Making sure I understand Limb Timing

[RedStag5728]

Hey guys I am currently working on a hickory self-bow for my father for Christmas. I read up on the Limb Tillering and Timing thread, and had a basic understanding on what you guys are trying to accomplish.

But I have one question in regards to my set up and how the bow is behaving. I screwed a 2x6 board  to the wall in the shop, screwed a metal plate that is the same width as the area in-between my pointer and thumb and drew straight lines from each side of the board to indicate the tip movement and measured down to 7" to get 7" of tip movement for a brace at 50# on the long string.

I placed the bow on it's fulcrum point on the metal plate and rigged up a double pulley system set for a 3 under (dead center of the bow) and split finger (I used 1 1/4"); I used these measurements based on my completed bow, the nocking point and where my middle finger lied on the string.

When I string the bow with the rope riding the split-finger line and pull point on the string (my dad shoots split, I shoot 3 under), the right limb (which I dedicated as the upper limb) droops and bends down to about the 3" mark on the wall where the lower limb (left limb) bends, but sticks way up.

This means that the left (lower) limb is still way to stiff right? and are those measurements ok for 3 under and split or should I redraw those lines?

I'm taking lunch from the shop right now, as soon as I get back out I'll take pictures, I just want to make sure I've got the right idea.

[Roy from Pa]

I'd have to see the pictures. I don't follow your explanations.


Here is my tree setup, the bow handle is 4 inches wide as is the trees cradle. Note how the bow riser is cut out and how it sits in the tree cradle which is cut out at a slight angle to hold the bow nicely. The right edge of the trees cradle is where the top of the handle is placed, " arrow shelf ". The 2 black lines you see, the right line is for split finger and the left line is for 3 under, as I assume a 3/8th high nocking point on the bow string when shooting. Top limb is to the right. The trees pull rope will " Always " drift towards the stronger stiffer limb. So that's the limb to remove wood from. Every time you remove wood, exercise the bow 25 to 30 times on the tree before removing anymore wood. You want to see the tree pull rope travel straight down whichever black line you are tillering for. In this video the bow is only braced to about 2.5 inches.

         

In this next video, you can see the black line on the bows riser that indicates the top on the handle, " arrow rest ".

     

[RedStag5728]

Better than pictures I took a short video for demonstration hopefully this explains it a little better than what I did in the post. I'm 75% sure the problem is a stiffer left limb but I want to make sure. I know it's hard to see the lines on the wall and the relation of the tips to those lines, I apologize for that.

The two measurements for the split and 3 under lines are based on the bow's center (center on the board).

 http://vidmg.photobucket.com/albums/v352/Number01hunter/bowtreetiming_zpsh7kkbwua.mp4

[Roy from Pa]

If you look at how the bow's handle is positioned on the tree cradle, it is slid way over to the left, leaving very little handle on the right side of the cradle and much more handle extending out to the left of the cradle. I would change that and even it up, then redraw your black lines. Now with that said, as you start to pull the rope, the bow does seem fairly stable. And yes the right limb is coming down more because we are applying more stress to the right limb as we tiller. "Don't" be concerned about how the limb tips are bending. ONLY be concerned with the pull rope traveling straight down the black line. So yes you need to remove wood from the left limb. Another suggestion is, shorten up the string on the bow. Those super long tillering strings lie. Shorten the string so that it lays tight against the belly of the bow when it's strung. Sometimes, or more often that not, as you begin to tiller a bow, there is an abrupt shift between static balance and dynamic balance. Meaning that the top limb will start down like it's out of balance and then as the dynamic balance comes in, the bow will level out.

Sooner or later, my limb timing mentor, Ole Bowjunkie, will see this thread. And he just loves limb timing threads..    He is a little more articulate and knowledgeable than I am. Not much mind ya, but a little..  
 

[RedStag5728]

Thanks Roy!

I see what you're saying but I thought that all bows are gripped above center?

So you're saying shift the handle in the cradle to the right so that the bow is cradled in the center of the bow and redraw the lines? And what measurements should I use?

I will surely shorten up that string, I made my last bow lighter than I wanted because I left it too long on that long string.

