Primitive Archer
Main Discussion Area => Bows => Topic started by: Lee Slikkers on May 24, 2011, 11:19:19 pm
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OK, so here is my question on Tillering to reach a specific draw weight. For an example I currently have an Osage that is drawing #48 @ 16"
I've read that a bow will typically add 2lbs of weight for every inch of additional draw. So with that theory in mind, if I knew I wanted to hit #56 @ 26" I could work my way back and that would indicate that I can reduce this bow to #37-ish @ my current 16". If I am way off base or totally lost I'd love to hear any help or opinions on the best way to hit close to my target weight. I really don't want to come in on the light side.
Many thanks folks!
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Get the tiller perfect at 20-30 #'s max. Once you have the tiller correct you can pull the bow until you hit your desired draw weight. Remove wood evenly (or not) until you hit "x" pounds @ "x" inches with proper bend. Math never seems to work well with wood..............not with me anyway. Hopefully your tiller is dead nutz already if your pulling 48# 's , regardless of inches pulled.
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Here is where I am at...not "dead nutz" but there is a wavy hump/wind check and a knot that kind of messes with the bend in the left/lower limb.
(https://lh4.googleusercontent.com/_neJ--vb8EaA/Tdw7VmPt5DI/AAAAAAAABnE/Ih41XScJMq4/s912/CIMG0838.JPG)
Thoughts?
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Im confused ???
Why is the string nocked 3-4" from the end on the left limb. If its extra why not cut it off? Is that where your string is supposed to be? Please explain
Oh and what's sitting in the garbage can? :'(
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That is just an extra 1"+ that haven't taken the time to cut off...bothered me too for a while but I guess I got used to it ::)
That isn't really my trash, its a can I sweep all my shaving into (good for mixing in parafin for fire starters) and I simply had traded out the ERC build off the tree and layed it there...she's still alive >:D
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Build a tillering tree with a scale this way you hit your draw weight with the draw lenth perfect every time. You can't go by the 2 pound thing and hit it right. All wood is different through a knot in there that really puts a screw into it. I'd build a tree.
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Oh ok...wheeeeeeew. u had me nervous there :D
That extra length is messing with my eyes.....cut it off.
Tiller looks close but I don't know what the unbraced looks like. Id say a tad more near the fades. And yes get that wood moving under that big purty knot a lil bit. And maybe a wee bit stiff out towards tips but that's ok too cus then you can really narrow them and lose mass and make a sweeter shooting bow.
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Ok, thanks for the feedback guys.
Chris, the area at the knot has me a bit nervous about removing much more wood there but I will see where it takes me. Good thought on slimming the limbs towards the tips too...it is fairly narrow now but I could stand to loose a touch more.
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Here's my 2 cents - I agree that it looks like it should be bending a little earlier on the left limb. I'd take a few scrapes off just to the left of that knot. Or maybe it's just the knot messin with my eyes. If I was you I'd be careful not to develop hinges where the red is. I'd just scrape where the green circles are until you get a nice arc, then proceed with full-limb scrapes. I wouldn't be pulling over 25 lbs till that's sorted out. You don't want excessive set, especially at the fades. The right limb looks perfect to me, once you get those slight hinges worked out of the left limb, just keep taking wood off evenly across both limbs.
Or maybe it's just the picture and the left limb is fine too ;)
(http://i162.photobucket.com/albums/t253/cbergerman/640/CIMG0838.jpg)
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No no no no no! Don't work on the 2 pounds per inch thing :o.
It's just a useful guide when you are very near draw or you are wondering what will happen if you pull your 40#@28" bow back to 31" (assuming it doesn't goe BANG)
I you want to hit 56# at 26 then you have to hit 56 @ 16" first, then 56 @ 17", then 56@18" etc whilst trying to get the tiller perfect and maintain it as you slowly get it back all the way to 56 at about 24" then you stop and finish it and shoot it and fancy it up and you'll probably find you've lost a couple of pounds and gained a couple of inches and all of a sudden you are spot on your target weight. Do it like that and you have some chance of getting there.
