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Thread: *Secrets* Distal Taper

  1. #1
    Angus Trim is offline Moderator
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    *Secrets* Distal Taper

    The first secrets thread broke down into steel and heat treat..... very important things to be sure, but only a part of what goes into a blade to make a successful sword.........

    Distal taper today, has become a bit politicized. I don't really understand this, distal taper isn't rocket science, and its not really that complicated. To read some stuff written over the last three/ four years, one would think that distal taper comes in about four flavors, linear, convex, concave, and complex....... True enough, but in "effect", there's only three, linear, convex, concave..........

    Distal taper is one means to control the following: handling, cutting performance, thrusting performance, total weight, structural integrity, harmonic balance, and probably a few others.......

    For beginning swordmakers and sword designers, the structural integrity is the most overlooked. If you read enough, 50% distal taper looks pretty normal for a western double edged sword.........ok, as far as that goes.....

    But, lets take a not so typical type XVIII blade, intended for cut and thrust. We're going to design this for "cut and thrust" sword play, and to be an effective cutter as well as a decent unarmored thrusting sword. And we want a 33 inch blade...... a good manly length for a single hander....*g*

    Lets start with 1/4 inch material, and we want a 50% distal taper, starting at the cross going to where the blade's linear profile taper "curves to the point". When the finish grinding is done, we're at .24 inch at the base of the blade {a hair over 6mm}, and .12 inch thick at where the blade "curves to the point" { a hypothetical spot on the blade, in this case we'll arbitrarily tab it at 1.3 inches behind the point}...........

    We're now going to assume a finished weight of 2.2lbs {1kg}, a cog of 5.5 inches..... which would make for a fairly responsive cut and thrust sword, and a reasonably stiff blade. Not armor piercing stiff, but reasonably stiff....

    All other factors being decent, there's no reason this can't be a successful sword blade........

    Lets now take things just a bit different, but still use a 50% distal taper. For whatever reason, we're stuck with 3/16 inch material.... but we still want that 50% distal taper {for whatever reason}.......

    If everything else is the same, we're going to wind up with {approx} a .18 inch thick base {a bit over 4.5mm} and be .09 thick behind the point. What we have now, is a blade that could very well be "whippy", won't have the same stiffness, and structural integrity might not be that great {might bend relatively easy}. It'll be light, probably too light...........

    So, lets say we want to have a successful blade, similar to the first one, but only have 3/16 inch material. One way to do it {there's always more than one way}, would be to scratch the "50%" distal taper, and settle for, say a distal taper that will give you .13 inch point {distal taper still linear}. This will give you the structural integrity you need, to make things work....

    But now, in order for this to work out "harmonically", the cog is going to have to be more like 8 inches........

    You've likely read, that everything done to a sword blade, affects everything else...... it does.......

    One small look into what distal taper is all about {and I doubt there's anyone "in the game" that knows everything about distal taper}.......
    For Good or Ill......

    What Comes Around Goes Around.....
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    You Reap What You Sow...

  2. #2
    Whew, that made my head hurt, but very informative.

    These secrets threads of yours out to be stickies at some point
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  3. #3
    Angus Trim is offline Moderator
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    Quote Originally Posted by mikejarledge View Post
    Whew, that made my head hurt, but very informative.

    These secrets threads of yours out to be stickies at some point
    Hi Mike

    One of the things I'm trying to do is demystify some of the stuff us swordmakers do, and use for our marketing.........

    Its time now, the time is right, because once again it looks like we're going into a phase of more reviews.....the stuff goes hand in hand....

    Yes, I like what you're doing......
    For Good or Ill......

    What Comes Around Goes Around.....
    and

    You Reap What You Sow...

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    That is indeed enlightning, but I'm not sure what "distal taper" is... I get that the blade has to taper at several places, but which one is the distal taper?

    And thanks for writing this stuff out; I'm looking into starting knifesmithing (hopefully bladesmithing in the future) and this kind of documents are very nice to have around.
    Beauty is a pattern

  5. #5
    Angus Trim is offline Moderator
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    Quote Originally Posted by Christian Borg View Post
    That is indeed enlightning, but I'm not sure what "distal taper" is... I get that the blade has to taper at several places, but which one is the distal taper?

