE such a thing), I've arranged for some reposts.


Today's Friday Weird Science comes to you courtesy of Marc Abrahams, the founder of the IgNobel Prizes (which I'm going to next week! So excited!!). The study was featured in his new book, This is Improbable, and Marc was kind enough to send me a copy of this paper when I asked about it. (Ok, honestly, Marc has sent me a freakin' AVALANCHE of papers...because there were just that many awesome ones. And those were only the first 40 pages of the book! Marc Abrahams will be the official patron saint of weird science for the next year at least. Worship him, ye masses).

I didn't even have to come up with a fun title for this one!

Charles E. Siem "A Stress Analysis of a Strapless Evening Gown" (last edited online 7/2010).

This is a funny little paper. I'm not sure it was ever peer reviewed, you can only find copies of it online, I have no record of where it was published, etc, etc. Not only that, it is entirely theoretical in nature, containing no references to literature on the subject, and with no studies into the actual physics (apparently due to a lack of female volunteers, as you read'll probably figure out why).

In this paper, the author lays out the physics of the strapless dress. He begins by rhapsodizing on the strapless dress, and the many other ways in which women dress "to bring about [the] libido-awakening infliction on the poor male". He touches briefly on sheer tops, skin tight bodysuits, sweaters ("Another powerful attractant is the tightly fitted garment. A well-known example of the type of weapon is the sweater" You can't make this stuff up), and makes a brief mention of the bikini. He then moves on to his main subject, the strapless dress:

A delightful device which has sufficiently aroused the masculine sex is the use of durable but fragile-appearing cloth which gives the impression that at any moment the garment will slip down or that, better yet, certain parts may slip out of place. The best example of this method of attracting the attention of the weak and susceptible male is the strapless evening gown.

(Sci must note that I have worn a good share of strapless dresses in my time, and I never once thought of them in this light. This is something about the male gaze that I never needed to know. I will never look at my old bridesmaids dresses the same way...)

Once over the lingering pleasure of the many ways in which women dress, the author gets down to the question at hand, namely: How DOES this type of dress stay up. And being a guy who, I conjecture, has never seen a woman getting into or out of a strapless dress, he did not go to the immediate and sensible answer: Boob Tape.

Nope. He went to physics. And there certainly is a good deal of physics involved.

To aid us in our scientific foray, the author presents us with Figure 1:

It was here that I began to wonder if the author had ever seen a woman at all, let alone one wearing a strapless dress. But I think mostly he just couldn't draw.

But here we can see the main forces at work here. We have the forces F1 and F2, equal (presumably) and opposite, forcing the breasts apart (lift and separate!). You have the weight of the top (W), and the upward force of the fabric (V), which is due to the tightness of the fabric above the navel (plane A). Enough upward force (V), and the whole thing is at equilibrium and nothing falls down.

But that's ASSUMING there is enough upward force. Is there? If you take plane B alone (B for boobs! And obviously not for scientific reasons, no indeed!), you will see that there's not enough upward force to counteract the weight of the fabric (and, presumably, the breasts in it, which are not made of air, though silicone is of course an option). If you can't hold that dress up by sheer force of lift and separate...well you can't hold it up at all. The author claims that "If the female is naturally blessed with sufficient pectoral development, she can supply this very vital force and maintain the elemental strip at equilibrium." But I can tell you that sufficient pectoral development be damned, fabric won't stay up of its own will up there.

So how do you make up the difference? Here we have two options. The designer of the dress can use friction (F) to keep the dress from moving. If you increase F, the perpendicular normal force will also be increased, and the dress will stay up. When I think of increasing friction, I think of the rough side of velcro against my chest, and that doesn't sound pleasant, but what he means is that you can increase normal force by making the point at the tip of the breasts as tight as possible, which does indeed work, but can produce boob-squishery, or what is colloquially known as "baby heads".

Next, the author gets into the issues at hand when a lady decides not only to go strapless, but also to go BACKLESS ("some females require that the back of the gown be lowered to increase the exposure and correspondingly attract more attention.").
(Again...has this person EVER seen a breast in its natural habitat?! That shape's...oh dear)

Now he refers to the downward angle known as "t", but which I cannot find in either of the figures. Anyway. Now you're backless. How do we keep these puppies from basking in the sun? Since you have less force coming in from the sides, you need to increase the force from below.

And as many women will know, this means boning.

This, my friends, is the inside hardware of your strapless dress. The thin lines you see are flexible plastic (or metal or even actual bones) boning, which gives the inside structure and allows the top to remain vertical despite whatever is inside it. If you ever see a strapless bridesmaids dress, for example, feel the inside of the top. It's firm. Some of them freakin' stand up on their own. That's boning.

However, as the author notes, there are other forces at work. Most particularly the downward forces caused by things like dancing, walking,, and which require people wearing strapless dresses to haul them up when they think no one is looking. Strapless dress wearers of the world? I give you, BOOB TAPE. Know it. Love it.

But you have to keep in mind, this is all theoretical! "Many females have been asked to volunteer for experiments along these lines in the interest of science, but unfortunately, no cooperation was encountered. There is also the difficulty of the investigator having the strength of mind to ascertain purely the scientific facts." wonder he had trouble getting volunteers.

The author maintains that the engineering of strapless gowns will have to remain trial and error. I think many of the people at this past week's New York fashion week could easily tell him it's been done. And the answers are tightness, fit, fabric, boning...and boob tape.

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