Traditional knife homework - Blade length to handle length ratio.

[Just Tom.]

I tried this out of curiosity, inspired by the questions posed about true cutting edge length on blades with more 'belly' curvature. I'd never given it much thought until reading this thread.

(1) Use something like a piece of heavy/thick cardboard, laid flat on a table or bench with one edge flush to the edge of the table. Make an index mark at the edge of the cardboard with a pencil.

(2) Place and hold the blade's cutting edge vertically (spine UP) against the face of the cardboard, with the heel of the cutting edge (like at the plunge) aligned at the mark you made, flush at the edge of the cardboard.

(3) Lift the butt end of the knife upward, allowing the cutting edge's belly curvature to 'roll' forward on the cardboard (without sliding), until the tip of the blade's cutting edge is flush to the cardboard. With a pencil, make a mark where the very tip of the blade lays flush to the cardboard.

(4) Measure from the edge of the cardboard, at the index mark you made there, to the mark you made for the tip.

I just tried this method with a Buck 110LT folder with its upswept tip on a clip blade. I measured 3.375" cutting edge length accounting for the belly, as compared to a straight-line measurement of 3.250" as measured directly from the plunge to the tip. Handle length is 4.875" (4-7/8"). So, accounting for true cutting edge length as I measured it, I'd have this result below, for the ratio of cutting edge length relative to handle length:

3.375" / 4.875" = 0.692

Or, if just relying on the straight-line measurement from the heel of the cutting edge to the tip, as per the OP, I'd get:

3.250" / 4.875" = 0.667 ( Note: I just noticed I typo'd the edge length incorrectly here at 3.125" - edited to 3.25" & recalculated, to fix that. )

I suppose some blades with recurve could be measured in a similar manner, but perhaps against a somewhat radiused or bowed surface to allow full contact along the recurve portion and all the way to the tip. Measure with a flexible ruler.

Ok, since you HAD to go measuring the belly, here are my measurements of the length of the cutting edge of a knife with a lot of belly using 3 methods:

1. Using a ruler, a right angle, and trigonometry
2. Using a ruler and a piece of string
3. Using your cardboard method

I am somewhat surprised that the results of the 3 methods were practically identical, considering the uncertainty in the measurements made in dim light with a wooden ruler and my 1.25 magnification Easy-Readers.

I think my conclusion is that using a piece of string is good enough and a whole lot quicker…

(The triangle formulas were photocopied from the cover of an old fieldbook. I keep them on my desk in my “book of smarts” binder, along with all sorts of other handy reference materials)

 

[Rsmith_77]

Hah! Called it
Pythagorean theorem!

 

[Just Tom.]

Hah! Called it
Pythagorean theorem!

There’s an old shaggy-dog tale that ends with the punchline “the squaw on the hippopotamus is equal to the sons of the squaws on the other two hides”, but I’m too lazy to type it out here, and nobody wants to suffer through that anyway…

 

[jc57]

I am so happy that I was able to shift this thread into a direction it did not want to go! Makes me feel like my life finally has a meaning.

 

[dantzk8]

This thread is a railway disaster. It didn't begin well.

if I boogered something up here, let me know…

It turned bad.

Your math is off.

GT and Vince were not of a great help.

It's my bedtime...
Tomorrow I'll try...

Too difficult an assignment.

Fortunately jc57 delivered the coup de grace. Thanks, someone had to do the dirty job.

I am so happy that I was able to shift this thread into a direction it did not want to go! Makes me feel like my life finally has a meaning.

Nevertheless, as all this can't fall lower, and as we have some mathematician aboard the train, i have a practical math related question. Here's.

How do you measure the height of a tree you have to fell and which leans toward a house ? As you know trees always lean in the wrong direction.

This, without endangering your life by climbing up the tree. Without jeopardizing your sanity by using an app on your phone. Without risking a calculation error knowing that there are only 3 categories of people, those who know how to count and those who don't.

Math teachers are allowed to answer though i don't always rely on their practical sense.

Dan.

 

[Just Tom.]

How do you measure the height of a tree you have to fell and which leans toward a house ? As you know trees always lean in the wrong direction.

This, without endangering your life by climbing up the tree. Without jeopardizing your sanity by using an app on your phone. Without risking a calculation error knowing that there are only 3 categories of people, those who know how to count and those who don't.

I think the short answer is to use a clinometer and trigonometry. The long answer will have to wait until I get some coffee…

Wild Willie might have a better or more practical answer, though. I think he is a tree guy.

Edit:
I found this - no trig involved, but you do need a clinometer:

Measuring Tree Height using a Clinometer

Download as a pdf The following article was authored by Mike Steiner and Jason Baker.

grazingland.cssm.iastate.edu

 

[dantzk8]

I think the short answer is to use a clinometer and trigonometry. The long answer will have to wait until I get some coffee…

Much more simple. Get some coffee.

Dan.

 

[Will Power]

Frankly, I just do it by eye: if it looks long & right it is, if it looks foolish & underdeveloped it is

But then, I didn't fail Maths at school I just wasn't allowed to enter the exams- waste of tax-payer's money...Biology saved me, thank the gods


Carry on calculating, but which of these knives cuts the best?

 

[Just Tom.]

Much more simple. Get some coffee.

Dan.

I edited my post to add this link. No trig involved, but you will need a clinometer:

Measuring Tree Height using a Clinometer

Download as a pdf The following article was authored by Mike Steiner and Jason Baker.

grazingland.cssm.iastate.edu

 

[Just Tom.]

Frankly, I just do it by eye: if it looks long & right it is, if it looks foolish & underdeveloped it is

But then, I didn't fail Maths at school I just wasn't allowed to enter the exams- waste of tax-payer's money...Biology saved me, thank the gods


Carry on calculating, but which of these knives cuts the best?

