Well I discovered today that I think I like to shoot 3 under. my groupd improve quite a bit.
Any way when I build a bow I usually build it with the bottom limb 1" to 1.5" shorter. I have always shot split finger.
Do I really need to be concerned about tillering for three under when I build my next bow or will I fine just going like I'm going?
Stiks
Good question Stiks. I've been wondering somethign similar. I'm thinking you get the same bend profile on bows tillered with limbs that are the same length. And you build them with even limbs for three under shooting. Is that right?
Thats how I do it B glass.
There have been some past posts where some great theory has been shared on this question. I think the best thing to do Stiks is take your bows out and shoot them 3 under....if they still shoot the way you want them, perfect. If the bottom limb is recovering more quickly than the top, then start building them with less positive tiller...I try even tiller to slightly positive (1/16th positive tiller) for 3 under.
Sounds good.
I was out shooting with my youngest girl today and told her to try it cause I thought it might help her. I was shooting the character bow I just finished and tried it myself and it was putting them in there better than shooting split finger.
Gonna try it with some other bows. I may have to start building them for three under.
They say if you are building a self bow that it is important. It is more gimmick than necessity on laminated bows.
BigJIm
Chris, I shoot both 3 under and split finger. I tiller all my bows with a slight positive tiller for 3 under and just a touch more positive tiller for split. However, that doesn't matter near as much as raising your nock point and raising the brace height slightly when shooting three under. That's made the most difference for me. So, spend a little time tuning your bow, but don't worry much about tillering it for a particular finger orientation. That said, I do adjust tiller for shooters who have a high or low wrist position in their bow hand. That'll throw the tiller out of whack faster the three under/split finger.
Best of luck!
I sometimes think about tillering differences for split or three under, and it drives me crazy. Then I see guys post about tillering their bows on the tillering tree, and they are pulling from the center of the handle. Myself, I like to place the tillering pull rope about where the arrow nock will end up being on the bow string when you shoot it. Afterall, that is where we will grip the bow string when we pull it back to shoot. So all I can say is Stiks, I still don't know. LOL
Striving for tiller perfection is always good and shouldn't be discouraged, but,,,,
Regarding selfbows: Would primitive man be concerned with positive tiller? Does it matter at 15yrds? In my opinion, No, not enough to matter!
To me getting too technical takes the fun out of it. I do believe that each bow shoots differently. Finding each bows sweet spot w/brace, nock point, arrow spine and adjustments to shooting form is the fun part to me. Some I shoot 3 under, some not. Some I shoot with a heavey cant to the bow, some not.
Besides, I believe with humididty changes, winter to summer the wood expands and contracts to some degree, surley affecting your tiller & possibly string allignment if you've ever put any heat bend in the bow. And if not, the shoot in period of the bow will change things a bit which would mean some readjustment to tiller.
I know hand shock is an indicator, but how the heck else can you tell one limb is recovering quicker than the other? Slow motion video?
Regards,,, It's early before work and I probably should have kept my mouth shut as I never get into these technical discussions.
Ok, so can I ask a basic newbie question here? Which direction is "positive" tiller?
To the last post, one of the reasons I'm finding self bows so addicting is that not knowing what you guys are talking about, I was still able to make something that shoots well (even if a bit light.)
Joe,
I ain't gonna lie, I kinda feel the same way. LOL
I think I will tiller till they look and shoot good and leave it at that.
Canopyboy positive tiller is when the lower limb is atouch stiffer than the top and will be indicated in measuring from the string to the limb a little past the fade. For example the top limb would measure say 6.25 from string to limb and the lower would measure 6 giving you .25 positive tiller. (At least I think that's right)
Stiks
When I was placing a shelf on a recent self bow I experimented with location in the same way I would with nock point height during arrow tuning. I put the shelf dead center on the handle, shot it, then moved the shelf up in half inch increments and reshot to note any differences in performance. I also flipped the bow upside down and did the same.
There was very little, if any, noticeable difference in actual shooting even though tiller may be noticeably changing with the varying changes of pressure points from moving the bow hand up and down.
Also, I shoot split finger and tiller by actually pulling the bow by hand and using a mirror to note limb affect because hand placement and pressure affects tiller.
Try it sometime...then flip the bow upside down and note the tiller change. The positive tiller, for example, may not stay with the top limb as it is flipped, it may move to the new top limb.
