# NARROW FORKS V's WIDE FORKS - INTERESTING CHRONY TEST RESULTS



## gamekeeper john (Apr 11, 2011)




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## dgui (Jan 12, 2010)

John, You have proven a definite advantage in having a smaller or rather a more narrow fork. In some cases smaller is better or more desirable. Your shooting videos are right to the point and indisputable. Some of what were once thought to be uncontrollable variables now have a foundational reference point. 

Very interesting,
Good video,
Good work.
Thanks


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## slingshot_sniper (Feb 20, 2011)

Thanks for the video tests I always thought my PF shooters shot faster,now I know they do


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## AZshooter (May 1, 2011)

Thanks for the information, John...Did you try the 1/4 turn twiist ( and tweek ) on the pouch?...Most have found this useful in eliminating the handslap problem...


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## gamekeeper john (Apr 11, 2011)

i always shoot with the poch twist now, its only recently that i'v started doing it though


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## lightgeoduck (Apr 3, 2011)

Thanks John, that was a very informative video (as always) Thanks for giving me another reason to use as to why I like short and narrow... I have to admit though that wide fork looks insane







.. almost worth caring around just for the "fear factor"







but apparently based off of your results it would be more bark than bite

Cheers

LGD


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## flippinout (Jul 16, 2010)

This is something I too have long suspected, including the hand slap theory.

Thanks for taking the time to do this test. I think it is pretty conclusive that narrow forks generate more speed, it only makes sense!


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## gamekeeper john (Apr 11, 2011)

lightgeoduck said:


> Thanks John, that was a very informative video (as always) Thanks for giving me another reason to use as to why I like short and narrow... I have to admit though that wide fork looks insane
> 
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your right lol, its not how big it is its what u can do with it that counts ......







john


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## gamekeeper john (Apr 11, 2011)

flippinout said:


> This is something I too have long suspected, including the hand slap theory.
> 
> Thanks for taking the time to do this test. I think it is pretty conclusive that narrow forks generate more speed, it only makes sense!


thanks, i realised somethink wasn't right when i was chrony testing a pickle fork last week and i just could't get my head around why it was consideraly faster, i just had to do the test to confirm what a few other thought, but its clear to see that the narrower the fork the faster the shot







thanks john


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## Tex-Shooter (Dec 17, 2009)

I had run a simular test, but not the that much difference in width, so not near that much difference in speed. However on bench test I found that there was a difference in accuracy between the the two that I tested (1.5 inches verces 2.75 inches). The 2.75 inch fork shot a tighter group. Of courst that was from a bench test. -- Tex


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## Dayhiker (Mar 13, 2010)

Because of the radically wide fork used in this experiment, I don't think it's very useful. As Tex says, when you get down to realistic dimensions, there probably isn't enough difference to worry about. And for me, at least, a 2 - 2.5 inch opening is quite a bit more accurate.


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## gamekeeper john (Apr 11, 2011)

Dayhiker said:


> Because of the radically wide fork used in this experiment, I don't think it's very useful. As Tex says, when you get down to realistic dimensions, there probably isn't enough difference to worry about. And for me, at least, a 2 - 2.5 inch opening is quite a bit more accurate.


there was 20fps difference from a pickle fork shooter and a catapult from my range, there is only about a 2" difference in that gap, but i do see your point, i think i'm more accurate with a wider fork


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## harpersgrace (Jan 28, 2010)

Nice test, but for me it really makes no difference, I shoot for pleasure not speed or records and I enjoy a wide fork more, but for those that such things matter it's useful info. Keep up the good work John always good to watch your vids


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## dgui (Jan 12, 2010)

flippinout said:


> This is something I too have long suspected, including the hand slap theory.
> 
> Thanks for taking the time to do this test. I think it is pretty conclusive that narrow forks generate more speed, it only makes sense!


It has been my opinion for a couple of years now and this is based on my search for the perfect slingshot that more narrow forks do produce faster speeds. But now John has proved it. As far as accuracy and a larger or smaller fork, this will come in time I am certain. And hand slaps never have to occur with simple remedy.


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## Dayhiker (Mar 13, 2010)

Well if we take this line of reasoning to it's logical conclusion then it is likely that a stick-shot will be the superior weapon. And, Darrel, your flat top shooter (which is just a stick-shot with 4 bands instead of two in my opinion) will prove superior to the pickle fork as you continue to merge the bands closer (stick-shot).
Stick-shots aren't slingshots, and until I see somebody win a tournament or start bringing in game steadily with one, I'll stick with my story.

