What design for competition cutter?

[DaQo'tah Forge]

So the other month I was reading an article in BLADE Magazine about this world famous cutting competition winner and his knives.

There was a photo of the knife he used to cut a bundle of hanging ropes and the odd part of this was in the curve the blade had.

The knife had a curve that went forward and the end of the knife didnt seem to have a point but ended rather bluntly.

However in a later issue of BLADE there was a description of a cutting competition and in one of the photos a guy attempts to stick the point of his knife into a pingpong ball, something that the other winning knife with the blunted end could never do?

Now I am planning on designing my own cutting competition knife. I like the idea of that forward curve. It would help flow the rope into the cutting edge correct?

But I would need a point at the end of such a knife , yes?

 

[rlinger]

There is a fellow that explained to me that he learned from another about a convex grind which has the maximum width of blade at center of lateral of blade, in that the spine is also thinner than center lateral of blade.

RL

 

[DaQo'tah Forge]

if you were going to just design a knife for a hanging rope cutting test, what would it look like?

would it have a curve that swept to the front ahead of your hand?

the Rules say that the blade can not be over 10 inches correct? Do they count the unsharpened areas like the Racasson that is just in front of the handle in this 10 inches , or is it just 10 inches of sharpened blade?

 

[Daniel Koster]

the 10 inches is from the tip to the start of the handle.

Not sure who you're thinking of, DF....but Ed Schempp (sp?) is the one setting the rope cutting records out on the West Coast. Do a search on "moby" here in this forum and you'll see my first attempt at a comp. knife. I made this long before I knew of Ed, but his ideas are very similar to mine. Also do a search on "reverse distal taper".

If you look at Jon Graham's knives, his have a chisel grind and a 90 degree point that could very easily be used in the "ping-pong ball test". And you would still have a lot of the weight "forward" in the blade.

The balance point for my Lil' Moby was an inch in front of the false guard.

 

[DaQo'tah Forge]

now about that "moby"...

In your knife you have an area that is used as a finger groove that is not sharpened.

But then this must take away from the amount of space left over for the cutting areas correct?

Did you notice the rope getting snagged in this unsharpened area?

If you had slanted the knife forward, like something Gurkha looking, whould that have helped hold the un-cut rope as the cut was being made?

 

[Daniel Koster]

A recurve does improve rope cutting, in my experience. It also improves the 2x4 cut. However, you are limited in any "one chop" type cuts such as the "top-to-bottom" plastic bottle cut, etc.

I had no hang-ups in the rope cut. The blade is 10 inches long....only need about 3 inches toward the end for the rope cut.


One more note about a recurve. Beware using this style in a competition unless you have spent some hard time using it. Most of the times I have seen recurves used in cutting competition, the person using it was not using it to it's fullest advantage and this caused missed shots, inefficiency, etc. It doesn't take much, but if you find that you are swinging your recurve the same as a bowie, then you need to take some time to figure it out. I feel justified in saying this because I swung my first few khukuris like bowie knives, and got blisters, sore hands/arms, bad cuts, etc.....until I finally relented and let the knife "talk to me"....only then did I learn the right way to use it and now I get much more efficient cuts.

 

[Terry_Dodson]

Daniel can you describe the correct way to swing a Kukri type knife? i have a couple older ones that look like they may be cheapie ones, but i would like to know how to swing it properly for when i make my own.

 

[Ed Schempp]

Hi Daniel,
The knife design must reflect the medium or mediums that will be cut in competition. My rope cutting knives are designed to meet that challenge specifically, althought some of the attributes of a good rope cutter translate to cans and two by fours.
In designing a rope cutter, I looked to the Phillipine Islands and thier many bolo designs for inspiration. One area of the PI they raise hemp, rottan. and sugar cane, this is where my hooked profile came from. The reverse distal taper is to put as much mass as possible on the end of the piece. My last knife for rope cutting is .200 on the end of the blade goes to .090 on the end of the handle. The Japanese styled cross-section moves weight forward toward the edge. The reverse curve and the diamond cross-section make the knife self aligning while cutting a target that moves at impact. A bicycle is a good example of what happens with this geometry. If you push a bike forward the front positive raked fork will wobble and the bike will crash in short order. If you turn the front fork around and push the bike the negative rake fork follows and aligns the direction of the tire with the mass and the bike will roll much further without crashing. The reverse curve puts mass ahead of the cut and directs the knife straight following the edge. A spine heavy knife has a tendency to try and lay flat when the rope moves, rather than aligning the during the cut.
The handle is designed to hold the knife as far out on the end as possible. This gives added length to the arch of swing and more speed. I cut like I'm pitching a baseball, I lead with my left leg amd step into the cut, this lengthens the distance the knife moves to the rope, hence more speed. The further the knife is from your body the longer the arc and you have more speed. Whether it is one or 10 ropes the cuts are made in the middle of the blade, the sweet spot. If you try to cut further out on the blade you are out of the sweet spot and the handle force will pull the knife forward out of your hand. You need the balance of the weight on the end of the knife to balance the cut. The edge geometry is critical. I thin the edge until it fails cutting about 30 pieces of rope. I strenghten the edge geometry until the edge doesn't fail on the same test. This method works for all steels. I hope this information helps...Take Care...Ed