On a limb.. Center not center

[DanielB89]

I am curious of how common it is for the center of a limb to not actually be the center of the limb.  

For example, When you're bow in strung and you're tracking the string in the center of the limb it may be more to one side than another.  

Is this very common?

[stickmonkey]

Only if it’s not aligned properly or the string grooves are not equal in depth. Could be how you pull the string a little as well

[kennym]

Yup, like Shane said , you can torque a little letting down. I like to look after a shot...

[Bvas]

Several factors can cause an offset string.  Limb twist, uneven string grooves, or poorly constructed string. I would think its more common in recurves than longbows as the thinner/wider limbs are more prone to twist.

[DanielB89]

I don't mean upon shot or anything like that.  I mean like the bow is not being touched at all.  

Just the place the string goes straight down the limb.  I have read where sometimes the center of the limb isn't necessarily the "center", as confusing as that may sound. lol.

[Crittergetter]

South Cox made the statement, " the torsional center is not always the numerical center".  But that being said, once the center is found and the limbs are profiled then they should always be centered unless a problem develops over time.

[Bvas]

Originally posted by Crittergetter:
South Cox made the statement, " the torsional center is not always the numerical center".  

So the string is always in the center. But the outer edges of the limbs might not be in the right place  

[Holm-Made]

The dynamic center of the limb is not always the measured numerical center.  This is especially true with a recurve.  

Often times a limb needs to be laid out to one side or the other so the limb bends without twisting.   If the limb is tapered from the fade outs to the string groove, like a black widow, you will never notice this.  If a recurve limb is only tapered the last 8” or so you may notice a little more limb on one side of the string.  This doesn’t hurt a thing as long as the limb tracks without twist and the string falls into the groove every time.

I only make R/D's for now and I have found that if you do all of your homework by having a straight form and that is a true 90 degrees on it's surface and your laminations have even thickness across them, your dynamic center should be very, very close to your numerical center...
 Very Important:  Also make sure your limb profiles are sanded evenly...

[DanielB89]

Originally posted by Bvas:
 

Originally posted by Crittergetter:
South Cox made the statement, " the torsional center is not always the numerical center".  

So the string is always in the center. But the outer edges of the limbs might not be in the right place      [/b]

Exactly. that's what i'm referring to.

[Eric Krewson]

If you are talking about selfbows; a perfectly centered string is a rarity. It usually takes some handle bending, limb tweaking or nock adjustment to get even close.

[mikkekeswick]

Originally posted by Eric Krewson:
If you are talking about selfbows; a perfectly centered string is a rarity. It usually takes some handle bending, limb tweaking or nock adjustment to get even close.

not if you wait until the bow is tillered to brace before shaping the handle  
Anyway they are talking about glass bows.

[stickmonkey]

The was a guy once that used a set of washers on each end of the limbs to determine torsional stability. Its been a few years but i think POA Pirates of Archery had a how too on making and using them.

I build my blank oversized and determine true center. layout the limb profile 1/8 oversized , 1/16th either side. I use a file guide to set nock depth and if there is twist in the limb I check the nocks depth again then address sanding the edge of the stronger side if needed. Reguardless of numerical center or torsional center this will bring it true.

[Crooked Stic]

Most time working off a center line will get you where you need to be. on a recurve leave the tapers a bit wide and work your grooves untill you have it tracking straight then even up your edges. Very important to have a good form. A good grind on your lams. A lot of grain runout on the lams can cause problems also. That would be where the dynamic center would come in. Another thing on a curve is while working the grooves be sure your string is not binding on the corners and giving a false reading.

[BrushWolf]

I use to fight lining up limbs on my recurves. But since then I built steel hooks for a lack of a better word and string the limbs with them. I make the limbs to size with the drum sander leaving them square to the tips. Then bolt them on with a center line  for a reference and string with hooks. I can move hooks back and forth if needed to get limbs pulling straight. I put a till stick that's about 18" long to bend limbs so I can check twist. Most of the time the numerical center is close but not always. Once limbs pull straight I mark (true center) and lay limb profiles off of the new center. The bows after profiling and cutting string grooves string up and pull straight. It has treated me well since I have started to use it.