Arrow mytsery or what the hell?

[g_r]

Hi Guys,

ok, i know that a trad bow needs a fitting arrow to work. at least i thought i knew. With my 45# longbow i used to shoot Easton Legacys in 2016, 30 inch with 125 up front. Although guys round here told me they are tooo heavy in spine it worked well for me.
Few days ago, sadly my last one of them got lost thanks to high grass and experimental shots. Had some old Game Getters 2215 lying aound in 31inch and 125 up front. The surprising thing, they worked the same way, no changes noticed.

?????????????????????????
So whats going on? Is it all just mysteries? Do they both work in the same unfitting wy and i did not notice and have to find the right one still or what?

would be nice to hear some opinions.

[Antonio]

Hi good to hear from you .If it aint broken don't fix it .But I understand you want to know what's going on .I find with my longbows spine has a lot to do with them shooting good .
And I use wooden arrows .There are a lot of different variables in bows .How you hold it ?.
How fast the bow is ?.how Different the draw length is in a different handed bow ?.
How much of a center shot is it? Did they mark the arrows wrongly at the factory? .
Are you using a different string .

Sorry I just reread you're post and noticed that you only changed the arrow .
Longer arrows tend to weaken the spine so if you have an inch longer than before it could make a difference .Also brace height can make a difference .So the shorter the arrow the stiffer the spine of the arrow .That's the way it works with wood .

I for one am very grateful when things are shooting good .

[longbowinfected]

I think that you really should get various sizes bare shaft them.
In my case
I found that from 43#-49# both jazz 1916 and x7 1914 work really well with 125 grain points but with no overhang.
If you use timbers get various sizes and spines as close in mass as your alloys.

always bare shaft them out as far as you can starting from in close to really see what is happening. Get someone knowledgeable to watch and give their opinion.

For all of my longbows whether they are 43# or 49# I find timber arrows spined for 45#-50# work best if there is no overhang.

Your set up may be different.
With longbow you have to really tune your arrows to your bow. Make sure you check your brace height and string nocking point every time you set your bow up. Slightest change and it all turns to doo doo.

Kevin

[Dennis La Varenne]

g-r,

Like Antonio suggests, if there is not a problem, don't try to fix it. If your arrows are flying well, don't worry about it.

This is different however from wanting to understand spine theory which can be a bit difficult to get a handle on.

I have used longbows of both glassed and wood in flatbow and ELB designs for most of my archery life and have had no problems with arrow spine so long as my arrows were not seriously UNDERSPINE. I have found that underspined arrows slap audibly against the arrowplate and bounce away from that side of the bow. If they are seriously underspine, you will see them snakewriggle in flight.

On the otherhand, I have often used groups of arrows up to 25lbs overspine and had consistently perfect arrow flight. I never worry about overstiff arrows.

However, there are some basic rules of thumb in regard to spine which go something like this -
1. For every inch longer, spine weakens by approx. 5lbs;
2. For every inch shorter, spine stiffens by approx. 5lbs;
3. For every 10gns increase in arrowhead mass, spine weakens by approx. 5lbs;
4. For evey 10gns decrease in arrowhead mass, spine stiffens by approx. 5 lbs; and
5. The further the arrow plate is out of centreshot, the weaker the necessary spine - approximately 5lbs weaker for every 1/8" and vice versa.

In spine theory, there are two basic concepts. These are static and dynamic spine.

Static spine deals with the stiffness of any arrow shaft of given mass, length and diameter.

Dynamic spine deals with the behaviour of any given arrow in flight. It is influenced by such factors as stiffness, balance point, vibration harmonics and aerodynamic shape.

If you google 'archery arrow spine theory', you will find some resources which will help explain spine theory.

Even though in your particular case, you haven't got an actual problem in practice, you clearly do not understand the 'why' of what is happening and that is important.

I hope this helps a little.

Dennis La Varenne

[g_r]

Thanks alot, I think im getting nearer to it.

I now recogniced that the heavier stiffer ones fly perfect up to 20 m, than my hits tend to the left and up. So i think ill have to get some other ones again.....(In these situations i sometimes wish i would have gone the wheelie way.....)

[Dennis La Varenne]

g-r,

When using a longbow, overspined arrows will tend to fly slightly left at longer distances if the bow his held close to vertical like a target bow. However, if you cant the bow, dass heisst, if you hold it a little out of vertical by perhaps 5-10 degrees or more, you will find that the arrows will fly straight, and not to the left.

