Help with Handshock - tillering

[bubbles]

Got a problem with handshock on this bow I'm tillering - 66" ntn, Red oak with Rawhide backing. 2" wide most of the limb.  Width tapers from 2" to 1/2" at the nocks, staring at mid limb.  I'm at 50#@25" going for 50#@27".   I'm not sure if I should be taking wood from the bottom limb or top limb or whip the tips a bit (which i started doing, then thought I should ask for advice).   The limbs seem pretty matched up to me, but I am a newb, so I could be way off here.   

[Ifrit617]

Tiller doesn't look bad. I'd reduce the outer limbs width a bit. Should take care of hand shock.

Jon

[BOWMAN53]

Inner limbs arent bending at all. most of the bend with a pyramid designs should happen on the inner 2/3.

[bubbles]

Not a pyramid design, sides are parallel (2" wide) until midlimb, where they taper to the nocks (1/2")

[Hamish]

Tiller looks pretty good. What does it feel like when shooting at 25"?Is there any handshock? As you are new to making bows then you have already done a good job. The nuances of improving can be left to subsequent bows. 
Interpretation of handshock, can be very subjective. Try using heavier arrows. Gluing  leather shims onto the back, at the handle then shaping to fit your grip can also do wonders, to improve shootability.
 As its not a pyramid bow, you don't want the inner limbs bending more, as you will just get more set than is necessary, possibly even worse shock with tips doing even less work.
                                   Hamish.

[SLIMBOB]

Tiller looks damn good to me.  Narrow the tips and reduce the weight of them some. 

[bubbles]

I usually start to put some arrows through my bows for the last 4 inches of tillering which is also when I get it to full brace height. This one seemed to have  above average handshock. Maybe it will even out once I get it to full draw.  I havnt put a grip on yet, but I was trying to tame this beast a little.  My arrows are all 500+ grains.

[bow101]

Maybe, maybe, just a little stiif inner thrid bottom limb.   But overall looks great.

[bubbles]

Yeah, I see that. Top limb starts bending a little earlier.

[Cameroo]

If your limbs are symmetrical, then your lower limb should be slightly stiffer, which it looks like it might be.  So it's probably better that the lower limb is a tad stiffer out of the fade.  I usually tiller mine so that the lower limb is about 1/4 - 1/2" stiffer than the upper at full draw.  This is easy to see on the tiller tree, but not quite as easy when drawn by hand.  Some guys measure the positive tiller at brace, but I never really tried that myself, and I'm not sure what kind of measurement you'd be looking for.

You may already know this, but the reason that the lower limb has to be stiffer when the limbs are equal length is because you are knocking your arrow and pulling the string back about 1 1/2" above center, which effectively makes the lower limb longer.  If they were both tillered the same, then the top limb would return "home" before the lower limb, and induce a vibration into the bow (hand shock).

Another thing that you can do to help reduce the handshock, as suggested, is to reduce the weight of the tips, which is usually done by removing mass from the sides rather than the belly, to keep the last few inches stiff.

[bubbles]

Thanks Cameroo,
I usually measure the limb difference at brace, for exactly the reason you mention. Its about 1/8" different, bottom limb being stiffer.  I have my arrow "rest" (where it will eventually be) 1" above center. With my arrow nocked 1/8" above that. Would moving my nocking point/arrow rest location help? Right now my arrow rest is my hand, so its easy to move.  If I moved it higher and that helped, would that mean I need to weaken the top limb or the bottom limb in order to make the original nocking point perform with less handshock?

[bubbles]

Oh, and yes limbs are same length.

[Cameroo]

Would moving my nocking point/arrow rest location help? Right now my arrow rest is my hand, so its easy to move.  If I moved it higher and that helped, would that mean I need to weaken the top limb or the bottom limb in order to make the original nocking point perform with less handshock?

There is most definitely a sweet spot that has to be fine tuned a bit on each bow you build.  I would say try moving your knocking point/arrow rest up or down, and if you find it shoots better, just make that your new knock point.  It's not unusual for an arrow to be nocked as much as 1 5/8" or even higher above the center line, so you have some leeway that you can experiment with.  I'd say adjusting your tiller should be a last resort, because it looks pretty good the way it is.  I'm thinking that theoretically, if you move up and it shoots better, that would mean that your bow would prefer a longer lower limb.  The way that you would make it act as if it was longer (if you want to go back to your original nocking point) would be to make it bend more.  Therefore I would think weakening the bottom limb would help in that particular case.

Of course I'm no authority on tillering and other people might have different opinions.  You may want to wait for other opinions before proceeding.

[Del the cat]

I'm with Ifrit in post 1.
If you look at the angle the string makes with the tip of the limbs is no where near 90 degrees yet. That implies the outer 1/3 could bend more. They also look a tad stiff, loosing a bit of weight there will also reduce shock.
Another way to look at it, is:- the weight you take off the tips can go onto the arrow instead, giving you more kinetic energy in the arrow and a smoother shot.
(Not strictly true of course as the arrow traves much faster than the tips of the limbs!... in case that sounds daft:- the arrow draws back say 16" but the tips only come back about 8" ,but they both get back to brace at the same time)
Del

[mikekeswick]

From mid limb out it needs to bend a little more.
The bend in your limbs needs to be part of an elipse. eg. bending only a fraction out of the fades and then the bend slowly increasing all the way along until around 8 - 10 inches from the nock. This last section should be more or less stiff.
The reason for this is that your limbs taper in thickness. As wood gets thinner it can and should be bending further.
I have to disagree with the comments recommending you to just narrow the outer limbs to reduce outer limb weight. This is a good general principle to stick to eg. have your outer limbs as narrow as possible...yes great but the first priority is that the tiller is good before altering the widths. I would bet my bottom dollar that any handshock will go completely when it is bending perfectly. However taking 1/8th width off a bow with bad tiller will not correct any handshock issues by itself. Also sure you can use heavier arrows but a well tillered bow can be shot with 7 -8 grains per lb arrows and not have handshock issues.
As for your bow you are very close to your intended drawlength/weight go very slowly and don't worry if you come in a bit underweight - strive for perfect tiller!