Author Topic: Tillering issues  (Read 5653 times)

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Offline Calios

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Tillering issues
« on: November 02, 2021, 12:27:52 pm »
Hi everyone, I'm new here, I'd like to ask for some help in tillering a hazel bow. I am relatively a novice, so I'm currently learning from mistakes and different experiences. I have recently got into making a hazel bow, and wanted to give a try to recurving the tips too. The bow I am making is 170mm, and I have been stressing it no more than 40#. I then decided to heat treat each mid part of both limbs, as it was bending too much in those areas. There goes the main problem...as soon as i have put it on the tiller, i noticed that i screwed up something, the bow wasn't bending correctly, one limb more than the other, and a hinge appeared near the handle, causing a crack on the back (crack on the bark, as i wanted to leave it for aesthetic purposes). I stopped my work here, and i'm not able to carry on with the tillering process. if any of you could kindly give me a suggestion i would really appreciate it. let me know for any incomprehension, as I'm no native speaker. thank you all in advance ;D
P.s. I tried to post some photos, but it seems that the files are too big for the server, i hope i will be able to sort it out.
« Last Edit: November 02, 2021, 09:06:58 pm by Calios »

Offline ssrhythm

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Re: Tillering issues
« Reply #1 on: November 02, 2021, 10:00:03 pm »
There are far, far better boyers on here than me, but I’ll give you my take fwiw.  My first thought is “don’t complicate things.”  With that in mind, the more variables you add to an equation, the more complex it gets.  When I get a bow bending decently, I’m going to manipulate only one variable to get it bending like I want throughout…if that is possible.  The variable is going to be the thickness of the limb, because at that point, my overall profile and limb width and length and width taper will be complete. 

You say certain areas were bending too much.  I’ve never (I believe) seen or read where you would heat treat a section of a limb to reduce too much bend there.  I understand the thought process, but you just introduced a two very inexact variables that you had no way of guesstimating what the results would be.  The way I see it is the only way to know that a piece of wood is heat treated equally throughout is to be very deliberate and consistent along the entire length of the wood.  But I digress.

If a spot is bending too much on a limb or both limbs, remove wood on either side of the bend until you get the consistent sweep you are looking for.  Will you lose draw weight in the process?  Yes.  So, go slower and get your tiller close on an overbuilt, too heavy bow…then go slow and be consistent with your scrapes until you hit your target weight.

In this case, you’ve passed that point, so remove wood where you need to without touching the too-bendy areas, get the bend like you want it, and proceed.  The bow will be underweight, but you can remedy that once you have the tiller right.  At that point, heat treat the entire belly in a consistent manner.  You can remove length.  You can add recurves.  You can back with sinew.  You can do all or any combo of the above. 

I have no clue as to your best move with this current stick…take advice from the many awesome boyers on here other than me on that front.

Good luck with the current project…keep at it!

Offline ssrhythm

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Re: Tillering issues
« Reply #2 on: November 02, 2021, 10:05:28 pm »
Or…heat treat the entire belly of the bow FIRST to harden it along the entire length…then remove wood on either side of hinge and on either inside of areas bending too much and go from there.

bownarra

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Re: Tillering issues
« Reply #3 on: November 03, 2021, 03:53:01 am »
The bark will come off anyway, it will make some horrible cracking noises as you progress! Just remiove it all when it is easy to do so.
Never heat treat one part of a limb to 'stiffen' it....bad things will happen!
As you have already heat treated part of it...do the rest. Take some pictures of the unstrung bow and it partially bent.
Somebody just posted a thread on photo sizes.

Offline Don W

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Re: Tillering issues
« Reply #4 on: November 03, 2021, 06:41:26 am »
I agree with removing the bark. My first thought was I wonder if the cracked bark caused the hinge, not the hinge caused the crack.

It's also common to retiller after heat treatment. I would also treat the whole bow.