Not everybody can shoot with a canted bow in a consistent manner, but my normal holding position is with a cant of about 5 degrees and that seems to overcome any problems with left shooting of overspined arrows. Jeff (Stickbow Hunter) on Ozbow holds with a much greater natural cant than me - perhaps closer to 15 - 20 degrees and he has never had any problems with left shooting overspined arrows of any kind.

To find your natural cant, if you wish to learn this style of shooting, hold your bow out with your bow arm, then twist your wrist fully to the left in a propeller movement then relax it till it comes to rest, then twist it fully to the right and relax it again until it comes to rest.

THAT NATURAL RESTING POSITION OF YOUR BOWHAND WHEN HOLDING A BOW IS YOUR NATURAL CANT.

You will be able to maintain that bow position consistently every time you shoot without having to force your bowhand into position because it is your natural hold. When you grip your longbow to shoot with a canted hold, grip if firmly with your bowhand and lock your wrist, but not your bow arm which should be slightly bent at the elbow as a sort of shock absorber.

When you loose the arrow, nothing should move except the arrow of course.

Please also try Longbowinfected's suggestion above if my suggestion doesn't work for you. I have never tried bareshaft shooting my arrows because I have never had any problems with them, so I cannot comment on the technique.

Dennis La Varenne

[g_r]

Hi, i tried the finding of my natural cant process and came out with the same position i used to shoot. so this seemed to be one thing i did wright without knowing.

Perhaps ill try the bare shafting next, i just would have to get an fletching-utensil because i used to buy them ready-made. (Yes, i am lazy )

THX for all youre suggestions.

[Dennis La Varenne]

g-r,

Trying the bareshafting method at this stage makes sense, but if you know the spine rating of the arrows you have, perhaps try 5lbs lower spine before bareshaft testing.

As I understand the process, for bare shafting, you do not need to fletch the shaft. You just make up arrow a few arrows with different spines without fletching and shoot it at a target at close range. One of them will shoot perfectly.

Perhaps Longbowinfected (Kevin) could explain the technique further, as it is not something I have had any real experience with.

Dennis La Varenne

[Brumbies Country]

Great thread this and I read Denis comments re the influence of point weight, shaft lenth etc with interest. It's topical for me. I finished a Meare Heath style flatbow last week and tried a variety of arrows with it. It's around 43lb at 28". I started with sitka spruce shafts spined at 30-34lbs@28" with 100 grain points. I got them for my Elbs with the reasoning that shooting round the handle rather than with a cutaway shelf you needed lower spine. Same reasoning applies for this flatbow.They shot nicely out of the flatbow but 5 of the same arrows that I had broken the point off shot slightly better with 125 grain points and that should have marginally lowered the spine and their performance goes a bit against what I would have expected. Next surprise was that Forro's VA shafts spined 45-49lbs @28 also shot nice nice and straight out of the same bow although with a bit more drop off over 30m compared with the sitka spruce (SP around 375 grains, VA around 450 grains). More influential is the brace height with this bow. I've settled on 5" brace height. Tried it higher but I shot more left arrows ( the brace height seemed to have more influence on arrow path than static spine) and the 5" is good for minimising string follow

For some reason I seem to be able to get away with what I would have would have thought were significant spine variations. I miss at least my fair share of left and rights but they are faults of shooting form rather than static arrow spine variation.

Simon

[g_r]

The bare shafting thing is still to come for me.
But i ll soon have more problems as i will get my new bow this week. My first recurve with 53lb. I just think i will try my already made arrows and see what happens.

What you think of 2016 shafts with 125 grain in 30 " for a 50# @ 28 " recurve wich i draw to 29" ?

Any suggestions?

[longbow steve]

They will be a bit stiff G_r unless the window is cut past centre. 2018 would be the shaft plus smaller diameter aids penetration and is less wind affected for target or field shooting. Steve

[g_r]

@ longbow steve:

sorry, my fault. i meant 2016, was a writing mistake. they are quite thin...its easton legacys

[Dennis La Varenne]

g-r,

The other blokes can advise you better on syntharrows than I can. I don't know a thing about them. However, if you find a syntharrow which shoots, find its spine rating on a spine jig when you make or buy one and match all your other arrows to it.

