Negative Tiller Revisited

[Dennis La Varenne]

Back in May this year, Timmah (Seeking Advice 21st May) posed a question about a choice of wood from a timber merchant. His thread developed into a debate on the issue of whether it was correct bowyery technique to tiller an even length limbed selfbow with a weaker upper limb (positive tiller) or a weaker lower limb (negative tiller).

The thread was split later in the debate as the issue went off on this tangent and away from Timmah’s original request for advice on wood selection. Clearly, Timmah was quite new to the game, and the principle advice given on tillering technique was from Glenn Newell.

Much of his advice was contested on technical grounds which, I do not think helped Timmah’s case.

Astonishing for me was the insistence on negative tiller being the only way to tiller an even limbed symmetrical selfbow maintained by Glenn. I found it difficult to believe that with his level of experience he could insist so strongly on a technique which was so clearly wrong. It wasn’t simply a matter of different means of achieving the same end.

Glenn’s thesis contradicted everything developed in bowyery from ancient times to the present. His claims were breathtaking. They controverted the whole of tillering theory since bowmaking began and the present practices of the modern archery industry.

And . . . he would brook no criticism from anyone, despite two trained engineers endeavouring to explain to him where he was wrong. Make no mistake here. Bows are a feat of engineering technology. The principles by which they function are well understood in engineering.

At any rate, I was working through a protracted illness at the time and I decided his view must and should be challenged. Beginning bowyers going down the path of negative tillering are certainly in for a lot of unnecessary hardship for which they will not find easy answers. I decided his claims must be answered and if possible, refuted. To that end, I wrote a longish essay on the matter which can be found at the following URL -


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EDIT Ozbow Admin
http://www.ozbow.net/articles/WHY%20NEG ... 0WRONG.pdf
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My essay is not a personal attack on Glenn’s integrity, but a critique of his claims for negative tiller which I consider to be quite wrong in this matter and misleading to beginner bowyers. I have known Glenn for a long time and have a lot of time for him, especially since he broke a lot of early ground in selfbowery in this country by showing us all that indigenous wood species were every bit as good as that from the northern hemisphere.

However, I could not allow his claims in support of negative tillering to go unanswered. My essay is in answer to those claims.

Dennis La Varenne

[ed]

I feel the need to respond to this comment of Dennis’, not because I am a bowyer – indeed I know bugger all about it. But his reply to Glenn's assertions has some circular and flawed argument in it that needs to be addressed before real discussion is even possible, much less useful.
I find such long arguments too much like reading research and so it is often left un-answered because of the number of topics raised rather than the validity of any of the individual points themselves. I hope Dennis can see what I am aiming at and not take it personally. I think there has been a misunderstanding of reasonings on both sides here and with some thought I think there could be some valuable discussion for wannabe bowyers like myself, and what I really want to do is set the groundwork for the discussion to run well.

Before I get into the points though I would like to state that as a principle I dislike calls to historical methods as evidence of the best method, it is not. It merely points to what has been done before, good or bad. Calls to historically recognised authorities, also holds no weight in any scientific discussion – and we are discussing bow physics here. As a health care professional (physio) I am damn glad the medical community has disregarded most of it’s past authorities, and I suggest that in fairness to the points Glenn has made we do the same – for he can not call on a historical figure to back up his theory (well maybe the Japanese but we will get to that later).

So point-wise on the critique:
1. in the section on “Why we tiller bows”, it is raised that the bow hand is the reason for a force angle difference of 5 to 10 degrees. Please note that for most mechanical systems angles of less than 5 degrees are considered of little to no consequence as they are effectively the same as zero degrees.
a. Assuming the force is at the centre of the hand – why? This is a biomechanical issue, and the torque of the bow will pivot around the top of the hand as you admit to yourself later. It is quite easy to see with recurve fashioned grips but even with a straight grip the bow itself will try and pivot around the top of the gripping hand. This is based on the asymmetry of the bow due to the hand gripping close to centre and the string therefore also being pulled from just above centre to shoot above or on the knuckle.
b. This would place your lines C and D closer together and make the whole issue less important.
c. Stored energy is not dependant on the strength of the limb when they are pulled with the same force. 50# of force will make a 50# at 28 limb store as close to 50# as it can (depending on efficiency), and 50# of force on a 60# limb will not move it as far and still (depending on efficiency) only store 50#’s of force. Lets say it makes the weaker 50# limb move to 28 inches of draw and the stronger 60# to 25 inches – same stored energy. Where does the area under the curve come into it – well it does only if the two limbs have the same strength. If the strengths are uneven then it is always going to have less area under the stronger limb. Discount this comment of Dennis” completely. Actually it is even less of an argument as there is more compressive vector force on the longer limb, and more lateral vector on the shorter limb anyway. This complicates the “area under the curve” to the point of near useless (too many variables).
d. Bow tip alignment – some kind of aesthetic ideal. Given that both of you make asymmetrical bows by choice then this is a null argument. Does it mean anything with an equal length bow? Maybe if the limbs were equally long either side of the arrow rest but that is not what we are discussing is it – lets keep it relevant.
e. The grip being non-central makes it somewhat, and to a lot smaller extent the upside down version of physics for the Japanese Yumi. Which has a stiffer shorter limb, and as you admit shoots quite well. The fact that you think the yumi shoots well and choose to use long upper limb bows yourself makes a total mockery of the “past experts” and their theories. Lets not confuse the ELLB as being symmetrical around the arrow rest and grip.

2. issue of balance
a. see the above again
b. another visual/mathematical aesthetic?
c. Lets not confuse the shape of the draw bow with torqueing of the bow or hand shock – again reference your own comments on the yumi.

3. Zero tillered bow example
a. If zero tillered then how is the upper limb stiffer? By hand position you change the force angle but not the tiller of the limb. In fact your draw force has more of a lateral (in the direction of the draw) vector than compressive no – so it would in effect be more effective in bending the limb – making it appear weaker.
b. Elmers experiment is pointless as there is no vectoring of the force as happens in reality.
c. Your argument actually supports negative tiller in my opinion, as you would have to tiller the upper limb stronger to make up for the more lateral force vector.

4. Positive tiller section
a. Mathematical neatness argument has what relevance to the physical facts?
b. G does not equal H as the weaker upper limb would bend easier and therefore the distance vertically to the arrow would shorten more.
c. Again the aesthetics of tip alignment, being in parallel with the axis of the bow – an argument you discount automatically for the yumi and even to a lesser extent your own longer upper limb bows.
d. If it is for hand torque then surely a stronger limb is heavier per unit cross section, so a longer heavier limb is not going to be equal weight with a shorter lighter limb. In fact it would have to be the other way around.

5. Centering the bow in the hand
a. If so then you increase the distance between the C and D lines and so make the balance of limb lengths worse, and the angle of force on the drawn string worse.
b. It would actually increase the amount of torquing in the hand as you have shown in your diagram. The stiffer the top limb the more so, and so you would have LESS heeling of the grip.
c. Bringing the lateral force vector closer to the top of the hand reduces the C-D line difference, reduces the torqueing, and I expect arrow porpoising.
d. It would also accentuate the issue of limb strengths.

6. Blind Tillering Test
a. Why measure from the centre of the hand grip. You admit yourself that the balance point is closer to the top of the hand near the arrow.
b. That would make the effective hand position much closer to centre of the bow – Not having done the test I can not say just how close or even on it, but your description alone contradicts your point.

