Tillering Stick "oddity"

[manysteps]

Hey all, first time post here.

I noticed when tillering a wood longbow (using a tillering stick loose string), whichever limb is on the left side of the stick seems to flex more than when the same limb is on the right side. (my right when facing it flexed)...

I also read that it is a common thing in the bowyers bible, so which way do I trust it?

For example, if I'm trying to even out the limbs, one way they're even, and the other way they aren't, so how would I ever know if they're even?

[willie]

welcome Manysteps

hope you can post pics as you go along, it makes it easier to answer questions.

I also read that it is a common thing in the bowyers bible, so which way do I trust it?

generally you can trust TBB, can you cite the volume and page you are reading?

willie

[manysteps]

Here's an example of what I'm talking about...

In this first image, the two limbs appear to be bending about the same.



Flip the bow around, and they're definitely not bending the same



No tillering was done between these images, the bow was simply flipped 180 degrees and pulled to strength again.

To answer your other question, it's volume one of the bowyer's bible, in the tillering chapter, but I don't remember which page.

[willie]

Ok, I see what you mean now. One thing that is going to help is if you have the tillering stick plumb each time you use it, and the bow sitting level in the seat.

Here is what I see in the pics
pic 1, the stick is leans to the left, (looking at the vertical door frame behind), the bow is not level, (looking at the horizontal trim)
pic 2 the bows looks more hortizontal, and the stick looks better.

it is easy to not put the nockpoint on the string in the same place in the stick noch each time, swinging the bow off level.

I would take a minute to make a temporary mark on the door casing to see when the stick is plumb, and make a reference mark on the string.. center is ok for a first bow, and a center mark on the handle, so that you are looking at everything the same each time.

before you pull the bow further, can you see where the left limb is bending the most?

[Hamish]

 Willie posted whilst I was typing my answer, so much of what I say is similar.

A little change in how the bow rests on the tree can make a big difference in the perception of how strong the limbs are in relation to each other.
If you look closely in the first picture, the top of the handle is actually slightly tilting downwards, towards the right, making it appear that the limbs are bending evenly.
In the second picture the top of the handle is sitting more level and it shows that the limb that is now on the right is too stiff, and needs to be weakened.

Emerging set in an unstrung bow will start to give you an idea if one limb is much stronger than the other.
Also stressing the lower limb when stringing  can cause premature set in the lower limb, and it can take quite a bit of tillering for the top limb to catch up.
I find it a good idea to get to full brace height fairly quickly before starting longer draws(providing you have no hinges and relatively even limb strength), as it gives a truer reading, of limb strength.

[Dances with squirrels]

I see what you're saying. Either limb, when placed on the left side, seems to flex more than it did when it was facing to the right. That tells me that something in the way it's being held, and/or the shape of the handle itself, or the precise point the string is contacting the notch in the stick, is causing it. In other words, the tillering stick's mounting surface is uneven... i.e. not square... AND/OR the surface of the bottom of the riser piece isn't parallel with the back of the handle, or there is variation in the exact point the string is placed on the stick each time... or a combination of such things. These things should be made unconditionally true, double checked, and triple checked before tillering progresses. A few thousandths can project out to quite a noticeable difference in the length/leverage of a bow. There's not a better indicator of the accuracy and relevance, or not, of our tillering setups than what's being shown to you there. Seek the root causes, and adjust until each limb shows its mirror profile left and right.

These are additional reasons why I prefer the rope and pulley type tillering tree over the tillering sticks. I just find it easier to be consistent with them, and pull and hold truer to reality.

Not that it would make that big of a difference, but make certain your string is being held on the stick at the exact same spot each time. I did a quick check on your pics and it appears it could be off a little bit.

[manysteps]

It "could" be that there's something not square with the stick itself... I've had this exact same issue no matter how level everything else is, and it would be hard to tell if it's off square by a thousandth of an inch somewhere.

What struck me odd is that this exact issue is mentioned in the bible, but no further explanation... I'll have to re-read that chapter and quote here what was said... (be back with that)

[manysteps]

FOUND IT! page 272 in paperback...

Whichever tool is used, take off only twenty or thirty strokes from each limb before partially drawing the bow ten times and re-checking the weight. The bow will draw a bit farther now when the final weight is reached on the scale. The bend should also be checked on the tillering stick. It is quite useful to mark the draw lengths on the tillering stick, so the bow can be pulled to the same degree as it is pulled on the scales. From now on, when it is on the tillering stick, the bow should be viewed from both sides, as a limb that appears too stiff from one side my sometimes look perfect from the other.

[Dances with squirrels]

I think what they are describing there is something other than the effects of inaccurate construction of bow, stick, or tree. Even with everything made just-so, sometimes a selfbow, especially those with more character, can appear to be bending differently when viewed from one side vs the other, and it helps to flip it on occasion to get a true sense of what the limbs are actually doing.

[PatM]

Your tillering string is not flipped with the bow and it doesn't appear to be pulling from the same point of each limb tip.

 In the first pic it's a bit inboard on the left and it is again on the second pic

[George Tsoukalas]

I think it is an optical illusion coming from staring at the stave for so long. A fresh set of eyes is helpful. I often call my daughter down for a look.

First photo-right limb seems weaker.

Second photo-left limb seems weaker.

Both limbs need to bend more  near the handle.

When dealing with log staves it is definitely a good idea to check tiller from both sides.

You might consider using a rope and pulley.

Jawge

[mikekeswick]

One easy thing for you to do to eliminate off square. Get a 4 x 1 1/2 square piece of wood and fit it to the top of the tillering stick ,making sure it is square. This gives a longer section for the handle to sit on.
Be aware that you should only use that tillering set up until about 20 inches then you need to be pulling it by hand.

[BowEd]

manysteps....Things said by others are all true.My take on this if you look at the background and level of tips 1 limb is bending more in the midlimb.The limb that has it's tip lower.In fact it's bending too much mid limb.It would be more pronounced at brace and I suggest getting it to brace too.Things get a lot easier then diagnosing balance.You'll have to take more of the outer third of that limb to get it bending evenly.The other limb is stiffer but is bending evenly.You'll have to adjust that limb to be as weak and bendng the same with overall even removal of wood from that limb.I suggest using an tillering gizmo to help yourself out for that nice even bend.
Your referral to turning a bow around on the stick to check it many times is on account of bows being made from staves.Sometimes there are what are called propellers in limbs that make the bow look different one way from the other.You have a board bow there?There should'nt be much difference then because no propellers are there to begin with unless uneven removal is done to keep thickness the same on both edges.
Anyway good luck.Keep us posted.

[Pat B]

Could the limb thickness be different from one side of each limb to the other. A pretty common problem when using a vice mounted to your work bench.

[aaron]

Good observations here, everyone. I agree with BowEd that the TBB quote above is referring to propeller twisted staves.

Watch out as you make those inner limbs bend, your fades are quite abrupt- this can lead to a hinge there. Making the fades longer, or with a larger radius would be good.

 Keep that tiller string as short as possible, and don't leave it drawn like that too long as you get further into tillering.

good job so far