The Origami Forum

Hi everyone, first post, hope this is the right board etc.

So I've recently been getting into modular origami, mostly from sonobe and phizz units.
I've been trying to fold the pentakis dodecahedron from sonobe units, but I'm a little bit stumped with something.

So I can basically arrive at what appears to be the right shape, except I need to use twice as many units as all instructions say I should. I've been using Meenakshi Mukurji's book Marvelous Modular Origami, but I've looked at other resources as well. Basically I should be able to fold this shape from 60 sonobe units, or 30 compound units, but my result requires twice as many, 120 sonobe / 60 compound.
This kind of makes sense to me as each of the 12 dodecahedral faces has a ring of 5 spikes made from 10 sonobe / 5 compound. 5x12=60.

I know I must be doing something wrong, possibly in the way rings of 5 are connected to each other, but I can't for the life of me work it out. Basically half the sonobes (one piece in each compound) don't see the light of day in the finished model - these are the pink pieces in the incomplete model on the right. They're crucial to the structure but not visible.



Somebody please help, my brain is boggling.

For some reason your picture doesn't work. Could you please check the link.
It is in any case mysterious that some of your Sonobe modules aren't visible, usually on those models all the modules are visible.

Edit: I can see the picture now.

A pentakis dodecahedron is essentially a stellated rhombic triacontahedron if I remember correctly.
So you need a compound unit for each of the 30 spikes, which totals 60 units.
I think I know why you're having the issue of some units being hidden, though. The creases in each unit should go mountain-mountain-valley (assuming you're looking at the top) so there won't be a need for the 60 extra units that I'm guessing are hidden in the edges.

(Then again, it's been years since I've folded a Sonobe, so I could be way off. xD)