7. SSLAB
a. It is positive tillered only by which way you hold it up.
b. It is exactly what Glenn has been talking about as the SHORTER limb is stronger. i.e. a negative tillered ellb turned upside down.
c. The rest of this section also continues to support Glenn.

8. Elliptical vs Cross section
a. I am not very knowledgeable here, but again there are things that make me wonder. The difference between Glenn’s elliptical and a rectangular is not so great admittedly. Some rounding of edges is recommended anyway for the integrity of the edge.
b. Your pictures and comments are misleading to an extent. There is always going to be bend forces on the wood all the way out to the edges of the elliptical – just not the same extent of tension and compression forces as a thicker section. All of the limb is bending after all, just lesser of the tension/compression is done closer to the centre of the limb.
c. I would like to point out that on a wood fibre – not being perfectly round or straight that there is not a direct line of force from back to belly. It is going to spray a little. Glenn’s ideas are not so radical here as O.L. Adcock has been working on the same with considerable success. Glenn is working it for both sides of the limb, so it is an extension of what Adcock has been doing at best.
d. All this is about static forces as well. We are not talking about a static situation and so it is at best a background physics from which to work forwards from. It reminds me of the static/dynamic spines of arrows and if your argument holds then we should be shooting square arrows – maybe we should but on what we know now can we be sure it is better to use a square arrow?

9. the final section.
a. There is nothing here of any worth to the argument. It neither summarises it nor ties it all together. What it does do though is show your reluctance to have theories fly in the face of “orthodoxy” (your word) , and so it is no wonder Glenn thinks he is fighting dogma. With this kind of attitude, regardless of what level of respect you hold for him, I can not see how the argument is reaching an open mind.

In all I think your document supports Glenn’s theories, despite your attempt to cut it down. You actually support it in some places, and too often call to historical authority to back yourself up. Glenn is postulating that they could all be wrong, and may very well be right.
Rip this apart, flame on, but do it point by point so that something positive comes out of it please.

[kimall]

Wow that was well put!
I know nothing about all the tech stuff but I HAVE shot plenty of bows and now own 2 of Glenn"s bows and I dont know how they work but they are the smoothest trad bows I have ever shot in both the draw and the shot.I would not swap my 70 pound longbow for ANY other trad bow in the world.
The proof is in the pudding.
Cheers KIM

[Dean Torges]

Interesting subject, Dennis, and a terrific, reasoned response from Ed.

Some of the confusion rests with a blurry use of terms, I do believe, and some of the disagreement rests elsewhere. There are countless ways to tiller a bow, and all of them serve the archer in different ways, especially if the bowyer knows what he's about. Some bows can be bent more near handle, some elliptically tillered, some whip-tillered, etc. All to different and hopefully desirable affects.

Balancing a bow in the hand is quite another matter, and that's really what Glenn is getting at. The archer's style of shooting must be taken into account for it, but suffice it to say that if you consider the analogy of a teeter totter (or see saw as we call it here), and how you balance it upon a fulcrum when different weights are placed upon the ends, or when the fulcrum position is changed, I think you will understand why Glenn advocates the tillering that he does, and why positive tiller belongs to the bow created with a shorter lower working limb.

The limbs will slowly degrade on same-limb bows with weaker upper limbs if the bow is shot often or long enough to really test it. The modern archer or backyard bowyer seldom encounters this reality, or does not recognize the cause when he does, because most of us are in a dash to finish a bow and get on with the next one.

[ed]

Welcome to Ozbow, Dean. (someone had to towelcome you eh!)
A shorter lower limb would make a whole lot of sense, much like a longer upper limb
Seen your video on bamboo backed bows, and working on a new bow now. You made it look too easy. The short lengths you make them is surprising, pretty good accuracy I see too.

[Dennis La Varenne]

To all the responders,

Thank you for taking an interest in my essay. I will most certainly be going through these replies carefully to see if I have made any errors in my analysis of the mechanics of tillering.

However, I have left off responding at this stage because I thought it fair debating protocol that Glenn have first right of reply. It was his thesis I was critiquing.

Ed, no, I don't take criticism of my ideas personally. One has to get over that if one is going to put them in the public domain.

Thank you also to those who pointed out a few remaining typos which I will correct as soon as possible.

Regards,

Dennis La Varenne

PS: Welcome Dean. On another issue from the above and arising from something you wrote about in your book Hunting the Osage Bow, you once mentioned that you once left a small amount of sapwood on a few bows which did not degrade the way it usually does with age.

I think you speculated that there may be an organism involved in the normal degrading process of Osage sapwood.

In Australia, we have some isolated stands of Osage brought into the country by 'Californians' following the rushes in the mid-1800s. These stands tend to occur in the gold rush areas.

I have made several bows from locally grown Osage (the one I mention in my essay was one such). Bearing in mind what you speculated on about sapwood degradation, I hit upon the idea that presuming bacteria were involved, I began chipping off most of the sapwood on the green split staves till mostly sapwood showed.

I then liberally sprayed it with a household surface disinfectant before sealing the ends to dry, and waited.

Some years later, the sapwood is still as white as the day I sprayed it. I have even made one English Longbow with the sap on to full thickness (7 rings) and it worked fine. I did quite a bit of shooting with it to see if it would fail, but it did not. It now lives in Queensland, but I don't know how it is fairing.

If it fails, I suspect that it will not be from sapwood degradation. However, the traditional manner of taking the sapwood off is known to be reliable of course.

I just thought it may be of interest to you.

[Dean Torges]

I've always felt welcome in OZ, and often said that if I were a younger man, I'd move my residence from here in a heartbeat. Dennis, I stopped by your house once for a visit and to shake your hand, but you were not at home. Was headed north to greet the red deer roar. Maybe next time.

I actually wrote "Hunting the Osage Bow" 15 years ago, though it's not been published that long. Point is that I've learned a few things since then about every facet of the craft (as we all have), and though the book is fundamentally quite sound, there are sections of it that I would like to update if I ever got around to doing a second edition.

Have built more than a few durable osage bows with sapwood intact. The trick is to keep the sapwood from the elements, to treat it just as you would a whitewood such as hickory or elm. If you dry it under roof, without subjecting it to the weather, it is indistinguishable in performance from heartwood.

I don't usually post on bulletin boards. Was a regular presence some 5 to 8 years ago or more, but since then the rise of organic bow information and the confrontational style of too many participants has given me good reason to back away. Nevertheless, I cruise around sometimes, quietly, and while cruising saw a post or yours months ago on this subject. Read it with great interest, but did not post. Hope you will forgive my intrusion here now.

One thing I have learned about bows is that just about the time you say "You can't do it that way" or "This is the right way," someone will come along with a successful refutation in the form of a bent stick and a taut string. Never fails.

That's not to say that anything goes and that one way is just as good as any other way. I'd be at the front of the line to whack on someone who maintained either of those propositions. But it is true that this simple craft is full of surprises, and much more varied in its permutations than initial appearances would lead one to believe.

[Stickbow Hunter]

Firstly, welcome to the site Dean.

I have read Dennis’s essay thoroughly – a number of times now actually - and I must say that I can’t find anything that I would disagree with. After many years of making bows my observations of the matters in discussion are very similar.

I have also read through the replies on this thread and am amazed by some of the comments and conclusions that have been reached.

Firstly it has been inferred a couple of times that there has been a misunderstanding of what Glenn meant regarding negative tiller, that what he was really talking about was the balancing of a bow and that this confusion resulted from the use of blurry terms. I have great difficulty understanding the reasoning behind such comments.