Also to Simon,

Yes, the braceheight does have an influence on arrowflight, but is not actually related to the arrow spine as such. Required spine is influenced by the vibration harmonics of the string as it moves forward off the string fingers and the number and position of the wave peaks between the loose and the end of the power stroke. What you have done is to match the peak of one of these waves so that the arrow leaves the string at an optimum position behind the arrow such that the push is closer to directly in line with the shaft.

To understand this concept, one needs to understand that the bowstring does not travel in a straight line from the fingers to the resting position when loosed. It moves in a horizontal series of waves in manner shown in the attached diagram (of a right handed shooter).

The diagram on the left is the arrow in the full drawn position. The red line is the bowstring. On the right, the diagram shows the motion of the string on its way to stop. The blue line is the former position of the string at full draw. At the stop, it actually continues to bounce and vibrate back and forth until all the remaining energy in it is dissipated into the atmosphere, some of which we feel as handshock.

As the arrow moves forward on the string, you can see that the horizontal waves of motion have peaks where the line of the arrow is closer to a line parallel with the centre line of the bow but nearer to the side of the arrowplate of the bow at points A, B and C. These vibrations decrease as the string nears the bow of course. But, the effect of altering your brace height has the effect of reducing or increasing the length of the powerstroke to the point where the arrow leaves the string. If it is closer to the high point of one of these vibration peaks, it has LESS bending to do to get around the bow, which means in turn that a stiffer arrow can be used.

Conversely, if the arrow leaves the bowstring when it is moving closer to the centre line of the bow in the 'valleys' between A, B and C, then the arrow is required to do MORE bending to get around the bow.

Obviously, the best and cleanest arrow pass around the bow would be near the A position, but there would be no effective power stroke, so we tinker with our braceheight to get the arrow to leave the string as near as we can to one of the vibration peaks on the arrow side of the bow so that it has the least amount of bending to do to pass the bow. This explains why we can often use arrows of much greater spine than we would otherwise use. Canting also helps too as I have found.

The ideal of course is to have our wood arrows doing a little flexing as possible for longer life because constant heavy flexing 'shoots them out' of spine eventually and they become soggy and start to fishtail or porpoise and then we have other problems sometimes wrongly attributed to nocking point position.

Please note that the number of vibrations I have drawn is not what happens in real life. There may be more or fewer vibrations in actual practice which some interested person may be able to research later. It is the principle of why changes of braceheight seem to have an effect on arrow spine which I am trying to illustrate. The two act in concert. That is why the static spine of an arrow is never a true indicator of how an arrow will behave from any bow - it is only a guide. The vibration frequency rate set up by the string is also affected by the forward mass of the shaft, its shape (bobbed, barrelled, parallel, tapered, etc.) and the drag created by the fletching.

There is also the effect of vibration waves created in the arrow as a result of its inherent stiffness and these also affect how cleanly it bends around the bow, but are a subject for another time.

Dennis La Varenne

[longbow steve]

Hi G_r, 2016 should be close. Especially if the bow uses dacron over fastflight.
Very interesting Dennis, I assume this is what Grahame keeps prattling on about good to see a diagram. Is there any footage demonstrating this?
Secondly, do you do your graphics from home? I recall you syaing you had a Mac, is there a programme you can recomend for graphics and design etc? Thanks Steve

[GrahameA]

Morning Steve

Very interesting Dennis, I assume this is what Grahame keeps prattling on about good to see a diagram. Is there any footage demonstrating this?

Have you checked your four flat tyres this morning?

Strange you should ask about video - there is heaps, but you have to either know what you are looking for or be inquisitive enough to watch stuff frame by frame.

This was posted on YouTube last night.

http://www.youtube.com/watch?v=Q-M7vCG2eEs

If you just watch the first bit, starts 0:14:00, where the arrow is in slow motion you can see the arrow starts to vibrate and then the size of the oscillation increases as the arrow is moved further by the bowstring. Those initial vibration also look as if they are harmonics. (You can scroll back and forth or use the stop button. You could also download the MP4 of the clip and play it frame by frame in Quicktime.

You should also note that the frequency of the bowstring is being driven by that of the arrow.

