The Origami Forum

Meguro's Sea Urchin is one of my favorite models because of the unconventional yet effective method of achieving points. I sent him an E-mail a while back thanking him for the model, and he responded very nicely.

I first saw it at the 1994 Origami USA convention. I was very happy to find the diagrams on the internet:
http://hansbirkeland.150m.com/meguro1.htm

Anyway, I thought I'd amuse myself by folding his Sea Urchin with every even-numbered grid division up to 16, the model's actual grid number.
Here's how you figure out number of points:

These are the precreases for the 8x8 version.
[img]http://img.photobucket.com/albums/v191/ ... o8x8-1.jpg[/img]
The red dots make a 5 across, 5 down square, and the blue dots make a 4 across, 4 down square.
4 is half of 8. 5 is one more than half of 8.
So, the formula is (x/2)^2 + (x/2+1)^2.
A chart showing the number of points for all my urchins:
2x2 = 5
4x4 = 13
6x6 = 25
8x8 = 41
10x10 = 61
12x12 = 85
14x14 = 113
16x16 = 145

The 2x2, 4x4,
6x6, and 8x8.
[img]http://img.photobucket.com/albums/v191/ ... ro2468.jpg[/img]

The 10x10, 12x12,
14x14, and 16x16.
[img]http://img.photobucket.com/albums/v191/ ... 121416.jpg[/img]

I actually tried making a 32x32 once.... after 4 hours of folding a huge sheet and starting a little knot in the middle roughly an inch and a half wide, I stopped. I'll have to find 10 foot x 10 foot paper for that one.
But, I may work my way up starting at 18x18 (181 points) and beyond, probably stopping at 24x24 (313 points.) But each will take a very long time.
Has anybody else gotten into this model? I see Joseph Wu has made one, and pinched the points to get them thinner.

Thats a pretty interesting model... I never really thought about the model much whenever ive seen it folded.

What size sheets did you use for each of the ones you folded? im just curious.

my fold!

yes its very nice although tedious, if you make it from somewhat white translucent paper which will allow moisture absoption and put a drop of deep red wine on each spine to tint it, and then a nice light inside it looks absolutely stunning.
so stunning I had to give mine away the next day after I finished it.
maybe I can get a picture sometime to show you.
X

How did you figure out the folding sequences for those? Or did you have to make your own CP?

They all use the same folding sequence that's in the diagrams up there.
You just start by dividing the square into a different number than 16.

I just don't understand how you'd go about doing that.

It's reallllllly simple. In the beginning steps instead of making a full 16 x 16, you make 8 x 8 or whatever. Then you follow the steps with your smaller grid. I did that sea urchin in 8 x 8 once, but it doesn't come out full enough.

By the way, very cool series, Kareshi. I'd like to see it continue up from 16 now!

Yes, I see. But if you're using, say, a 2x2 grid, you would do the precreasing, bla, bla, bla. But how would you do step 13? Once you've folded down the middle of a 2x2 grid, you can't really do another reverse fold. Or am I missing something?

Using a 2x2 grid would make a waterbomb base after step 13. Does that make sense?

Yes, it does. Now i feel kinda dumb...

I found a couple photographs from years back when I tried to make a 32x32 - for some reason I tried going straight to it after doing a few 16x16's.
There's a sheet of normal printing paper for scale (8.5x11)
I forget the actual dimensions of the paper, but you can see in the second photograph how unreasonable this was going to be. I made it 4 "turns" before giving up.
[img]http://img.photobucket.com/albums/v191/ ... G_7477.jpg[/img]
[img]http://img.photobucket.com/albums/v191/ ... G_7479.jpg[/img]

it´s too bad you gave up, actually I think the most difficult part is the beginning since the pleats after the sinks are so long and hard to manage but after you get the rythm it starts getting easier.
The super tedious process of shaping can be done over the course of days.
If you still have it you should keep with it because the results are very well worth the trouble.
X

I finally got some pictures of my sea urchins the small one is glassine and the large one is normal bond paper
I don´t remember what the number of lines is in the grid but I think the small one is 8*8 and the large one is 12*12
anyway here they are

I really like this model. The 8x8 version is my favorite since it's not that long to make and still gives a nice-looking urchin (better than the 16x16 version in my opinion). It's also one of the few models where copy paper gives a better result than most other papers. It's an excellent way to pass time during school time...
I remember folding the 16x16 version out of kraft paper. The result looked a lot like anonymous person's. Since it was more flat that round, you could almost wear it like a wig .