i aslo got stuck on this, and in fact achieved two different results and decided to sit on it, er, slang for 'think about it' - i didn't really sit on it
This actually would be an easy open sink in and out (like the ones you see often in box-pleated designs). The problem is that it's very hard to actually open the model to perform this step and it's very tempting to make a closed sink instead which would lead to problems in the further folding process.
It's possible to open the model but you have to be very careful not to tear the paper.
I managed this model a few weeks back, this step is hard the trick is to "force" the paper open without ripping it so that you can get ur fingers inside to do the sink. Also make te precreasing very sharp... Also if you use paper that not very thin this model can become umanagable
Open out the whole thing, locate the section, and box pleat it, then close it back up. This is just what I did, and it worked. It's probably not the best approach, but it works. Getting pretty repetitive, eh?
you will notice the subsequent steps (33-36)to release the workable layer. Do make sure you are working with a free layer or you'll have nothing but heartache. Personally I found step 30 & 31 far harder then 28, there's more chance of rippage here. Once you get these folds done, it's alot less daunting then Lang makes it out. Doesn't mean it isn't a seriouse challenge not to rip, but the folds ain't that bad once you see them.
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