    And thanks for writing this stuff out; I'm looking into starting knifesmithing (hopefully bladesmithing in the future) and this kind of documents are very nice to have around.
    Profile taper is the width, distal taper is the thickness.......
    For Good or Ill......

    What Comes Around Goes Around.....
    and

    You Reap What You Sow...

  6. #6
    Angus Trim is offline Moderator
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    A case for Convex Distal Taper

    A look at a convex distal taper, a sword that I used a bit of what I used to refer to as an accelerating distal taper.......

    Once upon a time I did a pretty much classic shaped type XVIII. The blade's profile tapered gradually and linearly for 2/3 the blade length, and then the profile taper "curved to the point" from there. Blade length was just a tad under 31 inches........

    The distal taper, did like the profile taper. The distal taper from the cross to the plane on the blade where the profile taper accelerated, was gradual. When the profile taper accelerated {curved}, so did the distal taper.

    I suppose that since the taper was initially linear, then curved, you could consider this complex, as you have both a linear move, and a convex move.....

    But, if you break things down, and use a straight line from the cross to wherever you want to measure the distal taper to {in this case, lets call it an inch behind the point}, you can see that the whole "line" of the distal taper is above the straight line.....thus the "effect" is convex.......

    In actual practice it is too........

    With enough experience, a maker will be able to tell the difference in handling between similar profile blades, with different distal tapers. The "effect" of a convex distal taper is a bit different........

    The effect in this case, is a rather stiff blade, that feels light in the hands for the weight. The mass at the end of the blade, recedes at an accelerating fashion....... The thicker mass from the cross to what winds up being the "cop", makes for a stiff, rather durable blade.

    Thickness dimensions? .24 inch at the cross, .11 inch, an inch behind the point.......
    For Good or Ill......

    What Comes Around Goes Around.....
    and

    You Reap What You Sow...

  7. #7
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    As opposed to a concave distal taper...

    ...which these days is usually used on swords that are quite thick at the base (.300-.360 inches.) These swords distal taper very rapidly for the first quarter to third of the blade from the guard to about .200-.250 inches. The distal taper then becomes 'flatter' to near the point- about .100 inch. This results in a relatively stiff blade with a greater portion of it's mass concentrated around the hilt- giving it a Low-Polar Moment (LPM.) Such a sword rotates easily in the hand and feels very lively. You do see this on thinner swords as well- particularly on antique sabers and some Tulwars. An 18th Century Tulwar in my collection is approx. .265 inches at the base and tapers rapidly to approx. .185 inches then has a flat taper to around .065 inches near the tip. This is a very light and lively litttle sword.

    Convex distal taper is great for super-rigid swords like type XVs and XVAs. Concave distal taper works better for swords oriented more toward cutting. Both work well for different uses.

    A flat distal taper seems to offer the most to a broad cutting blade like a type X or XII, or to light XVIIIs oriented more towards unarmored fighting. It seems to lend a bit more authority in the cut. I'm sure that Gus will elaborate on that in his next post.

    Distal taper of any kind helps you to distribute the mass of the sword to optimize it's performance for it's intended use.
    Last edited by Michael Tinker Pearce; 07-17-2007 at 08:01 PM.
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  8. #8
    Angus Trim is offline Moderator
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    Tinker pointed out a thing or two on concave distal taper......

    I have a sample in mind.......

    Tinker was given the specs for XIV.7 {Records of the Medieval Sword}, so that he could make an accurate replica of it. I got the opportunity to study the specs, and got permission to use this as an inspiration for a sword......

    The antique's thickness is .12 inch near the cross, and .06 inch near the tip. Yet, the distal taper is concave.........

    Well, I didn't feel comfortable making something that thin in crossection, even at the width, for the 21st century sword user. Instead I used .24 inch at the base, and was still .09 behind the point. This resulted in sword blade rigid enough for a cutter, and a quick sword for one so heavy {2lbs 10}. The distal taper's character is similar to the saber that Tinker mentioned.....

    This kind of distal taper is very common in single edged swords around the world. Its not so common with double edged swords, but there are some interesting medieval European antiques that feature this distal taper......

