I buy bows all the time. Most are tillered split and shoot them 3under. My nocking point is usually .5" over center with 3 under.
But I finally get a zipper that was tillered 3 under. And my nocking point is now like .25" over center.
Now, this is messing me up shooting my different bows. As my POI with the zipper is very high. I am thinking about adding more wieght to get it shoot more like my other bows.
But what does it mean when bow makers say its tillered 3 under.
bigcountry:
A bow tillered for 3 under will have more positive tiller on the upper limb. This will allow you to use a lower nock point. Its all about finger placement on the string. When you lower your fingers on the string the lower limb bends more, so you need to compinsate by tillering more the upper limb or raising the nock point which will raise your finger placement on the string. In order to achieve proper arrow flight both limbs must bend equally, otherwise one limb will give more thrust that the other causing porposeing of the arrow.
Bob
Thanks for the quick reply. So if I understand right, if I measured the tiller on my bow that is tillered for 3under, I would see the top limb bend more, or the distance between limb and string would be less on top limb?
I have never tillered a bow, so I am not sure where a bow maker would start pulling back (on the string), but I suppose if I requested a 3 under bow, they would start drawing on a drawing board, little below center for 3under and right at center for split?
QuoteA bow tillered for 3 under will have more positive tiller on the upper limb.
Are you sure of that? That's not what I've always understood it. When a bowyer tillers a bow for 3 under, typically they'll tiller the limbs even to no more than 1/8" positive on the top. Split finger tiller is usually around 3/16" to 1/4" postiive. A very slight difference, but enough to vary the nock point location. I've had a few tillered specifically for three under, but most of mine are standard tiller. I do have my hoyt set at even though.
So, You can shoot a bow three under that's tillered split by raising the nock point slightly. It would seem that it would be difficult to shoot a bow tillered three under with split fingers as the nock would need be moved to at least even..??
It also matters as to where you put the handle / pivot point when building the bow. Some will lower the handle putting the rest and fingers closer to dead center on the string. If I remember right the PSE Coyote is like that. The pivot point below dead center. Measure a bunch of bows, they are not all the same of course.
bird dog....You'd be surprised how well a bow with even tiller shoots with a split finger release.
When ever I order a bow I ask for even tiller. Easy to set-up for shooting either way and stays quiet.
So what exactly does a "more positive tiller on top" mean? Does that mean when tillering the top limb will have more or less the distance to the string than the bottom?
and when tillering a bow, does a bowmaker usually tiller with the arrow cutout in the center or center of the handle?
Thanks for the replies.
More positive tiller means the distance from the fadeout to the string (measuring device is 90 degrees with the string) is more than the bottom limb measurement. Bow design will dictate where the shelf is located. Tillering is measured from the fadeouts, or where the most bend occurs at brace height.
Chris: Yes I'm sure of that, there is a lot of misinformation on the net!!
Bowdude: Is also correct the way you grip the bow can and does effect tiller. more heal pressure will cause the bottom limb to bend more, than if your use a high wrist grip.
Keep in mind positive tiller is measured in 1/8's" of an inch. most bows will be positive by 1/8" because of the way I shoot I prefer 3/16" positive tiller. Zero tiller will work, the only difference will be a slightly higher nock point, I prefer my nock point lower.
Bob
QuoteChris: Yes I'm sure of that, there is a lot of misinformation on the net!!
Didn't find it on the net. Was informed by a reputable bowyer and a shooting coach on seperate occasions. Hmmmmm, looks like we need another opinion from someone who makes bows for a living. Anyone bowyers care to chime in on the subject?
Most bowyers make the tiller even for someone shooting 3 under and an 1/8" or more positive for split finger.Truth is except for the nocking point either works fine any way you want to shoot them because when you move the nocing point you change the tiller just like when you change your grip..The only time I worry about it is on a real short bow.Then I like more positive tiller just for the way I shoot to keep my arrow level on the shelf or rest.
On a takedown, where you measure this positive tiller?
Bigcountry - Tiller is measured from the point where the fades stop.
On the bows tillered for split,(3/16 to 1/4) but shot 3 under, the high nock point is the result of the finger pull point being lower. The nock has to ride higher to make up for the lower limb being pulled farther and thus reacts harder. Actually it doesn't now that you have moved the nock up because the high nock point has moved your fingers higher. The nock has forced you to migrate toward the opposite limb with your hand to get equal force on the limbs. Just as if you were shooting split finger.
The best scenario for a zero tiller bow would be to shoot 2 split fingers draw shooting thru your bow hand at the center of the bow. Can't be done. But close is good enough as we can adjust it with nock point as was described above and Vermonster has proven it.