Look, if we all wanted to be practical and use common sense, everybody would just carry an Opinel #8 and there would be nothing to talk about. I would then have to find a new, even LESS practical hobby.

 

[Just Tom.]

This thread is a railway disaster. It didn't begin well.

Was it the train leaving Cleveland at 7:15 AM going 40 miles per hour or the train leaving Chicago at 8:30 AM going 60 miles per hour that crashed?

 

[dantzk8]

Frankly, I just do it by eye:

Much more accurate. I talk about a one foot accuracy, at worse 3 feet.

I edited my post to add this link. No trig involved, but you will need a clinometer:

No need for a clinometer. With only the pocket tools you carry on a daily basis you can know where the top of the tree will hit the ground if you fell it or, if you don't, what the height is, measured in steps or in mesure units if you have a tape measure.

Was it the train leaving Cleveland at 7:15 AM going 40 miles per hour or the train leaving Chicago at 8:30 AM going 60 miles per hour that crashed?

I'm a former train driver and I refuse to contemplate such a nightmare, were it in the form of a math problem.

Dan.

 

[Just Tom.]

No need for a clinometer. With only the pocket tools you carry on a daily basis you can know where the top of the tree will hit the ground if you fell it or, if you don't, what the height is, measured in steps or in mesure units if you have a tape measure.

Ahhh, I misunderstood. I thought you were asking because you wanted to know, not asking to test our knowledge.

I would guess it involves finding the spot where a certain object equals the height of the tree when holding it out at arm’s length, then pacing (or measuring) the distance to the tree and applying some rule of thumb.

Or maybe pacing (or measuring) a certain distance from the tree and then holding a ruler out at arms lenth.

We used to do something similar for weapons range-finding, but that was many years ago and I can’t remember exactly how it worked.

 

[dantzk8]

Ahhh, I misunderstood. I thought you were asking because you wanted to know, not asking to test our knowledge.

I would guess it involves finding the spot where a certain object equals the height of the tree when holding it out at arm’s length, then pacing (or measuring) the distance to the tree and applying some rule of thumb.

Or maybe pacing (or measuring) a certain distance from the tree and then holding a ruler out at arms lenth.

We used to do something similar for weapons range-finding, but that was many years ago and I can’t remember exactly how it worked.

You got it.
Measure with a rope the distance between the eye and your hand palm, arm stretched out in front of you.
Report the measure on a wood stick.
Cut the stick at the right length.
Hold the stick at its middle, arm stretched out, walk forward or backward until you aim with the butts both the top and the base of the tree.
The distance between the tree and you is equal to the height of the tree.
It's an application of the Thales theorem (proportionality of the triangles). Simple and reliable.

Dan.

 

[dantzk8]

That's what happens when using a chainsaw without paying attention.

Dan.

 

[Just Tom.]

You got it.
Measure with a rope the distance between the eye and your hand palm, arm stretched out in front of you.
Report the measure on a wood stick.
Cut the stick at the right length.
Hold the stick at its middle, arm stretched out, walk forward or backward until you aim with the butts both the top and the base of the tree.
The distance between the tree and you is equal to the height of the tree.
It's an application of the Thales theorem (proportionality of the triangles). Simple and reliable.

Dan.

Haha! What do I win?

Here is a picture of a knife with a sharpened edge (chord length) to handle length ratio of about 0.8. Too late to save the train wreck that this thread has become, but maybe just enough to keep the wreckage from sliding down into the ravine…

 

[dantzk8]

Haha! What do I win?

All my consideration and i will post the results of the ratio calculations of some of my knives.
I hope it will contribute to put back this thread on it's way.
Thanks for this thread Tom.

Dan.

 

[Just Tom.]

All my consideration and i will post the results of the ratio calculations of some of my knives.
I hope it will contribute to put back this thread on it's way.
Thanks for this thread Tom.

Dan.

You are too kind.

Honestly, though, it’s the light-hearted mockery and the bizarre twists and turns which have made this thread so fun for me

Big thanks to all who have participated.

 

[Wild Willie]

I think the short answer is to use a clinometer and trigonometry. The long answer will have to wait until I get some coffee…

Wild Willie might have a better or more practical answer, though. I think he is a tree guy.

Edit:
I found this - no trig involved, but you do need a clinometer:

Measuring Tree Height using a Clinometer

Download as a pdf The following article was authored by Mike Steiner and Jason Baker.

grazingland.cssm.iastate.edu

You can improvise with a straight stick that reaches from the fork between your thumb and forefinger to your shoulder. Just line the bottom of the stick up to where you intend to make your notch, and back up until the tip of the stick is lined up with the top of the tree with your arm held straight out.

That being said, if you have to ask this question, you're probably not qualified to try and do a removal next to anyone's house...


Edit: I see it's been covered...

Edited again: I also see that nobody's trying to fell a tree by their house... This is a good thing.

 

[Obsessed with Edges]

Another example I looked at - an A.G. Russell 'Cowboy' model in black Rucarta. I seem to recall reading somewhere that A.G. deliberately designed this pattern with a goal of fitting as much blade into the handle as he could. I measured in two ways as I did before - one accounting for the belly of the edge profile, and the other just a straight-line measurement from the forward edge of the small sharpening choil to the tip.

Accounting for the belly:
Cutting edge length = 3-9/16" (~91mm)
Handle length = 4-5/16" (~110 mm)
Ratio, cutting edge length relative to handle = 0.827

Disregarding the belly:
Blade length, edged portion = 3-5/16" (~86mm)
Handle length = 4-5/16" (~110 mm)
Ratio, edged blade relative to handle = 0.781