If you work it out to say 37 @ 17 even with perfect tiller and then pull it back to 28, you'll proabably find the tiller is a mile out.
If you take a finished bow of 56@28 and measure it at 17... it may well be 37 or whatever...but this is hindsight, you can't do it the other way round (IMO)
Del
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Thanks Guys, both of those replies helped emensly! I've got the hinge warning marked now ::)
Del, not sure where or why I was headed in that direction with my "new" math and I've probably read what you described in various places but how you explained just really clicked for me so thanks a ton for taking the time to do that...very much appreciated!
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Lee it looks pretty close to me but I can see what Cameroo is saying with the red marks. These guys are good.
Lane
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Thanks Lane, yup...these guys and this site ROCKS, period! Headed down to the "dungeon" to see if I can't correct the issues. Hopefully I'll have some additional pics of the progress to add up here later tonight.
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Looks pretty good Lee, but I would try to get it bending a little closer to that knot. Del explained it perfect on the tillering.
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While I agree the 2# per inch projection can get you into trouble I disagree on the remedy. I find if I tiller a bow to max draw weight all the way up the draw lenght, and especially if I "work" the adjustments in as conventional wisdom suggests by pulling an arbitrary number of times at each station, each inch of draw say as I tiller it out, I finish with a bow drawing the poundage I wanted and making cast like a bow 5# or more lighter. IMHO you are better served by drawing the bow as little as possible in general, and only enough to find flaw with the tiller. Then proceed to projected draw weight at a particular lenght, eg. not the full draw weight as you continue to adjust tiller. But you do have to allow an extra 5#, on average say for a 50# to 60# bow at 28", of lost draw weight from set. So if I want a 50# finished bow, I project back 2#/" from 55# for my max weight at each inch of draw. The set will usually come when you get to about 22" to 24" of draw, again assuming a typical design, moisture control, all the normal stuff. I try to get my tiller dead nuts before I get to this point, to try to minimize the lost draw weight but more importantly the lost cast. Maybe not the best advice for a fellar just trying to get his first good bow, or having just made a few. But after you've made a dozen good shooters and you want more, that last little bit of performance, it's something that will open your eyes when you get it right.
To put it another way, if it were possible to cut a bow out to final dimensions, perfect tiller having never drawn the bow, then when you first work the bow it may drop a few pounds of draw weight to set but it will make cast like a bow 5# or more heavier.
When I first started out, after a couple three years and as many dozen bows, I was amazed at some of the chrono numbers I saw posted for bows very similar to mine. Eventually I figured this out. I think most bowyers follow the same path, employ the same technique without realizing, simply by developing a better intuition for tillering from experience. This having the net effect of not needing to draw the bow as many times, or to as high a draw weight/strain level to get it "right."
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Lee: Bring your bow to Marshall. As of your posting, you have about a 68 + pound bow. 2-3 lbs seems to be my experience. Bring it, we'll get your weight.
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@ DCM4
I'm sure your technique works well for you, I'd just respectfully suggest it's an 'advanced' technique rather than a 'basic' one.
I feel trying to juggle weight and length at the same time is beyond the relative beginer.
You are doubtless right to some extent, and I'm sure many of us won't pull quite the full poundage early on, say 5-10 pounds low, but bear in mind an unbraced tillering string isn't actually exerting full poundage anyway!
I feel that trying to project right down to the low draw lengths and weights is unwise if one isn't really confident with the process.
Del
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Del,
"I'm sure your technique works well for you,"
You don't sound very convincing, if you are sure.
"I'd just respectfully suggest it's an 'advanced' technique rather than a 'basic' one."
And I'd respectfully agree, having written just that in my post. But I think it has merit just in the consideration of it, if not in practice.
"I feel trying to juggle weight and length at the same time is beyond the relative beginer."
Please clarify. What does one "juggle" when tillering. It's simply a matter of looking at the scale, after determining by one mechanism or another the target draw weight at a particular draw lenght. Do you mean the math is beyond the capacity of the relative beginner?