Not trying to be argumentative here. Just trying to determine "when is a slingshot NOT a slingshot?" Otherwise, it's useful to know that a narrower gap is faster, but only marginally.


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## dgui (Jan 12, 2010)

As the PF is expanding and others may give it a try, there is something that goes along with the PF as you spend some time shooting with it your getting good results. Your accuracy with all slingshots will improve. As time goes on perhaps others will confirm this finding. It is possible that starting out with a small slingshot rather than a large one is actually a better choice in getting the knack for shooting a slingshot. 
Point with the forks
Turn the pouch
Only look at your target


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## Northerner (Nov 9, 2010)

So top velocity would be achieved with narrow forks and a full butterfly draw? Pound-for-pound of draw weight, the butterfly draw gives more velocity than a cheek anchor. Hopefully the shooter looking for top performance can shoot accurately with this style and small frame.

Cheers,
Northerner


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## Charles (Aug 26, 2010)

John, I am so glad you did that test, and I was not that surprised by the result as we previously discussed ... a very clear indication of force vectors at work! They should hire you to do demos for high school physics classes. I'm sure your would get their attention, and there would be no acting out in class!!!























As for the band slap ... I think you will see the answer if you just watch your video where you are holding up the two. When you are holding it up, the pouch on the wide fork is right at your hand, or just a tiny bit below. When the pouch recoils after the shot, it is going to naturally smack your hand. With the PFS, with the bands relaxed, the pouch is well below your hand. So when the pouch recoils after the shot with the PFS, the pouch is going to come back below the level of your hand.

Good job!!!

Cheers ........ Charles


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## gamekeeper john (Apr 11, 2011)

Charles said:


> John, I am so glad you did that test, and I was not that surprised by the result as we previously discussed ... a very clear indication of force vectors at work! They should hire you to do demos for high school physics classes. I'm sure your would get their attention, and there would be no acting out in class!!!
> 
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> ...


thanks charles, obviously the difference between a normal slingshot and a pfs wouldn't be as much, i'v just measured the gap inbetween the wide forks and it is 8 inches, and the difference in speed between to 2 was upto 40fps, so does this mean if the gap was 4 inches the difference would be 20fps, and if the gap was 2 inches the difference would be 10fps ??????????????

anyway i only did this test to show that a narrower fork is faster (fact), it might not seem like a lot but as the ever growing performance of catapults evolves it probaly will come into play at some point in the future, and it will definately come into play with speed tests,

whats the point in tapering your bands or having a light pouch to gain a few extra fps just to have wide forks and lose it?

thanks john


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## keef (May 27, 2011)

Really enlightening test there... Thanks a lot for your dedication.

I must admit, that I've always hated wide forks. I feel the accuracy levels go down for me with these.. I must use the forks as a reference, even though i dont notice it!

Hope that you get the good high temps down there in the next couple of days, will be great to see how the speed tests go

All the best mate

Keith


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## Charles (Aug 26, 2010)

gamekeeper john said:


> John, I am so glad you did that test, and I was not that surprised by the result as we previously discussed ... a very clear indication of force vectors at work! They should hire you to do demos for high school physics classes. I'm sure your would get their attention, and there would be no acting out in class!!!
> 
> 
> 
> ...


thanks charles, obviously the difference between a normal slingshot and a pfs wouldn't be as much, i'v just measured the gap inbetween the wide forks and it is 8 inches, and the difference in speed between to 2 was upto 40fps, so does this mean if the gap was 4 inches the difference would be 20fps, and if the gap was 2 inches the difference would be 10fps ??????????????

thanks john
[/quote]

Well, it is a little more complicated than that. The amount of force you are losing off of each band is roughly the length of the drawn band times the sine of the angle formed by the fork tip, the drawn pouch, and the line from the pouch through the center of the forks. As the pouch travels forward, that angle is constantly changing ... getting greater, so you lose more force as the pouch travels forward. You can see that if your draw length was, say 10 feet (don't we all wish!), that angle would be very small and you would lose a very small percent of the force. It would be complicated to work it all out mathematically, but the basic trend is clear ... wider forks mean more loss of power ... longer draw length means the smaller the effect of wider forks.

Well, that seemed pretty clear to me when I was writing it, but after reading it over I can see that it may not to be to others.







