Author Topic: FOC, center of pressure and performance  (Read 2321 times)

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Offline avcase

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Re: FOC, center of pressure and performance
« Reply #30 on: September 20, 2017, 10:36:13 pm »
And why do you believe, your heat treated spruce arrows would shine without rehydration - because of lower mass or higher spine or some other reason?

Third question - why those two arrows are so special? Have you compared them to similar arrows, which are not so good? Is there any kind of measurable difference? You have made a lot of split cane arrows but what makes some of them special? Spine, weight, diameter, balance point, some parameter we don't know yet.

I heat treated some Sitka spruce shafts in an oven set at 375 degrees f for just long enough that the color of the wood began to darken a slight amount. The stiffness of these arrow shafts were incredibly high afterward, which is just what I look for in an an arrow shaft material. Unfortunately, much of this benefit faded away over the next week as the arrow shafts regained moisture.

I will have to carefully look through all my flight arrows to see if I notice some traits that the best arrows have in common.  It doesn't seem very obvious to me right now.

Alan

Offline Tuomo

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Re: FOC, center of pressure and performance
« Reply #31 on: September 22, 2017, 09:37:10 am »
It is very interesting that one arrow functions well with 35, 50 and 70# bows. It seems that fine-tuning of bow-and-arrow is not so important. There has to be something else.

If release is good and arrow is leaving bow well and supposing that speed is same between different arrows, then the only discriminating thing is how the arrow is flying. We can measure speed of arrow, see how it is behaving at release but don't see how it is flying. Maybe there is something what you said about landing angle.

Offline Badger

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Re: FOC, center of pressure and performance
« Reply #32 on: September 22, 2017, 10:43:50 am »
  A good arrow you can't see at release at all they just disappear. Any arrow you can see is a bad shot it seems. About 320 yards is the maximum I have ever gotten for an arrow I could see leave the bow and track for some distance.

Offline JNystrom

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Re: FOC, center of pressure and performance
« Reply #33 on: September 22, 2017, 11:35:32 am »
  A good arrow you can't see at release at all they just disappear. Any arrow you can see is a bad shot it seems. About 320 yards is the maximum I have ever gotten for an arrow I could see leave the bow and track for some distance.
That disappearing arrow obviously leaves the bow cleanly and fast. BUT that doesn't mean it still can't have too much drag to slow it down and fast. Right? Not that it would be the case everytime, but just as a minor point.

I think those arrows Alan Case shoots from 30# to 70# pound bows, can't possibly leave all of the bows super cleanly (because of different spine), but still maintain their flight for "quite" :D long.
« Last Edit: September 22, 2017, 11:43:58 am by JNystrom »

Offline willie

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Re: FOC, center of pressure and performance
« Reply #34 on: September 24, 2017, 07:59:28 pm »
Quote
I think those arrows Alan Case shoots from 30# to 70# pound bows, can't possibly leave all of the bows super cleanly (because of different spine)

Perhaps the tapering in the rear half helps more than one would presume?, although that's quite a bit of range.

Alan, in addition to citing the poundage range you have had good luck with, could you comment on the handle widths of the bows in question?


Offline DC

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Re: FOC, center of pressure and performance
« Reply #35 on: September 25, 2017, 12:38:37 pm »
I think that it's the speed of the arrow rather than the poundage of the bow that determines the spine. In order to get to say, 180 fps the arrow has to accelerate at a certain rate. There is more involved than just bow draw weight. I believe that if you have a 70# bow that has a dry fire speed that is the same as a 30# bow the same spine arrow will work in both.
Vancouver Island

Offline willie

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Re: FOC, center of pressure and performance
« Reply #36 on: September 25, 2017, 01:47:30 pm »
you might have hit on something with that observation, DC.  Axial force is a function of acceleration.

I have been thinking of what constitutes a "clean release".  If an arrow leaves the string with the nock in-line with the direction of flight, then what could be better? Of course how much an arrow nock oscillates laterally is both a function of the arrows stiffness and the displacement of the string rolling off the fingers.
« Last Edit: September 25, 2017, 03:54:10 pm by willie »

Offline avcase

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Re: FOC, center of pressure and performance
« Reply #37 on: September 25, 2017, 01:48:05 pm »
I wasn't the archer or bow builder for any of the flight records shot with the arrows I posted earlier. I was just the arrow guy. The bows were built by Steve Gardner, Dan Perry, and Larry Hatfield. The English Longbow records were shot with a couple of hickory-backed Ike bows that are just under 3/4" wide at the handle (no cut-in arrow shelf, of course). Steve can best comment on the degree of center shot his self bows and simple composite bows have.  They usually have a shelf cut in to the handle. I think it is not quite to center. Same for Dan Perry's bows.  Larry Hatfield's Modern Composite Longbows have a shelf that is cut in close to center, which still leaves the arrow off center by some amount.

Alan

Offline willie

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Re: FOC, center of pressure and performance
« Reply #38 on: September 25, 2017, 03:08:35 pm »
Quote
This is interesting. The weight for my larger diameter spruce flight arrow and equivalent stiffness of the split cane Tonkin arrow is almost identical.