"You are doubtless right to some extent,"
To some extent... Why the qualification? You either have done it and proven it to have merit or not, or have not tried it.
"...bear in mind an unbraced tillering string isn't actually exerting full poundage anyway!"
I didn't see read anything about this bow being tillered with a long string! But I confess my intuition based on the pictures was he'd achieved the braced bow, tillering with a short string... hopefully at a low brace height. And if not, he's already off the rails if he's tillered to 37# @ 16" using a long string. Why is this relevant to the discussion, at this point anyway? Is he still on the long string, do you assume he is? But I'd agree, tillering with a long string wouldl give higher than accurate draw weight (from stack) and usually produce a whip tillered bow if taken too far.
"I feel that trying to project right down to the low draw lengths and weights is unwise if one isn't really confident with the process."
Why would one not be confident of the process, in particular when he hasn't followed and adopted a particular process yet anyway and is asking for suggestions? Perhaps you are not confident with the process, and assume he should not be or is not.
Just out of curiosity, after 40 years of bowyering (I'd read on your website) have you not heard this idea suggested before now? Do you (chrono) test? Frequently? Carefully, as with a shooting machine? What kinda cast do your bows make? Do you care?
I realize my tone is perhaps harse. There is rhyme to my reason, other than just being belligerent, which believe it or not I am not. Rather I'm indifferent wrt to your preferences but very interested that others, in particular new guys, have opportunity to hear and entertain ideas without being influenced by folks entrenched in their own methods or dogma in such a way as to as to discourage or discount them, from my pov without justification. I'd imagine you see it the same way, although obviously in justification of your own preferences.
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I unreservedly oppologise. You seem to have taken offense at my post. Non was intended.
What I was trying to say is I may have oversimplified my explanation of the tillering process in an attempt to be helpful.
I agree with your analysis that drawing to full draw weight from the start may overstrain the wood slightly and thus sacrifice some performance.
I did not mean to be argumentative and have no wish to argue.
Del
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Now I gotta most unreservedly apologize. No offense taken, and none offered. I'm just tickled we got to where I'd hoped. I'm much sympathetic to the difficulty of explanation (of tiller, et.al.) in the attempt to be helpful, herein being the relative bull in the china chop.
I see your point wrt to taking the estimate right down to the first inch of draw. It's just an estimate.
Take care.
David
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High, Dcm, you stirrin' it up again? LOL. To use the technique Del outlined above one has to really make sure the limbs are bending well and those are not. Supposition #1...get the limbs bending well before pulling to max draw. Supposition#2..never pull anymore than it takes to expose a problem. Supposition #3 ... work the stave at sort pulls after removal sessions to let the changes register. If you don't you you'll be playing catch up with one limb and then the other as the changes register. Next post problems with above stave. Jawge
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I do it like Del says here:
No no no no no! Don't work on the 2 pounds per inch thing :o.
It's just a useful guide when you are very near draw or you are wondering what will happen if you pull your 40#@28" bow back to 31" (assuming it doesn't goe BANG)
I you want to hit 56# at 26 then you have to hit 56 @ 16" first, then 56 @ 17", then 56@18" etc whilst trying to get the tiller perfect and maintain it as you slowly get it back all the way to 56 at about 24" then you stop and finish it and shoot it and fancy it up and you'll probably find you've lost a couple of pounds and gained a couple of inches and all of a sudden you are spot on your target weight. Do it like that and you have some chance of getting there.
If you work it out to say 37 @ 17 even with perfect tiller and then pull it back to 28, you'll proabably find the tiller is a mile out.
