My latest bow a Bamboo backed Ipe R/D 64 inches 51#@ 27"
It started out at 66" and 54#@ 27. Decided to lower weight by 3# , missed and cut it shorter to get weight.
Now the question, through the whole tillering process I thought
I had maybe hit my best yet. Now after a couple of hundred shots the tiller has changed so that the bottom limb is bending more by about 1/2 " at the fades. Did I not shoot it enough before? Is the best bet to work the upper limb to get it back and loose some weight?
I already plan to make another for the hunting season at the weight I want.
Thanks, Ron
The bottom limb takes more strain at full draw when drawn in the hand. It receives relatively even strain on the tiller tree, especially if you're centering the bow on the tree and the hook in the center of the string. I would suggest using the tree until you get to about 4"-6" shy of your intended draw length, allowing the bottom limb to remain slightly stronger, particularly in the inner third of the limb. Then finish tillering by drawing the bow in your hand and looking in a mirror. Just leave the bow strung, scrape where necessary, exercise 20-30 times to the previous draw length, and repeat.
For now, you could try flipping the bow over, provided you haven't cut the shelf in yet. Some selfbow bowyers/shooters do this over time, as the bottom limb will often manifest more set as the years progress.
Hope that helps a bit. :)
I agree with 4est. This is something that I have noticed in my bows and as such I always leave my bottem limb stronger then the top. If you were to look at a "final tiller" about a half an inch to an inch stronger. Like 4est said, I check it just by using a mirror and looking at the two limbs when I or a friend draws it to see if they are even.
-Mo
Thanks for the suggestions and it makes sense to me.
I do have a shelf cut into thIs one now.
It is the middle third that is,bending more.
Would cutting the bottom limb a little shorter help this one without loosing weight?
Would that remain true if you were shooting three finger under instead of split finger?
I shoot one over two under and cut my shelves so that the arrows go through the center line. Because of this, the center of where I pull on the string is below the actual center of the string. This means that there is a "shorter" string on the bottom and a "longer" one on the top. This is what stresses the bottom limb more and I think would only be more so with three under. But it does matter where the shelf is cut.
-Mo
What 4est said works. Also, I tiller the bottom limb about a 1/4 inch or so stiffer. A window at night works like a mirror too. Jawge
How much good exercising did you do while tillering? Sometimes if you skip that part your wood compaction takes place too late and your tiller changes while shooting.
Pearl, I did a lot of exercising both by hand and on the tree.
Did this after every reduction.
Any limb you take from the bottom will make the rest work harder causing yet more set. What you have going on isnt uncommon at all.
This is one of the reasons I'm very careful and deliberate to use my tillering tree to hold and draw the bow exactly how I will do it by hand... at least as close as I can humanly get it.
My tillering tree holds it like I hold it, and the hook on the string is exactly where the fulcrum point of my drawing hand is located(2/3 of the way down my middle finger) with the nock 3/8" above the shelf. My hook is NOT lined up with the center of the grip or tillering tree as I often see here. Think about it, it is impossible to shoot a bow in such a way... so why tiller it like that? So I can flip the bow if the tiller changes as I shoot it in? HA! That never happens. Read on...
It never made sense to me to tiller it meticulously, but differently than I shoot it. How could we reasonably expect it to maintain its braced or full draw profile and/or measurements with continued use? Tiller it to a predetermined positive tiller and hope for the best? No thanks.
Tillering all our bows to a predetermined braced measurement... i.e. 1/4"(or whatever) positive tiller is a mistake in my opinion. There's NO WAY that any particular predetermined measurement is the correct measurement for ALL bows. IF you're going to measure them, bows should be completely tillered to shoot an arrow well... mimicking the shooter's holds as closely as possible... THEN measured afterwards, just for future reference. IMO, brace height measurements, ESPECIALLY in the selfbow realm, should not be a guide during the tillering process. Our beacon should be excellent arrow flight... and let the braced measurement be what it is. Some of my bows have a 1/4" positive tiller, some more, some less, some even... it depends on the particular piece of wood, how it grew, how it acts... but ALL of them are tillered and trained to shoot an arrow straight away with a 3/8" high nock point. Tuning a bow is then an afterthought. It's predictable and does exactly what it's supposed to do... with a 3/8" high nock point... and bows invariably hold their tiller. Without needing to make 'adjustments' for itself, the bow comes straight back into the bow hand while drawn, and the arrow leaves with purpose... not porpoise :)
If we tiller it, effectively timing the limbs to draw and return in unison while holding the string at the center of the handle... then actually shoot it by holding the string 2" higher... how is our limb timing then? Do we know for sure? What is the nock of the arrow doing upon release? The bow is going to try to adjust to the change... which can cause changes in the tiller, and timing. Aside from building-in questionable limb timing and less than perfect arrow flight, are we creating additional handshock? Is leaving the bottom limb 'a little stronger than the top' always the correct answer even though staves can vary greatly in their unstrung profiles? Can we always, completely correct(cover) arrow flight discrepencies with nock point adjustments?
