BorderBows
New member
Ive been reading a thread that im unable to contribute to.
So here are our thoughts on it.
Limb designs are very complicated relationships in former shape, core taper, and stored energy.
things to consider are also Limb mass, and the distritbution of mass, as well as the shapes of the limb for regulations etc.
Some of the concepts made, that id like to pick up on are
"limbs that bend at the fadeout, have a negative aspect in thier design"
"The use of extreme recurves means your carring spare mass in the limbs."
so lets try and move this into an area where the engineer becomes a bowyer.
Engineers tend to see removing mass as the key, as all works, such as Klopsteg, and Kooi, all say that limb mass is detrimental to bow performance.
This it true to a certain extent. and one most whippy tipped bows fall into.
This concept is nothing new. its covered in the Bowyers Bible series of books.
so what are the three design concepts.
Whippy tipped bowsthe centre of mass of the limb is moved by reducing the mass of the outer parts of the limb. meaning a higher concentration of the movement is at the limbs outer reaches.
Whippy tipped bows tend to have short Working limbs by nature (not really defined by fadeout position as the first part of the limb can be so static, it could be called riser), but even if the limb is long, the tip is doing all the work, so the limb itself is might look long, but the working part is actually short. so in essence its a short limb.
Whippy tipped bows tend to stack, resulting in the same poor energy storeage problems of short limbs
There are two ways of making a bow whippy tipped. Making the first portion of the limb after the fade out so stiff, its not really part of the limb, or make the outer part so weak, it has no mass, there for over works
stiff outer limbs, Stiff outer limbs are those that dont bend in the outer reaches of the limb. This means that the limb stores better energy as the limb will be smooth (long lever, due to bending closer to the fadeout. recurve bows with Static recurves, have this, as well as alot of Hybrid longbows. (im going to stick with rest of world terminology and not british, a longbow is the british flatbow)
the down side of stiff outer limbs, is that they carry more mass, and while thats a problem it also moves the centre of gravity of the working limb moves outboard. which is the engineers perspective. (its almost all the engineers that see this as a problem)
Full working limbs tend to not exhibit either of these pros or cons. but they generate a very slick look. what they have done though is distribute the stresses evenly along the limb. This isnt that clean and simple with recurves though.
So what causes the Stack/smoothness. The problem of stack has nothing to do with materials. if anyone ever says its a carbon limb and its the carbon that makes it smooth, doesnt know what they are talking about. or if they blame the core. again, waffle. Simply put, the smoothness is all to do with angles, the limb to string angle. and short limbs open up this angle quickly. and this generates stack. Long limbs, or limbs that have long levers such as the Hybrids, or even designs like the ACS longbow protect the limb/string angle and deliver a smooth bow. which in turn stores good energy.
So, the flip side to what has been said here is a relationship of 3 things. Smoothness, Limb mass and Limb shape. We havent covered Preload
You can make a bow smooth with whippy tipped limbs, for sure. BUT there is a massive downside. if you slope the limbs back far enough (deflexed) then they dont need to be pulled back as far, defending the string angles, but the down side is VERY poor preload.
The shape of the limb unstrung, will determin the DFC, as much as the width or taper.
This point is HUGE in what has been said in the other thread.
The shape of the limb before its strung impacts its final DFC.
So if you look at DFCs, you have preload, and Smoothness.
ILF limbs really help here.
The inflection point of a DFC. the point where the graph goes from preload (bulging outwards) to stack, Bulging inwards.
if you wind limbs in, you increase prelaod, but you also pull the recurve round a bit, reducing the recurve size. this will shorten the inflection point in the DFC making the limb stack more. Another way to say this is with a ILF longbow, you will end up with a more aggressive angle of limb to string at BH, again increasing preload, and decreasing smoothness.
so if stored energy = a comprmise in Smoothness vs preload, then the games of whippy tipped vs Straight limbs really play ball.
You cant simply keep increasing preload without playing with other aspects of the limb.
So far, ive not mentioned bow performance being about core taper. Because taper is a small game changer in comparison to limb profile.
Lets explore that idea. If you increase the taper, you make the whippy tipped. if you bend that tip forward, you preload that section more. gaining stiffness. so former shape and core taper are related. and not a single aspect of the design.
on a petty note. i saw an "archer" comenting that he got his "bowyer" friend, put in a custom taper for him... i did laugh. because you cant put a random taper on a former not made for it. the two are related, based on the bowyers experience and intended design. that aside. lets continue.
