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Someone please explain a closed sink

PostPosted: June 7th, 2005, 1:36 pm
by hermanntrude
I have been origami-ing for a while now and have started looking for more advanced models, and one thing keeps stopping me in my tracks. the infamous closed sink. There are a couple of models in "folding the universe" by engels which i cannot do thanks to the poor explanation of this type of fold in the intro. Most recently i have been thwarted in the making of the cookie monster (http://www.keconnect.co.uk/~rglynn/cookie.pdf) because of another closed sink... i can open sink with no problems but it seems weird to me to ask for a closed sink... especially when you can open the folds to get a sink anyway... is the result any different? i get the idea it must be but the diagrams dont help. Does anybody know of an example somewhere which might help me practise this fold?
and while we're at it ive heard a lot about something called a closed unsink, but have never seen an example... any ideas?

thanks a lot,

Hermann

PostPosted: June 7th, 2005, 4:05 pm
by Frydrych
Preliminary base:
Image
Open sink:
Image
Closed sink:
Image
Another closed sink:
Image

PostPosted: June 7th, 2005, 4:49 pm
by origami_8
In some cases it can be important to fold a closed sink to lock the model. This is shown good in the third picture, were the layers of the closed-sink-side hold together as well, while the layers of the open-sink-side are loosey apart. But sometimes it is only an esthetic question if you make a closed sink or an open sink. It depends on the Model and the following steps. Than you can choose it for yourself which kind of sink you use.

PostPosted: June 7th, 2005, 10:58 pm
by Friet
The closed sink is indeed a bit more difficult the the open version. Since you can just unfold and refold for the open sink, but you have to push the paper inwards for a closed sink.

PostPosted: June 8th, 2005, 9:08 am
by hermanntrude
excellent advice, thanks for the pictures... i can see why they were needed... it's hard to explain in words isnt it? but i copied your pictures just now and i see what you mean about locking things together. could be very useful, although a little messy sometimes... i guess that gets better with practise.

thanks again, i can see this forum is going to be well worth joining

PostPosted: June 8th, 2005, 11:32 am
by hermanntrude
looking at the underside of the closed sink (the doubly closed one, shown in the third picture), i notice there is more than one way for the folds to lie... the flaps at the back can be either on the same side as each other or opposite sides. Presumably most of the time you dont get much choice about this as the back isnt often accessible, but i noticed i could reassemble this sink in three ways, the most pleasing being the one with the flaps on opposite sides... do these arrangements have names or uses? has anyone got a clue what i'm writing about any more?

PostPosted: June 8th, 2005, 5:46 pm
by origami_8
I don´t think that these arrangements have their own names, I´ve never seen something like that and I´ve folded a lot. Maybe if it is important if the sunken flap is lying on one speciall side the author could give a hint, but I can´t remember having seen that in praxis.

PostPosted: June 8th, 2005, 5:52 pm
by Joseph Wu
For closed sinks, it usually is not important how the internal layers are arranged. Usually, you should try for the most uniform layout possible, to avoid unnecessary thickness on one side. There are few models where they arrangement of these layers is important, and these are usually indicated in the diagrams.

PostPosted: June 8th, 2005, 7:45 pm
by Azuolas
http://nic-nac-project.de/~origami/inde ... ge=4&str=3 are some pictures. (but page not in english)

PostPosted: June 9th, 2005, 4:47 am
by malachi
Closed sinks are a pain (esp. with foil), but they did lead to one of my favorite quotes in Origami Design Secrets by Robert Lang:
A closed sink is an inversion of a point, but in such a way that it is not possible to open the point flat while performing the maneuver. This makes closed sinks extremely hard to perform. In fact, from a strictly mathematical viewpoint, it is impossible to perform a closed sink using a finite number of folds (and what is impossible in mathematics is usually pretty hard in reality).

picture three

PostPosted: June 9th, 2005, 7:43 pm
by omzig89
the third picture on there is the closed sink that I've seen before most commonly. It didn't take me that long to learn, I'll give a simple technique:

:arrow: First valley fold the tip down where you want the closed sink.
:arrow: Then Spread-squash the tip.
:arrow: Then invert it. Sink it in.

If you've made the very basic, fundamental, origami crane, remember pulling the wings apart to make the body round? and see how the tip squashes open, but not all the way?
For a closed sink, do the squash all the way and push it inside.

Also, you must have diagrams for something with pictures, so, combine the wonderful advice of all the people who posted here and your diagrams. Happy folding! 8)

Re: picture three

PostPosted: June 9th, 2005, 11:48 pm
by wolf
I'll call the third picture a partial closed sink. Perhaps sinks can be distinguished by the perimeter of the sunken area - a totally open sink is one where the perimeter is maximised, and a totally closed sink is one where the perimeter is minimised.

omzig89 wrote:and see how the tip squashes open, but not all the way?
For a closed sink, do the squash all the way and push it inside.

Doesn't that just give you an open sink?

Re: picture three

PostPosted: June 10th, 2005, 9:23 am
by hermanntrude
omzig89 wrote:Also, you must have diagrams for something with pictures, so, combine the wonderful advice of all the people who posted here and your diagrams. Happy folding! 8)


I dont understand what you mean. it seems you might be suggesting that i break copyright laws :o

no, not suggesting copyright breaks

PostPosted: June 13th, 2005, 1:21 am
by omzig89
I just meant that you combine ideas from different sources in your mind to help you fold things correctly. Also, I may have made a little mistake explaining the closed sink as well. I'll have to fix that.

Re: picture three

PostPosted: June 13th, 2005, 1:25 am
by omzig89
wolf wrote:Doesn't that just give you an open sink?


You are right my friend, I am currently thinking of the right way to explain the closed sink. Stay tuned for more alerts.