What if one limb is straight and the other has deflex or reflex? What do we use as a guide then?
I predetermine my nock point before the bow is introduced to the tillering tree, REGARDLESS of the bow's unbraced profile... humps, bumps, deflex here, reflex there, split finger, 2 finger split, 3 under, it doesn't matter. Every bow is trained throughout the tillering process to send an arrow straight away with the bottom of the nock point 3/8" above the shelf. When it's done, that's where I set the nock point, and I never have to adjust it.
Also, while we're on the subject... I have my tree set up so that I can tiller it for split finger, three under, or whatever I want by use of a piece of angle iron down by the floor with a bunch of holes drilled in it. I just move the bottom pulley to a different hole and slide the hook to the new fulcrum point for a different hold. Then, tiller for good arrow flight, and let the braced measurements be what THEY want to be.
Just something to think about :)
I've thought about this quite alot for the better part of the last two decades, and have to wholeheartedly agree, bowjunkie. tillering for balance and timing in the way you describe is more important than positive or negative tiller. actually, imo, proper balance and timing renders the notion of positive or negative tiller practically meaningless.
can a brother get an amen?
QuoteOriginally posted by J.F. Miller:
I've thought about this quite alot for the better part of the last two decades, and have to wholeheartedly agree, bowjunkie. tillering for balance and timing in the way you describe is more important than positive or negative tiller. actually, imo, proper balance and timing renders the notion of positive or negative tiller practically meaningless.
can a brother get an amen?
AMEN!
Regardless of your bottom limb length chose.
So how do you tiller bow for good arrow flight while its on the tree?
Do you tiller for even tiller, positive tiller, etc? Do you tiller it to your final draw on the tree then shoot it and tiller more by feel of how the limbs react and arrows fly when shot ?
good arrow flight is a foregone conclusion if limbs are balanced and sychronized. this can be done as bowjunkie described, by designing a tillering tree that mimics the pressure point of your hand on the bow grip and the location of your fingers on the string as closely as possible. I could care less about negative or positive tiller these days as I have found that these measurements are not fundamentally important to the outcome if limbs are balanced(the implication here being that balance is really the most important thing to achieve), but I do keep record of the tiller measurements for future reference. for my bow designs, tiller usually measures about even once the limbs are balanced and recovering in harmony, but often has either slight negative or positive tiller. and by slight I mean 1/8" or less. these measurements mean very little to me as I'm approaching full draw while tillering. if the bow is balanced, it will shoot well, assuming limbs bend gracefully, wood is dry, bow is designed correctly for the material, etc, etc.
I pretty much always tiller to the intended full draw length and to about 5 pounds heavier than target draw weight on the tree, but I don't ever pull it to that length until bow is balanced to my satisfaction and limbs are in sync. doing it this way, I rarely have to make corrections after I start shooting, and if I do, they are very minor corrections.
So basicly, assuming a drawing hand placement of the tillering tree pull rope on the bow string, a bow should be tillered so both limb tips are coming down the tree to the same length? And a nice even arc in both limbs.
"imo, proper balance and timing renders the notion of positive or negative tiller practically meaningless."
I'll give you an amen for that one Jamie!
"So how do you tiller a bow for good arrow flight while it's on the tree?"
Roy, we discussed this at my place years ago. By tillering for good arrow flight, I mean tillering so that the arrow nock comes straight back, perpendicular to the handle/shelf, and leaves along that same line when shot. This way the arrow won't have to recover from porpoising in flight, less energy is wasted, and the bow draws and shoots more balanced and sweet in the hand. These, and more, are natural bi-products of synchronized limbs.
