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Maurizio D'Angelo




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PostPosted: Sat 30 May, 2009 2:20 pm    Post subject: about POB         Reply with quote

Hi all,
I was invited to a medieval gathering.
With some friends, known at that time, we talked about POB.
swords for type XIII I said that I had a POB to about 120-130 mm. by the guard.
Almost everyone has challenged this measure. Their reasons are:
1) Only the cavalry swords were so heavy towards the tip.
2) It would not be acceptable for a combat sword so unbalanced.
3) a sword is slow, not suitable to the school of medieval fencing.
I am not a student of medieval fencing. I do not know almost nothing of fencing. My questions:
A sword is suitable for the cutting can be balanced as if it were otherwise?
Who teaches a school of medieval fencing should not respect the characteristics of that use? The air versatility of a sword to be considered respecting the use for which it was built in ancient times?
Reflections ...
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Nathan Robinson
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PostPosted: Sat 30 May, 2009 2:28 pm    Post subject:         Reply with quote

Simple measurements like that don't tell anything.

How long is the blade? how wide is the blade? how is the mass distributed? What is its purpose? What are the targets it will face? how will it be used?

A balance point of 4.5-5" on a 37" long blade is quite a different thing than the same balance point on a 31" long, 1.5" wide blade and even on a 31" long, 2" wide blade.

We all must always consider a sword as a whole and not by any single statistic or measurement.

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Bartek Strojek




Location: Poland
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PostPosted: Sat 30 May, 2009 2:30 pm    Post subject:         Reply with quote

I'm not sure if I understand you well -

Are your friends suggesting that PoB/CoG 130mm from guard means that sword is too blade heavy?

By that logic almost all medieval swords are completely unbalanced. (See Albions for example).
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Paul Watson




Location: Upper Hutt, New Zealand
Joined: 08 Feb 2006

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PostPosted: Sat 30 May, 2009 3:18 pm    Post subject:         Reply with quote

This might sound like a generalisation but I have found that blade length has far greater affect than POB and weight with regards to handling chatacteristics that are particularly associated with speed.

The shortest sword I have owned was the Sovereign, it was heavier than other longer single handers I have owned, but much quicker. POB also has to be considered from the point of view of employment of the sword. Some XIX's in production have POB's around 5", but as soon as the finger is looped over the guard through the finger rings this effectively brings the POB back by about 1". The more I handle swords, the more I am lead to believe POB is a by product not a goal.

120-130mm is not unbalanced. If the POB ends up being too close to the hilt I would imagine you would have no feel for the blade when striking. Not many swords appear to have a POB less than 100mm. Very few that I can note. I have owned a very fast sword with a POB of 127mm.

I do not love the bright sword for its sharpness, but that which it protects. (Faramir, The Two Towers)
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Maurizio D'Angelo




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PostPosted: Sat 30 May, 2009 5:00 pm    Post subject:         Reply with quote

Bartek Strojek wrote:
I'm not sure if I understand you well -

Are your friends suggesting that PoB/CoG 130mm from guard means that sword is too blade heavy?

By that logic almost all medieval swords are completely unbalanced. (See Albions for example).


Yes, they are.
They have swords (Type XIII) with blade length of 800 mm and a POB at 50 mm from the guard.
The fact is that their teacher is more than convinced.
This had me a bit confused. Now it's better.
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Paul Watson




Location: Upper Hutt, New Zealand
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PostPosted: Sat 30 May, 2009 11:24 pm    Post subject:         Reply with quote

Maurizio, is the sword in question an antique or based on research of historical examples? If not then it is simply someones version of what they think a XIII should be and may not truly represent the type..
I do not love the bright sword for its sharpness, but that which it protects. (Faramir, The Two Towers)
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Diviccaro Roberto





Joined: 15 Dec 2005

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PostPosted: Sat 30 May, 2009 11:49 pm    Post subject:         Reply with quote

Maurizio, the discussion is different from that you think.
1) single hand sword: POB into the guard.
2) one and half sword: the key of volta is the "posta". you must remember the "posta finestra". The POB is in middle of your eyes. You remember how i grip the sword into posta finestra. the distance from pob to guard is >= the distance from nose to ear.
into middle of your eyes the propagation of power must be 0 ergo POB.
I hope to be clear. Sorry for my poor english.

bye
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Jim Mearkle




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PostPosted: Sun 31 May, 2009 9:02 am    Post subject:         Reply with quote

Point of balance is only part of how a sword handles. The other is moment of inertia (rotational inertia).

Take for example, two swords with similar weights, lengths and balance points.

One has a thick ricasso and sharp profile and distal tapers. The other has a thinner ricasso but stays broad and thick towards the tip. The one with the broad tip will feel heavier and be slower to rotate due to the increased mass towards the tip.

