String Follow Fiberglass Longbows

[Chase N. Nocks]

Hi Dennis,

The question/comment about the bow fitting into Association Rules was just thinking out loud. If someone knew the answer great.

The link to the website was simply saving others the bother to find it. I agree it adds nothing.

The link to the post that included the Bowyer's hyperbole was pretty recognisable as such but he made comments about the design (forward handle) and along with the picture may relate to the comments from both you and Perry.

I neutrally left his comments for others to filter as they saw fit.

All good.

Cheers
Troy

[perry]

I thought I would post this link about defining Smoothness in a Recurve Bow Limb http://www.tradtalk.com/forums/showthread.php?t=23040 It has little to do with String Follow Longbows, there is no Formula attached but it describes how a Recurve Limb works and if you think a little laterally you can see how it applies to a Deflex Reflex Limb. You may gleam something about the importance of tiller and string angles to how smoothly a Bow Draws

I think the Author is part of Border Archery which has developed some very interesting Limb Designs over the Decades

regards Jacko

[Dennis La Varenne]

Perry,

An interesting read, but it says very little. The bottom line in regard to however you define smoothness is what you see on a force-draw graph. If the curve begins to go upward, that is stack which is exactly what this bloke is saying. The recurve example he uses talks about the leverage effect of the outer limbs. That has been well understood for decades. It was first discussed so far as I know by Robert Elmer in his book 'Target Archery' in discussing the original working recurve bows invented by Russ Wilcox in the early 1940s.

This bloke is making the point that in a 'smoother' bow, that point where stacking commences is later along the force-draw curve, that's all. I don't see that this is any different for deflexed bows.

The bottom line for all bows of every design is that a smooth bow does not increase the rate at which it increases its draw weight per inch of draw length.

An even more efficient bow design like the working recurves and some of the old static recurves, can even reduce the rate of increase slightly past the 'inflection' point as this bloke terms it. It all depends as this bloke says at what point along the draw-force curve that this inflection point occurs.

I have yet to see this phenomenon on any kind of straight limbed bow including the modern so-called deflex-reflex bows (called semi-recurves when they were invented in the 1950s). The good ones have a steady rate of increase and I have seen only perhaps two in my whole archery life which had an increasing rate of increase. All my string follow bows follow the same principle. The rate of draw-weight increase is directly connected to the final draw weight. But the rate of increase is steady on all of them. I cannot draw them far enough back to cause them to stack. I suspect that the wood would fail before that happens because of the way in which wood fails in bending tests, ie. as the wood begins to fail, the amount of load on the wood starts to decrease with the degree of rupture. However, stacking may be discernible with a 'straight' bow with fibreglass backing and facing which does not fail as easily as wood because of the very high MoR of fibreglass.

Most blokes who complained to me about having a stacking bow were simply overbowed. They just could not draw them back because of muscle failure. That is the most common source of complaint about bows which are not smooth if you bother to put their bows of these blokes on a scale.

[Chase N. Nocks]

Hi All

I just saw this topic "How to define smoothness" this morning on TradTalk.

At work so have not read all the posts but the opening post is quite interesting.

http://www.tradtalk.com/forums/showthread.php?t=23040

There is bucket loads of information about limb smoothness, and the convo generally turns into a useless bashing of subjective opinion.
I would like to clear this point once and for all...

The are two aspects to the DFC which defines smoothness.
There is a stage where the DFC is in a falling rate of pounds gained. and then there is an inflection point, where the curve changes into a climbing rate of pounds gained.

What i mean by this in more simple terms is, for every inch you draw the bow, there are two main types. One where the next inch of draw gains less weight, and then once the bow changes its style, it will start to gain at a faster rate in poinds for ever inch drawn.

The inflection point, or the point in which the bow changes its mode of weight gain is the crutial point.

Now... lets look at what happens in a recurve limb.
you have a set of limbs and un-changable amount of resistance to pull. and this should be a striaght 2lbs per inch for a 40lb bow.
but the way the limb geometry works, the weight gain actually climbs as the geometry gets horrible for the bow.
so in the ultimate form, its called stack, where you end up pulling 3+lbs in the last few inches.