Yeah I remember the brain stew I got from reading the timing thread, I felt like most of my college courses were easier! LOL!        But it's part of the process of learning and I want to be able to make a good shooter for dad so I will do my best to comprehend y'alls logic    

[Roy from Pa]

It all depends on how you lay out the bow and if you make the bottom limb a little bit shorter, and whether you use a low wrist grip, a medium grip, or a high wrist grip.. For 3 under, I make the bottom limb about an inch shorter, for split maybe an inch and a quarter shorter. Making the lower limb shorter moves the static balance up closer to the arrow shelf.

My lines on the tree are setup assuming that I place my string nocking point 3/8th above the top of the arrow shelf. That is my starting point. So for split finger, the right line is pretty close to the shelf or maybe 1/8th below the shelf. That is where the center of my middle finger will be when shooting the bow. For 3 under, the line is 3/4" to the left of the split finger line. Or about 1 inch below the arrow shelf. Of course this all depends on how fat your fingers are..  

[Roy from Pa]

I'll text Bowjunkie and tell him to get in here...

[Pat B]

Have you floor tillered to see that both limbs are similar? From the video it looks like the right limb is way stronger than the left.

[Bowjunkie]

Roy, limb timing/balance threads… It’s a love/hate thing… I love the bows that result from it and I’d love to see folks make and shoot bows as well behaved and predictable… without my input :^) That’s the only reason it lures me in. Git er done. Explaining this stuff over and over is like a curse... I hate that sense of it. Feels like Groundhog Day. Lol. I just spent hours talking with a budding bowyer from down yer way. Get ready for a Bownanza up here in the coming weeks.

Ok, maybe I like it a little :^)

Roy has quizzed me for years, then draaaaags me into these discussions and ultimately complains that my posts are too long. A book could be written about this stuff… and he wants it in a paragraph, post, thread, or email… Make up your mind old man… you want me to talk or don’tcha? Crazy ol’ son of a….. xoxo

Like Roy said, it’s kind of hard to envision exactly what you’re talking about. But if I understand your explanation well enough, ‘mostly’ what you are seeing with the initial tension on the string ISN'T that the one limb is necessarily stronger than the other, rather, it’s the teeter/totter effect due to the string hand fulcrum being above the bow hand fulcrum. It’s just geometry. Well ok, and physics too :^) It APPEARS stronger… now... but maybe not for long…. I’ll explain…

(I just went back and watched your video(well done by the way) and yes, the right limb is being pulled down simply because your bow is being supported at its center, while you’re pulling the string away from that center…. as many do… and your tillering tree’s cradle design is allowing it to tip… not that that’s a bad thing.)

As near as I can tell from here, your cradle and lines for three under and split are positioned reasonably well. Your bow is acting accordingly.

A bow acting as yours is at this early point “might/could” still be perfectly, dynamically balanced at full draw… meaning, the limbs may still be perfectly balanced at full draw relative to the archer’s holds on bow and string. But this slight, early misbehaviour reiterates some of the reasons I advocate designing the bow so that its center is at or close to the string fulcrum… and understanding their relationship and practical effects if they’re not. The farther the two are separated by design, the more the bow will try to tip in the tree(assuming we hold it and pull it in the tree how we’ll do it by hand).

In other words, the farther the fulcrums are separated by design, the greater the shift that must be navigated (or its effects WILL be later realized) between static balance and dynamic balance. Static balance being the balance point of the bow with no human contact, and dynamic balance being the balance point under the bow hand with full human effect at full draw.

The greater the shift, the more patient you’ll have to be in your hunt for dynamic balance.(i.e. the more it will fight, the more fickle it is and the later in the draw you’ll find it). So, if that’s the case… don’t try too hard to establish it too soon. If things are as I suspect, for YOU, now is the time to be patient.

Conversely… the CLOSER the fulcrums are oriented to each other, the less shift must be navigated, the less it will fight us, and the less negative effects bestowed upon the arrow and archer. Also, the closer they are, the sooner in the draw you can find dynamic balance and the easier it is to maintain it throughout tillering. Yours isn’t bad, and isn’t far from how one of mine would act if I set it in your tree and tugged lightly on it. I’m ok with a slight shift… and there are reasons why. You’re ok. Don’t despair :^) It’s what you do with it from here on out that matters.

