Flipped Tips or Limb Reflex?

[Eric Garza]

It took me a while to figure this out, but now I realize the 'experiments' you are running are being done on a computer program, and not with actual bows. How do you know that the computer program accurately represents actual wood?

[PatM]

 No idea on the speed, that is not something that can be analyzed mathematically. Or at least not something I can do with math.

Mark

  This struck me as an odd statement based on the whole point of the topic  and your interest in the engineering  side of things,

[willie]

 No idea on the speed, that is not something that can be analyzed mathematically. Or at least not something I can do with math.

Mark

  This struck me as an odd statement based on the whole point of the topic  and your interest in the engineering  side of things,

Pat,
 there are methods to make speed calculations, but there are also quite a few more variables that have to be considered which make the results less precise. ie, more like an estimated range of possible speeds.

[diliviu]

Anything else being equal (so same overall reflex and let's say an even tiller, so the flipped tips are bending exactly as much as the rest of the limb) flipped tips bow will store a tad more energy and be a little faster. A simple matter of angles and decomposition of forces. Flipped tips bow simply gains more in the late draw compared to what it loses in the early draw. Same amount of stress on 2 "identical" bows that only differ in shape doesn't mean also same amount of stored energy.

[PatM]

 No idea on the speed, that is not something that can be analyzed mathematically. Or at least not something I can do with math.

Mark

  This struck me as an odd statement based on the whole point of the topic  and your interest in the engineering  side of things,

Pat,
 there are methods to make speed calculations, but there are also quite a few more variables that have to be considered which make the results less precise. ie, more like an estimated range of possible speeds.

Yes, and i thought that would be a key interest for those of that inclination.

[Selfbowman]

Anything else being equal (so same overall reflex and let's say an even tiller, so the flipped tips are bending exactly as much as the rest of the limb) flipped tips bow will store a tad more energy and be a little faster. A simple matter of angles and decomposition of forces. Flipped tips bow simply gains more in the late draw compared to what it loses in the early draw. Same amount of stress on 2 "identical" bows that only differ in shape doesn't mean also same amount of stored energy.

Not a engineer but I think this is spot on.  One finally put it in terms I can understand. Thanks Arvin

[Bob Barnes]

A pyramid taper for a recurve isn't optimal and stiff tips on a pyramid also isn't optimal. So its a bit like comparing apples and oranges - that is what I was getting at. You are not making a 'fair' comparison. Indeed it is next to impossible to do so and come up with anything meaningful.
An optimised pyramid and an optimised flip tip bow - the pyramid will be faster.

Arvin?  This makes it sound like flipping or recurving the tips on your bows is a bad thing?  It's all over my head, but interesting none the less... 

[Selfbowman]

I’ve just been doing it because it works . Flipping the tips and a ease of building a pyramid on straight grain wood. The perfect Diminishing mass in a pyramid with some added back in fades and ends. The ends to hold reflex and the extra mass at fades for the extra strain at full draw because of the flipped tips.  I do this because I have not moved the mass else where yet. That was better. I’m looking at DC’s work though!  Arvin

[mmattockx]

It took me a while to figure this out, but now I realize the 'experiments' you are running are being done on a computer program, and not with actual bows. How do you know that the computer program accurately represents actual wood?

Because I have compared Super Tiller's output to David Dewey's design spreadsheet and to bows I have made. It isn't that hard to model structures and wood is not a totally wacky material that is unpredictable in its response to a load so it can be done with reasonable accuracy.

This struck me as an odd statement based on the whole point of the topic  and your interest in the engineering  side of things,

I would love to be able to model the whole shot, but it is extremely complicated due to the dynamics involved and the math gets beyond ugly. Developing that model would be a PhD or post-doc level project and I have no desire to subject myself to that sort of agony again.


Mark

[PatM]

Hasn't someone else done that math and you can just plug your numbers in?

[mmattockx]

Hasn't someone else done that math and you can just plug your numbers in?

Not that I have found. There are lots of people that have worked on numerous vibrations/harmonics/dynamics problems and there is software for some of it, but we are a small niche area and not on the radar of most academics in terms of areas of research.


Mark

[bradsmith2010]

shooting through a chronograph,, would give you useful information,,it wouldnt take many bows to figure what design had better cast,, of if it was a wash,, and might vary from bow to bow,,I have a feeling it would be close and depend on the wood and the tiller execution, more than energy storage,,I think I read everything, and no chronograph numbers,,,wouldnt that help with comparisons,,

[mmattockx]

I have a feeling it would be close and depend on the wood and the tiller execution, more than energy storage,,

This is the problem with comparing two (or more) bows. Even made from the same tree or board the wood will have differences and the fine differences in tillering are impossible to eliminate. It is a very challenging problem to deal with.


Mark

[willie]

I have a feeling it would be close and depend on the wood and the tiller execution, more than energy storage,,

This is the problem with comparing two (or more) bows. Even made from the same tree or board the wood will have differences and the fine differences in tillering are impossible to eliminate. It is a very challenging problem to deal with.


Mark

do you suppose it would be less challenging if we made FG bows?

[bradsmith2010]

  yes but there would be some patterns that would become apparent,, even with variations,, one can see that,, with the bows being posted here,,Badger DC Mark,, posting chronograph results that show performance, but so many variaitons on that,,even in one bow design, being over stressed or not,, does keep it interesting,,