;-)
I'm one of those guys where the techincal stuff puts the fun into my hobby. On the other hand, I've found no substitute for trial and error, just shooting the bow during the final tillering and finesse stage. While potentially not as important for glass bows, where there's gobs of extra work capacity in the material, getting the tiller to match the archer as close as possible pays dividends in performance, handshock and quietness.
That said, there's no harm in understanding the fundmentals of how a bow works, as if you are in it for the process, moreso than the product, there's always something to learn, or see differently. Another way to say, I've never built a bow that I didn't think I could build the next one better.
If your arrow pass is 1" to 1.5" above dimensional center, the upper limb is shorter, unless your handle is shorter than 3" total. The arrow doesn't know the "extra" lenght is the handle, versus the bending portion of the limb, from the geomtry and physics pov. Fold your bowstring together at the nock point and note the longer string segment. That's what the arrow sees at the start of the power stroke, a long segment (lower) on a long stiff spring, and a short segment on a short weak spring. The more asymetry, the more positive tiller you need... bearing in mind nock point is just a proxy for where you draw the bow, so drawing three under is counter intuitive, as it frequently take a higher nock point but actually induces less asymentry, by the drawing force being lower on the string, thus less tiller.
I don't actually know what I'm talking about, I just type this stuff to read challenges to it, which I welcome, to help either strenghten, or test my understanding of it.
Ok, this is starting to make a little more sense to me. At least the positive tiller and why you'd have some.
But now the engineer in me is trying to run through the dynamics of this 3 under vs split thing. Yes, when you are pulling back and when you are at anchor, the difference can affect your effective center of pull. Three under brings you closer to symmetric assuming the same distribution across the fingers. But once you release, the center of force quickly transitions to the arrow nock. So for the majority of the arrow's acceleration, the tiller is really controlled only by the arrow and the two different release methods shouldn't make a difference. No?
I like the engineer in you. I've chased that bunny trail a bunch, mostly in the context of nock travel, up and down, and the interlationship with limb/string lenght and static tiller. Seems like the more asymetry, the more tiller, the more nock travel. At one time "negative" tiller was suggested as appropriate for the typical arrow pass above center construct, and I thought effect of nock travel would negate it's use, even though it seemed plausible in terms of balancing the strain on the upper limb, relative the lower which gets a free ride on two accounts, being stiffer and longer.
On the three under question, maybe because it gets more "free travel" before the lower limb "sees" the arrow?
This stuff breaks my brain everytime I entertain it. To be so "simple" traditioal bows are maddening complex to model, imho.
You guys are giving me a headache! :banghead: :p
So when John Scifres shows us a picture with the two limbs of a bow transposed, he is NOT tillering for a positive tiller?
How was the bow tillered that you noticed the improved groups? This may answer your question for you. I would just go with that because it worked.
The other route is to build a bow like the one mentioned above with the other tiller in question. Then keep the one you shoot better with and give the other away as a present.
I can shoot this bow either split or three under, I just noticed a little better groups with three under.
It's tillered with lower limb a tad stiffer and the lower limb is 1.5" shorter than the upper limb.
I'm like Bona this stuff is giving me a headache LOL. I like simple answers and like to just keep it simple but that's just my flavor. All the technical guys are needed though or we would not be where we are today in this fine craft.
Stiks
i cant remember where i read it but i read that you should make the top limb longer for three under shooting anyway, as it puts more of the force on the lower limb.
Yep,,, :readit:
Yea B.Glass,,, wonder if John will chime in on the subject?
Looks like I opened a big ol' can of worms Joe :laughing: :laughing:
Well most folks add a positive tiller to their bows when shooting split finger. So if your tillering a bow for 3 under, then why shouldn't that bow be tillered with an even more positive tiller? Stiks, ya learn anything yet? LOL
Take a 66" 5/8" PVC pipe and insert it in a 4" 1" ( i think it will slide in there, it' s been awhile) PVC pipe for the handle.string bow to resemble a d shape bow. Move the handle up and down and create all types of tillers scenarios . You will find your answers :) . At least I did when I started makin bows
Yeah Roy I've learned enough to answer my question I guess LOL
Joebuck, that's a pretty good idea.