Now the question is how much more would you like to see? A few for starters:-
http://www.youtube.com/results?search_t ... otion&aq=f

Addenda

For those who are considering doing their own clips. I would suggest nothing less than 1000fps and then you can cheat a bit and slow it down to 2000 fps in your editor. If you are a bit more serious then 2000 to 3000 fps is a lot better. The higher the resolution the better and you will need extra lighting. For those who have the urge I can introduce you to a suitable camera supplier just bring large amounts of cash.

[longbow steve]

Sorry about that Grahame but I wanted a quick reply as I have a bow to make today . So do most arrows oscillate once or twice during the powerstoke or is there cases where they oscillate more than that? How wwould you put a measure on the frequency of the arrow?
Steve
I like the last clip, The string travels quite a distance left after leaving the fingers. Steve

[Brumbies Country]

Gee Dennis, that explains alot about some questions I've never quite been able to get to the bottom of. I'm now shooting self bows and was under the impression that I'd reduced the sport/addiction to something as simple as it gets. But I read this and realise how much more attention I should have paid to very small increments in adjusting brace hight. I look to have been lucky in this instance and with this bow, although in truth I started at 5 " to minimise early string follow, worked up and found nothing as good as the original. I didn't do it in particularly small increments though.

I've also taken on board your comments about the wood doing as little flexing as possible in the interest of longevity. Because of some shoulder issues I'm limited to bows of low 40lbs mark so I've become a bit obsessed with sticking with low arrow weight. If I was shooting 3DAAA it wouldn't be a problem (30 m max), but geographically 3DAAA is all a day's drive away. At 40m max for AA you start to get a fairly significant drop with VA arrows (which seem to stay stiff for ever) and at 48m max for ABA a bit more drop again. It's probably time for a rethink and perhaps concentrating on arrows that give better accuracy out to 30-35m should be the goal.

My very grateful thanks.

Simon

[GrahameA]

Hi Steve

Sorry about that Grahame but I wanted a quick reply as I have a bow to make today . So do most arrows oscillate once or twice during the powerstoke or is there cases where they oscillate more than that? How wwould you put a measure on the frequency of the arrow?
Steve

A quick and dirty solution. Most (all) go through more than one oscillation. In that clip there appears to be 3 oscillations.

The quick and dirty method, and making a few assumptions (this kitchen chemistry or physics), of determining the frequency would be to determine the arrow velocity and measure the distance from the bow to string at full draw. From that you can determine how long it would take the arrow to pass the bow. Assume that it does one oscillation it that time period and that the arrow is somewhere near that needed for the bow. The frequency is the inverse of of the period of oscillation.

As example it takes 1/60 of a second for the arrow to pass the bow then frequency would be 60Hz. 1/240 sec and it would be 240 Hz.

The answer will not be exactly correct but neither were the the original measurement - and we are only interested in an approximation.

The other thing to note with that clip in its entirety is that many archers shoot bareshaft arrows some distance with surprising accuracy. So there is a bit more explanation required in that area.

[Dennis La Varenne]

Well,
I seem to have been able to help a few people here which is gratifying and I was hoping Grahame had some further info on the matter.

Steve,

I do all my drawings in Photoshop with which I have a pretty fair handle on because I use it daily in my job with the Herald & Weekly Times here in Melbourne.

I think that some of the Autocad type programs will do it better and quicker, but I haven't used any of them. Yeoman (Dave Clark) has one which is a free download for PCs but I haven't been able to find one similar for Macs.

Dennis La Varenne

[longbow steve]

Thanks Dennis, I have been meaning to visit the Mac shop, I will let you know what I find. Steve

[g_r]

wow, i wouldnt have thought id learn that much about arrows with that question.....

[Dennis La Varenne]

Could I mention at this late stage that the horizontal oscillation of the bowstring is initially generated by the way it leaves the fingers at the loose. It doesn't oscillate at anywhere near that degree if a bow is dryfired or a release aid is used.

In Grahame's post with the YouTube links, you can see the severe lateral initial oscillation of the string at the loose - in this case, on the right hand side similar to what a left handed shooter would generate - because of the thumb release and the arrow leaving the RH side of the Yumi instead of the LH side as we shoot.

After the loose (from fingers), the oscillation of the arrow and the bowstring affect each other.

Simon said,

I'm now shooting self bows and was under the impression that I'd reduced the sport/addiction to something as simple as it gets. But I read this and realise how much more attention I should have paid to very small increments in adjusting brace hight.

The synthbows all have exactly the same problems as trad bows; there are just more wheels to fall off.

Dennis La Varenne