3 under

[stack]

When tillering a bow what is the difference between tillering for 3 under versus split finger.Just trying to get answers in advance of starting to build.

[Roy from Pa]

1/8 positive is a good starting point.

[jess stuart]

I think it varies somewhat from person to person depending on how you grip and hold the bow.  I do best very close to even with a medium style grip.

[Crooked Stic]

Most will tell you even for three under. I try to keep mine 1/8th to even and a person can play with nocking point placement to tune. How a person grips the bow does have affect on things.

[Bowjunkie]

Brace height 'tiller measurements' should be the RESULT after timing the limbs related to the archer's holds on bow and string... not something predetermined.

The resultant profile will also be affected by bow center relative to handle fulcrum.

So, it's not possible or proper to give you an exact answer. But generally, bows tillered for three under will be weaker in the bottom limb than bows tillered for split-finger shooters. I know... not much help is it?  

[Onehair]

Bowjunkie,give me a step by step on timing the limbs and how do you know it's correct?

[Bowjunkie]

I plan to do a build to show my process, and have the bow started, but I have a few bows in front of that one.

Basically, I use a rope and pulley type tillering tree, the cradle of which mimics my grip on the bow, and the hook is placed on the string at my fulcrum point, I.e. center of my middle finger. A verticle line is drawn on the wall to replicate perfect string fulcrum and arrow nock travel perpendicular to the bow handle... that is, with the nock point set 3/8" above the shelf. This is also where the pulley is set directly below. Then I time the limbs so that the nock follows the line down to full draw and back.

How do I know it works? The resultant bows' nocks are preset, never need nock point adjustment, bows don't shift tiller, don't tilt in the hand at all during the draw or at full draw, shoot an arrow perfectly straight away without porpoising, don't shock the hand, etc.

With this method, I begin timing very early in the draw, the first few tugs on the string actually... with asymmetrical bows anyhow. The osage bow I'm tillering now looks like it will probably end up with an even tiller, or possibly slightly negative. We'll see.

[Roy from Pa]

 With this method, I begin timing very early in the draw, the first few tugs on the string actually... with asymmetrical bows anyhow.  

What would be the difference between asymmetrical and symmetrical bows with your method, Jeff?

[Bowjunkie]

Same method, Roy, but in the symmetrical bow there is a greater shift from the static balance point to the dynamic, so the bow needs to be allowed to make that shift. If ya don't understand what it's trying to do, and fight it by trying to time it too early in the draw and tillering process, the bottom limb can be made too weak... then you'll be playing catch-up later and possibly induce unnecessary set, shifting tiller during shooting in, etc.

Asymmetrical bows, with the smaller shift needing made, can be timed earlier in the draw.

[Roy from Pa]

Looking forward to the build along...

[mwosborn]

[Roy from Pa]

Jeff, if tillering a symmetrical bow for shooting 3 under, then wouldn't the shift from the static balance point to the dynamic, be less than tillering a symmetrical bow for shooting split?

[Bowjunkie]

No Roy, it would/could be exactly the same... at least it is the way I most often offset my bows.... but it depends on how far the bowyer shifts the bow center away from handle center.

The big difference, among the most common approaches, the big shift in balances, happens when a symmetrical bow is shot split-fingered.

Ya want virtually no shift? Shoot an asymmetrical bow three under. I would, but I like the split finger release, like my bows balanced in the hand while carrying and don't have a problem with the tiny shift at the beginning of the draw.

[Onehair]

Jeff I look forward to the show. I have lost the lower limb more times than I can count. My tiller looks great and then some where along the first 100 shots or so I loose it. Thanks

[Roy from Pa]

The big difference, among the most common approaches, the big shift in balances, happens when a symmetrical bow is shot split-fingered.

Well that's what I just asked, first you said no, then you say that?

I confused.  

So lets say a bowyer who shoots with a medium grip, finds the center of the bow, measures up 1 inch for the top of the handle " arrow shelf ", and down 4 inches for the bottom of the handle. He accounts for a 3/8th high nocking point on the string. He shoots split, so the middle finger of the drawing hand will be at the arrow shelf, which is 1 inch above the bows static center. But if he shoots 3 under, then the middle finger will be 5/8th above bows static center.. That sound correct?  

[Bowjunkie]

You asked about shooting a symmetrical bow three under, then quoted my reference to a symmetrical bow shot split. You SHOULD be confused  

In regards to your last queston, no, the center of my middle finger is below the shelf when shooting split-finger. I figure for a 3/8" high nock point, subtract 1/4" for the thickness of the arrow nock, subtract half the width of the middle finger, about 3/8"... that puts the center of my middle finger 1/4" below the shelf. That's where I put the hook on the string.

Switching from split to three under moves my string hand down 3/4"... because that's the width of my pointer finger. So if I shot three under, we'd add the 3/4" to the 1/4" and the center of my middle finger would be 1" below the shelf... the bow center in your example..... no shift.

[Roy from Pa]

No, I said if tillering a symmetrical bow for shooting three under. Compared to tillering a symmetrical bow for shooting split. Wouldn't the difference between static and dynamic be less for three under tillering.
 
You said:
So if I shot three under, we'd add the 3/4" to the 1/4" and the center of my middle finger would be 1" below the shelf... the bow center in your example..... no shift.

 That is what I ask about the tillering difference being less than split.         Are you confused now?        

However, I see now that your 3/8 is the top nocking point and you place the arrow under it, I was assuming the 3/8th was the bottom of the arrow nock... Hain't this fun?    

[Bowjunkie]

Yep. I like it.

Yes to your question.... in a symmetrical bow, three under would require less of a shift than split finger.

3/8" is to the bottom of the nocking point. With a 1/4" thick arrow nock, and an arrow shaft slightly thicker than that, it sets the arrow just barely above perpendicular. .. which provides excellent arrow flight. You won't see a bow of mine with a jacked up nock point.

[Roy from Pa]

I understand now, Son.  

[Onehair]

No doubt I'm going to need pictures. And a drink