This thread over at SFI has a good discussion of the concept: http://forums.swordforum.com/showthread.php?t=51519

(edited to correct technical error discussed below)

Jim


Last edited by Jim Mearkle on Sun 31 May, 2009 4:26 pm; edited 1 time in total
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Bram Verbeek





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PostPosted: Sun 31 May, 2009 11:12 am    Post subject:         Reply with quote

An XIII with a POB 2 inches from the guard seems off to me, these swords have quite parallel edges, and are meant for shearing blows, that is better achieved with a blade heavier sword.
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Vincent Le Chevalier




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PostPosted: Sun 31 May, 2009 12:31 pm    Post subject:         Reply with quote

Jim Mearkle wrote:
Point of balance is only part of how a sword handles. The other is polar moment of inertia (rotational inertia).

For what is worth the correct term in this case is just moment of inertia. Polar moment is, I think, a term that Michael Pearce borrowed from cars, and actually means something else in physics. Even the Wikipedia page underlines this, and I'm not the one who wrote it Happy

Mass, Lengths, Center of gravity, Moment of Inertia. Neglect one of these things and you end up with a different handling... And all can be measured, of course, it's just a pity that the moment of inertia is never made public, mainly for antiques Sad

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Jim Mearkle




Location: Colonie, NY
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PostPosted: Sun 31 May, 2009 4:24 pm    Post subject:         Reply with quote

Vincent Le Chevalier wrote:

For what is worth the correct term in this case is just moment of inertia.


You're right. Polar moment is the ability to resist torsion, which is would be an important property of the blade cross section during a misaligned cut, but not relevant to this discussion.

The only thing I can say in my defense is it's been 20 years since I took Mechanics of Materials.

<sez to self> Bad engineer, no biscuit </sez to self>

Jim
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Maurizio D'Angelo




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PostPosted: Sun 31 May, 2009 4:46 pm    Post subject:         Reply with quote

Jim Mearkle wrote:
Point of balance is only part of how a sword handles. The other is moment of inertia (rotational inertia).
Take for example, two swords with similar weights, lengths and balance points.
One has a thick ricasso and sharp profile and distal tapers. The other has a thinner ricasso but stays broad and thick towards the tip. The one with the broad tip will feel heavier and be slower to rotate due to the increased mass towards the tip.
(edited to correct technical error discussed below)


Dear Jim,
In a sword, to be meaningful, the moments of inertia, are calculated the coordinates on POB?
IXX IXY Ixz
Iyx IYY Iyz
Izx Izy Izz
Where xyz = POB
You say: Two swords have the same mass, length, POB same. How is it possible that one has more mass in relation to the sword tip? Only if, instead, a Sword XIII, do a sword of imagination, this is possible.
If I have more mass at the tip to have the same weight should decrease the pommel. Change the POB.
But the numbers I am not interested at this time.
I have not heard any teacher of fencing.
What is their opinion? it is true that you have to sacrifice the features of the sword? This is a better fighter?


.


Last edited by Maurizio D'Angelo on Sun 31 May, 2009 5:41 pm; edited 1 time in total
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Maurizio D'Angelo




Location: Italy
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PostPosted: Sun 31 May, 2009 4:51 pm    Post subject:         Reply with quote

Vincent Le Chevalier wrote:

And all can be measured, of course, it's just a pity that the moment of inertia is never made public, mainly for antiques Sad


Vincent, to convince Peter to give the measures of the original and I'll calculate the moments of inertia ...
I believe that Peter is not very inclined to do this.
I'm kidding, of course. Razz
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Maurizio D'Angelo




Location: Italy
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PostPosted: Sun 31 May, 2009 5:05 pm    Post subject:         Reply with quote

Diviccaro Roberto wrote:
Maurizio, the discussion is different from that you think.
1) single hand sword: POB into the guard.
2) one and half sword: the key of volta is the "posta". you must remember the "posta finestra". The POB is in middle of your eyes. You remember how i grip the sword into posta finestra. the distance from pob to guard is >= the distance from nose to ear.
into middle of your eyes the propagation of power must be 0 ergo POB.
I hope to be clear. Sorry for my poor english.

bye


Are you sure?
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Bram Verbeek





Joined: 27 Mar 2007

Posts: 217

PostPosted: Sun 31 May, 2009 10:18 pm    Post subject:         Reply with quote

Diviccaro Roberto wrote:
Maurizio, the discussion is different from that you think.
1) single hand sword: POB into the guard.
2) one and half sword: the key of volta is the "posta". you must remember the "posta finestra". The POB is in middle of your eyes. You remember how i grip the sword into posta finestra. the distance from pob to guard is >= the distance from nose to ear.
into middle of your eyes the propagation of power must be 0 ergo POB.
I hope to be clear. Sorry for my poor english.

bye


I wholeheartedly disagree on the POB in the guard with any sword before a rapier. A POB there make for a very nervous cutter, while a few inches into the blade makes it track the cut more easily, and allows for greater power when connecting.



