Author Topic: Tiller advice needed  (Read 4841 times)

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Offline RyanY

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Re: Tiller advice needed
« Reply #15 on: July 04, 2021, 01:27:40 am »
That comment from you was argumentative, as most of your posts seem to be. But hey, maybe you know a few things about tillering bows that I don’t. And I am eager to learn from you if so. Is a bow, with a perfectly circular drawn profile, perfectly tillered?  I’m interested to know your take on this.

 ;D (-P

Offline scp

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Re: Tiller advice needed
« Reply #16 on: July 04, 2021, 02:38:50 am »
I would love to improve on Tim Baker's mantra. But I have no interest in learning and using higher math and physics, almost from scratch, at my age. I also have no time and energy to make hundreds of bows. I would love to have the ability to do thought experiments on mechanics of natural material, especially using ordinary language.

IMHO most hobbyists can only rely on their sense of "beautiful curves" and arrow speed or flight distance. But I have faith in our common sense. If we think hard enough, we might be able to come up with an ordinary language paradigm for making decent bows without too much trial and error. Therefore I spend more time thinking about the "best process" to follow in making good natural material bows, than actually making bows.

The only thing that's actually going for me for now is that I have no vested interest in any dogma. I don't have to commit to any of dogmas. They are usually too vague and ambiguous or way too specific, to be useful anyway. Common sense does not have to be simplistic. If you are cock sure about something in this life, you are probably clueless about it.

With humility but also with sincere faith in our capability, we need to tackle whatever that is worthwhile. If lawyers can decide life and death issues using mostly ordinary language reasoning, we can probably come up with an improved mantra useful for making good bows. As I said earlier, I think it would be useful to combine Tim's mantra with the mass principle. We are pursuing more efficiency here. Searching for perfection would be silly and counter-productive.

My current guiding principle is "the evil of banality". What is our most common mistake in making wooden self-bows? Most beginners are too eager to bend the staves when those are not ready. To many people, this kind of reasoning process might look silly. But this common sense reasoning is what actually prevails even in this forum. By and by, I will do my best, if my schedule permits, to flesh out how we can actually make our bows more efficient, by just talking about them using ordinary language. No technical jargon, no higher math or physics required. It has been that way for thousands of years and bow making did evolve.


Offline stuckinthemud

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Re: Tiller advice needed
« Reply #17 on: July 04, 2021, 09:38:17 am »
Woah, steady on guys, I asked for tiller advice because I don't like to work on my own.  This "project" in effect is a bend test.  I did in fact glue in a weak spot as I thought the splice would re-enforce the weak point. I was wrong.  Lesson learned. I am also testing  new (to me) glue.  It is brilliant,  definitely going to use it again.  Also a new type of timber. It is amazing, going to harvest as much as I can get.  Also suitable front profiles and thickness needed for desired draw-length/weight . I have that info now.  The mistake I made at glue-up has forced me to halve my draw weight but its been a very useful project. I'll post another picture soon. This is the unbraced profile

« Last Edit: July 04, 2021, 09:51:03 am by stuckinthemud »

Offline SLIMBOB

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Re: Tiller advice needed
« Reply #18 on: July 04, 2021, 10:15:34 am »
Hey stuck.  My thoughts, that pic shows several things. The bow has already taken set near the top fade or, as I mentioned, that is the natural resting shape of the stave.  Secondly, the outters show the same, and yet the drawn pic doesn't show them bending much at all.  If it is a hinge, you need to get the limbs bending mid limb and out.  Really, even if it is a kink, the the outters still need to bend more.
Liberty, In God We Trust, E Pluribus Unum.  Distinctly American Values.

Offline Don W

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Re: Tiller advice needed
« Reply #19 on: July 04, 2021, 10:21:18 am »
Hey stuck.  My thoughts, that pic shows several things. The bow has already taken set near the top fade or, as I mentioned, that is the natural resting shape of the stave.  Secondly, the outters show the same, and yet the drawn pic doesn't show them bending much at all.  If it is a hinge, you need to get the limbs bending mid limb and out.  Really, even if it is a kink, the the outters still need to bend more.

