Do we believe in nodes?

[Quadratus]

I have just seen the GRIV DVD 'Professional Tuning Techniques'. Ok, so he can't count past 3 - anyone who has seen the DVD will know what I mean - but most of it is pretty good stuff, especially the section on string making.

GRIV strongly recommends shooting a arrow with enough overhang for the 'node' to be directly on the launcher (or, next to the button). He also shows a way of finding the 'node'. This raised a few questions in my mind:

a) Do these 'nodes', ie points where vertical (or in the case of finger shooters, horizontal) vibration is practically nil, actually exist at the moment of the shot?

b) If they do, are they where GRIV says they are? He holds the full length shaft with point pushed in against a hard edge and twangs the shaft, moving the arrow backwards and forwards. The 'node' is the point wher the shaft hardly jumps against the edge. He then says something like "this shows the node of this shaft/point combination is 2 inches behind the point, so I'll cut it so 2 inches are in front of my launcher".

c) Does any of this matter in practice? Should we determine shaft length like this?

I'm not looking for a mathematical discussion of wave forms, harmonic frequencies and columnar compression - been there, done that, didn't even understand the T-shirt. What I want to know is whether anyone out there actually cuts their arrows on this basis and does it make a difference in practice.

Thanks Folks.

[Duss]

One of the nodes I believe has most importance is the rear node. Mostly the rear node in relation to the bracing height.

Joe Tapley has a very good illustration of that. First read his "Finding the Nodal Points" and then go to the "Bracing Height" paper here :
http://homepage.ntlworld.com/joetapley/

[geoffretired]

I guess it will make a difference. Will it be better or not? If it is better, is it the result of the extra weight in the arrow or the reduced stiffness?

[joetapley]

To start with arrow launch behaviour from a compound and recurve are very different so you can't lump them together.

Many (good) coaches have suggested that for a recurve if the arrow projects too far in front of the button then, in terms of groups, the setup becomes unforgiving. You can only speculate as to the reason why this might be as currently there is not the understanding of arrow behaviour or "tuning" at this level.

What people are suggesting for a recurve is using a rule of thumb e.g. you could say "keep the shaft length in front of the buttton below 4 inches". The node idea is a rule of thumb (it has nothing to do with whether nodes actually exist). It's saying "here is a defined point on an arrow shaft - you should be OK if at full draw this point is behind the button".

[TJ Mason]

I see so much variation in arrow length among setups that shoot very well that I'm not convinced nodes are worth worrying about. Also, how would you work them out? The position of the nodes in free flight are easy enough to determine, but they'll be different to when the back of the arrow is constrained by the string. Don't know how you'd determine those.

[mk1]

'oi I've got a node to pick with you!!



I went this route with a set of ACE's on my recurve when the trend started to keep arrows as long as possible and use the clicker extension plate. It worked well, but perhaps that was because my arrows were on the stiff side to start with and and inch longer weakened them a little. In principle I think there are so many other factors in play around optimum arrow set up and tuning its better to deal with the ones we understand and get them right.

[Jimster71]

Archer 1: My arrow has no nodes!

Archer 2: How does it group?

Archer 1: Terrible.

The dog joke works better, I'll get my coat....

[Duss]

I have measured node positions in the "free" and in the "constrained" modes. The difference in position between both modes is around 1/4". Not very significant a difference.

Here is the method : "SOURCE 1
Nodal point- To determine if you are at the front nodal point hold your arrow by the knock pinched between thumb and index finger (point down, allowing arrow to swing) held at about eye level. Next, with fingernail of other hand tap on the surface of the arrow shaft starting at the point and moving your finger nail in a tapping motion up the shaft until you feel a dead spot. (No vibration felt in hand holding arrow and finger tapping on shaft) probable between 2 ½” to 3” from the point. Mark this with a sharpie marker or other. Next, draw this same arrow in your bow and have someone else mark the point where your arrow and arrow rest contact. You would like to be as close to the nodal point at full draw. Give it a try "

The node that I find the most interesting is the REAR node in conjunction with the bracing height. It actually makes a lot of sense physically. It also would support the notion of a very forgiving set-up. Thanks Joe!

The rule I apply with the rear node is that my bracing height should be about 1-3/4" longer than my rear node position (to the bottom of the nock). My rear node is at 7-1/2" and my BH is 9-1/4". Spot on!

My front node is almost on the button and my clicker is at almost 4" in front of my button. Seems to work.

Originally Posted by TJ Mason

I see so much variation in arrow length among setups that shoot very well that I'm not convinced nodes are worth worrying about. Also, how would you work them out? The position of the nodes in free flight are easy enough to determine, but they'll be different to when the back of the arrow is constrained by the string. Don't know how you'd determine those.

[Quadratus]

Thanks folks.

Looks like something else to experiment with - on some cheap arrows!

[Duss]

Originally Posted by Quadratus

Thanks folks.

Looks like something else to experiment with - on some cheap arrows!

Interesting to do indeed. If you want to stay in the same arrow weight category, you might be interested in using carbon arrows for testing.

In that case I would give you a word of caution, especially if you want to apply your results back to A/C/E arrows for example. Carbon arrows tend to react more stiffly than other arrows like A/C/C or A/C/E. Not really bad since the carbon arrows may end up a wee bit longer.

With the A/C/Es there is the "barrelling" to contend with. The barrelling is not so much in terms of dimension (diameter) than in terms of spine difference between the rear, center and front sections. The trick is to tread carefully because every different "spine" of A/C/E (or X10) arrow has a different "recipe". They must then be cut cery progressively and carefully to avoid costly mistakes.

A simple look at the Easton Spine and Weight Comparison Chart may be enlightening : http://www.eastonarchery.com/spineWeight/target/