In both of the referred to threads, ‘Seeking Advice – My First Selfbow’ and ‘Selfbow Dogma’, Glenn goes into great detail as to why an equal length limbed bow when shot with the split fingered release should be negative tillered. To me there is simply no doubt as to what he was meaning.

Ed,

I don’t agree with other comments regarding your post. To me your post shows a clear lack of experience when it comes to bow making and you don’t seem to have an understanding of the fundamentals of bow making. I guess you do spell that out at the start of your post though which is fair enough.

However, having admitted your lack of knowledge on the subjects being discussed you then proceed to point out that many of Dennis’s theories are flawed and tell others to discount some comments of his completely. I think that was rather audacious of you.

Not once did I see anywhere that Dennis’s views supported Glenn’s negative tiller theory as you so clearly suggest in your reply.

May I suggest that you reread the section that deals with ‘Why we tiller bows’.

The reason a bow is tillered is because of the misalignment of the position of the hands when the bow is drawn and loosed. Glenn also agrees with that proposition. To date no one but you seems to disagree with this.

The only way to counter this misalignment of the bow and drawing hands (when the Mediterranean or split fingered release is used) is to positive tiller. It makes no difference if you have a shorter lower limb and longer top limb or equal length limbs, this misalignment is still there and relevant. The only way to correct it is by using positive tiller.

You also are very critical of references to historically recognised authorities and historical methods stating that they hold no weight in any scientific discussion. This is very wrong indeed. They are very valid if they can be proven by being repeatable through testing by others using the same techniques.

Dennis not only uses proven historical authority to back up his views on this subject but also that of his own observations as a very experienced Bowyer and the experiences of present day Bowyers. I don’t feel the same can be said of the proponents of the negative tiller theory.

Lastly, I wish to reiterate something for you in the hope that it may cause you to ask yourself just why is it so?

The negative tiller theory that you appear to agree with is in opposition to probably 99.9% of past and present Bowyers. In fact I would say that most, if not all, of the modern archery manufacturing industry uses positive tiller – that is at this very moment!!! That certainly suggests, to me at least, that positive tiller is necessary when making bows.

Jeff

[Dean Torges]

And that explains pretty much why I don't post on bulletin boards. People take ideas personally and get confrontational and defensive, and bulletin boards then become a time sink for me with no benefit commensurate to the effort.

I never implied that Glenn was misunderstood regarding what he meant with negative tiller, and he is talking about balancing a bow, and that indeed is how you balance a bow in the hand with same-length limbs.

The salient point Ed makes, and one with which I agree wholeheartedly, is this: "Before I get into the points though I would like to state that as a principle I dislike calls to historical methods as evidence of the best method, it is not. It merely points to what has been done before, good or bad. Calls to historically recognised authorities, also holds no weight in any scientific discussion – and we are discussing bow physics here." No one who holds free inquiry of value or respects the search for truth could disagree with such a well-stated sentiment. And I don't think anyone who knows me or has read my writings could suspect me of not holding our predecessors in great reverence.

As for 99.9% of the bowyers past and present? C'mon, Jeff. Pulling such a veil of authority over your ideas, one that is so patently over the top (and downright inaccurate), discredits them because it implies they can't stand on their own. It's one degree of frustration away from the "My-dad-can-whup-your-dad's-ass" defense. First off, no modern bowyer of my acquaintance who makes his living selling bows of the fiberglassed variety makes same-limbed bows. How many remain who make a living selling organic bows is probably an infinitesimal amount compared to the history of the bow, past and present, and how many of them make same-limb bows is considerably smaller yet.

I've a pretty good library of books from archery past by authorities on the matter. Elmer, Duff, Hodgkin, Pope, Klopsteg, Hickman, etc. Not one of them advocates a same-limb bow. 99.9% you say? Perhaps you are referring to all the bows that were ever built before the middle of the 19th C. That would be a significant number and might even amount to 99.9% of the bows ever built. If those are the foundation bows of your overwhelming percentage, tell me, Jeff, how did these bows shoot, and how did they feel in the hand?

When you appeal to history to substantiate an argument, and the recorded or working history available to us is completely irrelevant to your argument, where does that leave your argument?

It was a good visit, one like all visits should be—brief.

[MarkP]

I haven't made sufficient selfbows to wade into the debate in a technical manner here. What I have done however is shoot Glenn's selfbows, all-wood composite bows, and laminated fibreglass bows on many occassions, and again as recently as last weekend.

Knowing the topic of tiller was current I paid particularly attention to performance when shooting Glenn's selfbows on the weekend. As always I was impressed. Sure, feel in the hand and visual impressions are subjective. Glenn's selfbows shoot well, smooth, quite, very little handshock and ample performance. Might they perform a little better with a different approach to tiller? Maybe - who knows? In their current state they stand as efficient working examples of Glenn's approach to bowyery.

Its good to know that in Australia we have such an experienced bowyer, prepared to experiment and test accepted standards. The bows produced as a consequence are good, and the debate subsequently generated might hopefully add something to our undersatnding of archery.

Cheers
MarkP

[Dennis La Varenne]

By this time I thought Glenn might have composed some sort of response to my essay, but it doesn’t appear it will eventuate for whatever reason, which is a pity. I cannot understand his reluctance to defend his own hypothesis at the place where he proposed it.

To his supporters, please be clear that this is not a kind of ‘get Glenn’ campaign. The can of worms was his to open, and he did so. Once opened, his proposals are fair game for comment and challenge as they are with everyone, and so it should be. We don’t challenge the integrity of the man, we challenge his ideas.

In response to Ed’s comments, I sincerely hope that you do take up self bowyery. It is very clear that a lack of practical experience underlies your reply.

Although you may have a problem with my resorting to ‘historical methods of evidence’ as you term it, my use of them serves to illustrate the basis from where I am arguing the conservative case in defence of a proven theory of tillering.

Of course Glenn does not have access to the same resource. His thesis is the ‘new kid on the bowyery block’. It is up to him to provide credible proofs for his ideas, not for me to re-prove an existing proven theory. For the benefit of those reading this thread, I have merely explained where his idea is wrong in terms of the existing theory and why it is wrong. He has not defended his own hypothesis, and nor have you.

If there is any validity in them at all, it remains for bowyers to build negative tiller bows to test the veracity of his ideas and come up with supporting results. As it is, I have certainly built many ellsbs over the years and none of them has developed any signs of failure in the upper limb.

Because Glenn has built some/many which may have, does not overturn the present theory. It is cause for experiment to ascertain the reasons and modify the present theory only to the extent needed to explain this phenomenon if he can do so.

As for your own critique, you would have done much better if you had dropped terms like compression and lateral vectors so that those others less mathematically competent reading this post could understand what was going on. As it is, the manner in which you have laid them out and the way in which you have argued your case has effectively alienated many people from engaging in his issue, especially those wanting to understand the business of tillering. Your reasoning is very, very difficult to follow. Ask Kimall to write you a précis of your argument.

As it is, I cannot see where you have defended Glenn’s thesis. You have tried to validify his not by offering supporting argument, but by trying to undermine my explanations with a lot of casuistical reasoning. If my defence of positive tillering is flawed in some way, your comments do nothing at all for Glenn’s. You would do better to go about learning the craft, under Glenn’s tutelage if you like, and learn what he has to teach on negative tiller, practise it, then go and learn from another bowyer who tillers positive and practise that. Then you will have better understanding of what this is all about.

From scrutinising your arguments over the past several days, it appears that your have somehow got it into your head that underpinning my references to weakening an upper limb of a positive tillered ellsb, that I make the upper limb weaker than the bottom limb. I have not said or inferred that at all. Please re-read my essay again.