Quote:
You say: Two swords have the same mass, length, POB same. How is it possible that one has more mass in relation to the sword tip? Only if, instead, a Sword XIII, do a sword of imagination, this is possible.


If one has a thicker blade section close to the guard, as well as a thicker guard and tang, more mass is close to the POB than with a more even width blade. This will make a lot of difference to the handling, could be the difference between 1kgm2 and 1,5 kgm2.
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Maurizio D'Angelo




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PostPosted: Mon 01 Jun, 2009 2:29 am    Post subject:         Reply with quote

Bram Verbeek wrote:

If one has a thicker blade section close to the guard, as well as a thicker guard and tang, more mass is close to the POB than with a more even width blade. This will make a lot of difference to the handling, could be the difference between 1kgm2 and 1,5 kgm2.


Yes, it is correct. I did this test. So what Jim has said is fine. Even doing the same profile of XIII, you can leave the mass, length, POB, but have a different handling. To be honest the difference of the data was similar, in my test, but is possible.
I was not able to keep its equal the POB, but it was quite similar between my 2 examples of the test.
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Vincent Le Chevalier




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PostPosted: Tue 02 Jun, 2009 5:12 am    Post subject:         Reply with quote

Bram Verbeek wrote:
Diviccaro Roberto wrote:

1) single hand sword: POB into the guard.

I wholeheartedly disagree on the POB in the guard with any sword before a rapier.

Even rapiers are not balanced into the guard. If you look at these measurements:
http://www.musketeer.org/Garrick/Blade_spec_article.html
and work the numbers a bit, you'll find that the point of balance is always at least three inches into the blade from the end of the hilt (and on rapiers this is not the cross), up to almost six inches...
A CoG into the guard is a sign of a much too heavy pommel on single handers. Heck even sport fencing foils are not balanced like that... It will not make the blades any more handy, probably quite the contrary because the inertia you struggle against to make the sword move is completely unrelated to the static feel.

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Vincent
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Neil Langley




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PostPosted: Tue 02 Jun, 2009 7:27 pm    Post subject:         Reply with quote

Vincent Le Chevalier wrote:

Even rapiers are not balanced into the guard. If you look at these measurements:
http://www.musketeer.org/Garrick/Blade_spec_article.html
and work the numbers a bit, you'll find that the point of balance is always at least three inches into the blade from the end of the hilt (and on rapiers this is not the cross), up to almost six inches...


I know very little about rapiers, but I am a little surprised at how short the hilt measurements are in this article if they are inclusive of the hilt beyond the cross. Have I got this right, do these 'hilt length' figures include the finger rings etc., and if so - are rapier hilts normally this short?
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Jim Mearkle




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PostPosted: Tue 02 Jun, 2009 7:59 pm    Post subject:         Reply with quote

Back in the early days of European martial arts, when schlager blades became available and began to supplant modified epees as rapier simulators, people said that you couldn't do disengages or cavazziones with them. The problem was epee techniques don't work for schlagers. Now we do disengages routinely with practice rapiers.

Similarly, your friends may think swords with POBs 100 mm from the cross are poorly balanced simply because they haven't figured out how to use them yet.

Jim
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Roger Hooper




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PostPosted: Tue 02 Jun, 2009 8:08 pm    Post subject:         Reply with quote

Maybe we've passed talking about XIII's, but I recently bought an ATrim sword of that type. Almost everyone on this forum would agree that Gus Trim knows how to make and balance a blade. Some of its statistics in mm -

Overall length - 1010 mm
Blade length - 775 mm (30.5 in)
Blade width - 60.33 mm
POB - 114.3 mm (4.5 in)
weight - 1.19 kg

It has almost no profile taper, but its broad, flat blade has plenty of distal taper.

If the POB was closer to the guard, this sword would lose its authority and point control. The distribution of the blade geometry via the distal taper pushes the POB further down the blade. This sword had great maneuverability especially with 2 hands. It is not at all blade heavy and may be the most finely balanced of all my swords.

Maurizio, are your friends reenactors using reanactment swords? That type often has little or no distal taper with thick rounded edges to give it more durabilty. To bring the weight back towards the guard, a heavier pommel is then added, resulting in a very short POB.


Last edited by Roger Hooper on Tue 02 Jun, 2009 8:38 pm; edited 1 time in total
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