So, with this unchaingable weight, you can add a leaver to the limb to help with this climb, and thats where the recurve steps in.
SO at brace height, the bow thinks its say, 57" long, This is determined by the unsuported string length. The string thats not in contact with the limb.
As you pull the bow back, the unsupported string gets longer, and therfor so does the lever on the unchanging resistance.
in short, as you pull the bow back the bow gets easier to pull per inch of draw, because the lever you have gets longer.
This gives you the falling rate of increase.
For example, as you tighten the wheel studs on your truck, imagine if the wrench got longer as the nuts got tighter....then tightening your wheel nuts would be an easy task!
Thats what the recurve does to bow weight.
UNTILL the vital point.
The Inflection point...
The moment the limb cannot get any longer is the point where the bow weight stops going from a falling rate and changes into a climbing rate of increase.
This is where the limb STOPS being smoother.
This is where the smooth bows feel easy to pull.
This is where the subjectivity, irrespective of taper, width, contruction, carbon or foam, makes NO difference, nor does the price...
The bow where this inflection point, or the string lift point is closer to your face, is the smoother bow.
and this is where the test is simple.
Just like checking your draw length, you can pull the bow back, till the string lifts off the very tip (shoulders) of the limb.
This is the smoothest point on the draw.
Mark on an arrow this point, just like you would to check your draw length, and measure the distance, then repeat on a second bow, and the one where this lift point is longer IS the smoother bow.

For example, the lift point on a normal recurve target FITA bow is about 19-20.5" for a 68" bow.

Longer bows have a longer lift point, short bows have a shorter lift point.

hope this helps settle a few disscusions

Smooth limbs like the winnex lift on a 25" riser at the 20-20.5 inches... the not so smooth brands lift at the 19" mark.

Author : Sid

Cheers
Troy

[greybeard]

Troy,

Personally I think his explanation of a smooth draw is poor and a factual f/d curve graph with a stored energy chart showing the increase per inch of draw would be more beneficial. Bows having early draw weight and slight incremental increases per inch of draw can be smooth during the draw cycle.

Daryl.

[Bent Stick]

I use the emprical bent stick analysis algorythm which provides the followiing results; works pretty good in my books

"Nah don't like that one"
"Yep that ones nice"
"This ones the bestest, how much"
"You're #%^&ing joking aren't ya?"

This really is a great topic and i reckon if everyone puts their heads together there could be a new flavour of mathmatics to apply, but unfortunately the above algorythm will still remain predominant for most.

Did i tell you blokes it's about 4 Ghana Cedi's for a double johnny walker black and coke where i am at the moment ($AUD 2.18)

[Dennis La Varenne]

I am obviously with Daryl on this one.

A smooth draw is a draw which has a steady rate of increase throughout its length. That is all. It is not rocket science. Any f-d curve shows it easily and simply.

The tradtalk post talks only about a very specific kind of bow and how its limbs work to effect a smooth draw. It does NOT address the phenomenon of smoothness during draw and what it actually IS, which is something which has been well-studied and understood for decades. Even though its opening comments purport to be about to do so, the author goes off on a tangent and misses his own point.

Subjective opinions on smoothness are not verifiable in any way, and are of questionable value.

[greybeard]

Troy,

The following graphs illustrate what I consider to be a smooth draw in two bows that I made. Incidentally the recurve has stiffened tips and the longbow has mild reflex.

Note that draw length is measured from the draw length pivot point.

Initial rate of increase is higher for the recurve than the longbow but you will notice that as the draw length increases the rate of increase for each bow is fairly constant.

At the top of the recurve graph the line is starting to move more vertically, which in part I believe is due to the stiffened tips and with the longbow the upward trend is minor.

43# Takedown Recurve Graph.jpg (100.15 KiB) Viewed 1697 times

40# Longbow Graph.jpg (99.32 KiB) Viewed 1697 times

Daryl.