Limb mass, Limb mass is a dictator to limb length.
if the limbs were made of lead, as in HEAVY, then short limbs would prevail. you simply wouldnt want a heavy limb like that to have lots of length.
on the flip side, if limbs were made of Air, then the length would have no negative down side. so they would all be really long.
While limbs were made of Glass fiber, you have a compromise to find.
how long will the limb be, and how much of a working tip will you choose.
but the fun comes in when you use a full carbon limb. not a carbon limb with glass in it. Please note, Not all limbs branded as carbon are equal. THIS IS IMPORTANT here.
Carbon limbs can be a third lighter in mass than glass limbs. and this is significant.
the tip mass can be nearly half that of a glass limb.
So this starts to change things. as carrying extra length has less down side than you would expect.
What is important to Border Archer here, as our product was lifted in the other thread, is the term evolution and advancement.
Limbs dont have to be thicker to be more torsioanlly stable. and this is a new thing that started with the XP10 limb in 1999.
here goes.
with all this being said, we are of the opinion, that efficency is a bit of a black whole in bow design that leads the bowyer into whippy tipped designs.
its like being a King of nothing, vs master of alot.
High efficency with low stored energy is limited by design. King of nothing. supreme KING. 100% of nothing is still nothing.
Taking a hit on efficency for huge stored energy will deliver better preformance, Master of alot.
with Carbon though, its leading you into two areas of strength. you can sacrifice efficency, by way of long working limbs, and excess mass, BUT and the HUGE BUT, is carbon doesnt come with the weight penalty.
Excess limb volume doesnt mean excess limb mass. since the materials weigh so little, unlike glass. unlike Klopstegs work on turkish flight bows.
So, as bowyers set in our ways, we have had to evolve with the materials shown infront of us.
we have ran with the idea of short working limbs, and found it to be a dead end.
What has happend, the hex series of limbs has been our playground. New materials new concepts.
So with all this considered, what has been happeneing in our thought processes.
We have developed a techneque of making a bow too smooth.
this ox-moron of design has become apparent, as we have progressed.
The hex4 was a conventional limb, turning into a hex limbs. Smoothness explored
The hex5, was an overstep of the hex program as viewed conventionally, long limb working near the fadeout, delivering smoothness, and our new found recurve technoloies showing us what the average archer expects of a limb, indicating that we had an excess of smoothness, the two combined to create the first problem. The MK1 limbs were also a step too far, as stated above, we also relaxed the preload to deliver even more smoothness. This correlates with your findings.
The MKII Hex5s we shortened the limb, and increased preload. this was the first stages of our eyes being open.
We discovered full control of the smothness in a recurve limb.
Now we realised, we needed to increase the compound type preload.
this exagerates the smoothness.
With this idea. we started reducing the "long limb effect" of working near the fadeouts, and the stiffness of the recurve. moving towards a working recurve again.
and here sits the Hex6 and Hex6 BB2.
then we step into the hex7.
This combines all this understanding of working vs static recurve tecnology, and the spreading of the bend over the limb.
as you can see your investigations are looking at 2008 technology where we opened pandoras box and saw into limb design what i feel has never been seen before.
Lateral stability beyond anything seen before.
Combinations of Holistic bow design, from the engineers perspective vs a bowyers eye, combining everything in the view to improoving feel through the clicker, ease of expansion into propper back tension, and better cast.
the limbs mass is 150grams per limb, or about 50grams on the tip, unlike glass and glass carbon limbs which are 210 grams or 75grams on the tip.
the flip side is also, the extra curl in the limb reduces the size of the arc scribed during closure changing the centre of mass, and wind resistance, as well as providing more support for the string through its travels.
the energy stored has changed profoundly too. in terms of SE/PDF. conventional designs are sitting at 0.9 at 28, while we are looking at 1.2se/pdf at 28".
in short, the coments id like to adress above mentioned in the other thread are.
if two limbs are of equal length, having the string wrapped round the recurve is a redundant concept, as mass is mass, and equal in both designs. moving it unwrapped is the same as moving it wrapped.
and the negative aspect of the bows design bending at the fadeout is a leverage advantage in gaining smoothness.
the fastest bows in the world are NOT whippy tipped. they are ones that store the best energy.
examples of this are the ACS longbow, the Centaur Longbow, and our Longbows. (all long limbs)
and the fastest recurves ever produced, all look at stored energy as the main remit, and not at mass reduction as the main game.
granted to be the fastest, you need both mass reduction and stored energy.
all the longbows mentioned are vastly carbon powered if not all carbon powered.
hope this helps add to the confusion of bow design, as it is hellishly complex.
more descriptive text on this topic is in the bowyers bible Vol 1 2 and 3.
