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Discussion Starter · #1 · (Edited)
In one of the BB archery manuals I read about cutting one's arrow so that it hits the plunger on or just behind the forward node. During my online research I found this discussion in the AT archives where coach Don Rabaska answered an inquiry from JimC. The answer:

Hi Jim

Concerning the discussion on node positions, the plunger needs to be just behind the front node (toward the nock) at launch from button, i.e. at the completion of the 1st half cycle of the arrow. While the arrow is under column loading it bends toward the bow and at the completion of the first half cycle it leaves the arrow rest. The arrow then shifts to the next half cycle. Optimum cycling of course is for the arrow to complete one full cycle. Less than one cycle, the arrow is stiff and more than one cycle the arrow spine is weak.

The node position you find by vibrating the shafts between your fingers is not the node position during launch. That initial node position is further up the shaft toward the fletching. Remember, nodes move toward mass. Therefore, while the arrow is being moved forward by the bowstring the bowstring equates to mass, so both the front and rear nodes move more toward the nock during launch. Once the arrow is free from the influence of the string, the arrow nodes then shift forward (toward the point) and the arrow goes into what is called "free free" beam mode.

My guess is that the arrow is in its most stable position at about 1" past the free free beam node position when completing its first half cycle. That is something I have wanted to experiment with for a long time. I believe you can develop the most stable "arrow length" possible by calculating the position of the primary node and free free beam node, then cut your arrows accordingly so at launch from the button the arrow is in its most stable position. Of course this is with a set point weight, fletch weight, and all other components remaining constant. Change any of those parameters and all bets are off

I am sure it is no small coincidence that Korean archers tend to shoot fairly long arrows and long clicker extensions where the arrow "shaft" (not including point length) is well over 1" ahead of the button at full draw.

I hope that helps answer your question. Depending on point type and point weight, I think as long as you have roughly 1 inch of "shaft" ahead of button at full draw, you are in a very safe range to control left/right impact. It may not be absolutely optimum, but still good.

Best wishes,
Don
I wanted to experiment with this idea, but I didn't see how to determine where the "free free beam" node, or even the regular forward node, will be before the arrow is cut. I know about testing where it vibrates most. However, it seems a little tricky because if you cut the arrow, that will alter the node point, so how do you figure where to cut so it ends up where you want it?

Does anybody here cut their arrows to the forward node? If so, I'm interested in how you calculate that with a full-length shaft, and also if you've noticed it has made a difference to arrow flight.
 

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The forward node is the bending point furthest away toward the end of the arrow. The rear node furthest back and neither can be determined in the static state. Where the arrow bends in the middle determines the forward and rearward nodes dynamically at the peak of the power thrust on the rear of the arrow.
 

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Discussion Starter · #5 ·
The forward node is the bending point furthest away toward the end of the arrow. The rear node furthest back and neither can be determined in the static state. Where the arrow bends in the middle determines the forward and rearward nodes dynamically at the peak of the power thrust on the rear of the arrow.
Thanks Sam. I think I understand what the forward node is. I've identified it in my cut arrows by how long vibrations persist in the forward spot when I bang the arrow on something.

What I'm trying to calculate is where to cut a full-length shaft so that the plunger ends up on the forward node. The problem is that before cutting, the forward node will be in one place, and in a different place after cutting.

It seems like nobody knows the answer, so I'll probably estimate it by putting a point, nock, and fletching on a full length shaft, finding where the node is that way, and then extrapolating somehow where it will be after cut for my DL.
 

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Yes I have heard of this.

OK, so say you accurately determine where to cut in order to get your nodes "correct." What if that's a 26" shaft and you have a 28" draw length? Or if the "node correct" cut still leaves the arrow out of tune either too stiff or too weak?

I guess what I'm saying is that if you tune correctly, to begin with, then the nodes will take care of themselves. The arrow will make it around the riser properly. And if they don't get right, ...well, ...then obviously the arrow is still not correctly tuned.
 

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OK,,without extensive testing in percentages there would be no accurate to do that on a certain set up unless? You just tune with a tip weight 25 grains too heavy/then add an inch of shaft length on the next arrow and add the reduced tip weight and bare shaft to test and fine tune it with plunger tension.
 

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Discussion Starter · #11 · (Edited)
Good stuff, thanks for that. Of course, they didn't come up with a way to calculate the forward node to plunger either. What I'm thinking now is that the node might be consistently found at some percentage of the over all length (with point, fletching, nock all in place). Then, if I use what percentage of the length I find the node while the shaft is full length and apply that to a cut arrow, I might be able to approximate where it is. Or (more likely) I'll find the node at full length and then just cut a fraction off at a time until I find the right length to make the button line up with the node.
 

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Of course yo can always move the plunger to the forward hole............
 
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Good stuff, thanks for that. Of course, they didn't come up with a way to calculate the forward node to plunger either. What I'm thinking now is that the node might be consistently found at some percentage of the over all length (with point, fletching, nock all in place). Then, if I use what percentage of the length I find the node while the shaft is full length and apply that to a cut arrow, I might be able to approximate where it is. Or (more likely) I'll find the node at full length and then just cut a fraction off at a time until I find the right length to make the button line up with the node.
Here's some more.
http://www.archeryinterchange.com/f37/front-node-145619/
When l find time l will look at this closer. I think it pretty simple. FOC is the starting point, from I read. Look at the drawing closer.
DDD
 

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Discussion Starter · #14 ·
Of course yo can always move the plunger to the forward hole............
After hearing a couple of people here talk about doing that, I coincidentally moved my plunger to the forward hole (before getting into this node thing). I couldn't tell much difference to my arrow flight, plus my arrow rest no longer reached the button so I moved the plunger back. However, re: the node idea, if I did move the plunger forward, that would require the arrow be even longer to get the button on the node.