The idea is that the amount of force pushing the projectile forward is proportional to the distance from the middle of the forks to the drawn pouch ... your draw length. The amount of force lost is proportional to the distance from the fork tip to the middle of the forks. So if you increase the distance between the forks but keep the draw length the same, you lose more of the available power.

In other words, the ratio of the amount of fork separation to the draw length is a pretty direct measure of the percentage of power lost. Since most of us have a pretty constant draw length, we can decrease the power lost by moving the forks closer together.

Clear as mud???

Cheers ... Charles


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## tubeman (Mar 7, 2011)

" Only look at your target " Good advice from dgui. Your peripheral vision will see the forks/flat top and your brain will make the needed calculations with practice.


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## gamekeeper john (Apr 11, 2011)

tubeman said:


> " Only look at your target " Good comment from dgui. Your peripheral vision will see the forks/flat top and your brain will make the needed calculations with practice.


exactly what i do, there no need to look at the catapult, look at the target and shoot - john


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## Bob Fionda (Apr 6, 2011)

Thank you John for posting many interesting vids. I find it useful for us shooters. Cheers, Bob


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## Rayshot (Feb 1, 2010)

More information tested out for the science of slingshots.

Thanks John!


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## Ted (May 27, 2011)

This seems like a definitive empirical test. Thanks very much, John. When I made a really narrow-fork slingshot awhile ago (5/8" between the prongs), I thought it shot faster, but I couldn't tell for sure because i don't have a chrony.

Here is another attempt at the theory: After releasing the pouch, at any given instant as the band contracts, the band on each side of the pouch is exerting some force along the direction of the band. As Charles has described, that force can be viewed as a "forward" force in the direction of the line between the pouch and the midpoint of the fork tips, plus a perpendicular force from the midpoint of the fork tips to the fork tip that the band is attached to. These two vectors plus the band itself form a right triangle with the band as the hypotenuse. Since the hypotenuse is always the longest side of a right triangle, the forward force is always less than the force along the band. The forward force is the force along the band times the cosine of the angle from the fork tip to the pouch to the midpoint of the fork tips. We are interested in the forward force because it determines the speed of the projectile. The difference between the forward force and the force exerted by the band along its length is the amount of force lost due to the fork having width greater than zero.

Now to compare a slingshot with a wide fork against a slingshot with a narrow fork. For any given band length as the band is contracting, the wider the fork, the greater the angle whose vertex is at the pouch, so the smaller the cosine (since that angle is always between 0 and 90 degrees as the band contracts), so the smaller the forward force. This is true at each moment of time as the band contracts. So the wider the fork, the lower the speed of the projectile when it leaves the slingshot.


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## dgui (Jan 12, 2010)

Ted that is an explanation that in the past that the old time roof framers would have been able to solve. Now all of the information is built into small hand held calculators with one button and not rise sq x run sq = sq rt . would give the hyp and or stepping off with the framing square. 

Good explanation.


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## dgui (Jan 12, 2010)

Charles said:


> John, I am so glad you did that test, and I was not that surprised by the result as we previously discussed ... a very clear indication of force vectors at work! They should hire you to do demos for high school physics classes. I'm sure your would get their attention, and there would be no acting out in class!!!
> 
> 
> 
> ...


thanks charles, obviously the difference between a normal slingshot and a pfs wouldn't be as much, i'v just measured the gap inbetween the wide forks and it is 8 inches, and the difference in speed between to 2 was upto 40fps, so does this mean if the gap was 4 inches the difference would be 20fps, and if the gap was 2 inches the difference would be 10fps ??????????????

thanks john
[/quote]

Well, it is a little more complicated than that. The amount of force you are losing off of each band is roughly the length of the drawn band times the sine of the angle formed by the fork tip, the drawn pouch, and the line from the pouch through the center of the forks. As the pouch travels forward, that angle is constantly changing ... getting greater, so you lose more force as the pouch travels forward. You can see that if your draw length was, say 10 feet (don't we all wish!), that angle would be very small and you would lose a very small percent of the force. It would be complicated to work it all out mathematically, but the basic trend is clear ... wider forks mean more loss of power ... longer draw length means the smaller the effect of wider forks.

Well, that seemed pretty clear to me when I was writing it, but after reading it over I can see that it may not to be to others.







The idea is that the amount of force pushing the projectile forward is proportional to the distance from the middle of the forks to the drawn pouch ... your draw length. The amount of force lost is proportional to the distance from the fork tip to the middle of the forks. So if you increase the distance between the forks but keep the draw length the same, you lose more of the available power.