So here are our thoughts on it.
Limb designs are very complicated relationships in former shape, core taper, and stored energy.
things to consider are also Limb mass, and the distritbution of mass, as well as the shapes of the limb for regulations etc.
Some of the concepts made, that id like to pick up on are
"limbs that bend at the fadeout, have a negative aspect in thier design"
"The use of extreme recurves means your carring spare mass in the limbs."
so lets try and move this into an area where the engineer becomes a bowyer.
Engineers tend to see removing mass as the key, as all works, such as Klopsteg, and Kooi, all say that limb mass is detrimental to bow performance.
This it true to a certain extent. and one most whippy tipped bows fall into.
This concept is nothing new. its covered in the Bowyers Bible series of books.
so what are the three design concepts.
Whippy tipped bowsthe centre of mass of the limb is moved by reducing the mass of the outer parts of the limb. meaning a higher concentration of the movement is at the limbs outer reaches.
Whippy tipped bows tend to have short Working limbs by nature (not really defined by fadeout position as the first part of the limb can be so static, it could be called riser), but even if the limb is long, the tip is doing all the work, so the limb itself is might look long, but the working part is actually short. so in essence its a short limb.
Whippy tipped bows tend to stack, resulting in the same poor energy storeage problems of short limbs
There are two ways of making a bow whippy tipped. Making the first portion of the limb after the fade out so stiff, its not really part of the limb, or make the outer part so weak, it has no mass, there for over works
stiff outer limbs, Stiff outer limbs are those that dont bend in the outer reaches of the limb. This means that the limb stores better energy as the limb will be smooth (long lever, due to bending closer to the fadeout. recurve bows with Static recurves, have this, as well as alot of Hybrid longbows. (im going to stick with rest of world terminology and not british, a longbow is the british flatbow)
the down side of stiff outer limbs, is that they carry more mass, and while thats a problem it also moves the centre of gravity of the working limb moves outboard. which is the engineers perspective. (its almost all the engineers that see this as a problem)
Full working limbs tend to not exhibit either of these pros or cons. but they generate a very slick look. what they have done though is distribute the stresses evenly along the limb. This isnt that clean and simple with recurves though.
So what causes the Stack/smoothness. The problem of stack has nothing to do with materials. if anyone ever says its a carbon limb and its the carbon that makes it smooth, doesnt know what they are talking about. or if they blame the core. again, waffle. Simply put, the smoothness is all to do with angles, the limb to string angle. and short limbs open up this angle quickly. and this generates stack. Long limbs, or limbs that have long levers such as the Hybrids, or even designs like the ACS longbow protect the limb/string angle and deliver a smooth bow. which in turn stores good energy.
So, the flip side to what has been said here is a relationship of 3 things. Smoothness, Limb mass and Limb shape. We havent covered Preload
You can make a bow smooth with whippy tipped limbs, for sure. BUT there is a massive downside. if you slope the limbs back far enough (deflexed) then they dont need to be pulled back as far, defending the string angles, but the down side is VERY poor preload.
The shape of the limb unstrung, will determin the DFC, as much as the width or taper.
This point is HUGE in what has been said in the other thread.
The shape of the limb before its strung impacts its final DFC.
So if you look at DFCs, you have preload, and Smoothness.
ILF limbs really help here.
The inflection point of a DFC. the point where the graph goes from preload (bulging outwards) to stack, Bulging inwards.
if you wind limbs in, you increase prelaod, but you also pull the recurve round a bit, reducing the recurve size. this will shorten the inflection point in the DFC making the limb stack more. Another way to say this is with a ILF longbow, you will end up with a more aggressive angle of limb to string at BH, again increasing preload, and decreasing smoothness.
so if stored energy = a comprmise in Smoothness vs preload, then the games of whippy tipped vs Straight limbs really play ball.
You cant simply keep increasing preload without playing with other aspects of the limb.
So far, ive not mentioned bow performance being about core taper. Because taper is a small game changer in comparison to limb profile.
Lets explore that idea. If you increase the taper, you make the whippy tipped. if you bend that tip forward, you preload that section more. gaining stiffness. so former shape and core taper are related. and not a single aspect of the design.
on a petty note. i saw an "archer" comenting that he got his "bowyer" friend, put in a custom taper for him... i did laugh. because you cant put a random taper on a former not made for it. the two are related, based on the bowyers experience and intended design. that aside. lets continue.
