need help with Tillering - string causes bow to twist and string jumps off

[globalmark]

I Have been making 2 yew bows out of that dodgy log (on yew Billets and Bow build post)  i was given and run into a snag that i have not come across before and thought maybe someone has ??

Bow B the worst stave - seems to have some Deflex in one limb but that's all tillered OK and actually looks like might work out

Bow A - the better stave and more Even shaped one which was 2 sister billets which have been glued together -
I mostly tillered it with a loose string , However now have come to put on a shorter string to finish the tiller and get a rough brace height and the BOW just twists opposite and the string either jumps off or just turns over .
So obviously a fault in my Tillering or a fault somewhere - - the tiller looks perfect, Shape and sizes look good with the loose string , nice even shape
the Bow is 77 1/2" so could shorten , but basically it's almost correct shape now ..
any help would be appreciated - ?

Pics of stave here

thanks Mark

[JWheel]

Hey Mark...funny thing, I just posted a similar request for help only my bow is glass. I was told by a pro once before when this happened to one of my bows that my "tips were too heavy"...I guess making it able to easily bend laterally. I think I may be SOL with the glass bow but shaving a better taper on yours might fix it...Just my understanding of the advice I received a while back. I'll be curious to hear what others suggest

[globalmark]

HI Jwheel

Thanks for that - could be there is still quite a lot of meat on this yew bow - but tips are pretty much to size but there is natural recurve in the ends so maybe thats it -

[Flem]

I'm not completely understanding whats happening but if the limbs are twisting and you are planning on shooting the bow, you might need pin nocks.

[globalmark]

Hi Flem

the actual whole Bow twists when i try and put a bow string on with any Brace (rather then the loose tillering string)

i can use the tiller tree or a BOW stringer get a shorter string on the Bow but already try to twist around therefore the string jumps of or the bow turns upside down -

[Pat B]

It has a deep, rounded belly like an ELB. If the limbs aren't just right you can get lateral movement which can cause the twisting.

[globalmark]

HI Pat

So what can be done about it - still have a fair bit of meat so to speak and plenty long enough -
do you suggest that i thin the limbs a bit - think draw weight is fairly high maybe guess 60lbs so happily can take of 10-20lbs ??
just had a approx measure - got like places 25mm wide is 20mm deep or 30mm and 26mm deep  further up - same approx ratio all the way along except handle and Tips (which close to round)

mark

[Pat B]

Does it rest freely on the tiller tree or is it clamped? It looks good there.
 I've not made many ELB style bows but I have had the same problem. With those snaky limbs it will be tricky.

[globalmark]

Tiller tree held in with a block and wedge - due to the shape the snakey and natural recurve and handle being heavier it will naturally just flip upside down without a string so had to wedge in tiller tree .

[Pat B]

Can you hold it at partial draw and look down the length of the bow to see how the string tracks? Maybe make a second set of nocks just for bracing like some of the war bows had(have). Although if it is unstable bracing it will cause it to twist and come unstrung. You might have to get some of the snake out of it before it will brace safely.
 Maybe check with the war bow guys on PA.

[globalmark]

cant get even strung unless the loose string on the tiller - each time i tried today just rotates upside down or when turns string jumps off - you can feel the twist in the Hand
so only way get a partial draw is on tiller tree - guess must be a weak side and one limb wandering maybe ? but not sure where to start

the back is not a prefect arch shape as i had to remove some sapwood as over 1" thick , but have chased a ring pretty well but the profile now has places where high on one side or the other ?

yes maybe need speak to a Yew war bow person that found same issue before ..
thanks

[Pat B]

Isn't the bow yew? If so you don't have to chase a ring like other woods. You can get the sap wood even, about 1/4" thick whether you violate a ring or not. A few years ago I built a 95#@30" war bow with a beautiful yew stave that was given to me. I bugged the heck out of the war bow guys and they were gracious enough to walk me through the process and that is the info they gave me. I'm sure they would help you with this problem also.
 Even though the war bow I built came out beautiful I couldn't pull it more that 15" by hand.      
I gave it back to the guy that gave me the stave. Just building it with horn nocks and all was all the pleasure and experience I needed.

[Flem]

Thats serious twist. I thought it might be marginally shootable. I have used my share of marginal Yew.
Your going to have to think in 3D to tiller that one!

[Wolftrail]

Can you use steam or heat to correct it.

[Flem]

Just went back to see how long it is. You might cut that thing down. No point in tillering more that is necessary and it could make your job easier.

[Pat B]

In the pic where it is standing by the door if you could bend the upper tip(outer 1/3 of the limb) to the right a bit your string will line up better. I think that is where your problem is...and yes, like Flem said cut it down some . I'd say to 68" or so. The extra length only sucks the energy from a lower weight bow. It might be a good length for a 150# war bow but not a 45# to 50# bow.

[globalmark]

Hi Guys

yes its- YEW , and i do know i don't have to chase rings exactly ( have not done so much on other stave) but makes look nice and does help and thought it wouldn't help - maybe in yew you have to cut the rings .

Cut down - maybe will try that little by little

steam bend - yes maybe try that first - even though when hold a string tip to tie looks like through middle handle but maybe not precise enough ?

PAT - good eye - just drew line on computer and looks like tad out of alignment exactly as you say (i use pictures when tillering as often find parts need tillering you dont see by eye) - honestly with a string looks over the centre .

Thanks for all Handle thoughts and tips gives me more to try .
Try 1 straighten tips more exactly
mark

[Roy from Pa]

Running the pc line from tip to tip here shows the line way over to the left of the handle area.

[globalmark]

Hi
Same line as mine - I just zoomed in on the handle unfortunately cannot upload high quality pic - but can see my pic is not far off - that Knot also comes out the side I was planning to use that area as the arrow plate

Think the pic is also deceptive as leaning against a door at a 70% angle - handle
Starts only 1” from that knot
Anyway at moment I am steaming the bow Someone who makes heaps UK yew bows suggested take little recurve out of it AND straighten at same time so trying that at first - will let you know how it goes -
Thanks

[fujimo]

everybody may have different ideas here.
i build almost exclusively with yew- besides the few staves that i trade- and thats because of what grows here- so thats what i use
i agree with Pat totally, you can violate rings in the sapwood- just get a nice uniform thickness, 1/4" to 3/8"- that sapwood is tough.
if i were making corrections i go by this rule " wet heat for wet wood, dry heat for dry wood"

but if were this my bow, i might try these things first.
i would not take the reflex out
shorten the bow to 68" or a little less depending on your draw length
make sure that the handle and the nocks line up- wiggely limbs are ok
get it off the long string as soon as i can- the long string will end up putting a lot of emphasis on the tips, and if you are not careful, you will land up with a "whip tillered" bow-  i have found that the long string CAN torque the bow when working with it, especially if the tips have some snake you are then encouraging the snake to work, while the fade and closer to the handle resists.

i say all of this without actually seeing the stave in person.
my concerns with the bow torquing during tiller, is that it will want to do that when being shot-
the bow should rest freely on the tillering tree without torquing. imo
good luck- looks like you have produced some good staves out of some very marginal wood there