Hand Shock

[Jaenak]

Oh boy, that complicates things.  I forgot about the grip style effecting the limb strength.  So, would it help solve things if a person made the handle portion, figured out where the nock would be on the string in corilation to the grip and pull style (split finger or three under), then attached the string from the tiller tree to the nock point and adjusted the tiller according to what the tiller tree showed from the adjusted placement of the tiller pull string?  Then the tiller tree would be pulling the bow string right where your fingers would be pulling the bow string later and you'd be able to get an accurate measurement from the tiller tree then.  Would that work or am I just lost on this?

[Pat B]

A tiller tree is too static to get a "true" feel for the tiller. That will come with experience.  The way your hand(or any other shooter)cradles the bows handle isn't any thing like a tiller tree's  bow rest. Dean Torges tried to improve on this with a radiused bow rest. I find this hard to deal with in real life so I have learned to adjust. By looking at yourself pulling the bow to full draw in a large mirror or having someone take a pic of you at full draw will give you a better view of tiller...but a posed pic is different from a shot taken at a deer or even a target.     Pat

[ber643]

I did that on my Holmi, at the suggestion of Glenn and Dano, cause it made sense to me to at least try - it's do-able  and makes some difference (of course). You can see it, and read about it, near the last steps of my thread/build. Whether or not it makes enough difference to play with is gonna be for each person to decide for themselves, I would think. For those with the experience and instincts of folks like, friend Pat, they develope other ways to reach the same point or results, such as he mentioned. So, "many ways to skin a cat" comes to mind, and I, for one, as a rank amateur, love hearing, considering, discussing and trying them, or not - don't you?    

[DCM]

I use a single point of contact, versus a cradle, to suspend the bow handle.  Mine is a lag bolt wrapped in leather so I have a surface of about 1/2" to rest upon.  I find I can balance the bow at about 1" above center or thereabout and adjust the position of my draw hook to fine tune the balance.  My draw hook winds up somewhere below the final nock point, between an inch to zero I'd estimate.

The primary method for determining how well the bow is balanced, in terms of the balance of stress between the upper and lower limb, and even the bend within a particular limb, is the set taken from shooting by hand.  The earlier you start shooting the bow by hand, versus working it on the tree, the better matched your finished bow will be to your shooting style.  I generally start shooting at least 4" before final draw lenght.  And I try not to work the bow much on the tillering tree, or shooting for that matter, until I'm satisfied the load is well balanced and each entire limb takes an equal amount of set from work.  I also prefer lots of shorter workouts, with enough rest too fully recover the set, so that I don't permanently set the bow with some inherent flaw early in the tillering process.

All this being said, I'm not sure how it relates to hand shock to be honest.  I'd rank outer limb mass and low stretch string above tiller "timing" (more or less positive tiller) for it's relative influence on hand shock.  

Perfect tiller, in as much as it can be achieved, has other, more compelling justifications anyway, predominantly premature work fatigue and the overall design requirements.  More specifically, a really short bow should bend generally more on the inner limb, and longer visa-versa, imho.  I find full arc of circle tiller not necessarily as desirable in as many cases as not.  In fact one could make a compelling argument full arc of circle might be more likely to contribute to hand shock than other forms, based upon the idea (demonstrated in high speed film) that it's the mid limb area which tends to distort or "bulge" the most at the end of the power stroke.  Full arc of circle would tend to exaggerate this, I would think, by virtue of the mid limb being necessarily weaker relative to the other two forms.

[Art B]

I appreciate the offer Glenn, but like yourself, I have many bows that are being neglected also. I've given many bows away over the years so I'm very aware of the treatment they receive. Hard to make a selfbow bomb-proof but I do my best.

About one tenth of what I use to know is about all I have left Bernie (no kidding).

I try to keep my bow building as simple and as quick as possible. I use a tapering method to get the limbs bending and pretty much all I have to do is scrape the entire limb from tip to fade (no tillering gizmo used for selfbows) to reduce weight. By keeping the bow's static balance in line with it's dimensional center at the floor tillering stage I know I'll be very close to having an even tiller at brace height on the tillering board. Once the bow shows even tiller on the tillering tree I go straight to full brace height using the short string. From there I draw the bow by hand keeping an even tiller to just under desired weight. Then I'll set the appropriate tiller for the bow.  -ART B

[DCM]

Art, how do you determine the appropriate tiller for the bow, I'm assuming you mean the degree of positive?