Where I place the hook on the string(middle finger fulcrum point) is less than a half inch from where the actual arrow nock will be on the string, so as I draw the bow on the tree, with no tipping of the bow permitted, I watch how that hook travels down towards the floor. I have vertical lines on the wall which replicate the arrow nock's travel in relation to the arrow shelf on the handle. When the limbs are timed equally, the hook will come straight down following the line. If one limb is stronger, the hook will be pulled toward the stronger limb. This is what I use to judge relative limb strength/timing... from the very first pull on the tree to the very last. Since I wish for this to be a pretty precise ordeal, it's imperative that the handle is sitting level in the tree and held the way my hand will hold it. It's important that the HANDLE is level, not necessarily the whole bow. I want the handle level and don't care where the tips are in relation to one another. One can actually be higher than the other, and the limbs can still be perfectly timed.
If you would like the bottom limb a little stronger, as some do when it's designed shorter for balance, you can tiller the bow so that the hook slightly fades towards the bottom limb as the bow is drawn and arrow flight and shooting quality is affected insignificantly.
"Do you tiller for even tiller, positive tiller, etc?"
No. I don't tiller for even tiller, positive tiller, negative tiller or ANY of that jazz. That is NOT my guide. It's a false prophet. It will lead you to tiller some bows sub-optimally. I tiller so that the arrow's nock comes straight back, perpendicular to the handle, and leaves along the same line... straight ahead... with practically NO THOUGHT GIVEN WHATSOEVER to how the bow measures at brace.
How COULD you tiller to a predetermined measurement if you have one limb with reflex and the other with deflex... or like some of the bows I've made, with a big hump at the dip right where you're 'supposed' to measure them? If you have a selfbow stave with one limb reflexed and the other deflexed and build the bow to say... a predetermined 1/4" positive tiller, the limbs can be far out of time. It will have more handshock that it should and you'll have a harder, if not impossible, time tuning it. If, instead, you completely ignore any such brace height measurements, and you tiller it so that the arrow's nock travels straight away from the handle, then straight forward upon release... the limbs will be timed REGARDLESS of what the bow looks like or measures at brace height. As such, with perfectly timed limbs, bows may end up with positive, equal, or negative tiller, but they'll all be perfectly balanced during the draw and shoot wonderfully right out of the gate.
When I'm in bowyer mode, I like to spend my time making bows, the best bows I'm capable of making. I don't care for messing around trying to tune a bow that doesn't want to be tuned or 'settling' with arrow flight that is just passable.
"Do you tiller it to your final draw on the tree then shoot it and tiller more by feel of how the limbs react and arrows fly when shot?"
I tiller to final draw on the tree with maybe a couple extra pounds for shooting-in. If I do my job properly there on the tree, the limbs will react harmoniously, pulling the handle straight back, balanced, into the palm of my bow hand all the way through the draw, and stay that way at full draw, without me having to heel it to keep it from tipping, and the arrows will fly perfectly... every time. I've never had it any other way. I cannot be this precise by finishing the tillering of the bow 'by hand', looking in a mirror... or even taking and studying pictures of it on the computer. None of that will tell me as much as my tillering tree will tell me.
This method works equally well regardless of how a bow is designed... i.e. symmetrical or asymmetrical limb design, funky lumpy selfbows, bamboo backed bows, d/r glass bows, recurves, or whatever.
"So basicly, assuming a drawing hand placement of the tillering tree pull rope on the bow string, a bow should be tillered so both limb tips are coming down the tree to the same length? And a nice even arc in both limbs."
No. That is not the same thing. There are many reasons I can think of that would cause such a bow to still be out of time. They don't all have a perfect, symmetrical shape. They shouldn't all be tillered with nice even arcs(another pet peeve of mine). They don't all have both limb tips starting the same distance in front of the handle, etc. And if designed so that the bottom limb is shorter, it shouldn't necessarily come down the same distance since it travels in a tighter radius.
Bowjunkie -
Will a stationary pulley on the tillering tree have an impact on how the nocking point travels as the bow is drawn? Or will the nocking point always move off line toward the stronger limb. Fairly new to this bow building and really like your thinking.
Thanks!
Mitch
Well Jeff. I remember tillering bows on your tree and you was telling me, we wanted the pull rope drifting left to the stronger lower limb. And this was after ya told me the top limb should come down the tree an inch more than the bottom limb. Seems like ya keep changing yer mind Jeffro:) Or maybe yer just getten better at this tillen stuff as ya get older..
But anyway I understand ya on the tillering pull rope coming straight down the tree. It makes perfect sense to me now:) I always level my handle to sit in the cradle. So that's how I'll do my tillering from now on, just like ya just said above.