I have said that the upper shorter limb must be weakened to match the stiffness of the lower limb. The upper dynamically shorter limb WILL ALWAYS bend in a more curved arc so that the drawn tips are in the same vertical plane to ensure synchrony. THAT is why g is larger than h, for this style of bow. Nowhere have I said that g is equal to h for an ellsb. I don’t know where you got that idea from.

The upper limb of an ellsb is not shorter by virtue of its physical length. It is shorter by virtue of the dynamics of the action of the limbs in applying force to an arrow through the string. We are trying to make the limbs apply force equally to the arrow despite their being of uneven length as measured from the dynamic centre of the bow - the arrow line.

You raise other issues such as where a bow pivots which are irrelevant. I am not concerned where it pivots, but where it balances – in line with the radius (main load bearing bone of the forearm). In the case of holding and drawing a straight handled bow, where it pivots and where it balances are NOT the same because of the width of the hand.

Your take on my citation of Elmer’s experiment on limb strength is wrong because of your lack of understanding of tillering. In a properly tillered bow of any design, both limbs are of the same strength and stiffness otherwise tillering would not need to exist.

We don’t make bows with limbs of different strengths. We make them with the SAME strength and stiffness. This example was to demonstrate that, with a properly tillered bow, there was no reason to assume that one limb was inherently weaker because of design alone. You seem not to have understood that at all.

There is only one reason that the upper limb of an ellsb could possibly degrade in the manner in which Glenn says, and that is, if the upper limb IS made, deliberately/accidentally weaker than the lower limb as opposed to matching it to the lower.

Later in your critique, you make much of my preference for asymmetrical bows and seem to imply to readers that my preference for this design controverts what I have written on ellsbs. The two have nothing to do with each other, other than that they are both positive tillered.

I have a preference for the sllab for the reasons I clearly explained. I did not change over to this design because all my ellsbs were degrading in the upper limb which your comment implies. Except for my apprenticeship jobs, most of my bows have been ellsbs and not one of them has developed the problems which Glenn declares to be their inevitable end as a consequence of positive tillering.

The principle thrust of my defence is toward positive tiller in ellsbs. Following Glenn, I brought in the topic of sllabs to explain the differences between the two and how the sllab worked which he neglected to do. He made a flat statement in the form of dogma and left it at that. If anything, my description of the mechanics of the sllab would, I hope, support Glenn’s statement.

I did not use the Yumi to justify any of my explanations as you wrongly assert. The word was mentioned twice – once by me as an extreme example of an sllab, and the other in my quote from Elmer in his context that the Japanese may have some better understanding than American bowyers of that time about how the sllab worked. I elected to use that quote in the same context as Elmer of offering a possible reason why the sllab did not seem to have the same degree of hand shock as the ellsb sometimes does. You have drawn conclusions from this use which are simply not indicated.

The blind tillering test also appears to be misunderstood by you. Please re-read it carefully.

The drawing indicates where, inevitably, the hand position will come to rest in a balanced position somewhat below the physical centre of such a bow. It may be an inch either way. However, the BALANCE POINT will be below the physical centre of the bow to allow a natural dynamic centre to occur rather than a built one. If you understand this, you can see that the natural tiller for bows is positive. That is the point of the exercise.

Regarding your comments on limb cross section, whether or not there is any ‘spraying’ of compression forces in wood is conjectural. For all practical purposes, the possibility was ignored by the early experimenters as inconsequential. The predictions made for the rectangular cross-section based on the conclusions of their experiments were so reliable they inspired a whole generation of archers at the end of the wood bow era. They built bows premised on those findings with the result that they were able to make shorter lighter limbed bows well able to withstand the rigors of bending and loosing without anything like the degree cellular collapse and string follow (which plagued earlier designs) to produce trajectories and durability which were inconceivable 20 years previously. If anything, we are only now regaining that lost skill.

Your analogy that if the rectangular section were correct for optimum performance in bowlimbs, then arrows should also be made rectangular is not well thought through. Here is why it is wrong.

Those of us who use them know that they DO inevitably degrade (lose spine) for the very same reasons that all forms of rounded bellied bow do. They are referred to as having the spine shot out of them. That is a fact of wood arrows, less so of alloys and probably never with carbons because of the increasing modulus of elasticity for each – a function of the materials from which they are made.

We make arrows round for ballistic reasons such as surface friction co-efficients among others. Roundness almost certainly originated because the natural materials from which they were made occurred in nature as rounded in section. Edged arrows would be uncomfortable in use if they struck the bowhand and unnecessarily difficult to make from round base stock such as coppiced stems.

Because arrows are arrows and not bowlimbs, ballistics form the principal consideration in their making.

On my lack of a decent summary, I will take advice and promise to do better next time. But my essay is not a doctoral thesis. I suspect that the majority of those who read it didn’t even notice.

And finally . . . in my essay, I described the negative tiller hypothesis as wrong. That is a strong word implying that something is clearly and unassailably invalid. Its use should always be with caution. However, in the subject under debate, its principal proponent advanced his hypothesis as right – being clearly and unassailably correct, but did not offer anything in support. He was particularly clear and adamant in the veracity of his assertions more than once when challenged. There was no cause for misinterpretation of his meaning.

So, I will continue with my counter-assertion as strongly as Glenn maintains his unless and until uncontrovertible evidence is demonstrated that the extant theory does not hold. To this time, this has not been done. Therefore, in the fact that the present theory is maintained each and every time I build a bow, ellsb or any other type, and that I have yet to see collapse of the upper limb in actual practice, I consider myself justified in maintaining my position and defending the current theory as strongly as I can.

That being said however, I am not so dogmatic that I will deny changes to the theory which can be proven valid. My personal integrity requires that of me as it should of everyone. But first, as the Minnesotans like to say – “Show me!”

Dennis La Varenne

[kimall]

Dennis in the one paragraph you criticise others for big words and then use a word like "PRECIS" and my name.I am not sure what that means and could not be bothered looking it up but from the use of it I guess it was a dig at my simplictic reply.So be it I am what I am and that is at best a simple man but I do work a bit with my hands and do shoot a bit and can tell the differance between a nice shooting bow and one not so good.I am not getting into the debate on the physics of all this and I dont think I have said anyone is wrong I was just stateing that regardless of how they work Glenns bows DO work.I have no axe to grind and I will shoot ANY bow I think shoots in a way the suits me but I will agree with Dean and that way to many people argue armed with info gleaned from books and other peoples studies and not real life experiences.That is why I am not dissagreeing with anyone on this if I do so I will fall into this cat. also.This is why my reply is I guess very simple I am just telling what I DO know.Sorry Dennis not to be in your articulate class.
Cheers KIM

[Stickbow Hunter]

Dean,

I stand by what I said about Ed’s comments regarding the use of historically recognised authorities and historical methods. As I said they are of great value if these views and methods can be proven by being repeatable through testing by others using the same techniques. After all, any scientific equation or experiment can only be said to be ‘Science’ or have any value if it is repeatable by others.

I never said, or insinuated, that 99.9% of the bowyers past and present built bows with equal length limbs. I said they used positive tiller, vastly different to what you are saying.

Jeff

[Dean Torges]

Dean,

I never said, or insinuated, that 99.9% of the bowyers past and present built bows with equal length limbs. I said they used positive tiller, vastly different to what you are saying.

Jeff

You called on 99.9% of bowyers past as corroborating your claims that same length limbs should be positive tillered. Yours is a distinction without a difference. They used positive tiller on bows with shorter lower limbs. Irrelevant altogether to your argument.

