Primitive Archer
Main Discussion Area => Bows => Topic started by: BarredOwl on May 04, 2015, 10:13:30 pm
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If one limb of a bow takes a little more set than the other is it simply a sign of a less than perfect tiller? Or does it just happen sometimes?
It is the bottom limb of the bow in this case. I did have it slightly stiffer than the upper limb when I started shooting it. I have finish drying on it right now and will take a FD photo and compare to the FD photo when I started shooting it. I probably have 100 - 150 shots through it. The overall amount of set doesn't seem to be changing. I check it by putting the bow up against the wall right after unstringing and several hours to a day later and it doesn't appear to be changing between shooting sessions.
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Not sure if this is your issue or not but I used to store my bows in a big plastic drum. The bottom limbs would have higher moisture than the top limbs and would take set if I pulled them out of the drum and started shooting them without giving them to time to equalize.
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I had that problem with a bow recently. It is a billet bow.....sister billets. The bottom limb took more set than the top limb. I heat treated the bottom limb twice but nothing seemed to fix the issue. A piece of wood with a mind of its own I suppose. Ya gotta love figuring out the mystery of a piece of wood :-)
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Well at least the first two replies didn't overwhelmingly say it was a tiller problem for sure so that has me feeling a little better. I noticed it was harder to chase the ring on one end of the bow compared to the other. Didn't pay attention at the time to which side it was. If I ever notice this phenomenon again I will mark which side it was. I suppose there could easily be that much variation in qualities of the wood in a 55" run of osage.
I did tiller this bow during a wet rainy spell and I kept thinking I should probably wait for a week with lower humidity, but I was making good progress, I had the time, and didn't have the self discipline to wait for drier weather.
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I think it is one kind of tiller problem. What you see in tiller tree is not what you get in real full draw. Take full draw pictures in tiller tree and in your hands. I really suspect that bottom limb is bending more in your hands than in tiller tree.
There is two reasons. The pressure points (in handle and in string) you use in tiller tree are not the same than when you are really drawing the bow in your hands. Or, the pressure points are correct but you interpret the bending of the bow in the tiller tree wrong way.
Depending your grip, is it high or low, the pressure point in the handle can vary quite much. With high wrist grip the pressure point is close to arrow rest (if you have one...) and with very low grip, the pressure point can be up to 7 centimeters lower. And it really affects to the tiller!
Of course, the reason can be that bottom limb is shorter than top limb, so it is bending more -> more stress -> more set.
If you watch full draw picture here and there, bottom limb is bending more almost always. It is also common that bottom limb is taking more set, in fact, it is nothing special. Of course, it should not be so!
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Agreed Tuomo.
I don't really use the tiller tree now after 20 inches. all the rest of my tillering is done by hand drawing and keeping an extremely close eye on any set the bow is taking.
Set in one place or one limb shows 100% that that spot/limb is taking more strain than it should.
Before starting tillering I strongly recommend tracing the side profile of the bow onto something. So every time you unstring it after exercising you can see immediately (before it relaxes) where the set is. Set is your teacher and friend!
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I regularly encountered this as long as I stored my staves standing upright. It's like badger said, but without the drum. Bottom limb just had more moisture.
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I do not believe to the theory that bottom limb is more moist, if bows are stored upright and bottom limb is at floor. We have discussed this subject here in Finland. So, I made a test. I checked relative humidity at floor and at ceiling - no measurable difference. Checked it many times, same results. In normal home air is circulating so much that relative humidity is the same all over, unless you have some kind of very special conditions - like plastic drum, etc.
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Many people draw their bows on the tillering tree different than they do by hand, then they're surprised when the tiller shifts as the bow is used. I have my tillering tree set up to replicate my holds on bow and string, pull the string relative to a specific nock point height I'll use when it's all done. If the limbs are sync'd, tillered, and exercised relative to that nock point and me, then as I use it, there are no changes for the wood to account for, no reason for one limb to begin taking more set than the other.
