Primitive Archer
Main Discussion Area => Bows => Topic started by: Kidder on November 14, 2023, 03:25:43 am
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I’ve been thinking through this for a while now and wanted to post up some thoughts on tillering. Well, it’s more like an often overlooked thought on tillering. What I mean by that is that when we talk about a tiller we are judging the final tiller or even tiller at a specific time in the process and saying “that’s a nice tiller” or “this tiller is unbalanced”. But what we never seem to talk about because it’s so difficult to judge is the quality of the “process”. I’ve come to believe that the perfection of the tiller is not just the final product but how you got there. For example you can have a perfect final tiller but if you spent your time chasing a hinge, the wood will show it with uneven set. I’ve also come to appreciate that the very early stages of tillering are often most crucial - establishing a good taper and even floor tiller and balanced limbs at first stringing are just as important or even more important than the last few scrapes. As is minimally stressing things until it’s as close to perfect as possible. If I look at two bows I’ve built in full draw pictures they might appear identical, but when they are unstrung I can tell the better bow based upon a better tillering “process” and what that has done to the bow to get there. Maybe this isn’t news to some of you, but it really does seem to be overlooked, at least in the literature and the chatter from the many of us. I’d welcome others thoughts on the topic.
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Hardly overlooked!
There are plenty of videos on my youtube channel (Del cat) showing the process and some where I deliberately start with a very uneven tiller, and slowly get it true.
There's even one called "Del's tedious tillering video" >:D
We probably all have our own style to some extent. I tend to get some flex at the inner limbs and work out, I know some do the opposite. I get the outers moving a bit more as the tips are narrowed for horn nocks.
Del
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Great topic! I to have tried starting at getting the inner limbs moving and the also starting the outer limbs first. I’ve had set happen in inner limbs and I have had set happen throughout the entire limb. I was told this set happening throughout the limb may be a sign of good tiller but bad bow design. But yes I agree a perfect full draw pic tells you nothing about how much or where there is set in a finished bow. I’m going to check out Dells info.
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Del I noticed you don’t use a long string that hangs below the bow but is tight up against the bow at first of the tiller process. Also why the ring in the string. How do you center the ring as the tillering process goes. I have a good eye for even bending but must be over straining the wood at some point causing set. Most of my bows end up with 1-2” of set when shot in. That’s with 2-3” of reflex in the outer limbs.
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So true kidder. I think we don’t seem to talk as much on the process and maybe tend to focus on final tiller. We will see pics posted here of mid way through sometimes for a “tiller check” Often I will have set happen on wood that has little more retained moisture and will resort to heat to drive some of it out slowly. Set may not always come down to less then perfect tiller methods. It could also be attributed to the wood to some degree. For the last little while I’ve been using the yard stick method in the early stages with long string on tiller tree. It gives me a perfect profile early on balancing both halves of each limb and then against each other. A mid limb pencil mark as a reference point as I look at the arc of that specific limbs bend. I’ll use a depth measure at these marks and compare with both limbs to get a good start. Can’t remember where I saw this now but remember liking the simplicity of it. I’ll use this till low brace and move to my regular method up on my tiller rack on the wall. I find that with this early focus helps me fight against my impatient nature and slow down. The nice thing I like about doing it this way is it allows you to balance both inner and outer limb bend together through the process. Not the only way to do it for sure but just another way. Prior to this I did much like del does and left my outers stiffer till I got the inner bend a little. This method works well too. I preferred this method over the getting the outers bending early then working towards the inners. I found the risk of whip tillering with working from outers toward inners. Del I love your channel! I know how obsessed you are with tiller and love your process. I’ve learned a lot on your channel and often refer to it whenever I dig out a yew stave to work. 😄
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I knew the old sages of Bowery would get it. But I’m going to articulate it a little better: the quality of the process impacts the quality of the bow, regardless of the quality of the final tiller.
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Proper full draw tiller is the destination and the tillering process is the journey. Pretty simple, eh? To get to the end of this journey we have to start with a stave that is shaped evenly before any bending has begun. From this point our journey leads to both limbs bending evenly and together. For me it starts with floor tiller, making sure that both limbs are relatively close but my eye doesn't necessarily see that clearly until I put the stave on the tree with a long string. Initially this is any long string at any length but only pulling the stave enough to see what going on at this stage but in small incremental pulls. If both limbs look to be even I shorten the string so it just fits the stave. All along I mark places that need wood remover and places that already bend too much. Each step of the tillering process, to me, goes through these bending and marking steps and as I'm sure both limbs are bending evenly and together I progress with the bending of the limbs until I can achieve my first low bracing of about 3" to 4". This is a critical point in the tillering process because it not only lets me know how the limbs are bending and in comparison to each other but also how the string is tracking. For me, this is when I work on heat corrections like removing twists and bends and aligning the limbs to the string under tension. Once I'm assured everything is in order and both limbs are still together it can be as simple as just reducing weight evenly without causing other problems but things happen so slow, thoughtful actions from here are necessary.