Now arguing for the sake of arguing is sometimes a worthy pasttime. And fun to boot if all keep this in perspective.
To be honest, on a 62+" bow, I can only barely see a difference in placing the hook of my tiller tree 1/2" lower on the string which is about what 3 under does for my shooting that length bow.
Take into consideration that best flight is attained by raising the nock point at least 1/4" higher and you really are talking very little difference in where the bow is pulled. Now on shorter bows, the relative difference is greater.
Still, all-in-all, that's graduate level work when most of us is freshmen :)
WARNING -- Some may not want to read the rest of the post unless you're masochistic or have already taken painkillers...
QuoteOriginally posted by DCM:
I like the engineer in you. I've chased that bunny trail a bunch, mostly in the context of nock travel, up and down, and the interlationship with limb/string lenght and static tiller. Seems like the more asymetry, the more tiller, the more nock travel. At one time "negative" tiller was suggested as appropriate for the typical arrow pass above center construct, and I thought effect of nock travel would negate it's use, even though it seemed plausible in terms of balancing the strain on the upper limb, relative the lower which gets a free ride on two accounts, being stiffer and longer.
On the three under question, maybe because it gets more "free travel" before the lower limb "sees" the arrow?
This stuff breaks my brain everytime I entertain it. To be so "simple" traditioal bows are maddening complex to model, imho.
Yeah, see, this is the kind of stuff I contemplate while going to sleep at night. Which is probably why I never get a decent night's sleep.
Once the string is tight to the arrow, it is the arrow nock location that would determine the tiller of the bow during the rest of the shot. But there is that transition period between where the string is released, and where it draws a tight V to the arrow. And how that transition occurs can affect where that nock actually ends up on the string assuming you don't have top and bottom nock points.
See if this makes sense to anyone:
At the instant of release, imagine the back of your string (or bottom of the "V" shape) is actually about where your middle finger was, and the arrow nock is slightly above that. The action of the lower limb is pulling against that slack in the string ("free travel") and so accelerates very quickly with really only its own mass to work against. The upper limb sees the arrow nock, but since it's not in the bottom of the V, it's relatively free to travel down the string until it reaches that bottom (assuming your nock isn't that tight.) In this sense the top limb is also accelerating only against the slack in the string and the arrow starts to slide down the string slightly.
At the moment the string slack is gone, a bow with positive tiller will have a bottom limb moving forward faster and with more kinetic energy than the top limb. This leads to unequal force at the arrow nock point, and the nock would want to slide back up the string slightly until it hits the nock point on your string.
A three under release moves the bottom of your string V farther from the arrow, which would cause the arrow to slide down the string farther before the slack is gone. Adding a bit more positive tiller would therefore be useful in sending the arrow nock back up the additional distance to the nock point when the slack is gone.
Ok, that is all well in good if your arrow is really seeing low enough friction to slide on the string. With a tight nock this might all be moot. But the forces are high, so maybe... When I got up this morning, I decided to go look. My new little self bow is sporting an ad hoc spectra braided string with some serving that doesn't really bring it anywhere near tight in the nock. It's also showing a little wearing in after several hundred shots. And you know what? The wear area is about twice the thickness of my nocks. It definitely looks like the nock is traveling on the string slightly at release. A bit more positive tiller might help keep it tighter to the nock point....
All said and done though, I think we're talking about something that happens in the first few fractions of a second during the shot with effects that are small and probably overcome by other factors by the time the arrow is clear of the bow. But what fun is that?
:coffee: Ok, sorry about that. I just couldn't help myself.
If you want to do some futher reading on the subject then do a search for "arrow pass". Or check out this thread http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=002170 .ART B
You know I'm just play'n right? :D
Really, when you can transpose pics of the limbs and they are nearly identical, you have tillered with no positive tiller. Yes?
A lot of times, the upper limb will be longer so, in effect, despite a nearly perfect overlap in the ghost image, there is some amount of positive tiller. I like 1/4" or so it seems. Final tiller is always done by shooting. If the overlap is perfect on the tree and the computer but the bow shoots like crap, then something is wrong.
Geeze I'm getting a headache. Might just go out and buy a pair of wheels and see if I can do away with this tillering problem we have:)
LOL, Not..
A slow motion video, taken of the side of a stickbow being drawn and shot would be really cool.. Anyone know if their is such a video?