Tiller Changed, Help me understand why?

[RT]

Hi all,

I just completed my boo back and belly bow two week ago, specs are 60" NTN 24 at 56lbs, the tiller looks spot on. During the tillering process,
for each incremental inch, i exercise the bow approx 30 times on the pully from 15" all the way to 24 " .

After the bow, has reached final tiller, i have so far shot the bow approx 150 times between intervals. Today, i decided to do some target shooting but after shooting
20 plus shots, i realised that the bow has changed it's tiller...........the top limbs tends to bend more in the middle limb than the lower limb(before the top and bottom limbs seems pretty identical)

Sorry, i dont have a digital camera handy , or I will post a pic, but i guess you will get the pic from the above explaination. Why has this happened?   

[artcher1]

First, you can't accurately duplicate the drawing forces of the bow/drawing hand on the tillering board. So, drawing your bow down on the board between adjustments that many times is a big mistake in my opinion. Shooting the bow/drawing by hand is the proper method for setting the tiller, not a tillering tree. The tree is fine for seeing overall tiller but unless you exercise between adjustments by hand you can't properly set the bow's tiller. You can however manipulate the bow's tiller somewhat by the heel pressure (or lack there of) of the bow hand while shooting your bow. To help even your tiller back out try shooting your bow with more heel pressure on the bow's handle.

ART B

[George Tsoukalas]

I agree with Art on this. I check to see how it feels at partial draws. I pay attention to handle pressure and if the bow feels tippy when I short draw it. I check the tiller in a mirror and have my wife snap a digi before I'm "done". Then when I go out to shoot I pay attention to how it feels when I draw and shoot. I try to sense the handle pressure. My t tree doesn't duplicate my draw and release. Anyway it happens so fix the tiller. Jawge

[Aosda]

I posted a pic for you to see.  Say the red line is where you're tillering from on the tree, you get a spot on tiller. Then you go to shoot, but when you shoot you're pulling from the green line.  Try exercising in the hand like Jawge and Artcher said, after a few pulls, mark the spot on the string that feels natural (like a nock point).  This way when you put the bow on the tree, you can off set it (making sure it's level), so that you can somewhat duplicate your draw.  That's just my opinion, makes sense to me though.

[attachment deleted by admin]

[NOMADIC PIRATE]

Completely agree with Art and George on this one, after 18" I hardly use the tree anylonger, it's all shooting and excercising by hand, even when I have to check final weight I don't even pull to full draw on the tree, but stop a few inches short and compute the weight in, and I offset the bow on the tree so that the hook is closer to where my hand would be

[RT]

Hi all,

Thanks for the advise..........let me rationalise.....looking at Asoda pic, this is exactly what how i tiller my bow on the tree (on the RED line of the bow) so when i have reached final tiller and start shooting the bow.......I am drawing down  from the Green line and my bow hand/ index finger is alos at the green line, thus in terms is giving more pressure to the upper limbs, could this be why the upper limbs tiller has changed?

Nomadic, in this case, for tillering after 18" onwards, u would actually tiller by 1) slide the bow left , ensuring that the Green line is one inch right og the RED line?   2) draw down on the green line to 25" for a 28" draw bow. Hope I am reading this correctly............  3) from 18 inch onwards, exercise many times by hand drawing............

My question is then, if u are hand exercising the bow, you will not be able to see if teh tiller has change (as oppose putting it on the pully) how would you know if the tiller has change at all?

Appreciate alll your help on this as I am still learing new things when i correspond with people on PA..............RT

[Timo]

RT, I start shooting a bow when I get to 20" draw on the tree. Shooting them as you tiller, makes the wood cells take corrections better than many pulls on the tree. If you remove wood, then the wood has to move. (clear as mud) or you make corrections over uncorrected wood. Then all the sudden it changes to much and ya start flip flopping.

[DCM]

RT,

All these boys have been 'round the mulberry bush a few times.  I think perhaps what's not being said is "we" generally have all the big adjustments done by about 20" of draw, and are fine tuning the tiller.  I for example am more interested in how the bow shoots, and the shape it takes from work fatigue when I get to this stage, because I already have the tiller fairly right and regular.

