Can we hash this out? neg vs pos tiller***Clarification

[k-hat]

I'm a new bowyer so i'm no expert at all on this issue, but i've seen in come up in past posts with a lot of "this is what you do" but no "i tried that, and it screwed up my bow" or any evidential remarks.  Most guys on here advocate positive tiller (lower limb stiffer than upper).  Has anyone tried it the other way around?  I would normally go with what the experienced guys say, but it's not making sense with my physics teacher brain and what i've read elsewhere.  I know Dean Torges is highly respected in bowyer circles, and he has some interesting things to say about this issue here:

   http://www.bowyersedge.com/organic.html  


I would like to know what y'all think about what he says here, but ESPECIALLY about any experiences tillering this way.  And if i'm simply misunderstanding Dean, then please by all means tell me that too!        


****See post below for my proposed solution and experimental results    

[bigcountry]

I think your reading it correctly from Dean.

But the big thing is Dean himself told me he always makes his bows with longer top limb up to over 2" he says.  That could be the difference.

My goal is at full draw, for the bow to be balanced in my hands as Dean says.  

Everytime I use a tiller tree to get limbs bending perfectly the same, take off the tiller tree and pull back (with my 3 under draw), it always shows that bottom limb bending much more than top.

Only way to overcome is to make the top weaker.  I keep this up until the bow is balanced my hand with my draw, and it always ends up with top limb bending more undrawn.

[Shaun]

Dean is advocating dynamic balanced tiller - not negative tiller. Same length limb bows are problematic as he states and sometimes a negative tiller is required to achieve balance on these bows, especially with three under shooters. He has always advocated a shorter lower limb for dynamic balance reasons.

[bigcountry]

You know, I have read thru that article twice and its about confusing.  I am not sure what dean is advocating.

[Javi]

Originally posted by bigcountry:
I think your reading it correctly from Dean.

But the big thing is Dean himself told me he always makes his bows with longer top limb up to over 2" he says.  That could be the difference.

My goal is at full draw, for the bow to be balanced in my hands as Dean says.  

Everytime I use a tiller tree to get limbs bending perfectly the same, take off the tiller tree and pull back (with my 3 under draw), it always shows that bottom limb bending much more than top.

Only way to overcome is to make the top weaker.  I keep this up until the bow is balanced my hand with my draw, and it always ends up with top limb bending more undrawn.

That's why I've always thought it funny when folks say they can't tell the difference in tiller between 3 under and split.. To me it is readily noticeable on the first draw of the bow..

[k-hat]

So does it really just come down to fine tuning the tiller based on how it feels in the hand?  Applying this to my latest bow:  arrow rest is 1.75" above geo centr, planning a pistolish grip so hand pressure is concentrated about .75" above geo center, do i need a stiffer upper limb or not?  It makes sense that i should, either way i just finished putting tips on the nocks, so i'm gonna see how it feels, put a bump on my tiller block to represent hand pressure and draw it out.  But what am i looking for?  should tips line up evenly if i'm correctly approximating actual draw?  I guess i'm more experienced at bowyering than archery, so i'm not exactly sure how it should "feel"              

[vanillabear?]

[PEARL DRUMS]

I tiller both exactly the same at the same lengths and use my nock point and arrow pass as my adjusting points for tuning and balance. Sure is easy.

[Art B]

Give that same bow to someone else that grips different than you Pearly and "easy" goes out the window.

If you shoot a layout like Dean, and grip a bow like Dean, then Deans explaination is right for you.

If you read Dean's article real close, you'll notice that he's baffled to why and how same length limbs can functions properly according to his own logic. Well it can't, because he mistakeningly assumes that dynamic fulcrum is two inches above center, when in reality (say, using split fingers), dynamic fulcrum is centered or below.

That's why with Vanillabear's bow, the lower limb petered out on him.

I really like Vanillabear's approach though. Experiment for yourself, if it doesn't work, move on and find what does.

Too much taking someone's word for things these days. We seem to want things "easy"   :D   .........Art

[k-hat]

Thanks guys.  What you're saying makes sense as well, which means i may just be more confused!!  Anyhow, my bow is now with a handle layout which puts hand pressure .75" above ctr and arrow pass 1.75 inches above ctr.  I shot her some yesterday and today the negative tiller was a little more than it was yesterday.  Don't know what that means i should do?  I just shot some more down at cabelas (fun place!).  She shoots fine, doesn't feel off in any way.  Do i leave her?  Am i on a path to destruction?