If the earth revolves around the sun because Copernicus said so, then I would agree with you that Glenn should make an appearance before this court to defend his heresies.

As for Ed, well, I think of Klopsteg, Hickman and Nagler in refutation. They were engineers, not bowyers. If only experienced bowyers should open their mouths, then most of the revolution in bow physics from the first half of the 20th C. would not have taken place.

To my mind, questions have more value than answers, and I've always sought the company of those who asked questions, avoiding the company of those with the answers. In that spirit, let me ask you, how would you tiller a 68" bow with an upper limb two inches shorter than the lower limb? And, as briefly as possible, please explain why.

[ed]

aarrgghh

By this time I thought Glenn might have composed some sort of response to my essay, but it doesn’t appear it will eventuate for whatever reason, which is a pity. I cannot understand his reluctance to defend his own hypothesis at the place where he proposed it.

I can't speak for him, but for myself I can say I find you aggressive and confrontational. Maybe that is reason enough eh. This conversation already tires me, and unfortunately has not come up with anything educational - which is what I was hoping for.

To his supporters, please be clear that this is not a kind of ‘get Glenn’ campaign. The can of worms was his to open, and he did so. Once opened, his proposals are fair game for comment and challenge as they are with everyone, and so it should be. We don’t challenge the integrity of the man, we challenge his ideas.

as are all peoples comments regardless of which century they were written in I hope. I think Glenn's "supporters" have been well mannered and open. Kimall, MarkP, and Dean Torges were not derogarotory of you or your opinions at all.

In response to Ed’s comments, I sincerely hope that you do take up self bowyery. It is very clear that a lack of practical experience underlies your reply.

absolutely, i am interested to know the why's of bow design.

Although you may have a problem with my resorting to ‘historical methods of evidence’ as you term it, my use of them serves to illustrate the basis from where I am arguing the conservative case in defence of a proven theory of tillering.

well lets get somethings straight here. Firstly a lesson in English - yes even for someone as articulate as yourself.
Proof: a fact or piece of information which shows that something exists or is true
Theory: a formal statement of the rules on which a subject of study is based or of ideas which are suggested to explain a fact or event or, more generally, an opinion or explanation
Research: a detailed study of a subject, especially in order to discover (new) information or reach a (new) understanding
Anecdotal Evidence: describes information that is not based on facts or careful study - a story
Empirical Evidence: based on what is experienced or seen rather than on theory
Double-blind: describes a study or trial, especially in medicine, in which two groups of people are studied, for example with one group taking a new drug and one group taking something else, but neither the people in the study nor the doctor knows which person is in which group - can be applied to all forms of research to avoid false claims like "antigravity gyroscopes", and the numerous "cold fusion" flops.

Now when people put forward a theory, they then set up some research to test it. The results will determine if the theory is "proved" (see below). Now I don't know how much research you have read/done but I will bet you that we have not had a double-blind trial of bow making methods. What we are therefore using as "historical evidence" is empirical studies and anecdotal evidence. "I did it this way and it worked better than when I did it that way" - basically next to useless in anything other than coffee shop conversation. Why? Too many variables. To argue the case of negative vs positive tiller in EQUAL LIMB LENGTH BOWS (or any other scientifically testable peice of engineering) we would have to eliminate as many variables as possible.
These sorts of studies have not been quoted by you, I assume they have never been done then. So what we have is conjecture on both sides of the arguement, backed up by empirical studies at best, many of which are mere anecdote (that includes anything written in a book without the research stats and having been reproduced by independant reputably impartial researchers). Do them again sure and you have another empirical study, do them 100 times with controling all other variables, with independant testers and statistical analysis and maybe someone outside a coffee shop might be interested.

I am not argueing for Glenn, I am not even against a conservative approach to changes in bow theory. Lets just be sure to be able to stay open minded to possible innovations, and logical in our investigations of both new and old. "Grandad did it this way", is not a scientific arguement.

Of course Glenn does not have access to the same resource. His thesis is the ‘new kid on the bowyery block’. It is up to him to provide credible proofs for his ideas, not for me to re-prove an existing proven theory. For the benefit of those reading this thread, I have merely explained where his idea is wrong in terms of the existing theory and why it is wrong. He has not defended his own hypothesis, and nor have you.

Well for myself, I did not even try to defend Glenn's theory. I admit not having the background to do so. What I do have the background to do, is to read an arguement or research paper and rip the **** out of it. That is what I did, your arguement was schoolyardish at best.

A note on the scientific process. Theorum's are never considered beyond question, and so are never considered "proved". They are said to "holding true given the parameters of the research situation", and SEEN TO BE "holding true in practical applications".
Hence if Glenn chooses to question the theory, so be it. Does it mean he has to prove his alternative to be allowed to speak? No. Does a lack of proof of his theory add weight to the strength of the long held one? No, and even more so if the theory has only had minimal testing. Yes thousands of empirical studies mean something, but are far from a detailed study. The arguement you are putting forward reminds me of the arguements that supported alchemy for so many generations.
If you don't have proof, then say so. If all you have is historical figures backing up the arguement then say so. But for me the words of some past patron saint of bowyery mean little. back them up with some real tests and lets see it.

If there is any validity in them at all, it remains for bowyers to build negative tiller bows to test the veracity of his ideas and come up with supporting results. As it is, I have certainly built many ellsbs over the years and none of them has developed any signs of failure in the upper limb.

Because Glenn has built some/many which may have, does not overturn the present theory. It is cause for experiment to ascertain the reasons and modify the present theory only to the extent needed to explain this phenomenon if he can do so.

this shows me that you atleast understand what I have written above, but lets be fair and say both theories have little to back them up.

As for your own critique, you would have done much better if you had dropped terms like compression and lateral vectors so that those others less mathematically competent reading this post could understand what was going on. As it is, the manner in which you have laid them out and the way in which you have argued your case has effectively alienated many people from engaging in his issue, especially those wanting to understand the business of tillering. Your reasoning is very, very difficult to follow. Ask Kimall to write you a précis of your argument.

I did try and keep it as straight forward as possible. I was honestly hoping for answers and comments from both sides. As for a "summary" of the important parts of my critique. Well it was actually under 5 pages, yours was what, 24 pages? , you numbered your arguements, and I did likelwise so they could be easily referenced and discussed pointwise - which I requested as I knew this was going to get silly otherwise - oh it did anyway eh.

If your reasoning is true, that an upper/shorter limb should be weakened i.e. positively tillered, then please explain to me why me finding that inconsistent with the Japanese bow example is difficult to see. I merely referenced it seeing as you stated that the Japanese yumi is a good shooting bow. The Japanese yumi has a stiffer shorter limb than the longer limb. And yes I have seen more than a few being shot, shot a few myself. I lived a short walk from kyudo ranges in Tokyo (mind you it is the most boring form of archery I have ever seen).
The point is, IF the Japanese yumi shoots well by your empirical evidence, and by others anecdotes, then how does that support the idea of having a weaker shorter limb design?
Only thing I can see that is different is bow orientation, hmm I will ask to shoot a yumi upside down next time I get the chance.