It should also be understood that the shift, when it exists, can be adjusted for/allowed, to ‘some’ degree depending on severity, under the bow hand during the draw. But when it’s so bad that it can’t be, that’s when you see guys’ bows leaning heavily in their full draw pics. It’s all a matter of degree. Personally, I think degrees of unbalance add to less stable bows, handhock, tuning hurdles, shifting tiller, poor arrow flight, and more, so the key, the goal, for me is… to design and tiller/time the bow so that the shifts are minimal enough that any effects NEEDN’T be accounted for or felt by, or dealt with, by me or the arrow. If you have never shot a bow coordinated for you as such before, you’ll really appreciate it, and want to settle for nothing less after you do.

In essence, in your video, you’re witnessing the beginning of a shift. And that degree of shift isn’t bad. I’ve seen folks’ proclaimed “well-tillered bows” flip right out of a 'proper tree' onto the ground. The only way a bow WON’T shift at all, is if the bow hand fulcrum, string hand fulcrum, and bow center are all one and the same. Center/Center/Center…. how MOST folks design, place, tiller, show, and ‘balance’ their bows ‘centered’ on their tillering trees and tillering sticks…. The problem is… when it’s done, most of them hold them and shoot them very differently… and the bows react accordingly… sometimes desperately.

For every action…...

[Bowjunkie]

Happy now, Ropy?

[Roy from Pa]

Jesus boy, that was a short version. I'm happy ya didn't disagree wif me.. XO Cool on bownanza..

[Bowjunkie]

Got another guy today too. Compound shooter... but serious woodworker and bowhunter. Known him for 20 years... first time he's ever seen my bows.

He picked up Raven, fondled her, and balanced her on his middle finger and said... "That feels as light as an arrow. I need to make me one of these."

Set the drag, baby. He's hooked.

[RedStag5728]

I gotcha Bowjunkie, and yes I understood everything. So to proceed from here I should center up the bow, and make the limbs bend evenly, then from there adjust for the shift later on when I move to the shorter string.

And like roy said I should move those two lines over accordingly to the shifted handle in the cradle.

Now to achieve that dynamic balance at a later draw, typically the lower (in my case the left) limb will typically be stiffer than the right (positive tiller) correct?

[Bowjunkie]

Mine aren't. My selfbows vary enough that it's hard to call anything 'typical', but they're often even or slightly negative. It depends on where the center is located relative to our fulcrums, and disparities in the bow itself.

To avoid the bow tipping so that you can move forward easier, another tillering option is to set the handle centered and level on the tree and immobilize it so it can't tip when drawn, draw your vertical line exactly where your string hand fulcrum would be, and then draw/flex the limbs. Done this way, the hook on the string will ultimately drift toward the stronger limb, but initially, we should expect it to move toward the bottom limb if we pull above center. It will do this instead of tipping, since we immobilized the handle area. This is how I usually do it, and can soon have the hook following the line down the wall, and later verify the exact dynamic balance point by allowing it to pivot.

[Pat B]

The static hold on the tree doesn't accurately simulate the more fluid hand hold. It will get you into the ball park, though.
 I do like Bowmonkey does and place the bow handle centered on the tree(my bows are symmetrical) and pull down from the center of the string. As I get near full draw(where it matters with a selfbow) I make the lower limb slightly stiffer than the upper at full draw.

[Roy from Pa]

Bowmonkey, LMAO..  

[Bowjunkie]

I don't pull from the center of the string, Pat. I pull it from exactly where I'll pull it while shooting it, assuming 3/8" from the shelf to the bottom of the nock point. This way, I can aquire limb balance, relative to me, earlier in the tillering process.

It works, and I must be mimicking my holds closely because I set the nock point there at 3/8" as soon as the string is done, it always feels well-balanced from the first draw, and I virtually never have to move the nock point for any reason.

[RedStag5728]

thanks Bowjunkie that's a good idea! I've got several clamps at my disposal. In the video where I have the hand clamp is typically where I do like to grip the bow, and as you see it is level there with no tilting.

My last self-bow I made with the same hold in the tree and tillered it with both limbs even (symmetrical tiller) and it shoots perfectly with a little hand shock but not much (I think the tips are still a little wide). I just never tillered a bow specifically for split finger before let alone on a pulley system, so I assumed that the lower limb should be stiffer.

I really would like to thank both you guys so much for the time and input. You are the epitome of why this board is so great!