If you take a finished bow of 56@28 and measure it at 17... it may well be 37 or whatever...but this is hindsight, you can't do it the other way round (IMO)
Del
I am no Steve Gardner, and I don't hold any flight bow records, but I can make a bow with pretty good cast. I also feel that a bow built this way is a lot more stable than a bow that is not drawn and worked as it is built. Having said that, you got some pretty good advice on tiller, and I would fix the slight problems as best you can before you draw any farther. That may mean you are 10# below the target weight, but good tiller is more important. If you get the tiller spot on at 15" and are 10 pounds below the target weight you don't have to worry because you can get some of that back as you draw farther. Next you will draw to 16" and pull it a bunch of times while watching the tiller. If it stays good, move to 17". You really NEED to pull it a bunch of times each time you pull farther because it helps to reveal changes in the wood. By pulling once it may look good, but pulling it 20 times might start to reveal a weak spot in the limb. If you pull once and move on then pull once and move on, you might go 6 inches only to pull once and have a massive hinge show up and do irreparable damage to the bow.
Some may disagree, and that is fine by me. I have made my share of great shooters, and blown up plenty of bows too. I think you will find this a more reliable method and the preferred method of a lot of top bowyers.
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Both limbs need to bend close to the handle. I would start the bending at the end of each fade. That's a personal reference. The knotted area has to worked with care. Let the knotted area be stiff. But the wood before and after needs to bend. Next post I'll outline how I approach the weight issue in keeping with Suppositions 1, 2 and 3. Jawge
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A lot of great advice being discussed here. I like the way George stated it in simple layman's terms for a beginner to understand,he nailed it on the head.
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Thanks, Blackhawk. The easiest method is to pull to target weight as soon as the limbs are bending well...pretty perfectly actually as they will be under much strain. My advice is follow the suppositions I outlined in my first post. I used to tiller that way but don't anymore. Credit goes to Jim Fetrow for this. My bows seen to gain 3# per inch. So I get the limbs bending well asap. That's not always easy but that is the goal. I have a 26 in draw. Let's say I want a 50# bow which is what I like. I go for low 40's for # at 20 in. and then as i approach 25 in I want 50 # or my target weight. I stop and shoot it 2-3 doz times, check tiller and finish sand. Note I never hit target weight until 1 in from my draw. Jawge
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Wow, you folks really put up some seriously good information and how-to's...I've read through this a number of times and feel I could still use a few dozen more looks at it all. I also really appreciate the fact that despite differing views, opinions and beliefs everyone kept there head in the game and their eye on the prise. I sure wish a few dozen of you lived just down the road ;D but you'll all be happy you don't as i'd be there waiting on your doorstep on a regular basis.
Anyway, after reading and trying to digest all of the suggestions and help on my tillering issues I couldn't help but go down to the "Dungeon" and work on her tonight...here she is #56 @ 26"
(https://lh3.googleusercontent.com/-xcDL1Zk8kCw/Td76fQGPDZI/AAAAAAAABqE/ByNKP0sfRnw/s800/CIMG0846.JPG)
Time for some slight finish sanding. There aren't really many tool marks since it's been fine toothed rasp (love the Shinto Rasp) scraper and 220 grit. Need to mull over some thoughts on finishing off the tips/nocks and handle/wrap considerations. Likely going to leave her colors alone and skip any dye job as I'd really hate to muff it up at this stage...
Thanks~
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I basically do it the way George does, but I don't exercise the limbs as much as everybody else does. I think that with the drastic temperature and humidity change we get here during the day it changes the wood too much. So I pull on the tiller tree to the target weight, mark the trouble spots, and unstring it and tiller it some more. When I hit the weight, then I'll shoot, tiller, and fine tune it. It works for me, but maybe not for everybody else.
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You posted when I did, then I saw you picture. The tiller looks good, but I got a little pucker looking at the limb on the right. You almost have a hinge at the bend coming out of the Fade on the right. Don't touch that area. And I'd remove just a tad about 6" from the tip on the left limb.
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Like I said before these guys are good. I did not notice what Eddie saw til I read his post but now I do.
Lee you ever wonder how they got so educated on the the tillering art? Reckon they have built a few? ;)
Bow looks sweet btw.
