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Author Topic: Need some tillering advice  (Read 2123 times)

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Offline gudspelr

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Need some tillering advice
« on: June 03, 2012, 06:34:59 am »
I've been trying to remedy a "problem" with my hop hornbeam stave.  It's a really straight stave from tip to tip, but one end had a natural deflex to it.  When I got it barely bending, I put it on the tillering tree and then I was really able to see it.  Thinking I could solve this, I applied some heat and clamped the stave flat, which brought it closer to the other tip, but still deflexed a bit.  Then I thought I really had a plan and re-clamped it all, inducing some reflex to the whole thing, figuring both tips would come back the same amount and I could start tillering with both tips even.  That's apparently not going to happen...

As it stands now, the deflexed tip is right about even with the back, the other is about 3/4" reflexed.  I guess I have a few questions for you experienced folks.  First, is this even a "problem" I should be thinking about?  If it's something I should try and fix, how would you suggest doing it?  In my little pea brain, I was thinking if I left things how they were, I would inevitably have to remove more material from the "stronger", less deflexed limb to catch up with the other one.  Is that correct and is that wrong to do?  For some reason, I hadn't really thought about tillering from a point where the tips weren't starting at the same point.

Any insights would be much appreciated.


Jeremy
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Offline Del the cat

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Re: Need some tillering advice
« Reply #1 on: June 03, 2012, 07:33:56 am »
To me it's a feature not a problem. (same as bugs in Microsft software).
You can have the deflexed limb at the bottom as the lower limb is under greater strain, but you'll get people telling you the tiller is wrong and the bottom limb is 'weak'.  >:(
Or you can have the reflexed limb at the bottom and have it looking a tad strong and having to bend much harder.
It's up to you.
Luckily there are only the two options else you'd get even more opinions!
When I have a stave with one slightly deflexed limb (relative to the other limb) I put it at the bottom.
Del
(Maybe hold the bow horizontally to confuse the issue?)
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Offline Gordon

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Re: Need some tillering advice
« Reply #2 on: June 03, 2012, 10:47:30 am »
What Del said. Uneven limb reflex/deflex is not a problem unless the visual bothers you.
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Gordon

Offline PEARL DRUMS

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Re: Need some tillering advice
« Reply #3 on: June 03, 2012, 11:08:45 am »
HHB moves easily with dry heat. You can warm that area up and move it where you want it. Let it sit for 4-5 hours and continue on. If you tried once and it didnt work you probably didnt get it warm enough to "stick". Try again!
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Offline Pat B

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Re: Need some tillering advice
« Reply #4 on: June 03, 2012, 11:54:34 am »
The main purpose of tillering is to get both limbs bending evenly and together at full draw(where it really matters) and to achieve the desired draw weight at full draw.
  With a stave like you have there are a few options...1) tiller the bow out so both limbs bend evenly and together. This means removing more material from the strong(reflexed) side. 2) Even up the reflex with heat on a form. No matter which way you go you still have to remove wood from the strong side(or area) to get both limbs bending evenly and together.
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Offline dwardo

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Re: Need some tillering advice
« Reply #5 on: June 03, 2012, 04:20:26 pm »
I would tiller it out a little more then get it clamped and heated again. Put a block under the side with natural deflex and get it to where you want it plus another inch past where you want it. Then when you remove it when cold and cured it should settle to where you intented it to be.
I find it a pain to tiller with uneven limbs.
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Offline JW_Halverson

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Re: Need some tillering advice
« Reply #6 on: June 03, 2012, 04:34:44 pm »
I guess I fall into the category of people advising you try heat correcting again.  Take your time heating slowly and evenly, let it cool 24 hours while clamped into position, and then give it a few more days to re-hydrate to a steady state. 

Good luck!


...and post pics!
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Offline gudspelr

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Re: Need some tillering advice
« Reply #7 on: June 03, 2012, 06:29:14 pm »
Thanks for all the advice, I really appreciate it.  I think I'll try taking a little bit of wood off so the limbs are bending just a little more, then try re-heating and clamping again.  I'm sure I'll be back with more questions when somthing else doesn't work out :).

Jeremy
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mikekeswick

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Re: Need some tillering advice
« Reply #8 on: June 04, 2012, 05:29:20 am »
If you make the reflexed limb 'catch up' with the deflexed one then it will be weaker and therefore lighter (in weight) this will mean that when you release the string the heavier limb will have more momentum as the limbs return to brace. It stands to reason that the bow won't be balanced in your hand. It would also mean that the weaker limb is over strained compared to the deflexed one - which is a bad thing!
If you don't correct it with heat then the deflexed limb should look 'weak' when braced AND drawn.
Keep on balancing the bow on it's center point to see how it balances.
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