Back to my other question:  If i put her on the tree with a raised shoulder and the fulcrum concentrated where hand pressure should be, and pull exactly as i would with arrow nocked, should it balance, and should the tips line up or should they not line up?  I'm fine with experimenting (hence my 3rd and 4th bows nuking on me!), just want to know what to look for on this one.

[Swissbow]

IMHO the lower limb should be stronger than the top one. Static tiller is only one side of the coin. Much more important is the dynamic behavior. How does it shoot ? Is the limb mass well balanced ? If the limbs are not well synchronized and the limb mass is not equal then the bow will have some handshock and a lot of the stored energy will not be transfered on to the arrow.
With a slight positive tiller ( approx 1/4 for split grip ) I get the best results and the bow ( d/r-design ) shoots without any handshock, even with very light arrows.

----------
Andy

[k-hat]

Well, as i said, she's shooting quite well.  The arras zip in and get good penetration.   Was gonna try cabelas chrono just to see, but it wouldn't pick up for some reason (can't be that slow    lol.  Anyhow, thanks guys for your input, and i'd still love to hear more/others.  It's good to hear some of what you've tried and works/doesn't work!  Good things to think about, even better if you can understand!

[k-hat]

BTW, i don't know about you guys, but when i draw with split finger at nock point on the tree, the bow rocks toward the top limb, UNLESS i place a fulcrum just under the arrow pass(about 1.25" above center).  Now if you strangle the bow in this dynamic, i can see it will put a great deal more strain on the upper limb, yes? since you are still drawing the string from just above that point.  Where as if you hold with pressure concentrated at the v of your thumb/forefinger, that will reduce the strain on the upper limb for this type (which means in any case it's gonna bear the greater load, so it should be stiffer?).  Gotta love it, tell me if my thinking is screwy:)

[Stiks-n-Strings]

I tiller on a fulcrum and try to replicate hand pressure and all that stuff. I get her close and start shooting her and final tiller with a mirror and in my hand. I do usually make my bottom limb shorter like Dean and go for a little stiffer than the upper limb.

 They shoot good, feel good and do what a bow is supposed to do so I leave it that. No since in overthinking it IMO. If I go getting into dynamics (whatever that means) I'll really be in a mess. LOL

 Stiks

[SEMO_HUNTER]

I shoot 2 under and I can actually "Feel" if the top limb is weaker or stronger.
For my 2 under style of shooting, a slightly positive bottom tiller works out the best for me.

But here's the thing, you can achieve an effective positive bottom limb tiller in several different ways. First was is by where you place your hand on the bow, and another way is the length of your limbs. Top limb a little longer than the bottom will achieve that positive tiller on the bottom.

Just gotta play around with it and what feels right, and shoots the best for you.

I want the web between my thumb and forefinger to be as geometrically center of the bow as possible and my arrow nocked about 3/4"-1" above that center.......basically right above my knuckle, and if the working part of the bottom limb is slightly shorter than the top limb, my bows will shoot like a dream.
That's just what works for me, you will be different from me or anybody else so all we can do it offer advice based on our own experiences.

[George Tsoukalas]

How it feels in the hand is important. I've made bows with stronger upper limbs, stronger lower limbs, bend in the handle bows, rigid handle bows, narrowed handle bows, wide handled bows, no shelf, shelf and probably some others I can't think of. I can't remember a miss where I could blame it on the bow.  Make a the way you think it should be made and that will make you feel better and you'll probably shoot better.    Jawge

[PEARL DRUMS]

Quit that crazy talk Jawge!

[bigcountry]

People can say, "just do what feels right", but what one has to remember is new bowmakers do not know what feels right until have went thru many wrongs.  

So, newbies, need some guidelines to get started.  And ultimately thats what this thread is about.  I think older folks forget what its like to be new.  

For instance, when I started, I had severe trouble reading tiller.  I had to use all kinds of tools, like the "kizmo", digital cameras, photoshop, etc.  Now, I think I can spot a flat spot 100X easier now.  I remember experienced makers, saying, "just draw it in the mirror and make adjustments".  That seemed like an impossible task. I had to train my eye what to look for.

[Roy from Pa]

Tiller for a 1/8th to 1/4 positive tiller on top limb , then fine tune to your grip.

[matts2]

As a newbie, I am more lost now then when I first started.  Definitely a lot to read and read and read again to understand.  I am thinking now I need to get out the video camera and draw all my bows with different finger grips and record how it all feels.