I am stating that the example of the yumi makes empirical evidence against having a weaker shorter limb. This evidence as good as cancels out your arguement. The past patron saints of positive tiller can all have a ripping catfight with the past masters of Japanese bow design for all I care. That would not prove anything. I don't have the facilities to test both theories in a way that would satisfy any form of engineering research, I suppose you probably don't either. Therefore it would seem on a lack of sensible arguement from either you or Jeff, it would seem that both theories stand unproven and opposing.
Jeff, what did you say exactly that added anything at all to the discussion? Oh yes positive tiller is when the bottom limb is stiffer, regardless of what lengths the limbs are. That is a definition actually. So regardless of if a lower limb is shorter or longer than the upper limb, it should always be stronger? Hand position doesn't count either, well it can't if it doesn't matter what lengths the limbs are.
Jeff wrote

The negative tiller theory that you appear to agree with is in opposition to probably 99.9% of past and present Bowyers. In fact I would say that most, if not all, of the modern archery manufacturing industry uses positive tiller – that is at this very moment!!! That certainly suggests, to me at least, that positive tiller is necessary when making bows.

used to have this schoolyard joke when I was a kid - "eat ****, ten billion flies can't be wrong". All you are stating is the state of affairs, that you think anything that flies (sorry) in the face of the status quo is unjustifiableand must be wrong. I don't know if Glenn is right but your argument would have prevented the wheel from being used/invented, or aeroplanes etc. Man wasn't meant to fly, I am not riding on that damn contraption, god gave us feet.
Did you actually read what I posted first? I doubt it.

Dennis, If you choose to actually discuss any of the points of your own original post vs my questions, I will listen - that is why I asked.

Let me state a few things so you can understand whay I am annoyed here. I did not try to defend Glenn's theory - nowhere even hinted at it.
I am open to a reasoned arguement in congenial tone. This is a hobby for me, and I do enough conflict resolution in my job to not have to calm people down here to the point where they are thinking with the correct head.
You seem to assume I am on Glenn's side, well I admit to having asked him many questions over the last year on other forum's. He has always been helpful. It is because of him I came here as he told me there were more people discussing topics I was interested in. I didn't know having discussed things with him in another forum made me his lieutenant as soon as I asked a question of someone I learned later is a protagonist. I asked an honest set of questions after a logically unsatisfactory diatribe was posted on your pdf file. In fact I feel your post was intended to shout down all opposition to your viewpoint.

So far you have tried to explain that you are trying to match the limbs strengths not actually make the upper limb weaker. Thanks for pointing that out, I do appreciate it. Unfortunately I do not understand you fully, so if we could start again by explaining why you think that the upper limb if tillered to even weight (on an equal limb length bow) is effectively stronger than the lower limb due to hand placement, then we have a starting point to understanding this positive tiller theory.
Oh, and before I tire of typing, the anatomy of the bow arm. The radius being the line of force only workes (in any plane) if you are limp wristed, and even then not well as foreaem alignment may indeed put the force down the line of the ulnar (and increase the C and D line distance). If we are to assume a healthy person's grip, then we have different grip styles putting different lines of force down the arm and hance a different "pivot in the grip" point of the bow. It is not consistant with a line down the radius unless you are talking a totally straight bow arms elbow and are drawing the string to your collarbone. If you draw to your face the force line is always above the bow arm. So it is going to balance in front of the hand obviously, but "in line with the radius" it is not. Adding a string being pulled from above center, distances the force line further away from the line of the radius. Actually to be pedantic, if you wanted the force line "in line with the radius" you would have to draw the bow behind your back.

The drawing indicates where, inevitably, the hand position will come to rest in a balanced position somewhat below the physical centre of such a bow. It may be an inch either way. However, the BALANCE POINT will be below the physical centre of the bow to allow a natural dynamic centre to occur rather than a built one. If you understand this, you can see that the natural tiller for bows is positive. That is the point of the exercise.

So the bottom limb would be shorter due to hand position, and so the shorter limb is needed to be stronger. And so if we look back to the original thread where Glenn was advocating a negative tiller for a central hand positioned ellb - where the shelf and arrow nock are above center, we see you two agreeing on the physics that the "shorter" limb should be stronger.

We don’t make bows with limbs of different strengths. We make them with the SAME strength and stiffness. This example was to demonstrate that, with a properly tillered bow, there was no reason to assume that one limb was inherently weaker because of design alone. You seem not to have understood that at all.

well lets see a better explanation. It might add something to my and maybe others understanding. I have read your pdf file several times now, and I stand by the questions I raised.
ok positive tiller is the bottom, shorter limb being stronger, negative tiller on an ellb with central hand position make the top limb "shorter", Glenn says make it stronger. You say make the bottom one stronger anyway just like it was being "balanced" at the center for both hand position and drawing point on the string?
The limbs are stronger but not stiffer? (this discussion gives me anything but a stiffy I can assure you).
Do they have to draw back equal distances or arrive back at the same time?
Draw back in the same plane ( assume you mean the lines are parralell?) as the bow or assymetrically is ok? (darn those Japanese!)

oh and for arrows, the physics of your arguement would imple that a square arrow would have greater strength for it's weight. so we could all shoot lighter arrows to acheive the same spine and either get greater speed or add a heavier point, and still make up for the awkward aerodynamics given that it would also have a smaller cross section and so the difference in surface friction would not be much if any.Uncomfortable on the hand I agree, but that is not the unnecessary sideline I started.

[Dennis La Varenne]

It has probably occurred to all those participating in this debate that it is fast coming to a stalemate of conflicting opinion and counter opinion. Whilst this may entertain those of us who have strong views on the subject either way, including myself, it informs no-one of our membership about the intricacies of tillering and why it is done.

I suspect that the relatively small response this thread has aroused is indicative that the majority of members and casual browsers do not want to become embroiled in what is becoming a fairly heated debate, and we are certainly not informing those just entering this fascinating craft about one of the most important facets of it.

Enjoying a good debate as I do, I can go on for months along the lines we have been going as I suspect can others, but we do nothing for the general education of aspiring bowyers or the furtherance of our craft.

Of course, I do not resile my position on positive tillering, but it is quite clear that there are three apparent options -

1. That positive tiller is the correct method;
2. That negative tiller is the correct method, or
3. That there is something about tillering that neither of us is aware of.

Clearly, what is being argued on this thread infers that both sides are correct; that a bow can be made with either positive tiller and still work, or that negative tiller can work just as well.

Both Dean and Glenn, and Jeff and I together have made many bows incorporating our respective tillering methods with complete success evidently. Can there really be two equally valid schools of tillering perhaps????

Certainly, my position and consequently the drawings in my essay derive from carefully studying what was happening each time I made a bow. They are empirically based, not the prognostications of some kind of intellectual exercise. I presume it is the same for both Glenn and Dean.

Rather than go on with an alienating debate, why not Glenn and Dean combine together and write something similar to what I have done which expounds the how and whys of negative tillering for ellsbs - the main bone of contention.

With the tillering of the sllab, I don’t think there is an issue between us.

I have posted my detailed essay on positive tillering, but Glenn has not done one as yet, and, in fairness to his case, he should avail himself of the opportunity to do so as well. That done, anyone can use the methods of both/either school to build bows and see what comes up.

At any rate and for my own information, I have begun the process to examine if there is any validity to the negative tillering case. It will take a while to build two or three bows to test because of the illness which was annoying me, but it will get it done.

My main problem will be with ascertaining just how much negative tiller to build into a bow go get it right according to its proponents. I know what needs to be done to get a positive tiller bow to work, but the geometry necessary to make a successful negative tiller bow whose tips align on the same plane and in parallel to the long axis of the bow will be challenging to say the least.

I will give it a go, but I am sceptical obviously and I will keep everyone posted on my progress.

Dennis La Varenne

PS: Sorry to Kimall if you thought I was having a go at you.