Also I exercise the limbs by pulling the string, to a measured length multiple times(20-30) but not going over my intended final weight. Once I get to full draw and I'm sure both limbs are bending evenly and together and I'm near the final draw weight I brace the bow at regular brace height and let it "sweat" for an hour or so. I'll also put a few arrows through the bow and gradually make the sweating process longer and longer. BUT, you have to be sure everything is even or you can cause tiller problems even at this stage.
What I've shown here is my process. Everyone has a different method but the final goal for everyone is the same. Their journey may be different but the destination is the same, both limbs bending evenly and together at the intended full draw draw weight.
There are other things you can do like reflexing limbs and/or tips, recurving tips, heat treating the belly, etc but these things come later in the learning process. To begin with simply getting both limbs to bend evenly and together is the goal.
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The process of tillering a bow is a crucial part of the bow building process for sure. The contributions on this forum have helped me a lot in this aspect. Tank you very much guys :)
Over the last few years, I have picked up several methods that have helped me improving my bows. I feel that it's extremely important not to overload the wood at the early stages of tillering. Here are techniques I've learned:
1. I used to floor tiller my bows excessively. This was the point where my bows developed a lot of set. My bows have improved since I don't do this anymore.
2. Instead I started to tiller more with the long string. At first I switched to to normal brace height at about 1/2 of full draw. Now I see even more improvement when I do long string tillering until I reach almost full draw. This is also the point when I do a slight heat treatment on white wood bows. After that I switch to full brace height. Then I gradually increase draw length until I reach full draw. Often, there are only minor tiller corrections needed
3. I like drawing a pencil line along the entire bow length before I start tillering. This helps me to see the true bend of the bow even when the grain is wavy. After each increase of draw length, I look along each bow limb to monitor the exact spot where set develops. I try to keep it little and even through the entire process of tillering.
4. I usually shoot some arrows at the last few inches of the tillering process, monitoring hand shock and string vibration. I remove some wood at the mid and outer limbs, when I'm not happy. This helps me to reduce hand shock improve arrow speed.
lonbow
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Del I noticed you don’t use a long string that hangs below the bow but is tight up against the bow at first of the tiller process. Also why the ring in the string. How do you center the ring as the tillering process goes. I have a good eye for even bending but must be over straining the wood at some point causing set. Most of my bows end up with 1-2” of set when shot in. That’s with 2-3” of reflex in the outer limbs.
I do use a 'long string'... but a long string should be as short as possible! E.g. the bow isn't braced, but the string only hangs down a few inches. When it's done like that the poundage and draw length, correlates closely to the figures when braced. (you can prove it by taking a finished bow and putting a long string on it)
The ring is to allow me to use the same long string on any bow. By threading the string round the ring I can adjust it's length from long right up to braced... then I use that length to make the proper string... fool proof way of getting the string length right.
Del
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Del I noticed you don’t use a long string that hangs below the bow but is tight up against the bow at first of the tiller process. Also why the ring in the string. How do you center the ring as the tillering process goes. I have a good eye for even bending but must be over straining the wood at some point causing set. Most of my bows end up with 1-2” of set when shot in. That’s with 2-3” of reflex in the outer limbs.
I do use a 'long string'... but a long string should be as short as possible! E.g. the bow isn't braced, but the string only hangs down a few inches. When it's done like that the poundage and draw length, correlates closely to the figures when braced. (you can prove it by taking a finished bow and putting a long string on it)
The ring is to allow me to use the same long string on any bow. By threading the string round the ring I can adjust it's length from long right up to braced... then I use that length to make the proper string... fool proof way of getting the string length right.
Del
I like it Del! I may have to try that. I’ve seen you use it but didn’t clue in that it was adjustable. Slick!
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Thanks Del I’ll be trying that method.
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Seems to me this is what Dean Torges was trying to teach us long ago.
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I think I agree the faster and smoother you reach a good tiller the better.
For me the first step is good floor tiller and thickness taper. Then I can go straight to a low brace with an even bend.
What changed my bow making most is I did away with the tiller stick/ tiller tree. I instead check the bend in the reflection of a window. I often felt the tiller looked slightly off in the hand compared to a tree and would spend time tweaking the tiller after I had reached or was close to FD. By tillering the bow in my hand I reach the tiller I want fast and I can judge by pulling the bow if bend is out of balance.
Last trick -to curb my impatience- is to keep the belly surface smooth with a scraper to avoid creating weak spots.
Switching to reflection-tillering reduced the set of my bows often from 1,5 -2" down to 0,5-1"
Only downside of tillering the bow in the hand is that I get used to making bows of the draw weight I prefer (around 45-55 lbs). It would be more difficult to make a bow much heavier and I would probably have to use a tree for that.
