Advantage with heavy points?

[T101]

i was wondering what experience anybody has had with varying their point weight.

i am aware that heavier means less wind drift but what about the loss of speed? is this significant?

my 400 spine arrows clocked 274fps @ 27.5 inch @58lbs and 110g points. (this may be 265fps as chrono possibly facing wrong way)

i determine my arrow point weight by finding one third of total arrow weight(inc point). now although 110g was a match when my arrows were 28.5 inch, now they should be 100g with this caculation.

i think my arrows would benefit with 100g as i think they require a bit more stiffness, but would i be sacrificing to much wind stability?

[Marcus26]

Decreasing arrow point weight will NOT change the spine of the arrow. The spine is the amount that the arrow flexes and this has no relationship to point weight. The only difference it CAN make is that a heavier point may have a longer internal shaft, which will stiffen the arrow.
For wind drift weight and diametre are everything. Speed means nothing. If you go for FPS coming out of the bow then you will lose ALOT of FPS after 70m which will cost you more points.
Thinner = Better
Heavier = Better
Lighter = Worse

Also a heavy but thicker arrow can be as good as a thinner lighter arrow.

[niceguy]

Decreasing arrow point weight will NOT change the spine of the arrow.

Not so Marcus. Adding weight at the front or back of an arrow changes it's dynamic spine and it will act stiffer or weaker. A longer pile insert also changes the effective shaft length as you say but the weight has a major effect also. I have done this many times and the effect of 20 grains can be significant. I recently brought my daughters arrows into tune with a simple change of pile weight.

[BowSurfer]

Originally Posted by Marcus26

...snip...For wind drift weight and diametre are everything. Speed means nothing. If you go for FPS coming out of the bow then you will lose ALOT of FPS after 70m which will cost you more points.
Thinner = Better
Heavier = Better
Lighter = Worse

Also a heavy but thicker arrow can be as good as a thinner lighter arrow.

Surely if an arrow takes twice as long to reach the target it will be more affected by wind? Also the effective wind direction is the vector sum of the wind and the arrows flight speed, which will be further forward (more in line with the arrow) for a higher flight speed and more to the side for a slower flight speed.

[Marcus26]

Originally Posted by niceguy

Decreasing arrow point weight will NOT change the spine of the arrow.

Not so Marcus. Adding weight at the front or back of an arrow changes it's dynamic spine and it will act stiffer or weaker. A longer pile insert also changes the effective shaft length as you say but the weight has a major effect also. I have done this many times and the effect of 20 grains can be significant. I recently brought my daughters arrows into tune with a simple change of pile weight.

Rubbish.
How did you measure the tune of the bow? Or is this more recurve stuff in the wrong section again?

With a recurve you can move the bareshaft location by changing the spoint wieght, but you have not adjusted the spine in doing so.
Dynamic spine doesn't exist. Only actual spine and resonant frequency.

here is a quote from James Park on it

An aside:
We don't actually adjust the arrow's spine by changing the point weight. The 'spine' is how much the arrow flexes with a certain span and weight and depends upon the shaft stiffness. Changing the point weight does not change this. What it changes is how fast the arrow flexes (but only by a small amount).

[Marcus26]

Originally Posted by BowSurfer

Surely if an arrow takes twice as long to reach the target it will be more affected by wind? Also the effective wind direction is the vector sum of the wind and the arrows flight speed, which will be further forward (more in line with the arrow) for a higher flight speed and more to the side for a slower flight speed.

So you are putting so much weight in the front as to half it;s speed? Lets stick to realities please.

A lighter arrow will extract less energy from the bow and thus as the energy is shed due to drag will not maintain velocity as long.
Compare the wind drift of a ping pong ball to a brick. Go out in string winds and throw both and see how you go.

[Jerry Tee]

Two things. The fastest arrow out of the bow is not always the fastest arrow at the target. Secondly, an arrow does not achieve its terminal cross wind speed as soon as it leaves the bow. The cross wind will cause a force proportional to the cross sectional area to accelerate the arrow down wind. The only thing that will oppose this is the inertia and hence the mass of the arrow.

[The Meggy]

I'm not able to measure arrow speed as I don't have the kit, but I have recently changed from 28.5 inch ACC's 500 spine with 100 grain points to 29 inch Navigators, 430 spine with 120 grain points - i.e. to a heavier but thinner arrow. My subjective impression is that the Nav's are an improvement, and significantly better in the wind. So that would tend to bear out what Marcus is saying. My sight marks are a little down on the ACC's but I think the arrows are indeed extracting more energy out of the bow, so have more momentum. The bow seems to shoot a little more sweetly too.

[sambow]

I share your reservations becuase I have always had them too. Is it better to have a heavier arrow that offers greater wind resistance but has to fly slower and higher. Or a lighter arrow which flies faster and lower but has less resistance to wind?

I have to bow to the majority of more experienced archers than me who say heavier is better.

Earlier tonight I did a very unstructured/unscientific experiment. I could only shoot 30M and was running out of time. I shot 30 arrows with 90gn points into an 80cm target and 30 with 125gn points. The 125gn points dropped 6 inches more than the 90gn, but the grouping was definately tighter. I intend to repeat at 50M later in the week and see what happens then.

[phil_r_58]

Originally Posted by niceguy

Decreasing arrow point weight will NOT change the spine of the arrow.

Not so Marcus. Adding weight at the front or back of an arrow changes it's dynamic spine and it will act stiffer or weaker. A longer pile insert also changes the effective shaft length as you say but the weight has a major effect also. I have done this many times and the effect of 20 grains can be significant. I recently brought my daughters arrows into tune with a simple change of pile weight.

My 'A' level physics may be rusty, (1976), but isn't the bending on release caused by a moment of inertia? the point weight resisting the forward push momentarily ? And if you increase the weight, you also increase the resistance of the point to beginning to move. (Come on sp220, you're supposed to be the ace physicist, enlighten us!)

The bending on a spining jig is done by holding the arrow between two points, exerting a force in the middle, and measuring the bend. Not the same as forcing 120 grains from rest to over 300fps in microseconds.

Having said that, over the years I've heard so many claims about altering arrows that are too stiff/weak by point weight. In my experience, the effect is very small, almost at "micro tuning" level. And yes, the amount of shank in the shaft affects the stiffness.