Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on April 02, 2017, 10:48:32 pm
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This is a Douglas Maple I'm playing with. The full draw looks awful but if you look at the unbraced and braced you can see that the left limb starts with a little deflex and the right limb has a kind reflex, deflex and then reflex thing going on. In the full draw(well 23" of it) the middle of the right limb looks hinged in the middle and too straight in the outer third. But I think it's following the initial shape. I need some more experienced eyes to tell me if I'm following it reasonably closely. I've got another 4-5" to go.
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The left limb looks good. The right is doing most of its bending in the first 3rd near the fades. But the 2nd and 3rd thirds of the bow are almost straight. I would get it bending more in the mid and outer portions
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I agree, Don I'd recommend flipping the tip a bit on the left to try and get the tips even
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The left limb is weaker but you have got the shape on both good. As you say they shouldn't look the same.
This bow is a class example of a great bow to trace the unbrced prebent sideview shape on to the wall. Every time you bend it look super closely at any set that has shown up. Set will always tell you how good your tiller is and where to work on. It never gets it wrong either :)
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This is also a perfect example of why it's beneficial to tiller bows by holding them how we'll shoot them, and then adjust limb strength relative to those holds and each other. Done that way, there's no question whether they're equal strength, regardless of profiles.
For instance, I don't agree the left limb is weaker... at least not simply because it's coming down farther. It started that way, so it should be coming down farther... the whole way to full draw. The right is straight in the mid to outer limb because it started with reflex there, lost some at brace, and then lost more at partial draw, so it's working there. The inner limb is fine, not bending too much there.... since it started with a hump of deflex there. It's all relative. So I think the tiller is really quite good at this point. Things seem to be changing like the whole limbs are working evenly.... from what I can tell on my phone anyway. I like these kinds of bows.
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One word; Gizmo
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How long is the stave? What is your draw length?
That right limb looks a bit stiff mid limb on as you mentioned, DC.
How does she feel as you draw?
Jawge
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Eric, it would have to be very judicious use of the Gizmo. On a stave like that, the Gizmo could screw ya if you didn't really have your ducks in a row. I have a bendmeter that would work well too, used with the same amount of 'restraint'.
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Not so, I have used a gizmo on all kinds of staves the naysayers proclaim to be a bad idea.
Nothing unusual about that piece of wood except the right limb is bending only at the fade. Set the gizmo at the deepest part of the bend on the left limb (which looks pretty well tillered) and go to work on the right limb.
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Funny how people see the same thing differently. I see two completely different limbs that will look different at full draw. I think you are on the right track but feel the reflexed area on the right limb could bend a bit more. I like these kind of bows too. Take what the tree gave you.
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Yep, me too, two differently shaped limbs. I'd treat them as individuals except for the overall balance between them, and not look for them to bend the same at any point in the draw or any point along their length.
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Unless you're going to match the limbs with heat before any bending takes place they can't bend the same.
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Lots of perspectives presented on a tricky skill to master.
and then adjust limb strength relative to those holds and each other
BTW, Dances, how do you best "see" when the relative strengths need adjusting?
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To me it just looks like it has a bit of a flat spot between the end of the deflex and start of the reflex in the right limb. The left looks good to me. That's all I see going on. Personally I would just touch. That a bit and of the set looks good, carry on pulling back.
Kyle
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I glued bamboo skewers to the bow. Now I will measure the distance between the tips of the skewers. That will determine where it's bending and how much. Braced will be easy and I'll post the results but the "full draw" I'm not sure. I think I'll print out the picture and use a pair of dividers the compare distances. If anyone has a CAD program that could measure them that would be great. Maybe we can run a lottery ;D ;D ;D
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Quite the porcupine!! ...................Or bend magnifiers
in all seriousness, rather than measuring, just watching the skewer tips as you exercise the bow might be telling.
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They are quite close. My measurements didn't show up well on the picture so from left to right
6 3/16
6 7/16
6 5/8
6 3/8
5 3/4
5 13/16
6 1/2
6 7/16
6 1/8
6
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Willie, assuming the handle is level, with a vertical/plumb line drawn on the wall to mimic string fulcrum travel perpendicular to the handle, the hook on the string will leave that line and drift toward a stronger limb. If the limbs are balanced, it follows the line.
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I pulled it out to about 20"(roughly, I was in a hurry) so same order left to right
6 1/2
6 7/8
7 1/8
7
6
6
7 1/4
7
6 3/4
6 1/4
They look pretty close. I don't think it anywhere near as bad as it looks. Those that said the inner right was weak and outer right was strong got it. I think if I had started out with equal limbs I would have been happy. I'm going to try this on a bow i'm happy with just to see how close I'm getting.
With this one I'll leave the inner right alone and flip the tip on the left, like Goat suggested. I started this exercise to see if I could tiller a bow without heat correction. From now on I think I'll correct them first. It was interesting though :)
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Willie, assuming the handle is level, with a vertical/plumb line drawn on the wall to mimic string fulcrum travel perpendicular to the handle, the hook on the string will leave that line and drift toward a stronger limb. If the limbs are balanced, it follows the line.
The problem with using that method alone is that it only shows the overall strengths relative to each other regardless of deflex/reflex etc....whilst it is obviously a good idea to tiller the limbs so their strengths are even you have to take into account that a deflexed area has to be thicker to give the same resistance as a reflexed limb - this in turn leads to a thicker limb being more strained if bent to the same degree as a thinner reflexed limb, none of this will be shown by the 'Bowjunkie string following the line method'.
Watching the set tells the whole story. After all went we are tillering a bow we want the stress to be even along the limb without any areas working too hard or any areas loafing, spreading the set appropriately along the limb is the goal not just that the limbs are relatively the same strength.
Different folks different strokes ;)
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Where did I say to use that alone? It's one tool/gauge... albeit an important one. Unfortunately, many folks discount limb balance, and/or work counter to it until it's too late. If they designed their bows to facilitate it, and balanced limb strength earlier in the process, that too would help with set.