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The question I have about your premise Kidder is, to what degree does it make a difference? I think as people gain experience making bows, the tiller starts out even earlier in the process. I have seen or at least heard of bows failing later in the process where, even though final tiller looked good, there was a hinge that later broke the bow or failed in compression. A though experiment might be, how much would a bow that was tillered very carefully through normal means differ in performance/set from a bow that was cut perfectly to shape from the beginning? The only example I can think of would be bows by David Dewey where he used his spreadsheet to create dimensions and cut out the bow. I know Steve (Badger) tested one such bow and it was fast for the time.
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I have found that if you don’t get your heat treat on the belly even you can alter the the tiller at that point. I have corrected it sometimes by going back to the caul and putting more heat in that area. If you have gone to far with the draw it could cause a hinge. This reheat is not always a fix. As far as a bow failing after a good full draw it’s probably due to a knot or some other wood defects. I usually get the heat treat pretty even while getting the bow to match the caul. Some always pulls out though. Maybe a inch on each limb. This happens when it comes off the caul before I put any strain on it. So my cauls have changed slightly over the years to accommodate for this. This is with dry heat I haven’t tried steam that much because my wood is dry. I’m a firm believer in heat treat though .
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One aspect of tillering that a lot of us may do unconsciously is the monitoring of the condition of the wood by picking up on small amounts of set early on. The most common form of tillering is to evenly distribute the load. This is probably the overall best way. While we may not have monitored the process closely in the initial bow we were building it will help us to determine design changes we may want to make in our next bow. Now if we are looking to squeeze out a few extra ft per second by reducing working limb area then monitoring becomes more important. If we can detect small amounts of set early on we can make adjustments early on by employing more working limb area. Very often have set out to build a 120# bow for instance but careful monitoring of te wood forced me to back off all the way down to maybe 80#. But if you are dead set on the building say a 50# bow, then all you can do is try and distribute the strain better.
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Yes I agree on the design side of it . Steve You build a 80# bow 1” wide and you will have more set! But I think we are trying to address a normal bow design for example 67” Osage bow 1-1/4 to 1-1/2” at the fades 1-1/4” at mid limb. With less than 1” of set.
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The question I have about your premise Kidder is, to what degree does it make a difference? I think as people gain experience making bows, the tiller starts out even earlier in the process. I have seen or at least heard of bows failing later in the process where, even though final tiller looked good, there was a hinge that later broke the bow or failed in compression. A though experiment might be, how much would a bow that was tillered very carefully through normal means differ in performance/set from a bow that was cut perfectly to shape from the beginning? The only example I can think of would be bows by David Dewey where he used his spreadsheet to create dimensions and cut out the bow. I know Steve (Badger) tested one such bow and it was fast for the time.
I’m not sure we will ever know to what degree. I think we can say it’s noticeable though. Where the importance of the “process” over the end result became apparent to me was when I started using one of Eric’s tillering gizmos. I don’t believe that the final tiller is any better than I would have achieved before, after all the last few inches is done without it anyways, but you definitely get there quicker, and somewhat surprisingly given that it’s used on a tree rather than a pulley rack, you get there with less strain. The bows I’ve built since adding a gizmo to my process show substantially less strain when unstrung and maintain more even set and a higher degree of induced reflex.
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Tillering for me is more than just shaping the bow. It starts early in the process. How do I want to lay this bow out on the stave. What style and in what dimensions are best with the material I have. Then for me, it’s a slowed to a crawl process as I start taking wood from the belly. I want the shape I’m going for at the end, to be present from the beginning. If it takes hours or days, I won’t go farther than low brace, until it’s close to perfect. Then the end result will typically, if all goes well, settle into place. I’m patient to a fault early in the bending phase.
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One of the big insights I had over the years is that it is not necessary or helpful to over exercise a bow during the tillering process. I recognize that you may have to exercise the wood somewhat to register changes to tiller, but it is less than is commonly believed. For me, the keys to a good tiller with minimum set is to establish a tiller that evenly distributes strain along the limbs (with the exception of tips which I leave a little stiff until the end) as soon as possible with as little bending and exercising as possible. It helps if you are skilled at monitoring limb thickness taper using your fingers - I can usually feel where I need to remove wood without having to bend the wood enough to visually reveal an emerging concern and that helps preserve the belly. When I'm satisfied with the general tiller, I begin removing wood more or less evenly to hit my target draw length and weight while carefully monitoring for changes that may lead to problems. When I'm within 5# of target weight and 1 inch of draw length I adjust the thickness of the tips and remove all tool marks and that usually gets me to target. Then the gloves come off and I exercise the crap out of the bow to make sure that the tiller is stable, and the bow is durable.