    On a really thick based double edged blade, you can distal taper rapidly for three or four inches, and from there go linear, or even convex, to keep things rigid for thrusting work, or in the case of some rapiers, to make them harder to displace.....Not exactly sure why this last works, but it does seem to.

    When it comes to "mass distribution", or building the structure to support the working end {and building the working end for that matter}, distal taper is just one tool in the tool box. But its also the most influential. Still, you need to use it to work with thickness, crossection, fullering, blade geometry, blade length, width, profile taper, etc.........

    Taking distal taper by itself leaves some of the other important features needed to make the finished sword work out..... and its not a good thing to ignore these. Still, distal taper in my view, is the key thing to understand, to master dynamic balance, proper weight, handling, structural integrity, etc......
    For Good or Ill......

    What Comes Around Goes Around.....
    and

    You Reap What You Sow...

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    Gus, have you ever experimented on a blade, using different rates and types of distal and profile taper, just to see how the sword might turn out? If you did, were the results sometimes an unexpected great sword or sometimes a complete clunker?

  10. #10
    Angus Trim is offline Moderator
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    Quote Originally Posted by Roger Hooper View Post
    Gus, have you ever experimented on a blade, using different rates and types of distal and profile taper, just to see how the sword might turn out? If you did, were the results sometimes an unexpected great sword or sometimes a complete clunker?

    Hi Roger

    Yes, and no.......

    By that I mean that I've experimented....... But never really left the "historical model". If I was aware of a particular fashion of distal taper somewhere, I might design and make something........

    Most swords have a bit of more than one type of distal taper, and a lot have varying rates of profile taper. For me, its not every little change in angle on the distal taper, its the overall "effect".........

    And yes, sometimes I'd be surprised about how good a sword came out, and how poor one came out........

    Now, if you want to talk to a guy that's had some great successes varying profile and distal taper, talk to Tinker, he's the master of that.........
    Last edited by Angus Trim; 07-19-2007 at 07:45 AM.
    For Good or Ill......

    What Comes Around Goes Around.....
    and

    You Reap What You Sow...

  11. #11
    Angus Trim is offline Moderator
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    As many know, in some WMA practice, a sword blade is divided into three, with the forte the third closest to the guard, and the foible the last third towards the point.

    I think of the blade as three different segments too, but a bit different. Mine's the base, the support structure, and the working end {foible}. The only part of this that is the same as the WMA model is the foible {from the cop to the point}.........

    When designing a blade {for this sample, lets stay double edged}, its a good idea to design it around the "working end". A good cutting blade might be between .14 and .15 inch at the cop, and maybe around .1 "behind the point". Maybe a good cut and thrust blade might be between .15 and .16 inch at the cop, and between .1 and .13 at the tip....... {just sample thoughts, the reality is that there is a lot of variety depending on a lot of variables, including width at these areas, etc}....

    How long is the blade going to be? What thickness at the base? What is the purpose of this blade?

    If you start, lets say, with .187 inch material, and have a 32 inch blade, then you may get from the tip with a subtle convex distal taper, or a fairly linear distal taper depending on exactly where you want the cop and tip thickness' to fall.....

    If you start at .36 {close to 9mm}, then very possibly you'll drop the thickness very quickly over the first 3 to 6 inches from the cross, then flatten the distal taper out, and even maybe make a couple more adjustments further down.....

    In this last example, its that rapid drop in thickness area, that I consider the "base"...... How the blade is constructed from the base to the cop {center of percussion} is the support structure..... and of course then you have the working end {foible}........

    Its not just the distal taper however, though I have to admit I focus on this to a large degree..... this is also affected by the profile taper, the crossection, width, fullering if any, edge thickness and edge geometry, and a lot of other factors........
    For Good or Ill......

    What Comes Around Goes Around.....
    and

    You Reap What You Sow...

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    back to the top of the page

    Its rare and a priviledge to get information of this high a technical nature -

    personally I am fascinated to have some of the mystery revealed to me of the sword , its physics and structure ,


    just a bump to the top for the weekend crowd who may miss it otherwise


    Mick
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    Ephesians 6:11

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