Alan, are you saying the spruce and tonkin arrows spine about the same, and weigh about the same? Just the diameters differ?

.57 deflection 22"  O.C. seems soft, especially for a 75# bow. Seems like the bows you mentioned did not necessarily need to have the arrows spined as soft as they are for getting around the handles. As a generality, are most flight arrows sacrificing as much spine as possible, for the aerodynamic advantage of having minimal diameter?

« Last Edit: September 25, 2017, 03:58:03 pm by willie »

Offline DC

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Re: FOC, center of pressure and performance
« Reply #39 on: September 25, 2017, 03:22:45 pm »
I'm sensing a Mass Principle for arrows.
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Offline Badger

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Re: FOC, center of pressure and performance
« Reply #40 on: September 25, 2017, 06:14:05 pm »
  Willie, say you have a 70# bow with a 125 grain tip on it. You would want about 70# spine. Take away the tip and now you need 45# spind, take away about 100 grains of arrow mass from the front of the arrow and now you are down to about 30# spine. You don't need much spine for flight arrows. The spine protects against the weight forward of center that the arrow is trying to accelerate. If there is not much weight up front you don't need much spine to still be stiff.

Offline avcase

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Re: FOC, center of pressure and performance
« Reply #41 on: September 29, 2017, 04:14:33 pm »
Alan, are you saying the spruce and tonkin arrows spine about the same, and weigh about the same? Just the diameters differ?

.57 deflection 22"  O.C. seems soft, especially for a 75# bow. Seems like the bows you mentioned did not necessarily need to have the arrows spined as soft as they are for getting around the handles. As a generality, are most flight arrows sacrificing as much spine as possible, for the aerodynamic advantage of having minimal diameter?

Yes, the primary difference between the spruce arrow and Tonkin Cane arrow is that the spruce arrows are a bit larger in diameter.

It is most important to have clean arrow flight out of the bow. An arrow that wiggles too much or comes out of the bow at an odd angle doesn't go very far. Especially if it is a very light arrow. 

The "floating arrow" topic is an interesting one. I am still not sure how effective it is or how well it can be controlled, but I can try to show what I think is going on with some of these arrows using a rocket flight simulator.

Alan

Offline Badger

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Re: FOC, center of pressure and performance
« Reply #42 on: October 01, 2017, 05:55:47 am »
  I am seriously thinking a change in strategy. Longer bows, longer arrows more stored energy and heavier arrows. At around the 250 to 280 range they become a little more consistent even though they might be quite a bit slower. I know ranges are more consistent at that weight. The lighter arrows always have that chance of an outlier that took off clean and stayed straight but I don't like gambling on it so much anymore. Maybe use a range of arrows from 200 to 270 grains.

Offline Selfbowman

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Re: FOC, center of pressure and performance
« Reply #43 on: October 02, 2017, 01:23:31 pm »
I'm sensing a Mass Principle for arrows.
Well my wife has a 20 " draw and getting target arrows for 35# draw  draw weight that come in at 264 grains is not difficult if you can spine them . My spine tester required 26" arrow. So I got a hundred 1/4" by 24" shafts and weighed them , grouped them and built arrows from different groups. The ones that weighed in the 264 gr. Total weight shot the best. That being said I tried this to see if weight of arrrow could give you spine. I used same point and fletchings set up on  the different weights of shafts. It seamed to work for the most impossible client,.  ;Dh Arvin
« Last Edit: October 02, 2017, 01:30:34 pm by Selfbowman »
Well I'll say!!  Osage is king!!

Offline joachimM

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Re: FOC, center of pressure and performance
« Reply #44 on: October 03, 2017, 12:14:49 pm »
  I am seriously thinking a change in strategy. Longer bows, longer arrows more stored energy and heavier arrows. At around the 250 to 280 range they become a little more consistent even though they might be quite a bit slower. I know ranges are more consistent at that weight. The lighter arrows always have that chance of an outlier that took off clean and stayed straight but I don't like gambling on it so much anymore. Maybe use a range of arrows from 200 to 270 grains.

My 2cts: will a bow that stores more energy shoot farther if the dry fire speed is the same? I wouldn't think so. Energy storage and bow efficiency are not the bottlenecks in flight archery. However, heavier combos may be at an advantage if you can shoot heavier arrows at the same speed as light arrows. The reason is that the one thing we cannot scale up or down, is the physical environment. Light arrows experience the same air density as larger heavier arrows, but relative to their mass they experience more drag because the air in which we shoot is the same. Put otherwise, heavy arrows shot at the same speed have more energy to push away the air in front of them. All else being the same (but scaled up, say 25%), heavier combos should shoot farther.

To reduce drag, we shoot the shortest and thinnest arrows possible, but the trade-off is less energy per arrow. The other option is to choose heavier and slightly longer arrows. This will indeed require scaling up the bows.
Tillering is easy. Problems arise when a bowyer thinks he's right and the wood is wrong.