You chipped in with your defence of Glenn’s bows based on two you owned and you were the only other person at the time who was not directly engaged in the issues. As I was having difficulty following Ed Lomax’ reasoning, and Jeff wasn’t making much sense of his arguments either, you were the only other person on site whom I thought might have a go at making sense of them.

I also made the mistake of thinking that the word précis was commonly understood. It did not occur to me that it may not. Terms like vectors are specialist mathematical terms and I wouldn’t expect many to understand them.

Until this last several of my 40 working years, I worked with my hands also. That doesn’t reflect anything on a person’s mental faculties, mine or yours.

[Paul]

I like to know how and why things work the way they do and so I am very interested in the principles behind making a self bow. I don’t have a great deal of experience when it comes to making self bows as I have only made about half a dozen over the last few years (all equal length limbs with rigid handles) and two of those have been very low poundage bows for my children.

Until quite recently I have never thought about which limb on an equal length limbed bow was stronger, because it didn’t have any practical relevance to me when I tillered a self bow. I have only tillered the self bows that I have made on a tiller tree the way that I am going to draw them. When I shoot a self bow I hold the bow with the middle finger of my bow hand at the centre of the bow and draw the string with 3 fingers split. My tiller tree is the same width as what my drawing fingers will be on the string and the position on the string which is anchored on the tiller tree is the same position that I will draw from with my fingers when I shoot the finished bow. I tiller the bow so that the limb tips are even at my draw length. I have never taken the time to measure which limb was stronger, because if I have tillered the bow correctly to the way I was going to shoot it, then to my way of thinking it should be well balanced. In fact it never even entered my mind to question which limb was the stronger one until I started reading the debates on the subject.

Since then I have read and thought a great deal about the theories and I’ve drawn diagrams, checked the angles and distances and analysed my bows. I have also discussed the topic with Glenn a few times and my brother, who as an Engineer used to work designing timber roof trusses. After I put a lot of thought into the subject I have come to the same conclusion as Glenn, Dean and many others, albeit not through the vast experience gained through trial and error as they have, but by my own simple reasoning.

Am I going to try and prove my belief by using the principles of Physics and Mathematics? Hell no. I could probably put forth a good scientific argument backing up the theory if I took a few weeks to go and re-learn all of the physics and mathematics on the subject which I have forgotten, but I always found that stuff tedious and don’t wish to revisit that nightmare again. I was never that good at it anyway.

In my opinion Ed brought up a lot of good points in his posts and Dean’s analogy of balancing a see-saw is a brilliantly, simple explanation of why I believe an equal length limbed self bow when correctly tillered to the way I shoot it, will have a top limb stronger than the bottom, or be negatively tillered.

This is the way I see it in simple terms:
If I take a zero tillered equal length limbed bow ( tillered with equal strength limbs using the centre of the string when drawing) and hold it so that the middle finger of my bow hand is placed at the centre of the bow, I then have to move the 3 fingers of my drawing hand (3 fingers split) up from the centre point of the string(at brace height) to align the arrows nocking position with the arrow rest or my index finger’s knuckle. For me the centre point of my 3 drawing fingers has to be moved about 1 ½ “ up from the centre of the string.
By doing this an uneven force will be placed on the two limbs because the string is no longer being drawn from its centre point. More force is being placed on the top limb causing the top limb to bend more, with the tip coming back further than the bottom limb tip at full draw. To counter balance that extra force on the top limb, the top limb has to be made stronger. Because the top limb is stronger it is harder to draw back and therefore the bottom limb will bend more. This will cause the top and bottom limb tips to come back at the same point at full draw.

In my opinion this should create a better balanced bow with less hand shock, than a bow that has a top limb weaker than the bottom limb. Also the top limb shouldn’t degrade because it will be able to handle the extra stress placed on it because it is stronger.

I believe that by tillering an equal length limbed bow to the way I am going to draw it as described above, will always produce a stronger top limb- a negatively tillered bow.

I have an open mind and I have a lot to learn about most things, so I would welcome it Denis if you can explain to me, in simple terms, why you and a lot of other people believe that a self bow with equal length limbs if tillered so that the limb tips are even at the required draw length, and tillered so that the middle finger of my bow hand is at the centre of the bow and drawing 3 fingers split, will be positively tillered. I know that you explained it in your paper but I found it very confusing.

I am ¾ s of the way through tillering a self bow with even length limbs at the moment and once I have it tillered by the method I described above, I plan on measuring the strength of each limb to find out which one is the strongest. Even though I know that this is not an extensive scientific trial that will prove anything to anyone else, it will settle the debate in my mind once and for all.

I do have a few questions for you Dennis regarding your process of tillering equal length limbed bows. Do you tiller by drawing the centre of the string at brace height and purposefully make the top limb weaker than the bottom to try and compensate for the misalignment of the drawing hand to the centre of the bow?
If you do, how do you know how much weaker to make it and why don’t you tiller the bow the way it is going to be drawn or is that how you do draw it?

Paul

[Buford]

I suspect that the relatively small response this thread has aroused is indicative that the majority of members and casual browsers do not want to become embroiled in what is becoming a fairly heated debate.

To be honest, Dennis, to me, this sort of conversation belongs around a real campfire with the people you are talking to/ about.

we are certainly not informing those just entering this fascinating craft about one of the most important facets of it.

This is one reason.........

Another is the fact that I firmly believe the sort of points/ arguments posted in this thread can never truly convey the real intent they carry in black and white text. Body language and tone of voice are needed if for nothing else but to increase clarity of intentions.

I can't speak for him, but for myself I can say I find you aggressive and confrontational.

Mr La Varenne, I don't know you personally, but based entirely on your posts on Ozbow, I agree completely with ed. Which, for me, is a shame, because from what I've herd you have just as much valuable information to impart as the next person, but frankly, I would be reluctant to engage in a serious conversation with you because I fear it too would become mentally tiresome.
I would however like to meet you in person and discover the Mr La Varenne that doesn't have two to three days to formulate an "Essay" response to every thing that is said. That would be interesting to see if the company either confirms or refutes my current opinion.

Matthew Hood

[jindydiver]

I have to say I am very disappointed by this thread. For despite all the well written replies it contains I don’t think it has advanced to “art” of bow making one bit.

And this turned me right off everything else you had to say Dennis

By this time I thought Glenn might have composed some sort of response to my essay, but it doesn’t appear it will eventuate for whatever reason, which is a pity. I cannot understand his reluctance to defend his own hypothesis at the place where he proposed it.

The first sentence you ponder the reasons for Glenn not having replied, and then by the second sentence you seem to have made up your mind, that because he hasn’t replied he must be reluctant to defend his hypothesis. Don’t you agree it might be possible that in the time (less than 2 weeks) since you started this thread Glenn might not have even seen your lengthy essay?
It might be common in this information age to believe that the answers to everything are at your fingertips, but when you are wishing to ask something of a real person you have to be patient and just wait for them to reply. Common courtesy would dictate that you not jump to conclusions about someone’s motives based just on their not having posted a reply timely enough to suit you.

[clinglish]

I have nothing of value to add to this discussion .Perhaps if each of those within this discussion ,all of whom are bowbuilders by your own addmission , each build a bow in accordance with the particular stand that you are making.
Then if the bows are matched for draw weight 55#@28 and tillered for split fingered you can send them to me and I will test them .I will cover the cost of postage and my decision will be final.
The bow that I deem to shoot the best will then be the design of choice for the next century .If you all aggree to this please post so .

[GrahameA]

Hi All

My $0:02 worth

Firstly a quote. "Simplistic answers do not solve complex problems". So on that basis do not expect a simple answer or reply.