If I may ask a related question in a question, how would you tell (or can you) the difference between set or natural string follow unless you have the original picture of the stave before construction begins (which I really need to remember from now on)
Don

Offline scp

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Re: Tiller advice needed
« Reply #20 on: July 04, 2021, 10:24:38 am »
Thanks. The lower fade does show a slight deflex. It might have been that way or it can be the effect of set. Did you say how well seasoned the stave is?

Offline SLIMBOB

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Re: Tiller advice needed
« Reply #21 on: July 04, 2021, 10:36:52 am »
Don, I can't from a pic.  The maker knows what the original prestressed profile was and the rest of us only make assumptions.  The same goes for set.  The bowmaker knows the bow started with 1.5" of reflex and ended with 1".  Or, started with 6" of reflex and ended with 1".  They both look the same to us, but they can be different bows in performance.
Liberty, In God We Trust, E Pluribus Unum.  Distinctly American Values.

Offline stuckinthemud

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Re: Tiller advice needed
« Reply #22 on: July 04, 2021, 02:56:55 pm »
The only set the bow took at the point shown in the picture was a little straightening of the reflex the billet took while drying.  What deflex there is below the fade is the weak spot around a knot that caused me a lot of trouble.  Anyway, having failed to cause any set, I did manage to create a big hinge reducing the tips so I piked 4 inches off both limbs and cut straight through the edge knots just to see how much abuse the stuff can take.  Still got no set and it doesnt seem to care what you do with the knots, looks like they can mostly be ignored

Offline stuckinthemud

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Re: Tiller advice needed
« Reply #23 on: July 04, 2021, 05:12:23 pm »
It currently looks like this, drawn to 16 inches on a short brace height of 3 inches. No permanent set as such, 1/4 inch of "soft set" that disapears soon after unstringing   so need to go slowly now but top limb centre looks stiff at the moment.  Heading toward 30lb at 20 inches.  I'm thinking a 44 inch bow ttt with a 4 inch handle plus 6 inch of fades would pretty much max out at 20 inches draw length?


Offline stuckinthemud

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Re: Tiller advice needed
« Reply #24 on: July 06, 2021, 03:25:20 pm »
Stil at 16 inch draw, figure I need a  couple of scrapes on both outers and just a bit off the inner right,  centres are working too hard.

Offline stuckinthemud

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Re: Tiller advice needed
« Reply #25 on: July 07, 2021, 05:12:49 pm »
Its a bit better balanced now, this is at 14 inches, any thoughts on how I gain 4 more inches of draw length?


Offline SLIMBOB

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Re: Tiller advice needed
« Reply #26 on: July 07, 2021, 08:57:37 pm »
It looks to me as though you are not using the straight edge. It will dramatically help your tiller. This one appears to be headed out of balance.  Not too late, just check it and see what it says. It is better in the last pic, but it can be improved upon.
Liberty, In God We Trust, E Pluribus Unum.  Distinctly American Values.

Offline stuckinthemud

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Re: Tiller advice needed
« Reply #27 on: July 08, 2021, 04:18:13 am »
Umm, no , I am using a 4 inch straight edge, not gone full gizmo yet but will attach a pencil to the edge for final shaping. Theoretically,  the limit for this bow (43 inch ntn) is 17inch draw, its pulling happily to 15, showing a little soft set which disapears within 5 minutes of unstringing when drawn tp 16.  It looks to me like the tips could soften a little.  Would you shorten the fades at all or be happy as things are?

Offline scp

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Re: Tiller advice needed
« Reply #28 on: July 08, 2021, 07:49:19 am »
I would simply v-splice at least 6 inch long new tips and reinforce them with underlays and possibly even overlays. With modern epoxy, you don't have to to wrap them with sinew or other fibers. Even 12 inch glued on tips are not out of the question. They just need to be stiff. You have choices.

Offline stuckinthemud

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Re: Tiller advice needed
« Reply #29 on: July 08, 2021, 08:38:05 am »
Ordinarily that would be a good way to go but the extra length will push it too far under weight.  Its lighter than I would like as it is and going to be lighter by the time I'm all done, unless I sinew it of course