No Set Tiller/Tiller Logic

[Badger]

     I was asked if I would repost on the no set tiller theory I use. I may have changed some from the last time I posted on it but not sure.
No set tiller is simply a method of monitoring the condition of the wood as you tiller a bow out. It lets you know in the very early stages of set that we need to make some adjustments. Having a basic understanding of tiller logic is helpful in applying this method to your work. Tiller logic in its most basic form is simply knowing that the thickness of wood determines how far it can bend and the width determines how far it will bend.

    A pyramid limb is a good example to use, the entire limb is the same thickness yet it bends in a nice even arc because the sides are tapered all the way to the tip. A parallel limb profile has a taper in the thickness meaning it gets thinner as it goes away from the handle. Logic would tell me that if it gets thinner it can handle a little more bend as it thins out. I think most of us these days are using compound tapers, meaning we may go thinner until just past mid limb and then start increasing thickness as the sides start to taper. This gives us stiffer out limbs. Understanding the relationship between limb thickness, width and the bows ability to bend without damage is necessary when applying a no set tillering method.

     A lot of us have been doing this by feel for many years and never really give it much thought. Our sense of feel once we gain a little experience can be very sensitive and clue us in early if problems start to arise. The only reason I actually came up with this is because I was trying to explain to a student what I was looking for when I tillered a bow out and had no way of explaining it. Next time he came back I made sure I was able to explain what I was doing hence the name no set tillering.

     I am going to explain the way I use it but I am well aware we have plenty of fine bow makers here who do it successfully entirely differently. This past year I have found myself going on to the tillering tree much earlier than I used to and staying on it longer. Once I get a bow flexing I put it on the tree, The first few pulls are only used to even out the tiller, once I have the tiller evened out all my pulls from then on are all the way to target weight. I do basically all my shaving with a scraper on osage and tropical hardwoods other woods I use the rasp a little more and lightly with a spokeshave. I use a tiller string that hangs loose about 5" or 6" not more than 8".

    Now for no set tillering. By time my limbs are evened out and I am ready to start pulling full target weight I am usually at about 12" on the tree. I pull the bow about 10" carefully check the weight and then proceed on to full target weight for several pulls, maybe a 1/2 dozen or so. Now I come back to that 10" mark and see if my weight has changed. If it has I need to address it right away. In most cases if I know my dimensions are adequate I would assume moisture and put the stave away for a few more weeks. If I am in doubt about my dimensions I may reconsider the target weight I have decided on and drop it down some.   Most of the time this early in the game you won't see any change. Early on I like to try and pick up at least about 1/2" draw between each visit to the tiller tree and wood removal. With each visit to the tree I repeat the process of checking the weight a few inches below where I know I will be drawing, exercising the bow and rechecking the weight at that same point before leaving the tree. As long as there are no changes in that reference point weight I proceed with what I am doing. If you have a nice flat stave you might want to use the gizmo devise as it speeds things up quite a bit. You can develop your elliptical tiller a little later in the process if you like.

   Some may disagree here but something I have been doing for years and it seems to work almost 100% of the time is no more guesswork about where the weight of your bow is. It will read the same on the long string as it does as if it were braced. very close anyway. I keep it on the long string until I reach about 24" at full target weight draw and then I brace it. Once you have the bow braced this is where you are more likely to start picking up your first signs of set in that last few inches. Say you just braced the bow, check your weight at say 18", now excercise at 19", check weight at 18, excersice at 20" check weight at 18, excercise at 21" check weight at 18". Do this all the way to target weight at about 24'. If you notice any drop of weight at all anywhere stop immediately and examine your limb for areas you could get bending more. That one area that lost some weight has allready reached it's max and your only hope of not taking more set is to get other areas bending. This is the time you start to use your tiller logic and get the mid and outer limbs bending more if needed or get it bending more near the fades. Bottom line is you have to find somewhere else to bend the limb or lower your target draw weight. If you do this carefully you should be able to get all the way to your target draw length with very little set. Even small amounts of set really hurt performance and shorten the life of a bow so It is to be avoided as much as possible.

  Feel free to ask questions.  Steve

   

[LeightonM]

Thanks so much for taking the time to explain this. I've been hearing about this method but wasn't sure what all it entailed. I am starting a hackberry static recurve that I'll have to try this on.

[upstatenybowyer]

You're the man Badger! I love having this all together to refer to. Thank you!

[osage outlaw]

I think I go to the short string and brace to soon.  I'm going to try to stay on the long string a little longer on my current bow.  Thanks for posting this Badger.

[bradsmith2010]

thanks I got it saved,,,

[BowEd]

That was explained very well Steve.Thanks.

[bentstick54]

Thanks for posting. You explained it very well. The dozen bows I have made were tillered on long string pretty much like you described, but never thought of checking draw weight at a predetermined spot like you mentioned. I have noticed that my set has come within the last 2 inches of final draw length. This will be a big help to me in the future.

[simson]

Steve thanks for your explanations - always an interesting what you have to say!

Let me add my 2 cents:
I try to work as precisely as possible before I do any bend with the bow. On flawless sticks bracing is possible without floortiller (what I don't like) and long string) in most cases. If so, I leave them strung for 30 min and repeat after after another 30 min. I try not to go over target weight and keep on exercising the bow, doing very little scraping here and then. I aim for doing as less as possible tiller scrapings.
My best (fastest) bows did come along like this.
A few weeks ago I had a bow class and one of the students bows didn't need any tiller scrapings at all - never had this before!

