tillering vs. timing

[md126]

are tillering the limbs and timing the same thing??  

i understand that for a bow to shoot it's best the limbs should pull and recover equally. if the limbs are tillered properly does the timing take care of itself?

thanks for any info,    mike

[George Tsoukalas]

May be. May be not. Pay attention to how it feels on release. Are the limbs coming home equally or one at a time. Jawge

[bjansen]

I think these phrases are to achieve the same end result.  

Regarding timing, I sometimes videotape when I am shooting in a bow to see after the release how the limbs are reacting in relation to each other.  I think if I guy had access to a high speed camera he could really tiller a bow to achieve perfectly timed limbs....but I wonder how much advantage that would give to a bowyer.....maybe its not much (but I would sure like to try it)

[walkabout]

ive recently read some information on this subject, and from what i know, one should tiller so that the limbs are in time with each other. this is done(from what i read) by tracing the curve of one limb, then making the curve of the other limb match it. theoretically this would make limbs act the same. all the info i read was written by Dean Torges, in this web page    http://www.bowyersedge.com/organic.html  i found it really informative, and Mr. Torges really knows his stuff, so i figure its worth a read and some contemplation. ive found too many times drawing the bow and letting it down slowly will show timing, often the bow will try to tilt either up or down depending on which limb is releasing tension first.

[mater]

By measurement I had a bow perfect. It had a kick to it. I put a limb tip protecter on it and it kicked worst. So i put it on top, it got better.   Take it from there.  
Now if it doesnt feel right, I try this till I see witch limb needs to be slowed down. Then I make it weaker or the other one lighter.

 Mark

[John Scifres]

Exactly right.  Perfect looking tiller proves little.  Final tillering is done by shooting a bow.  If it draws and shoots like crap, something is wrong no matter how perfect it looks on the tree.  Usually though, they correspond to each other.

[Jason Scott]

Mater, it seams reasonable that your top limb is too stiff by your description is what you are saying, right?

md126, in theory if your curves match they should be in time. This is apparently true so long as the tiller tree is applying pressure the same as the shooter would at full draw. Depending on grip style and how high the shelf is. Though, I find that most of mine shoot best when it appears that the bottom limb is working a little harder than the top. I think it is an illusion but it seems to be bending more, especially when I have to cut the shelf higher like 1.5" or more like on a low wrist handle. On a higher wrist handle my shelf is lower than 1.5" and the bend is more symmetrical in both limbs on the tiller tree when shooting best. Most of the time it's a roll of the dice. Lately I tend to start out initially 3/16" - 1/4" positive tiller for the first shots after roughing everything in and take a sanding block with me to the target and if the bottom limb needs to be weakened I will sand between shots until it shoots best hoping it doesn't cost more than a pound draw weight until it is dead in the hand as I can get it. It doesn't take much sanding effort with the block to get the bottom limb to pull in enough by hitting the sides and slightly rounding the corners of the glass. It could take as long as an hour before I am happy with it. Then back to the bench to final sand and finish.

[mater]

Right on my post.  I should say I build laminated bows, not selfbows. There could be something differant, I dont know selfbows.

 Mark

[Jason Scott]

Should be the same principaly. You have more liberty in material removal with board or selfbows because you can take more from the face than you can with glass. Glass you have to be reasonably close to begin with but with all wood you have to go slower between material removals to exercise and reintroduce the surface compression to the newly exposed material using the 30x rule. I spent at least four hours on my first and only board bow getting the final tiller right. I bet I exercised that thing 200 times or more and that's not counting all the times to get it to my draw length.

[John Scifres]

It is much easier to get the mass uneven on a selfbow.  Uneven mass means uneven recovery.  That's why character bows are really hard to get to shoot real well.  If a selfbow shoots like crap despite apparently good tiller, check your tips and layout.  Something is off.  Also, due to the inherent variability of wood, even exact measurements from limb to limb do not guarantee even mass.

[Jason Scott]

Crafting selfbows is true bowyery for those reasons. It makes the glass lam building I do seem mindless.

[md126]

thanks to everyone for the info. it's very helpful.