Here's some more.
http://www.archeryinterchange.com/f37/front-node-145619/
When l find time l will look at this closer. I think it pretty simple. FOC is the starting point, from I read. Look at the drawing closer.
DDD
Interesting. Clearly "Joe" doesn't agree with the coach I quoted, but I'm not sure it's from experience or an untested opinion.

I realized that I shouldn't have assumed everybody knows what the nodes are so I'll explain it now. I read about it on the Archer's Reference, section 2.2.3.2. Here's what it says:

The point at which the arrow rests against the button at full draw should ideally be one of the two "node" points, i.e. one of the two points of the arrow which do not move laterally during flight. This will tend to reduce the effect of a poor release as the node points of a shaft in flight tend to stay nearly still compared to the point of the shaft as illustrated below.



So how do we find these invisible magic node points? A bit like tuning a string. Dangle the arrow vertically between finger and thumb somewhere near the tip of the arrow and tap the lower end against a solid object. Note the length of the vibration. Now move your hand down the shaft and try again. Repeat this process until you find the point of maximum duration. This is the front node point of the
arrow. Easy!
My current arrows are 29" from nock groove to tip of the point, and the node seems to be about 2.5 inches back from the point. I use Top Hat points, which have a long neck, so I think that affects things. Anyway, if I were to cut my shafts to put the button 2 1/2 inches back (about 3/4" more shaft), I assume a longer shaft will also move the node, so there's what I'm trying to figure out.

As I said, I'll probably experiment by cutting a little at a time. There's little risk since I can always go shorter if the node thing turns out to be of little consequence. It's just the complications of how stiffness is affected, FOC, arrow weight, aiming . . . :confused:
 

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"Anyway, if I were to cut my shafts to put the button 2 1/2 inches back (about 3/4" more shaft), I assume a longer shaft will also move the node, so there's what I'm trying to figure out."

It will.
 

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I already have too many constraints when I tune. Arrow weight, high FOC and preferred arrow length constrain me already and make tuning challenging, but still quite doable. I'm not about to add more trouble with this very nebulous constraint of having the button at an exact location relative to the node. Man, then I would have to do a difficult scientific experimental test for every arrow/setup choice.

However, the basic guideline to have the arrow shaft (not point) extend about 1 inch past the button at full draw seem like good guidance. That's simple to apply and good enough for me. ... Well, it's simple and good enough because that's what I always end up doing anyway without even know why. Now I can sound smart and give someone a good reason as to why I choose the arrow lengths that I choose. :)

It's amazing too me that we see so many different opinions about tuning. Some people don't worry about it at all and just chose something reasonable without even testing, and then the other extreme is to worry about nodes and millimeter precision. I guess I fall in the middle somewhere.
 

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Discussion Starter · #17 ·
I already have too many constraints when I tune. Arrow weight, high FOC and preferred arrow length constrain me already and make tuning challenging, but still quite doable. I'm not about to add more trouble with this very nebulous constraint of having the button at an exact location relative to the node. Man, then I would have to do a difficult scientific experimental test for every arrow/setup choice.

However, the basic guideline to have the arrow shaft (not point) extend about 1 inch past the button at full draw seem like good guidance. That's simple to apply and good enough for me. ... Well, it's simple and good enough because that's what I always end up doing anyway without even know why. Now I can sound smart and give someone a good reason as to why I choose the arrow lengths that I choose. :)

It's amazing too me that we see so many different opinions about tuning. Some people don't worry about it at all and just chose something reasonable without even testing, and then the other extreme is to worry about nodes and millimeter precision. I guess I fall in the middle somewhere.
Your common sense approach is one I like for most things in life. The exception for me is when nobody seems to have actually experimented to see what sort of difference something will make-who knows what treasure is yet to be discovered! Even the gentleman I quoted in my opening post said node positioning was something he "wanted to experiment with" (i.e., he hadn't yet).

Like you say, it complicates things, but is it worth it? I know some people leave their shafts at full length for aiming purposes, I wonder if they've stumbled on something else too. I have to buy new arrows anyway for my super-fast new Hex 6h limbs :) so I will experiment with shafts full length and trimming them to try to reach some optimal point.
 

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I agree les3564. I would never want to discourage anyone from experimenting and learning more. Maybe there is something useful to be discovered.

If you discover something, hopefully we can then distill the discovery down into some "easy-to-apply" instructions, for people like me. :)
 
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What about leaving a shaft full length but using a point with an extra-long shank to increase dynamic spine and move the node rearward? Perhaps combined with using the forward plunger hole to align the horizontal resistance point with the node.

-Grant
 
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I have looked at this a little more. If your arrows are 30" long. 15" center and FOC at 12" or 10% and if your not using Nibbs. Then the rear node should be approx at 7.5" from the nock groove. Since the front node is not the same as the rear. being the point weight is heavier than the rear, 10% front. The front will be approx 5.805" from the point or 0.93512304 x length. Work with this. look at your drawing above. redraw the front X. As you will see more FOC or less shaft lenght pushes the node forward. Well I think. I have to admit, I really didn't think about This much. All Approxmations.
DDD
 
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