Mitch, I think what Jeff is saying here is. His stationary pulley mounted on the floor is directly vertically in line with where his center finger on the bow string will be. He can move his pulley one way or the other to compensate for split finger or three under tillering. Therefore with the pulley being mounted rigid, he wants the pull rope to come straight down the vertical line on the tree, and there will be a couple lines on the tree corresponding to where the pulley is positioned. Yes the pull rope will "always" move towards the stronger limb, so if the pull rope drifts off to one side or the other from the vertical line, that means one limb is stronger than the other. So wood will have to be removed from the stronger limb to keep the pull rope coming straight down the vertical line. Jeff, post a picture of your tree setup.
I think I got that right.. LOL
As a general rule, the way you grip the bow also has a lot to do with how the bottom limb responds in proportion to the top. The lower the heel of your palm rests on the riser, the more the bottom limb has to work (i.e. the further the tip has to travel to achieve full draw). I prefer an Asbell-influenced grip in where the heel is completely off the riser. On most bows, this creates a more even tiller/timing/limb recovery scenario.
However, I'm NOT suggesting you change your form just to save a bow :) It was just some food for thought...or, more like the crumbs from dessert after the above posts! :)
Well good morning 4est, yer up late:)
I believe it's also true that shooting three fingers under puts less stress on the lower limb than shooting split fingers:)
4est, that's why it's important we set the tree up to hold the bow the way we do.
Roy, I told you that because we were building bows with shorter bottom limbs. A shorter bottom limb is under more stress per inch than a longer one, so leaving it a little stronger MAY help in some instances.
Also, if you think about it, since the limb is shorter, it travels in a tighter radius, so it will never come down just like the top limb. Imagine if you pulled them all the way down to the 6 o'clock position, the bottom limb tip would be above the top limb tip by the amount you offset the limb length. This helps you envision the fact that it will never travel in the same radius, and shouldn't be tillered to come down the tree the same distance as the top limb. Shorter limb = tighter radius = less distance down the tree.
When you, or anyone, was just starting out making bows up here Roy, I tried not to give you too much info. Until you gain some understanding of this stuff, too much information can get in the way.
Read this article Torges on tillering (http://bowyersedge.com/organic.html) It's Dean, so read it several times over. I believe you'll get English Lit credit for it. ;)
I try to duplicate hand placement on my tiller tree too. I also use an arrow puller to help simulate the effects of three fingers on the string, to radius the string at the pull point. I have a rounded chunk of wood for D-bows that allows me to slide the bow to different pressure points on the handle in order to compare tiller and I have a rectangle chunk for stiff handle bows. Its offset so that I can pull the bow as though I'm hand-drawing it, 2 or 3 fingers under, etc. It seems to work.
Here I'm actually trying to break a stick of vine maple that had 6" of reflex. It was too twisted to make a bow so I decided to test its flexibility. I could not break it. I went from floor tiller to 20+ inches repeatedly. It lost 2" of reflex...in case you're interested.
http:// (http://i588.photobucket.com/albums/ss327/SteveBush1/Untitled-7.jpg)
Tom, yes, Dean describes things well in that article. I've read it several times and picked up on, and affirmed in my mind, more each time. That's what happens when you read Dean's writings. There's more quality, helpful info packed into his careful selection of words than their sheer quantity would lead you to believe.
That article and discussions I had with Dean are what prompted me to step back and be more objective and critical of my tillering methods and goals... which I continue to do... always trying to learn, always trying to improve.
Dean is my mentor and inspiration... whether he knows it or not :)
mwosborn, the stationary pulley can have an effect on how much the hook pulls to one side... how much depends on how far out of sync the limbs are... the harder the stronger limb pulls to the side, the more the stationary pulley will try to hold it back... but, it's not a real problem. It will never hold it back to the point that you can't see the discrepency. You can still see that it's being pulled sharply to the side and which limb needs weakened. And, if one limb is CONSIDERABLY stronger, you won't have to watch the hook because the whole bow will tip in the tree.
This is why it's also a good idea to have a bow cradle on the tree set up like Dean's and Steve's(picured above), convex shaped, which will permit the bow to tip with the slightest discrepency in limb timing.
I plan to rework my tree, yet again, so that I can change out my cradles at a moments notice. Using the stationary version to get it close by watching the hook, then the convex version to fine tune by how the bow tips, or doesn't, as it's drawn.
Both methods reveal the same thing. Relative limb strength and timing.
Wow, lots to digest and I'm working on it. I see where this all works.
The original problem was the first time I'd had such a drastic change.
I shortened the bottom limb a little and reduced the top limb a little, not looking bad right now. I'm only 2 pounds lighter on weight.
Thanks guys - appreciate you answering my questions. Can't wait to get some time to work on some bows!
Mitch