The best way to keep tiller to a minimum would be to put the pivot point slightly below center with a low arrow shelf. Whether you shoot split or 3 under does not matter as it will force you to move your hand to the required location to get good arrow flight as described above.
Some bowyers will put the pivot point dead center of the bow, yet this is not a requirement for a good shooting bow. Some Japanese zen bows and Mongol? horse bows have much shorter lower limbs, but the rest of the bow is designed to make this work. It all boils down to one thing. Push/pull must be equal on both sides of that arrow nock or it will get propelled incorrectly. Wow thats a lot isn't it?
Thanks for taking the time to answer my questions. When people refer to fade, are they talkin about there the limb is basically same thickness all the way up to the nocking point?
The fades are the wedge in the middle of the limb where they mount to the riser. As it goes off into the limbs they... fade... away...
(http://i146.photobucket.com/albums/r257/bow_dude/fades.jpg)
Bob; I'm afraid i'm with Chris on this one. Positive Tiller generally means the distance from the limb fadeout to the string at 90 degrees is more than the distance measured at the same spot on the lower limb, approx. 1/8 to 1/4' max. it can be measured in8th or 16 teenths' it doesn't matter. bows shot 3 fingers under are tillered even on both limbs or 1/8th more on the lower limb depending on the amount of pressure one puts
on the lower limb, for example by heeling the bow. Actually the correct term for "tiller" is "static balance" , because the string is at rest when this is measured. The greatest benefit of tillering for 3 fingers under is a quieter shooting bow, other than that i don't find much if any difference.
Thanks bowdude for the pict. Thats what I thought. And I see that on my longbows, but on other takedowns, I do not see that.
Does anyone ever measure tiller anywhere else or only here.
On tds you can just measure at the limb butt next to the riser.As long as it is the same place that you measure from it will work.
What james said.
what sergio said both times. :thumbsup: :coffee:
Ok, I measured the tiller on my martin savannah and my martin dreamcatcher. Both are dead even at the fades and both, I nock the top of the nock of the arrow 1/2" over center shooting 3under.
On my zipper, I measure more than a 1/4" difference with the top being 8 1/4" from limb butt to string and bottom being 7 7/8" from limb butt to string. So that means my zipper is tillered for split finger? But strange thing is my zipper likes the nock point to be only 3/8" over center shooting 3 under!!
Sorry for these stupid questions. But seriously, you guys are really helping me.
Where is the center of the pivot point??!!
Sorry man but it is relative. So is length of working limb, is one fade farther from center or equal, etc. You can't focus on 1 feature and say ok this is right wrong or whatever.
But to add even more to the complexity, the top limb unbraced is 25" long and the bottom limb is 24.5". Unbraced, the zipper is 58" long from nock to nock point but shelf is 28 1/2" from top of top limb and pivot point on handle is 29 1/2" from top of top limb.
I am trying in my head to figure out how this thing is balanced. Ah shoot, lets just it and be happy.
On my Martin Dreamcatcher that was tillered even at the fades I measure 56" total length from tip to tip, with pivot point right at 28". This bow likes its nocking point (top of the arrow nock)to be 1/2" over center (pretty high).
Reason I am asking all these qeustions is I am taking a bow making class and would like to understand the basics before I start cuttin. I am also reading thru the bowyers trad bible vol 1 and 2.
I don't know no "Tillered 3under". I just know me, "3under"!
Dang,
I thought you guys shot these bows because they were simple.
For years guys have been telling me to get rid of those complicated training wheel bows and go simple.
I'm not sure I'm smart enough for this.
My head is going to explode.
Well, hoyt it is simple if just buyin them and shootin em. But I plan on building them. Or attempting
QuoteOriginally posted by bigcountry:
Well, hoyt it is simple if just buyin them and shootin em. But I plan on building them. Or attempting
Who knows Big Country. I may be buying one of your bows someday. :archer:
Good Luck.
Let me ask a question or give my thoughts on this. If a bow is tillered so the bottom limb measures say 1/8 less than the top. Seems like most would agree it is tilled for split. I think it is done like this because most of your fingers are placed below the true center and you are pulling closer or more on the the bottom limb. Therefore you need the bottom limb "stiffer" hence the 1/8 less measurement,
Now if you shoot this same bow 3under, your fingers are even closer to the bottom limb because you have now moved your hand down the string by one more finger width and therefore pulling even more on the bottom limb. So why wouldn't this bow need to be tillered say 3/16 or 1/4 less on the bottom limb therefore makeing it even stiffer to equal out the hand moving closer to the bottom? Seems logical to me from a physics standpoint? This is how I have been doing the bows I have made and it seems to work better for me.
