tiller question...

[medicinewheel]

hi all!  -  what do you think of the tiller of thisone?? bow's pulled to 26" which is the final draw length, upper limb (on the right) has 1/4" positive tiller. not sure whether the lower/left limb bends enough!?
what do you all think?

thanks, frank

[attachment deleted by admin]

[Ryan_Gill_HuntPrimitive]

i would personally take a few more scrapes off the left limb.

[Justin Snyder]

If it has 1/4" positive tiller on top it should be fine.  I would shoot it before I did anything drastic.  Justin

[medicinewheel]

yes, the bow has 1/4" poitive tiller on upper limb and upper limb is an inch longer then lower!

[1/2primitive]

Yes, I would take a little more off of the left limb, but the tiller looks nice and even, good job!
    Sean

[Badger]

To me the right limb looks longer than the left, do they measure the same? Steve

[ricktrojanowski]

I would shoot it before I did anything else.  I found if the difference in pos or neg tiller is too great the bow has a lot of handshock.

[Gordon]

Looks about right for asymetrical limbs.

[Ryano]

I'll never understand the that whole Torges shorter lower limb thing, they just never look right to me no matter how well they are tillered........

[Badger]

Ryan, I am the same way, I do them on occassion but they never look right. I think it works at least just as well to keep both limbs the same length. Steve

[medicinewheel]

I'll never understand the that whole Torges shorter lower limb thing, they just never look right to me no matter how well they are tillered........

hey ryan and badger!  -  i'd believe a shorter lower limb is not better or worse then symetrical limbs; it's just a question of personal preference.
i have almost no experience with symetrical design, but i have a symetrical boo-backed cherry with ipé belly in the works. we'll see...

thanks all, frank

ps: wel, ryan: you complimented the tiller of my hickory-backed black walnut which was asymetrical. so i believe they can look right, too?! 

[DCM]

I like the tiller, but would rather see it drawn by hand.  1" and 1/4" is a lot of tiller, at least for my personal bows.  I get usually get by with 1" to 1 1/2" shorter and 1/8" or less but I tend to favor my lower fingers, kinda of 2 under with the index just hanging.  Also I'd be mindful of how the bow sets from work.  If it is concentrated in the inner limb, and you have weight to give, you might consider softening midlimb, which I see as very mildy flat on both sides.  Again, it depends upon how you shoot it.

If you study the geometry of the drawn bow, you will find an inherent asymetry in EVERY bow.  This due to the placement of the arrow above the pressure point of the bow hand, as we can't pass the arrow thru our flesh.  However, it is not just related to the lever arm of the bow itself, but also by the bow string, and the angle each segiment (lower versus upper) makes with the corresponding limb.  The result is this, positive tiller, in combination with nock point, had been developed and employed to offset this asymetry.  It allows us to negate the tendancy toward rotation of the bow on the loose.  Rocking lower forward is the tendancy we avoid, in order ensure force is applied to the arrow in a consistant, slightly upward way.  When we fail to achieve this the bow tends to push the arrow into the rest on the loose. 

Another method for combatting this inherent asymetry is to place the arrow pass closer to the dimensional center, negating the asymmetry of the upper segment versus lower segment string lenghts.  Once you get used to the idea, every "even" bow you see will look like it is straining to make the distance at full draw on the upper, and slacking it's duty on the lower limb.  These bows will tend to pull out of tiller on the upper, pull more positive tiller over time, if you aren't careful in awarding it enough extra wood to carry it's extra work, particularly during tillering.

That's just my opinion based upon study of the Tapley discussion of tiller and bow mechanics, and to some extent Kooi, linked therein, but mostly from just common sense.  Again, would love to read citations which might contradict it.

http://goarchers.org.uk/mechanics/#

[George Tsoukalas]

Looks  pretty good.  I  would just  make sure the stave is starting to bend where you want it to. For  me that is usually right at  the end of the fades. I can't tell if your  stave is doing that  or  how long your non bending handle is. Jawge

[medicinewheel]

I like the tiller, but would rather see it drawn by hand.  1" and 1/4" is a lot of tiller, at least for my personal bows. ...

DCM! - maybe i misunderstand terms: by 'positive tiller' i mean the distance between belly and string is bigger on limb then on lower limb, in this case here by a 1/4"
besides that, my lower limb measures one inch shorter then my upper limb. i never thought of that as 'positive tiller', but just as 'longer upper limb'.
what's right?
thanks, frank

[tom sawyer]

David will answer, but I think you might want a different set of conditions for an assymmetric limbed bow.  The 1/4" positive tiller advice is generally for symmteric bows, I'd listen to David when it comes to tillering assymmetric bows as he's experienced and really good at it.  By shortening the lower limb you are already making it a stronger spring, so there is less need to accentuate that difference with positive tiller.  I think he's saying that an inch shorter does much the same as a 1/4" positive tiller, as far as making the lower limb stronger.

David, I agree theres no symmetry when it comes to a bow.  So you pick your style and tiller it to be stable.  I don't discount Torges' explanation of the benefits of assymmetrical limbs, but based on experience I think it can't be a huge advantage or the symmetrical design wouldn't be so widely employed, and successful.

I totally agree about doing final adjustments from hand shooting a bow.  They look different from the tree (more or less depending on how your tree is set up) and even depending on who is shooting it.