Limb mass, Limb mass is a dictator to limb length.
if the limbs were made of lead, as in HEAVY, then short limbs would prevail. you simply wouldnt want a heavy limb like that to have lots of length.
on the flip side, if limbs were made of Air, then the length would have no negative down side. so they would all be really long.
While limbs were made of Glass fiber, you have a compromise to find.
how long will the limb be, and how much of a working tip will you choose.
but the fun comes in when you use a full carbon limb. not a carbon limb with glass in it. Please note, Not all limbs branded as carbon are equal. THIS IS IMPORTANT here.
Carbon limbs can be a third lighter in mass than glass limbs. and this is significant.
the tip mass can be nearly half that of a glass limb.
So this starts to change things. as carrying extra length has less down side than you would expect.
What is important to Border Archer here, as our product was lifted in the other thread, is the term evolution and advancement.
Limbs dont have to be thicker to be more torsioanlly stable. and this is a new thing that started with the XP10 limb in 1999.
here goes.
with all this being said, we are of the opinion, that efficency is a bit of a black whole in bow design that leads the bowyer into whippy tipped designs.
its like being a King of nothing, vs master of alot.
High efficency with low stored energy is limited by design. King of nothing. supreme KING. 100% of nothing is still nothing.
Taking a hit on efficency for huge stored energy will deliver better preformance, Master of alot.
with Carbon though, its leading you into two areas of strength. you can sacrifice efficency, by way of long working limbs, and excess mass, BUT and the HUGE BUT, is carbon doesnt come with the weight penalty.
Excess limb volume doesnt mean excess limb mass. since the materials weigh so little, unlike glass. unlike Klopstegs work on turkish flight bows.
So, as bowyers set in our ways, we have had to evolve with the materials shown infront of us.
we have ran with the idea of short working limbs, and found it to be a dead end.
What has happend, the hex series of limbs has been our playground. New materials new concepts.
So with all this considered, what has been happeneing in our thought processes.
We have developed a techneque of making a bow too smooth.
this ox-moron of design has become apparent, as we have progressed.
The hex4 was a conventional limb, turning into a hex limbs. Smoothness explored
The hex5, was an overstep of the hex program as viewed conventionally, long limb working near the fadeout, delivering smoothness, and our new found recurve technoloies showing us what the average archer expects of a limb, indicating that we had an excess of smoothness, the two combined to create the first problem. The MK1 limbs were also a step too far, as stated above, we also relaxed the preload to deliver even more smoothness. This correlates with your findings.
The MKII Hex5s we shortened the limb, and increased preload. this was the first stages of our eyes being open.
We discovered full control of the smothness in a recurve limb.
Now we realised, we needed to increase the compound type preload.
this exagerates the smoothness.
With this idea. we started reducing the "long limb effect" of working near the fadeouts, and the stiffness of the recurve. moving towards a working recurve again.
and here sits the Hex6 and Hex6 BB2.
then we step into the hex7.
This combines all this understanding of working vs static recurve tecnology, and the spreading of the bend over the limb.
as you can see your investigations are looking at 2008 technology where we opened pandoras box and saw into limb design what i feel has never been seen before.
Lateral stability beyond anything seen before.
Combinations of Holistic bow design, from the engineers perspective vs a bowyers eye, combining everything in the view to improoving feel through the clicker, ease of expansion into propper back tension, and better cast.
the limbs mass is 150grams per limb, or about 50grams on the tip, unlike glass and glass carbon limbs which are 210 grams or 75grams on the tip.
the flip side is also, the extra curl in the limb reduces the size of the arc scribed during closure changing the centre of mass, and wind resistance, as well as providing more support for the string through its travels.
the energy stored has changed profoundly too. in terms of SE/PDF. conventional designs are sitting at 0.9 at 28, while we are looking at 1.2se/pdf at 28".
in short, the coments id like to adress above mentioned in the other thread are.
if two limbs are of equal length, having the string wrapped round the recurve is a redundant concept, as mass is mass, and equal in both designs. moving it unwrapped is the same as moving it wrapped.
and the negative aspect of the bows design bending at the fadeout is a leverage advantage in gaining smoothness.
the fastest bows in the world are NOT whippy tipped. they are ones that store the best energy.
examples of this are the ACS longbow, the Centaur Longbow, and our Longbows. (all long limbs)
and the fastest recurves ever produced, all look at stored energy as the main remit, and not at mass reduction as the main game.
granted to be the fastest, you need both mass reduction and stored energy.
all the longbows mentioned are vastly carbon powered if not all carbon powered.
hope this helps add to the confusion of bow design, as it is hellishly complex.
more descriptive text on this topic is in the bowyers bible Vol 1 2 and 3.
