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In a comment to my recent question about covering segments by a disk, Gerhard Paseman has suggested a generalisation: replacing the segments of the original $n$-gon by a simple closed (say, convex) curve, of which a certain number of points are removed. How to pack the pieces into a minimal disk without rotation or overlap?

Of course this "curve puzzle problem" (as I'd like to call it) opens a bunch of possibilities. So I'd suggest to start with a circle, from which $n$ equidistant points are removed. What we want is thus to pack the $n$ remaining arcs into a minimal disk.
(EDIT) To keep the scaling similar to the one used before, we'll require the endpoints of each arc to have distance $1$.
That doesn't seem very different from what Gerhard suggested as variant to start with: removing the midpoints of each segment of an $n$-gon, which amounts to 'bending' each segment in the middle slightly by $\frac{2\pi}n$ (so it is replaced by the legs of an angle $\pi-\frac{2\pi}n$). Note that in either case, we cannot cover all pieces by a half unit circle anymore (a nice fact allowing the general constructions in the original thread).

For $n=4$, if the four arcs are assembled in the shape of a windmill (shutter), we can pack it at best into a disk with $r=\dfrac{\sqrt{5}-1}{2}$. I think this construction is best possible for $n=4$.

What happens as $n$ grows? I'm still working on the trig for the general $n$-fold shutter construction, thinking it should tend towards $r=1$, but there might as well be a better construction, like in the case of straight segments. So:

What are good constructions for packing those $n$ arcs into a disk?

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    $\begingroup$ I am glad to see that you asked the question. I would suggest that something like all pieces be unit arc-length is considered as a restriction and to make comparisons with the original problem easier. However, you know your motivations for the original problem, so shape it as needed to suit those. Gerhard "Looking Forward To Generalized Answers" Paseman, 2015.11.14. $\endgroup$ Commented Nov 14, 2015 at 22:14
  • $\begingroup$ @GerhardPaseman Yes I messed up the scaling, sticking to the idea of unit circle where I shouldn't. I have updated the question (and also corrected the $n=4$ case, where I had done a sign error.) $\endgroup$
    – Wolfgang
    Commented Nov 15, 2015 at 16:10
  • $\begingroup$ Actually, for small n you can "double up", making a regular polygon half as wide, in the midpoint case. Gerhard, "Just Think Twice As Small" Paseman, 2015.11.15. $\endgroup$ Commented Nov 15, 2015 at 18:04
  • $\begingroup$ @GerhardPaseman I'm trying hard to think twice as small, but I don't get what you mean. The legs of the angles still go in all directions. (And why would that work only for small n?) $\endgroup$
    – Wolfgang
    Commented Nov 15, 2015 at 20:49
  • $\begingroup$ To personalize temporarily, for n=3, your stick version allows no reduction in the size of the circumcircle, while my corner version allows me to push the three corners together to produce a circumcircle with radius not much larger than half the original radius. Incidentally, this means for both n=3 and 4 the corner packing fits in a unit semicircle. This generalizes to larger n but for n greater than, oh, say 12, the circumcircle is larger than unit radius. The fan construction still works for large n. Gerhard "When All Bend The Same" Paseman, 2015.11.15. $\endgroup$ Commented Nov 15, 2015 at 21:17

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