How sharp is sharp?

I have cut silk before. I was talking to Donna B., awhile ago in email about this and she took several of her blades to hanging silk and cut them to ribbons. She sent me some of the material to have a look at, including the bits cut up. Which made quite an impressive package to open up in front of a few friends.

If you want to cut a falling piece, the further it falls the easier it will be to cut as well as the larger it is, as it will be heavier that way. You want to use a draw stroke and have the blade with a decent curvature so as to make the silk have to travel up along it on the draw, and/or rotate the stroke. Well suited to the curvature of Japanese swords, or a khukuri for that matter.

The edge finish should be decently aggressive, I think I did it with 1000 SiC lightly stropped on canvas + chaulk paste. If you go a lot coarser the silk tends to just catch and be hauled around, and on really high polishes there isn't enough bite to cut it well. Then again the higher the polish the more skill is required to get the necessary edge alignment.


-Cliff
 
Send a video. I still have yet to see a free falling silk scarf cut in two by a stationary blade.
 
Cliff,

I think the silk scarf will reach terminal velocity rather quickly. The distance it falls might not make much of a difference. Of couse you can assist it air movement in the room. As suggested wetting it will have its merits.

It will be interesting to see.

Will
 
"Specially if he gets a light fixture or two along with the scarf. HAPPY 4TH!!
 
I don't think I could cut it all the way in half with my puukko -- you can't do much of a draw cut with a 4" blade -- I'm just saying I think I could make a cut in it.

I think cutting a silk scarf all the way in half would require a great deal of skill as well as a sharp sword (or long knife). I wonder if Gaucho has tried it ... I think I'll email him....
 
witchhazel1.jpg

"Why thats sharp enough to split a hare..."
 
Originally posted by Cougar Allen
... now it's 1:00 in the morning here, all the stores that sell silk scarves are closed and shuttered, (am I the only one whistling Scarlet Ribbons?)
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YES, AS A MATTER OF FACT YOU ARE.

Rusty
 
Originally posted by Bill Martino
Send a video. I still have yet to see a free falling silk scarf cut in two by a stationary blade.
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I just read that post a little more carefully and suddenly I realize we're talking about two very different things (the root of many of the arguments in this world).

No, I don't think we're ever going to see a video of a silk scarf drifting down through the air over a stationary sword and being cut neatly in half when it reaches the blade. If we do it'll be a fake.

The same applies to the story of the three samurai who got to bragging about how sharp their swords were. Finally they left the teahouse and went to a nearby stream to try conclusions.

The first samurai thrust his sword into the sandy bottom of the stream and then he carefully floated a sheet of rice paper on the surface. The rice paper drifted down to the sword and was cut in half as soon as it touched the blade, and two pieces of rice paper drifted on down the stream.

The second samurai thrust his sword into the sandy bottom of the stream and then he floated a sheet of rice paper on the surface. The rice paper drifted down to the sword and was cut in half as soon as it touched the blade -- and it was cut so cleanly it joined back together on the other side of the blade, and a single sheet of rice paper drifted on down the stream.


Then the third samurai thrust his sword into the sandy bottom of the stream and he floated a sheet of rice paper on the surface. The rice paper drifted down almost to the sword -- and then it turned and went around the sword and drifted on down the stream unharmed.

I have a friend who could make a video of that for you, but digital effects like that don't come cheap -- he has more invested in his computer than any dozen of us, and he has to recover that investment somehow....
 
Rusty: Oh ... um ... then ... am I the only one playing Scarlet Ribbons on a slide chromatic harmonica accompanied by friends on hammer dulcimer and plectrum banjo?

I suppose I probably am ... oh, well.
 
Yes, due to the very high drag, I would not assume much of a drop is necessary at all, however up to that point it would get easier. If you are not allowed to move the knife at all then it is much harder still. Would it still count if the slik was allowed to travel along the blade and thus be sliced in two ? If this is the case then you would want to tilt the blade down so as to get the silk to slide along it, but at the same time have the curvate to force the cut, again suited to the geometry of most Japanese swords .

It does seem difficult to me, but hardly impossible. To put this into perspective, take a look at the cutting that is done in the ABS and other cutting competitions, much of that is *very* difficult. It you really want to be amazed then try to duplicate that cutting as just reading what is done doesn't give the impression at all as actually attempting it. However theses feats can be done by very skilled individuals with top quality sharpened blades.

I have some slik on hand, I'll do some cutting with it and see how difficult it is to cut in more detail.

-Cliff
 
I'll need a long scarf -- a few inches wide and maybe a hundred yards long. I'll stick my sword out a window of the Empire State Building and have an assistant drop the scarf off the roof. We'll have to pick a day with no wind. The long scarf won't fall any faster, but after it drifts down to my blade its weight will pull it down with sufficient force to cut it.
 
:
Won't fall any faster?

I thought the further something fell the faster it goes.:)
Doesn't a falling object fall with a speed of 32 feet per second per second?
Seems like I heard that from a group of skydivers talking about freefall one day.

The scarf would fall at the same rate a 300 Lb anvil would, but both would be going faster and faster the further the drop.:D
 
Yvsa,
that's true, Galileo first noticed that and reported it in his law of falling bodies. Then Newton built upon Galileo's research and came up with what we call gravity. And at sea level on the planet Earth all objects fall at approximately 32 feet per second squared.
Well, that's how it works in a vacum atleast. Once you introduce an atmosphere you introduce drag, and once you introduce drag you introduce a terminal velocity. For a human being in freefall you hit your terminal velocity around 300 miles per hour, assuming one standard atmosphere. In project Excelsior, back in 1959 a guy jumped out of a balloon at over 100,000 feet, and broke the sound barrier in freefall, he still holds the record for being the fastest moving human being without the aid of a vehicle. :D

With a piece of silk the drag is very high and the mass is very low. So it has a very low terminal velocity, so it just won't move that fast without the aid of an outside force. That's also why soaking it in water helps. It adds to the mass of the item, which adds to its inertia, which means that it gives more resistance to being pushed out of the way with the blade, so it is more likely to be cut. Same thing with a water bottle. You have a free hanging emty bottle, and you're not going to cut it. You fill it up with water, and you're going to split it like a ripe watermellon. :)

Have I, in the past few days, displayed my true nature as a science, and computer geek???? :D :D :D

I really need to get a girlfriend.
 
:
Bob wrote:
Have I, in the past few days, displayed my true nature as a science, and computer geek???? :D :D :D
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YUP!!!!:D

And thanks for the clarification Bob.
I saw on TV the other day where some gal is going to take that same jump and break the sound barrier without the aid of a vehicle.:D

Me Personally?
I Am keeping my feet and therefore my arse on good ol' solid Terra Firma!!!!:D
 
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