[Stick Bender]

 Thanks Steve it is nice having it in one place !

[RatherBinTheWoods]

Thank you for reposting, this is gold dust

[Wooden Spring]

    Even small amounts of set really hurt performance and shorten the life of a bow so It is to be avoided as much as possible.

With respect, I disagree. While large amounts of set can be a detriment to performance, small amounts of set are desirable - bows with small amounts of string follow (say, less than 3 inches) don't have the kind of hand shock that is often felt with reflexed limbs, and this leads to more accurate shooting. Bows with heavy reflexes have a pre-strung zero position that is forward of the handle, and upon release, the bow limbs attempt to return to that pre-strung condition, causing the handle to jump forward in the hand, resulting in less accurate shots - bows with slight string follow do not do this. After all, this is the reason that reflex-deflex bows exist - they attempt to maintain the faster performance of reflex bows, but they then have a deflex in order to maintain a zero position that is in line with the handle so as to remove hand shock. Both Howard Hill and John Schulz were advocates of bows that maintained string follow since accuracy was much more important to them than the speed of the arrow.

[BowEd]

The health and longevity of the wood is of more concern here from what I gather with no mention of excessive reflex implied.

[Marc St Louis]

    Even small amounts of set really hurt performance and shorten the life of a bow so It is to be avoided as much as possible.

With respect, I disagree. While large amounts of set can be a detriment to performance, small amounts of set are desirable - bows with small amounts of string follow (say, less than 3 inches) don't have the kind of hand shock that is often felt with reflexed limbs, and this leads to more accurate shooting. Bows with heavy reflexes have a pre-strung zero position that is forward of the handle, and upon release, the bow limbs attempt to return to that pre-strung condition, causing the handle to jump forward in the hand, resulting in less accurate shots - bows with slight string follow do not do this. After all, this is the reason that reflex-deflex bows exist - they attempt to maintain the faster performance of reflex bows, but they then have a deflex in order to maintain a zero position that is in line with the handle so as to remove hand shock. Both Howard Hill and John Schulz were advocates of bows that maintained string follow since accuracy was much more important to them than the speed of the arrow.

This is an error, string follow or its lack has nothing to do with hand-shock.  By your reasoning a bow with string follow should shoot a 3 GPP arrow and have no hand-shock, we all know this is not the case.  I have shot many highly relexed recurve bows using 5 GPP arrows with hardly any hand-shock, I've also shot a few bows with 3" of string follow that kicked horribly even with heavy arrows.

P.S. Good treatise Steve, I usually brace once I get to about 20" on the long string

[Wooden Spring]

You said: "By your reasoning..."

Well, it's not my reasoning, this comes from Howard Hill, and I was merely paraphrasing since I do not have his statements sitting in front of me. I have not looked at the mathematics on string follow yet since it has never been a major concern to me - a small amount of string follow, in and of itself is a poor determiner of the quality of a bow; it simply is not enough data. When I get a chance, I will see if C.N. Hickman, Forrest Nagler, or Paul Klopsteg ever wrote on the topic. I'm pretty sure that they did, but if my memory serves, it was only by means of a passing comment or anecdote rather than by extensive computation as they did other aspects of bow design and construction.

From what I can gather, the philosophy of bow construction has evolved somewhat over the years as regards string follow - where once it was deemed by many to be a desirable trait in accurate and comfortable shooting bows, now it is largely stigmatized. Why? I don't know... I would wager a guess that the construction of our wooden bows has been highly influenced by bows made of modern materials that are not given over to the same kinds of stretching and compressing that we see in wood, so builders attempt to make their bows reflect them because they "look better." There's nothing wrong with that of course, but by the same token, there's nothing wrong with a little bit of string follow either, and according to the mathematics (which I would be happy to share), building a bow according to the MOR of the wood you are using (not merely generic, published numbers) always results in a bow with a little bit of string follow. It is possible to reduce or eliminate this or course, but my suspicion is that in doing so, we are actually building the bow closer to the breaking point. Is a slight gain in the speed of an arrow worth losing a safety margin? I don't know, that's up to the builder.

But if someone is making the assertion that "even small amounts of set... shorten the life of the bow," it's simply not true, and I would direct any naysayer to the works of the gentlemen listed above to prove the point.

[Badger]

    Almost all bows will take some set, the more experience you get the less set you can try for. Another thing not all set is equal. Some set doesn't cause hysteresis and some does. If you heat treat a bow and put some reflex in and then loose some of it while tillering it is not necessarily all set, some of it may be that your bend just didn't hold all the bend. The main thing I look for when I am done is that once a bow is finished and has gotten some arrows through it I like to have some good tension at brace. The other thing I look for is the first pull on a bow after bracing is the same weight as the second pull. Some bows when rested will give you a nice tight braced string when first braced but after a few shots it will loose a little tension. That is set and the kind of set that causes hysteresis. Another thing I have noticed is that if a bow does not recover any reflex once unbraced but stays the same it is usually better than a bow that recovers ever resting.

   As for hand shock, most handshock is geometry related. R/d bows with stiff outer limbs and low string angles seldom have much shock. Nice round tillers with full working limbs will often be shocky if not made a little more elliptical. Low string angles give leverage back to the arrow and allow it to suck more energy out of the limbs. Recurves seldom have much shock.