Figuring out the picture thing will help
Don

Offline Calios

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Re: Tillering issues
« Reply #5 on: November 04, 2021, 01:29:45 pm »
I'll try to send some pictures in a few days, thanks to all people that helped me so far

Offline Calios

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Re: Tillering issues
« Reply #6 on: November 07, 2021, 10:03:40 am »
Hi, I am posting photos of before heat treatment and after, i'll send photo of the crack i was talking about, and a photo of the bow unstrung, thanks again :D

bownarra

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Re: Tillering issues
« Reply #7 on: November 07, 2021, 02:51:30 pm »
I don't see anything drastically wrong. The unstrung picture will help. With it being hazel how wide are the limbs? How crowned is the back? What diameter was the log that the stave came from?
One thing I do see that you need to work on is the fade from the handle into the limbs. At the moment it is too angular. This area should be concave and blend into the limb very gradually.
The limbs need to bend a bit more near the handle but sort out the fades first.

Offline Calios

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Re: Tillering issues
« Reply #8 on: November 07, 2021, 04:56:25 pm »
The bow is 50mm wide at the fades an 40 at mid limb. I usually leave some spare width at the tips to work with, so they are yet to be reduced. The bow was worked down from a sapling, about 80mm wide, and crown was not 'too steep',just right for making a suitable taper for a flatbow. Here are some other picures, the bow unstrung and the crack on  the bark. ask me anything you want to know in addition to this, Atb :)

bownarra

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Re: Tillering issues
« Reply #9 on: November 09, 2021, 03:46:59 am »
Ok thanks for the pictures.
I asked about the width and crown because hazel is a wood that likes a crowned back (strong in tension wood) but it isn't the densest wood out there so needs a decent width to take the compression on the belly. Your dimensions sound good. Hazel varies quite a bit from one tree to the next so it is always best to start off a bit wide.
So the first thing I would do is to remove the bark. It can hide issues and lead to problems. You need to go slowly and not touch the wood underneath. Best to get it down to the cambium along the whole back first then slowly remove the cambium. Not all the way to the wood at once.
In general I like to brace a recurve quite early to see the true shape of the bend. So once you have the bark off and the back cleaned up. Go over the limbs very carefully and make sure the bark wasn't hiding any thin spots(dips in the back can lead to a thin spot on the belly if missed and not compensated for). Then shorten the string and get it to a low 2 - 3" brace.
If it looks good braced then slowly draw to your intended weight (if the tiller remains nice as you draw it further).
Take some more pictures of braced and drawn to your weight.

Offline Calios

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Re: Tillering issues
« Reply #10 on: November 09, 2021, 06:39:01 am »
Thank you, i am going to do everything as soon as possible and send you the results; i'll reduce gradually the width of fades as well then, atb

Offline Calios

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Re: Tillering issues
« Reply #11 on: November 13, 2021, 08:22:05 am »
Hey there, here's my progress so far, removed bark and worked along both fades. It looks like the left limb is bending more than the right one, i fear that by bending it more, it is likely to break the left limb near the fade, hope the image is quite clear, atb

Offline stuckinthemud

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Re: Tillering issues
« Reply #12 on: November 14, 2021, 04:46:54 am »
The centre of the limb is working nicely, but the outer third could be a bit stiff? Have you run a straight adge along it to gauge things? The right limb is too stiff it needs to be softened to match the other limb

Offline Calios

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Re: Tillering issues
« Reply #13 on: November 14, 2021, 05:05:55 pm »
Hmm...i'll probably remove some more wood on the right and near the grip thanks  :OK

bownarra

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Re: Tillering issues
« Reply #14 on: November 15, 2021, 02:16:50 pm »
There is a spot mid limb on the left that is looking a little weak. Remove some more wood from near the fades to mid limb and that spot should look better.
Overall the right limb is stiff. It is also a little stiff coming off the fades to inner mid limb.
A great idea at this point is to unstring the bow put it on the tiller tree and trace the profile of the back onto your wall.
This gives you a reference as you progress through tillering and the bow starts taking some set. Every time you unstring the bow after exercising it you can instantly see how the limbs are different and where your set is showing up.
As a rule you want no set in the inner limbs. A little set mid limb and the rest out to towards  the tips.
The idea behind this is to strain the limb optimally. You always get some set. Watching it as you progress through tillering will show you where weak spots are. Eg. if one limb is taking set  then it is weaker overall.
Good luck!