Reason I ask is I'm not real sure how I do it myself, other than trial and error by shooting manners and watching for set on one limb versus the other, giving much more priority to the latter.  I'm afraid I've become so used to doing the same thing over and over, I'm not real sure what or why I do what I do.  I think the set issue is the primary driver, and the shooting manners naturally follows.  I know most of my bows wind up with about 1/8" of positive, even when the offset of the arrow pass to dimensional center can change by as much as 1" from one bow to the next.  Kinda makes me wonder whether or how the handle config effects the amount of positive "required."  I've always assumed, based upon what I've read about bow mechanics, that more offset of arrow pass from dimensional center would require necessitate more positive tiller for good shooting manners.  Curious about your experiences with that.

[Art B]

Setting the appropicate tiller for me is a combination of drawing the bow my hand (keeping an even tiller while having even strain on both limbs by using proper hand placement) and shooting the bow. Once I feel even strain on both limbs I then apply a little heel pressure to the bow's handle to make sure I feel the lower limb stiffen ever so slightly. This will on average show a bow with around 1/8" positive tiller as you mentioned.

The shooting part is important as well. If your bow shoots where you're looking then you're ready to shoot the bow in. But if the bow consistantly shoots low then the lower limb needs strengthening (or weaking the upper). This is what works best for me for the handle (straight) style I prefer and type shooting I do.

Due to the greater angle between the bow hand and drawing hand created by the higher arrow pass this will cause more "heeling" of the handle David. So yes, on most bows I will beef up the lower limb creating more positive tiller. Heck, I do this deliberately when I'm making a give-away no matter the arrow pass placement. But in spite of instructions most folks will heel these bows to death destorying the bow's profile. Better that they feel a little kick in the bow then having a bow that will be useless sooner than later.

But there's much more to tiller than that with the higher arrow pass. Higher arrow passes creates an asymeticial string which can be compared to a short and long tillering string. Upper limb's string angle (long tillering string) strains enter limb. Lower limb's string angle (short string) strains mid to outer limb. A little balance is needed here to equal the strain to both limbs. Your thougths on that David.       ART B

[George Tsoukalas]

Nothing is going to simulate the actual shooting of the bow. I go out and draw the bow trying to sense the handle pressure. Is it even or is the bow tipping in my hand. When I shoot I forget about hitting the bull. Instead I try to feel the limbs as they slam home. Do they do so at the same time or are they out of sync? Is the arrow release silent? This is all part of the tillering process and through all of this I never once used my eyes. The bowyer that uses only his eyes to tiller is 1/5 the bowyer he could be. Use as many of your senses as you can.    Jawge

[Art B]

Yeah, you're right George. Positive/negitive tiller is more a feel for balance which can't be achieved on a tillering tree. My tillering tree is only used to exercize bows over my draw length. My eyes are going bad George so now I'm down to one tenth of 4/5 of a bowyer. Talking about having to work by feel.......................:)ART B

[George Tsoukalas]

Sorry to hear that, Art. I'd happily be 1/5 the bowyer you are. Jawge

[ber643]

You've got that right, Jawge, and that's far more of a statement, coming from a bowyer like you. How I wish I had started building bows when I was waaaaaaaaaaaaaaay younger - but I'm sure glad my friend, Mike, wouldn't stand for me waiting any longer, or my saying that there wasn't time enough left anymore, so at least I've got the thrill of doing a few -    

Tomorrow AM I go Deer hunting with my own Osage  self bow, "It", - never woulda thunk it -  

[Art B]

You are too kind George! What little I know won't fill even one of your boots.    ART B

[DCM]

Art,

"Higher arrow passes creates an asymeticial string which can be compared to a short and long tillering string. Upper limb's string angle (long tillering string) strains enter limb. Lower limb's string angle (short string) strains mid to outer limb."


My thinking is like yours.  I love your analogy, which describes perfectly the asymetry inherent in the so called symetrical, or 2" above center handle config.  It's asif the lower limb is that of a longer bow, attached to an upper limb as if from a shorter bow.  By making the lower stiffer, we make it "seem" shorter to the upper, essentially inducing "stack" but as true draw weight from the outset in order to balance out the stack, in the classic sense of the word, the upper limb sees by virtue of it's wider string angle.

