Question:

Why do round cross-section shoelaces untie more easily than those with an oblong cross section?

This was a question that was recently posed to the experts. From my experience of attending our club just about everyone is an expert.

So I wonder what our experts would say about this question?

As I remember it being able to tie shoelaces properly is one of the most important landmarks of growing up and one of the first really difficult tasks we meet in early childhood. Many of the other ones like our first steps and riding a two-wheeled bicycle seem to come by instinct but any parent who has struggled to teach an infant this landmark of infanthood knows that this is often a frustrating experience.

I decided to investigate the question and probably many of you like me probably came up with the obvious answer.

If you rub two wooden rods of circular cross section together, there is very little friction because the point of contact between the rods is small. Compare this with rubbing two flat, wooden slats against each other. There is much more friction because there is a much greater contact area. The same principle applies to shoelaces. Added to this, flat laces have an extra degree of freedom in that they can warp across their width, in effect wrapping around other bits of shoelace and increasing friction even more.

Seems obvious when you look at it this way. But wait a moment! Woodturners, however, know that the obvious is often not the answer. A little investigation on the internet reveals that though there may be a marginal effect of friction the real answer is that many of us have forgotten that early childhood first lesson and no longer tie our shoe laces correctly. So as a reminder consider the following.

The standard shoelace knot can be described as a doubly slipped reef knot. It comprises a reef knot in which both loose ends are fed back on themselves to create a method of rapidly undoing the knot. The crucial point in tying a reef knot is that the two overhand knots of which it is made are of opposite handedness –left over right, then right over left. If the handedness of each overhand knot is the same, then one ends up with a similarly doubly slipped granny knot.

Such knots have a tendency to come undone more easily than a correctly tied shoelace knot. The way to tell if you’re tying a granny knot or a correct shoelace knot is to see how the laces and the loops lie. With a shoelace knot, they will naturally lie across both sides of the shoe.

With a granny knot they will lie perpendicular to the tied lace, pointing up your leg and to your toes. If you have a granny habit, the easiest way of correcting this is to simply reverse the handedness of the initial twist of your laces.

The tying of one’s shoelaces is discussed in wonderful detail on Ian’s Shoelace Site, along with helpful pictures (at bit.ly/TheGrannyKnot). My ongoing straw poll would suggest that about half of people tie their shoes with a granny knot and that problems of them coming undone –be the cross section round or flat –invariably disappear once they start tying them correctly.

So! You experts follow the above advice and never have to deal with your shoe laces coming undone ever again whether they have a circular cross-section or not.

So if you have taken the time to come to my corner and read my epistle and now look down at your shoes and discover that you are using Velcro to secure your shoes you will find that this has been a complete waste of your time, which is something some of your friends remind you when you tell them that you spend hours and hours “turning” wooden bowls and “stuff.”