For the less experienced, yes you want to setup your tillering apparatus to as closely as possilble duplicate your shooting style.  So that means putting it on the tree with the draw rope nearer your actual nock point, and the handle fulcrum closer to where you put bow hand pressure.

My tiller tree does not have a "cradle", rather a lag bolt with leather wrap.  This gives me a single point of contact and lets the bow rotate on the draw if it wants to.  I try to design so the center of gravity of the bow is about where I suspend it from the tree (and obviously where I'll focus my bow hand pressure).  For me this is usually dimensional center.  I also try to tiller to limit rotation, and believe I am aided by putting the arrow pass at a point which allows me to do the aforementioned, 1/2" to 1" above center.  Some people, erroneously in my view, call this a "shorter lower limb" design or "asymetrical" when in fact the opposite is true in reality.  For example, if you fold your string together at the nock point on a typical bow, you'll find in most cases the upper segment 2" to 4" shorter than the lower.  No wonder the upper limb takes more set....

[artcher1]

Not to muddy the waters with any counter points, but would rather suggest that you have a ruler on hand while shooting the bow in (if you're not already doing that) to monitor any tiller change. Constantly check tiller at both fades after each group. Any change in measurement may require adjusting tiller.

ART B

[George Tsoukalas]

LOL, DCM, most of us here have been "round the mulberry bush a few times". I used to play that with Ma. Never around an osage tree though.  You crack me up. I've also played "catch up" many a time. Fix a limb. Other limb needs attention. Fix first limb again. Now the seond is off again. Back and forth. It's maddening. I haven't had that happen too much these days. Not exercising the stave at short draws or pulls(20-30)  on the tree are the chief culprits for me. If I do that tiller doesn't change really. Also, working wet wood may cause that as well. Art, what's the ruler for? Checking tiller at brace? That's a good thing to do on a straight stave, a board or I would imagine a bamboo backed bow. Though I've never done one of those or a wood backed bow. Jawge

[Mechslasher]

i excercise a bow 50-100 pulls everytime i take wood off a limb.  i rarely have a bow loose weight or take set at the end excercising the limbs that many times. 

[Gordon]

Now a days I pay far more attention to thickness taper than what the arc looks like. I use the tree mostly for exercising the limbs between wood removal. I rarely have problems since employing this method. And it works better when I'm tillering limbs that have character.

[artcher1]

The ruler is used for checking any positive tiller changes during the shooting-in period George.  I start my break-in period usually with a 1/8" positive tiller. And I try to maintain that distant throughout. I just measure the widest distant between the string and belly of the bow outside each fade. The distant isn't really all that important so long as I maintain an 1/8" difference between the the two limbs at their widest points.  If that 1/8" distant grows larger then I know I have to do some work on the lower limb to bring that measurement back in line. And if I notice any reduction in that 1/8" measurement I know I losing my positive tiller and will have to lighten the upper limb to bring my tiller back in line. If the bow's tiller holds for several weeks or many hundreds of shots then it's ready for a finish job.

David and Chris, you guys make mostly Osage bows, right?

Taper tillering is the only way I do a bow Gordon. And I don't worry about the arc of the limbs that much either. Comstock got it right when he said that good tapering produces good tillering. And if you don't like the bow's profile just change it's taper.  With a good consistant taper you will not have hinges or weak /strong places in the limb. Exercise away when you can achieve this.

ART B

[NOMADIC PIRATE]

Like Art, I too have a ruler at hand at all times, I mark 2 spots 7" from the center of the handle and continually monitor my positive from my first low brace to final shoot in.

Gordon, .....spot on !   lately I put a lot of time tapering my limbs, as a result my bows have a retty much done tiller at very first brace,  .... from then on is just about taking of weight


RT,

 the tree is a great tool, however you got to be carefull of relying in it to much and missusing it,......how do I know if I'm still in tiller excercising it by hand ?

....I primarely use a full lenght mirror.

[George Tsoukalas]

That's what I figured, Art. I do the same but not usually with staves. I look for a a positive tiller but at full draw. Don't care much about brace with logs staves. Too may variables. But that's me. Thanks, Manny. Jawge