Author Topic: Tillering question  (Read 897 times)

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Offline DC

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Tillering question
« on: January 12, 2019, 08:45:05 am »
I've got this on the tree and I'm just pulling it about 10". The cradle is curved so the bow can rock. When I start to pull it the bow rocks on the cradle. The left side, where the arrow is, goes up just a bit while the rest of both limbs bends down. If I slide the bow to the right 1/4" it stops doing that. If I slide it 1/4" to the left it gets worse. I think it means that the right limb is stiff but I thought I would check with you guys.
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Offline Del the cat

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    • Derek Hutchison Native Wood Self Bows
Re: Tillering question
« Reply #1 on: January 12, 2019, 09:02:25 am »
Yeah, the stiff limb will pull down.
Del
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Offline Badger

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Re: Tillering question
« Reply #2 on: January 12, 2019, 10:09:48 am »
   Nice profile on that bow. Looking forward to seeing how it does. Is it a self bow?

Offline DC

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Re: Tillering question
« Reply #3 on: January 12, 2019, 10:19:20 am »
Yup, it's a spliced Doug Maple selfbow. I actually got more reflex in it than I wanted but I'm sure I'll lose some.
Thanks Del
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Offline Sticks

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Re: Tillering question
« Reply #4 on: January 12, 2019, 10:25:53 am »
Probabley nothing but I noticed the tillering string looks like it is pulling off the side of the bow on the left limb below the reflex.

Offline DC

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Re: Tillering question
« Reply #5 on: January 12, 2019, 11:45:57 am »
It does look like that but I haven't moved it since I took the picture and I just went out and looked and It's all OK.
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Offline DC

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Re: Tillering question
« Reply #6 on: January 13, 2019, 06:04:12 am »
I may have discovered something. I was thinning out the outers trying to get them to move a bit. Nothing seemed to be happening then all of a sudden it bent. Didn't break but it bent quite a bit and then returned. It took quite a bit of set. I've had this before and couldn't figure out what was happening. This morning just before I got up it occurred to me that the string was just lifting off the section that bent. Is it possible that before the string lifts the limb is in compression and removing wood doesn't do much and then as the string lifts off all of a sudden there is a bending moment and it just bends? I'm thinking that with working reflex/recurves that a person should not tiller a section until the string has lifted or at the very least go real careful in areas where the string hasn't lifted. Maybe this is a place where a long long string might help. It would put some strain on more of the limb. Any ideas whether I'm right about this? It's a new idea for me but I'm sure it's well known if it's an actual thing :D
  I've heat treated the spot that bent in hopes that there is still enough life in it to make a bow.
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Online Pat B

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Re: Tillering question
« Reply #7 on: January 13, 2019, 07:02:00 am »
DC, did you exercise the bow after each wood removal session?
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline DC

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Re: Tillering question
« Reply #8 on: January 13, 2019, 07:47:28 am »
Yup, maybe not enough?
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Offline Badger

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Re: Tillering question
« Reply #9 on: January 13, 2019, 08:21:06 am »
  When you have a bow with curves you have to keep in mind that you will have sudden leverage changes as it starts to bend. Every part of your limb is responding to the string according to its current string angle. If you take an arrow and push straight down on it it will support a lot of weight, as soon as it starts to bend it will suddenly just go all the way if you don't back off the weight. This is one reason I use full target weight pulls from the very beginning. I attempt to keep all parts of the limb too strong until I hit my target draw weight at target draw length.

Offline bradsmith2010

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Re: Tillering question
« Reply #10 on: January 13, 2019, 09:27:10 am »
I even feel like the full draw will put a different pressure on the bow,, like Badger said the string angle is different,, I am always prepared for the bow to shift a bit,, shooting at full draw,, and will make adjustments as the wood stabilizes,,, if needed,, I have also noticed the sinew bows take longer to reveal any tiller adjustments or removal of wood,,

Offline DC

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Re: Tillering question
« Reply #11 on: January 16, 2019, 09:35:12 am »
This thing is giving me fits!! I heat treated the portion of of the limb that was trying to hinge. I did the same area on both limbs. Gave it a day to rehydrate and back on the tiller It seemed nice and strong. I was getting 9-10" on the short long string. A few scrapes and then it happened again. It was threatening to hinge again just inside the portion I heat treated. What's happening is I'm drawing it to 40# at,say, 9". I exercised it 30-40 times no problem. Take another 10 scrapes, back on the tree and now it won't go to 40#. I can pull it to 12" and it won't reach 40#. It will go to 37 or so. It's like the belly is collapsing. No crysals. So I heat treated the rest of the limbs. Let it rest. Start again. Nice and stiff 40#@ about 8". A few scrapes. All of a sudden I can't reach 40# again. I cut the wood beginning of last May. It's stopped losing weight. It's Douglas Maple. I've made a few bows from Doug Maple and never had this before. I pull to full weight from the beginning. I exercised after every scraping. Ideas?

PS Is it possible that with this much reflex it's just too much for the wood?
« Last Edit: January 16, 2019, 10:00:27 am by DC »
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Offline Badger

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Re: Tillering question
« Reply #12 on: January 16, 2019, 11:44:18 am »
  Sounds like your belly is collapsing. Douglas maple is not really a bow wood, too soft.

Offline DC

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Re: Tillering question
« Reply #13 on: January 16, 2019, 01:17:54 pm »
I've had good luck with it before but not with a highly stressed design like this.

This is the previous one I made and kind of thought I could push it a bit https://www.primitivearcher.com/smf/index.php/topic,63332.msg889583.html#msg889583

Looks way different, think I overdid it ;D ;D
« Last Edit: January 16, 2019, 01:22:22 pm by DC »
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Offline Badger

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Re: Tillering question
« Reply #14 on: January 16, 2019, 01:56:02 pm »
  If it tested at .60 sg is should be a good bow material. I have made quite a few bows from it but all of them were simply board bows. The SG on the ones I tested were closer to .50. These were just home depot boards.