Granted, My bow building experience is limited but it seems logical to me? Just thought I would see what some others had to say? Steve
http://www.goarchers.org.uk/mechanics/
Click the menu [Bow Mechanics], then [Tiller].
Positive tiller compensates for drawing the bow string, necessarily as has been stated, above the fulcrum of the bow hand. In the most general terms three under tends to mitigate this effect and consequently requires less positive tiller to compensate.
DCM, I can't seem to find that webpage. But I appreciate it.
Sorry, I think the server is down right now. I'd try it again later.
I google "tapley tiller" and get "Tapley, Joe - Topics on Bow Mechanics -" as the title when I want to find it and don't have the url handy. It was working this morning. This is a topic which can melt one's brain. Tapley's explanation has helped me to understand the underlying dynamics enormously.
David....That's a good site. I'll have to book mark that one for future reference.
Are ya'll going to be at Twin Oaks in May?
I hope so Chris. Fighting chemo/radiation treatments for colon cancer which finish on that Friday. Probably, even if I'm draggin' arse and for no other reason than to see folks. Probably take the Monday off and stay over versus our traditional take the Friday and leave early Sunday. Hopefully will have opportunity to catch up with you Sunday morning that way. Hope all is well with ya'll.
Dang brother, first I've heard about you being sick. I'll keep you in prayers.
We've got plans to be up on Saturday this year. We're planning to pitch the tent and hang out through Sunday. Hope to see you there.
No worries dawg. 90% survival rate. I don't go parading my stuff around, but by now it's just old hat. Had colon re-section 6 wks ago, diagnosed in Jan. Large hassle factor, wearing a portable chemo iv around my neck (through a porta-cath) 24/7 for 5 weeks w/ radiation doses every weekday, then 2 days on the "bag" every two weeks for another 24 weeks. But I'll be done with the treatments and have it all behind me by archery season, well mid October. Life comes at you fast. LOL
Warden415
Almost, but remember that the center of the bow is not the arrow shelf, it is probably an inch or more lower depending upon the type of bow, therefore just the opposite is true. you pulling above the fulcrum and are bending the top limb a little more than the bottom limb at any given drawlength. The difference in tiller is to compensate for this. It seems to me that the further your string nock is above the center of the bow, the more you would have to compensate. Some bows have there selves an inch and a half or more above center and the string nock may be another 1/2 or 3/4 inch above that. Even if you shoot 3 under you would still be pulling well above the center of the bow.
I had never thought about tillering a bow by shorting the length of the lower limb. This would effectively move the fulcrum up. Hmmm.
Brad
"tillering a bow by shorting the length of the lower limb"
The beauty of this alternative in a wooden bow, in paricular one where you want to minimize the overal lenght, is you help relieve the strain on the upper thru the geometry, bringing the string angles more into parity by virtue of nock point nearer to dimensional center of the string. In the so called "even" limb design, where the arrow pass is 2" above center on a 4" handle, the upper limb is actually 4" shorter than the lower from the string's perspective AND is required to bend farther.
Notable bowyers have tried to advocate this alternative, and it is well practiced in antiquity, but for some reason there seems to be much resistance to the idea and much confusion circulating about it in more recent times. Evidently folks value the ability to "flip" a selfbow upper for lower limb at some point during it's construction over the theoretical benefit of arrow pass nearer dimensional center.
In a glass bow paradigm there's so much extra work capacity at hand in the material I'm not sure it matters, beyond the obvious need to give the bow enough tiller to be tunable to the intended archer's style.
DCM
I'm curious.
When making a bow with a shorter lower limb, would you adjust the demensions of the limb core accordingly?
In otherwards if I am making a take down bow would I want to reduce the limb length by shortinging the butt protion of the limb or the tip portion of the limb?
Brad
Sorry Brad, I've only made 2 glass bows from scratch. My intuition about core thickness would be to have the lower limb be relatively less thick, or less stiff, less positive tiller. But honestly I'd personally take this small adjustment with sanding over using stack height. Best I can figure, the limb you get out is a crap shoot at best, within the tolerance of stiffness you'd need for tiller, given a particular set of lam stacks and glue up cycle. Best to fall back to the tried and true method, figure the stiffer limb out once they are made and adjust if necessary.
I'd adjust the effective lenght with the riser, rather than the limb itself, by placement of the fulcrum and arrow pass.