Lane
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Lee I don't really have any more to add, these guys have already covered any advice I could have given. Just wanted to say I'm glad to see ya working some wood. The only way to learn is to start making some shavings, pay attention to what your doing, go slow and take your time, keep notes on your mistakes so you don't repeat them. That's the best advice I have to offer and if this one doesn't turn out perfect the way you want it to then just pass it along to someone who needs a bow and start on another. Nice job! ;)
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I tiller like Del the Cat does.
Make sure everything looks even with the long string and then shorten it as I go. I pull until I hit target weight and then keep removing wood until I reach full draw while still at target weight. I think this is called no set tillering in one of the bow building books, but I could be wrong.
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It is amazing that you can sometimes overlook or convince yourself everything looks splendid on your bow and then when someone points out the obvious (Thank you Mullet) it jumps out like a sore thumb. Gonna clean up a little bit in that area and remove a touch from each of the tips and then see where she settles in...
It is super cool the amount of time you folks give to others by sharing your wisdom and experience with those of us hungry folks who come asking on a daily basis. This IS a different site and one I am very glad to have stumbled upon.
Thanks gents~
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I brought this thread up from the dead because of it being related to a current thread. I had to do a little digging to find out what the "Jim Fetrow" method was that George mentioned. I am not trying to promote one method over another or wish to start a "whose way is better" discussion. Preventing overstrains of the wood during the tiller process seems to be the stated goal of each method profiled.
How can the guy that is new to tillering best prevent that from happening?
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I made some radical changes in my tillering process over the last few years. Mainly because I have been building a lot of weights and designs that I am not as familiar with. One thing that is glaringly obvious but for some reason I didn't see it for about 18 years is that I can't hurt a bow not matter how far out of tiller it is as long as all parts of the limb are too strong. I used to spend great care floor tillering until the limbs were very even, very often I would brace a bow up and it would be just a few scrapes away from being finished. Too close for comfort. Now I floor tiller just to the point I get a slight flex in the limbs and then go to the tree. Every trip to the tree I am pulling all the way to full target weight and all I do is start the process of evening up the limbs. At all times during the process all parts of both limbs are too strong so I can't hurt anything as long as I don't pull past target weight. Now as I close in on the final tiller, usually starting at about 24" I have to be a lot more careful as parts of the limb will start coming into their final bend and I will no longer be removing wood from the entire limbs.
The main difference I discovered in doing it this way is that a bow pulled to 40# has some chance of collapsing the fibers if pulled to 50#. Always working at target weight eliminates and chance of surprises. Another thing is that has really pissed me off on bows is that occasionally I will tiller a little too far at the lighter weight only to find out one limb or both limbs have areas that are bending too much and I am forced to tiller the entire bow to match those areas when it is not the tiller shape I had set out to accomplish. It also works very well with the no set tillering technique.
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It also works very well with the no set tillering technique.
I recall giving the "no set" method a go a few years back. It worked well once I had two things under control.
The first being what seemed at the time to be a catch-22 for learning how to tiller. As with all methods, advice is given to "not pull any further than needed" before taking corrective action. An eye for good tiller comes with experience, and I had to learn what that was before learning any tillering method.
Perhaps others might suggest ways for a new guy to develop an "eye" for good tiller? I had to start with simple bows and simple arcs.
The second challenge I faced before learning how to tiller was the selection of reasonable weight goals, and how to make adjustments when necessary. Springbuck mentioned this in the nearby thread. Monitoring set is a skill of it's own. I would be interested in how other have gotten past this hurdle when first learning. For me it was using the aforementioned "no set" method.
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"One thing that is glaringly obvious but for some reason I didn't see it for about 18 years is that I can't hurt a bow not matter how far out of tiller it is as long as all parts of the limb are too strong."
"At all times during the process all parts of both limbs are too strong so I can't hurt anything as long as I don't pull past target weight."
This is what I had understood to be correct. When I started doing it the way I have described in the other thread, three things happened:
One, I now finish almost all the bows I start. If I can get it roughed out, dried, and straightened, it's going to be a bow. Heat straightening and tempering is now where I lose the most staves. It used to be tillering.