I use my tillering tree right through to the very end... it is proven and I trust it entirely. I'm pretty anal about relative limb strain/balance. I don't guess, and I don't like unpredictability in my bows.
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It seems to be always the bottom limb, which is why we tiller 'em a bit stiffer.
I agree about drawing on the tiller tree.. it should be placed to replicate a real draw.
To test the "store 'em upright" theory... simply store 'em upright but upside down :laugh: simple.
I've only ever had it happen really bad, the once and that was an Ash primitive... (did I ever mention I don't like Ash? >:D)
Heat treating the lower limb can help get it back in balance.
Del
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I did tiller by hand at the end. My bottom limb was probably just not stiff enough compared to the top one when I started shooting it. I am nervous about weakening the upper limb now and overshooting then having to weaken the bottom and end up giving up too much weight.
I assume the problem will only get worse if I don't do something about it? I thought I had really gotten this one right. Guess that's part of the process. I hate to put heat to it at this point so if anything I will look at the tiller once the finish dries and sharpen up the scraper probably.
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Bettre to heat treat it now before it gets any worse. You can ease it back to straight as it's warming up too.
I wouldn't worry about finish.... until the bow is finished >:D ;)
Del
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The wood is Osage. How dark should I try to toast it to have chance at stiffening it up a little? I assume not necessarily real dark at this point. I assume I will need to sand any finish off first. I will also try to post some photos. I hate to ruin it now but if it's not meant to be it's just not meant to be.
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Also I assume I will need to sand all finish off ( back, sides, and belly) before applying any heat?
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How much set has your bow taken, BarredOwl and what is the difference in set between the 2 limbs? Jawge
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Also I assume I will need to sand all finish off ( back, sides, and belly) before applying any heat?
You don't want heat getting on the back. I clamp thin slats to the edges to chanel the heat along the belly and keep it off the back and sides.
You can leave any finish on, unless it's going to ignite :o
Del
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George,
The tips of the limbs are probably 2" back from where they started before any bending took place. After a few hours of rest there is a good half inch of air between the back side of the handle and the wall when I place the tips of the bow against the wall and the back of the handle just touches the wall good right after un-braced from a shooting session of 20 shots or so. I might guess the lower limb may have about 1/2" of set more than the top limb and it could be less than that but I don't think more than that. I will get some photos posted tonight.
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From my take,if you have a reflex limb and a deflexed one,even after heat treating most often the deflex will come back but will still be stronger than the reflexed one.so when unbraced it looks like the deflexed limb has taken set,were as it just fell back closer to the original profile.peanut gallery welcome!lol! Rob.
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BarredOwl, I'd leave it alone and enjoy it. Jawge
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It's probably not as bad as I am making it out to be but here's the best way I could think of to show the profile.
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Perhaps you should show a picture of the drawn bow to allay your fears.
Jawge
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sorry but that bow looks awesome to me... i wouldn't do a thing to it...
but that's me...
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I think you are being too hard on yourself from those profiles. Like the other guys say, show us a full draw pic(with arrow) to see if the lower limb really is too weak.
Hamish.
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Here's the FD.
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That is awesome! My advice is leave it. Enjoy. :) Jawge
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Good enough. I'm pretty new to this and didn't want it to get worse when it could have been addressed.
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LOL!
Ain't now't wrong with that. :laugh:
You got a tough of boyweritis and overthink...
Step away from the bow!
Del ;D
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To me it looks like the bottom limb is a little weaker in that full draw picture. It looks like the top limb is tilting back toward you a little, and the bottom limb is pushing toward the front... it's not much and is hard to tell with it held at an angle like that. Just my $.02
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send it to me... i will shoot it often and hang it in a place of reverence in my living room... :D
that is one sweeeeet looking bow... congrats and very nice work...
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Looks to me like the string could be a little shorter ;). Other than that I got nothin'.