As a start may I suggest a read of the "Archers Reference" Section 3.4, on tillering. Available as a download from here and IMHO the best read on the subject unless you are willing to invest some money on some of the excellent books on the subject.

http://www.archersreference.pwp.blueyonder.co.uk/

Try a google search for "tiller tuning bow" and read a few articles on the subject.

http://www.google.com.au/search?as_q=ti ... afe=images

Go here and download the article on "Controlling Bow Behaviour with Stabilisers" and note the comments on the effect of mass changes on tiller.

http://www.tenzone.u-net.com/Equipment/

Follow this link and have a read of what the people on TradGang have to say:
http://tradgang.com/cgi-bin/ultimatebb. ... 029934;p=0

Last build a bow, or two, with some tiller, see below, and shoot them then turn them around shoot them again and find out which they shoot best for you.

In the case of the two bows pictured they shoot noticeably smoother with positive tiller - BTW they were shot for the first time last night - and they are great at the moment for this sort of testing because it is dead easy to turn them around and try them the other way.

[Paul]

G'day Graham

As I said in my post I am interested in understanding more about self bows, so I have a few questions for you regarding the two bows you have just completed.

How did you tiller the two bows and by this I mean how was the bow placed on the tiller tree and from what position on the string was it drawn from when tillering?

And my second question, which is related to the first, is where is the position of your hand and drawing fingers when you hold and draw the completed bow?

When you completed each bow did you measure which limb was the stronger and how did you?

I am still trying to understand why some people come to the conclusions that they do regarding negative and positive tiller and I'm hoping that your answers will help me to understand a little better.

Paul

[GrahameA]

Hi Paul

Please note this refers to these bows only.

The bows are symmetrical through the centre of the handle. There is as much limb above the centre of the handle as below it.

The handle section is 4" long.

When you draw the bow the arrow sits 2" above centre.

My hand is central on the bow.

When it sat on the tillering tree the bow was central and the string sat into a notch.

It was tillered to provide a difference by making one limb slightly weaker than the other by taking a little timber off one limb it so it bent 1/2" or so more.

See also PM.

[Dennis La Varenne]

Thank you to all who have taken an interest in this issue.

I have gone back to the drawing board, so to speak, to re-check what I have already written about. So far, it confirms what I wrote about in my essay, albeit, in ways that I would never have thought about previous to the challenges put out here. I will post the results as soon as I have been able to compile them.

Paul,
As Grahame has just posted recently, the technique for tillering +ve is to tiller it first to 0-tiller, then simply weaken the upper limb ever so slightly that it balances in the hand thoughout the draw. The weakening is so slight, that if the curve of the limb is done well, there is no undue strain on that limb at all.

The tiller is placed centrally on the bow, but can also be placed contiguous with the line of the bottom of the arrow, so long as that is done after the bow has been tillered to bracing stage. Then, the string must be marked on either side of the tiller so the same line of draw is maintained during the rest of the tillering process.

Placing the tiller across the bow, ie. the notches at the drawing hand position and the jaw at the middle of the handle area will only cause it to spin off the tiller. Try it.

Jindydiver,
I haven't lots of time to formulate essays. I do them in any spare time I get after going to work, maintaining a house and looking after a frail elderly father. I am lucky to be able to touch type, so I can type almost as fast as I think.

Glenn has been spending many many hours on Ozbow since this business began. He has been posting about and criticising what I have been saying on other sites. He has had any amount of time to correct me. I have not made a single remark impugning his character throughout this issue. I have only ever asked/wished that he put up a cogent argument for his case.

Buford,
The matter of a perceived personality clash should not blind you or anyone else to the issue at heart and the validity of the argument from either side. If you are now against me, it should be on account of finding fault with my argument and showing me how. If you understood what I was saying, your disappointment about the way I argue my case should not detract from that.

I understand your viewpoint from the talk around a campfire, but important matters can only be debated for a short time, and unfortunately only the loudest and most aggressive often gets heard. At least with written explanations, all involved can go away with the same information and consider them in a cooler light.

It didn't occur to me that I was being confrontational, nor did I set out to be, but I was replying to criticism confronting my arguments which everyone has the right and even the duty to do. I haven't and don't take them personally.

I assume that they are all made in fairness and honesty from that person's perspective. If strongly put, I will reply as strongly.

I bear no animosity to anyone who has challenged me on what I wrote. It is the correct thing to do and for me to reply. I see it in no other way.

Dennis La Varenne

[GrahameA]

Good Morning Dennis

Very well said. And personally thank you for all the information you have given you are a rich lode of Archery information.

[Paul]

Hello Dennis
I agree with this statement:

Placing the tiller across the bow, ie. the notches at the drawing hand position and the jaw at the middle of the handle area will only cause it to spin off the tiller. Try it.

Maybe you misunderstood me this is basically what I do:

but can also be placed contiguous with the line of the bottom of the arrow, so long as that is done after the bow has been tillered to bracing stage. Then, the string must be marked on either side of the tiller so the same line of draw is maintained during the rest of the tillering process

I take it that we are of the same opinion, that if a bow is tillered in this fashion, and so that the limb tips are on the same plane at full draw, then it should be well timed and balanced if it is drawn using the same positions?

It seems however that we do disagree on which limb will be the strongest, as a by product of tillering in that manner.
As I have stated previously, I believe that if you measure the individual strengths of the limbs of a bow tillered in that fashion, the top limb will be stronger than the bottom for the reasons I have explained (though some what poorly) in my first post.

Paul

[Buford]

Buford,
The matter of a perceived personality clash should not blind you or anyone else to the issue at heart and the validity of the argument from either side. If you are now against me, it should be on account of finding fault with my argument and showing me how. If you understood what I was saying, your disappointment about the way I argue my case should not detract from that.

Dennis,
That was the most diplomatic "put up or shut up" I have ever seen.
I completely understand what your saying, As I have no self bow experience, obviously I cannot comment on the topic at hand.

In future Dennis, I shall not post on any of your topics unless you address me personally. I predict this wont bother you in the slightest.

[greybeard]

Hi,
It would appear that you all agree to disagree. In all the debate nobody has mentioned how much positive, negative or even zero tiller a bow should have. What is the tiller difference one should aim for from the fadeouts to the tips at say 6 inch intervals? I have found that self bows have their own characteristics and I treat each bow to suit. At the end of the day what counts is how does it shoot in the paddock.

Daryl.

[GrahameA]

Hi Daryl

IMHO (and sitting on the fence).

This post is more about the choice of "negative or positive tiller" as distinct to "How to Tiller a Bow". Thus there has been little written on 'how'.

I am of the opinion that once a person has decided what their aim is in tillering a bow it is up to the person working on it to decide how they achieve it.

At the end of the day what counts is how does it shoot in the paddock.

I would rather say. "It's your bow - do what you want so it ends up working the way you want".

As a small addenda:

For those people with bows that can have the tiller easily changed try changing the tiller and see what happens - just have the original measurement written down somewhere so you can take it back to the original settings.

I am firmly in the camp of, "If you are unsure what to do try some experiments", - and that goes for lots of things. eg What is the FOC of your arrows? What happens if you change it? Do barreled shafts fly better? Make some and see what happens. etc., etc.

[ed]

So when you guys positively or negatively tiller a bow, how much is the difference in the tiller?

I would also like to know why turning a "badly" tillered bow upside down makes it ok again. Must have something to do with changing the hand positions.....

been reading this site and thought you guys might appreciate it. Advocates zero tiller
http://homepage.ntlworld.com/joetapley/