Two, the bows I make seem to take less set and I'm happier with the tiller. I can't count the number of times I resorted to changing the front profile and weakening the opposite limb to accommodate a non-fatal hinge off one fade, or something like that.
Three: My bows now hit weight, at least within a few lbs. The first 20 bows I made all survived to be shot, but every one was between 25 and 35 lbs by the time I had figured out the tiller. And they all took a lot of set.
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"Perhaps others might suggest ways for a new guy to develop an "eye" for good tiller? I had to start with simple bows and simple arcs."
I honestly think THIS is the hardest part, and that is a GOOD, maybe the BEST place to start. I started on Bamboo backed R/D bows. DUMB, DUMB, DUMB!....
Seeing what you are trying to see is one thing I can't explain a good method for. Again, I vote for consistent thickness as a baseline, and endorse use of the tillering gizmo! I have spent hundreds of hours sketching bows during boring surgical cases, though. I draw a front profile, then draw the side profile to match, or vice-versa. I draw a row of limbs, each with a longer recurve than the last to see what HAS to happen to the curve, etc...
I never have actually tried to apply the "no-set' tillering method in an organized manner, but I have tried to understand the principles and keep them in mind. As a beginner, anything you can do to make things predictable helps.
For a while I thought of all styles as variations on the pyramid. If the sides are parallel, the thickness HAS to taper. If the thickness tapers that section HAS to have elliptical curve, aka, bend less where it is thick. If the sides taper, no thickness taper needed.
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I agree with ones who say not to figure outcome of draw weight by a guideline weight gain per inch by reducing weight to expected numbers at an early time while tillering.I've calculated those weight gains per inch many many times too and it's tempting to do but foolish really.It's cutting things too fine if any trouble arises.It also takes away any chance a person has to evaluate the condition of the wood as you tiller also.
Although it is nice to know at an early time while tillering that your gonna make the weight that you want.
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I've calculated those weight gains per inch many many times too and it's tempting to do but foolish really.It's cutting things too fine
I agree that trying to project with too much accuracy is futile. I do like to take a very close look at the bow when I reach brace height with the longstring. Having the bends even and smooth is one thing, having it bend the way it should is another. I will often have a pic of a similar design braced bow for comparison nearby. If the bend shape needs adjusting, I will use less than full weight to bend the bow to the brace height that I am using to make the comparison with the picture. I like to reduce wood until the bow pulls (with full weight) to at least 20" on the long string before actually going to a low brace for the first time.
I wish to encourage folks who are just starting out, to provide feedback about your travels along the learning curve. Sometimes those who offer advice have forgotten some of the challenges they first faced.
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It also works very well with the no set tillering technique.
I recall giving the "no set" method a go a few years back. It worked well once I had two things under control.
The first being what seemed at the time to be a catch-22 for learning how to tiller. As with all methods, advice is given to "not pull any further than needed" before taking corrective action. An eye for good tiller comes with experience, and I had to learn what that was before learning any tillering method.
Perhaps others might suggest ways for a new guy to develop an "eye" for good tiller? I had to start with simple bows and simple arcs.
The second challenge I faced before learning how to tiller was the selection of reasonable weight goals, and how to make adjustments when necessary. Springbuck mentioned this in the nearby thread. Monitoring set is a skill of it's own. I would be interested in how other have gotten past this hurdle when first learning. For me it was using the aforementioned "no set" method.
Willie, I have never had a great eye for tiller. I think that's why I find the method of keeping the limbs strong so much easier. I just keep making micro corrections instead of getting one part looking good and them letting everything else balance around it. I usually bring mine out to 23 or 24 on the long string before I brace. It reads the same braced as it does on the long string.
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The main thing I see of an important concern here is that the whole tillering process is slowed down and that's always a good thing.It's impressive to floor tiller and to brace a bow in quick fashion to impress and may work out great too but to try to get the absolute best out of a piece of wood slowing down always gets the best results I would say every time.