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Yes I agree the bottom is weaker.if you turn the photo sideways and upside down it's plain to see.i bet if you. Turned the bow 180 and made the top the bottom it would be near perfect.
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Also it's a good idea to take a full draw shot from opposite sides cuz. It can be slightly different and also it's natural to cant the bow a little to keep the arrow from falling off.
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Yes I agree the bottom is weaker.if you turn the photo sideways and upside down it's plain to see.i bet if you. Turned the bow 180 and made the top the bottom it would be near perfect.
As much as I would like to just leave it as is I see what you are seeing when I rotate the picture.
Due to a little snakeyness in the grain I may have to leave the top and bottom orientation as is. If so I probably need to just start taking a few scrapes at a time off the top limb till it evens up better?
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I would advise against flipping the bow now. It will have settled to being drawn the way it is.
Yes the lower is a bit weak. All you should need to do is use some 60 grit paper on the upper limb evenly. I would put a series of pencil marks over the whole belly of that limb and remove. Then work down through the grits taking one full pass each time. Just be gentle! Not much wood needs to come off and give it a lot of exercising by hand at every pass.
My main tip is to watch the set as you tiller. Trace the outline of the sideprofile onto something before you ever bend it. Any set at all during tillering is telling you where to remove wood....and the wood is never wrong!! Human eyes can be!
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Mike, I mostly agree, although an even amount of set all over doesn't tell us where to remove wood, it more tells us we could have left a little more behind... somewhere... somehow... during design perhaps.
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Many people believe that an even amount of minimal set shows that they are at optimum mass per design. Clearly they have gone a little too far but that seems to be the accepted thinking.
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Thanks a bunch everybody. I think I have learned a lot.
Many people believe that an even amount of minimal set shows that they are at optimum mass per design. Clearly they have gone a little too far but that seems to be the accepted thinking.
This is what I need to learn. What is "gone a little too far"? I started seeing some set in this bow at 20" and 50 lbs, which wouldn't have been an acceptable draw length for me at all.
Is that to say had I shot for a lower draw weight for the width/length I would have been less likely to have set at a longer draw length? or Had I went with a wider limb I would have been less likely to get set? Or would I have had to settle for a shorter draw length regardless of the draw weight if all other design elements remained as they are/were. It has always been my understanding that some amount of "set" is unavoidable in almost every bow. If you start tillering with reflex in the bow or in this case flipped tips you may only lose a portion of the reflex you started with and end up with no "string follow" or tips that are even with the handle even though the limbs took a little set.
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Yup ... set happens.
A bow that has taken NO set AT ALL during tillering is IMO not working hard enough.
Other opinions may vary, terms and conditions apply, contestants must be 18 years or over ;)
Del
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Mike, I mostly agree, although an even amount of set all over doesn't tell us where to remove wood, it more tells us we could have left a little more behind... somewhere... somehow... during design perhaps.
Even set everywhere means that it's working too hard inner limbs and not enough in the outers.
Set will tell you everything you need to know.
Remember the bowyers bible mantra.
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Now I disagree. If only the inner limb is overly strained, the limb will take irreversible compaction there, with the balance of the limb maintaining its original profile. That's different than a limb taking an even amount of set the whole way along the limb.
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wood is not perfect,, if it shoots good,, it is perfect,, if you want to make the bow have a positive tiller ok,, but if it is shooting good,,,at full draw the tiller may be great, and just look not great unbraced,,, :) looks are not the final definition of a bows quality,, the way it shoots is #1
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Good point Brad. With no experience with all wood bows just wanting to prevent any irreversible damage possible so that hopefully I will be hunting with it this fall. It is shooting good enough but I don't know what might be possible so I plan to sang the upper limb a little and see if I can get the top limb bending more like the bottom.
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i have done that myself,, I like the bottom limb to be a little positive,, most the time is easier for me to get good flight with my less than perfect release,, when you are getting perfect arrow flight,, the tiller is pretty good,,