[Glenn Newell]

At the end of the day the proof is in the shooting. You can make up a fiberglass bow and before the shelf and window are cut in mark 1.25" above centre where the arrow will pass and shoot the bow in the positive tillered position and then turn it up the other way and shoot it in the negative or reverse tillered position and see what you think.
With a selfbow that has been made with even length limbs and it is shot 1.25" above centre and has been positive tillered will take more set to the top limb because it has more pressure placed on it by the shorter string length...Glenn...

[Art B]

I know what you're saying Glenn. And I'm sure if your tillering method works fine for you then that'd OK by me. Got no ax to grind about the tillering method you use. Best I can do is explain why my method works for me and you can draw your own conclusions.

First and foremost I want even strain (both limbs sharing equal work) on both limbs. When this occurs both limbs will take equal set. I'm sure you will agree with that. If I get more set in the upper limb vs the lower then I realize I'm over stressing that limb (doing more then it's share of work). Here is where logic would say to beef up the upper limb to help to compensate for the over stressing (adding even more work-load to the upper limb and taking away from the lower limb)thus producing a stiffer upper limb or negitive tiller. Problem with that line thinking is that I now have one limb doing more work then the other. So that doesn't solve the problem of having equal strain on bow limbs. So to solve the problem I have to take some workload from the top and add to the bottom limb to even the strain back out. Now I have both limbs carring the same work-load and taking even set. And because of the the extra stress added to the lower limb by the forces created by the bow and drawing hand it will need to be slightly stronger to help maintain it's profile over time. I just added that last sentance to demostrate the need for positive tiller. In reality you shouldn't notice the stronger lower limb or uneven set if proper grip is used.-ART B

[Glenn Newell]

Art I don't any have any axe to grind either or how somebody wants to tiller their selfbow. I use to make my selfbow with equal length limbs and index finger of bow hand 1.25" above centre and tiller the bow with positive tiller. But I have always found that the top limb takes more set than the bottom. I have just found that since I started shooting equal length limb bows with negative tiller or reverse tiller the bows will take equal set and the bows are much smoother to shoot. Even the fibreglass bows made the same way are much more pleasent to shoot with reverse tiller. If you change your hand placement on the bow up or down tiller has to be adjusted to accomadate the different strains placed on the limbs. The closer to the centre the arrow passes the less strain on the top limb and more strain placed on the bottom.  Low and high wrist grips will do that also as well as split fingers and three under. There is not only tiller to consider but how does the bow balance in the hand when it is being drawn...Glenn...

[Art B]

I think that's what most folks fail to understand Glenn. Just because something works for one doesn't necessarily mean it's suitable for all. We all got our own needs and requirments. Heck, most of us are just doing this to suit ourselves anyway. Have fun! -ART B

[Glenn Newell]

No worries Art, it's been a good discussion anyway, back down to the shed now...Glenn...

[DCM]

I enjoyed the discussion as well fellas.  Thanks for posting.  The part that really soaked in for me was the passage which follows from Art.  I think it's the part I tend to focus upon, indirectly and oddly without realizing it, which means I misscommunicate with others who probably don't give it as much consideration.  I tend to take the balanced load aspects for granted I guess.

"The shooting part is important as well. If your bow shoots where you're looking then you're ready to shoot the bow in. But if the bow consistantly shoots low then the lower limb needs strengthening (or weaking the upper). This is what works best for me for the handle (straight) style I prefer and type shooting I do."

Obviously, whether a bow shoots high or low relative to "where you are looking" is so highly subjective, and so much a function of our individual form, it's not like we'll all be the same in that respect.  But this is the focus of most of the discussion of tiller and it's underlying purpose, and mathematical modelling with the incentive of having the arrow come off the bow as straight as possible (in the verticle plane).  But no matter how we tiller and shoot, we can usually find a nock point height which works for that unique combination.

[Roy Steele]

PAT'S right all the way around
  Heres a couple things not said,
  Poor tillering one limb pulling more than the other.Which is what happens if you make your limbs the same.You have make your bottom limb the right leanth acording to your shelf placement.
  Your limbs  are to thin not enough mass in your bow.This why heavey woods have less hand shock than white woods.
   Tips need to be stiff at lease 4"s down from the nock.Just heavey enough to keep them stiff.
    A to straight a grip.
    Like PAT said to big a string.
    High brace height.
    To light an arrow.
    Twisted limbs.
    I think you all have covered it all.