In other words, the ratio of the amount of fork separation to the draw length is a pretty direct measure of the percentage of power lost. Since most of us have a pretty constant draw length, we can decrease the power lost by moving the forks closer together.

Clear as mud???

Cheers ... Charles
[/quote]

Charles, that makes sense to me so I guess you know the condition of my brain stem. LOL


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## slingshot_sniper (Feb 20, 2011)

I trained first with a pickle fork,my only slingshot for many weeks,later i got traditional slingshot and there is no doubt both have equal accuracy as it will totally depend on the user...for me I can shoot well with both

[edit] I say I shoot well with both,well is a little over statement,what I mean I can hit any field from 100 M with either


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## lightgeoduck (Apr 3, 2011)

I see this as an excellent example of the physics of slingshots. now accuracy IMO falls under the psychology of the mind, or the lack there of








I hope more threads appear with "scientific" tests since that is the only way to grow.. though with out knowing the theory I will still enjoy shooting slingshots

I guess anything can bring the geek out of someone, now I am going to make my level 13 elf carry a slingshot









LGD


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## slingshot_sniper (Feb 20, 2011)

All I'll say is give someone a slightly less pound draw in bows and I doubt first off they'd be as accurate with it...that's all


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## lightgeoduck (Apr 3, 2011)

SS I see where you are coming from SS, I read through the thread and saw accuracy mentioned a couple of times,,, it just happened that my post fell under yours..my comment was a generic one (that's why I didn't quote anyone).

either way there is some useful data here, and with all tests there is room for progression.


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## slingshot_sniper (Feb 20, 2011)

And I'll add this: consistent poundage (per bands) consistent platform,consistent form and consistent ammo is what prevails in accuracy NOT the type of slingshot


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## slingshot_sniper (Feb 20, 2011)

Give me a lolly pop stick and some office bands put me on a Island for three days and I bet I'll shoot as well with it


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## Ted (May 27, 2011)

So that is why the PFS is a great design - narrow fork for greater speed, and low fork for less wrist strain. Plus it's lightweight, compact, and easy to make.


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## Jacktrevally (Feb 14, 2011)

A stick shot, a pickle fork and a very wide fork.

According to all the theory and scientific calculation given above the stickshot should get more speed provided you have the same bands, same draw...etc

But there is something fundamental everyone's missing?!?!

The drawn length of the elastic is not the same in a wide fork compared to a narrow fork.

You don't need to be an educated person to see that in a wide fork with the same length of elastic and same anchor point that the wide fork has more stretch in the elastic.

Now, press the 'prev' button and read what Dayhiker just wrote!

My guess being, there is an optimum fork with so that the energy stored in the elastic (stretch length) has to do with the resultant force! It has something to do with the hysteresis as well. This is a lot of thinking and scientific but I started to think about it how to find that optimum....

But again that might not have a a big consequence as Dayhiker stated.

Now John can come forward and ask how come he gain 20fps?

1) Resultant force is slightly more. Does this have a huge impact???

2) The PF allow you to flip the fork faster forward generating a speed gain! Since the profile is so low that the flip occur fast.
Take a 3ft stick and try to flip it, you'll see what I mean!


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## lightgeoduck (Apr 3, 2011)

Jack, thanks you brought up some valid points especially with the ability to flip the fork forward faster, especially as drastic as the huge fork John used. He did mention that the draw on the wide fork was longer.

Thanks for bringing up those points, I am finding this thread to be very useful.

LGD


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## Jacktrevally (Feb 14, 2011)

Cheers

The draw length is similar since he's using the same anchor point but the stretch length is more.

As if you draw 2 triangles one with a wide base and another one with a narrower base with the same height you'll see what I mean.


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## Rayshot (Feb 1, 2010)

Jacktrevally said:


> A stick shot, a pickle fork and a very wide fork.
> 
> According to all the theory and scientific calculation given above the stickshot should get more speed provided you have the same bands, same draw...etc
> 
> ...


I too was curious how much of an effect the flip has as I noticed the small one appeared to flip more vigorously.

this is not a criticism to the test but a nuance curiosity


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## Charles (Aug 26, 2010)

Hmmm ... I have a suspicion that, although increasing the distance between the forks does increase the tension on the bands at draw, that increase in tension is lost by the bands pulling against themselves. Just looking at the vector components, the vector in line with the flight of the projectile, call it Vp will remain a constant length, while the vector in line with the forks Vf increases. So although the hypotenuse increases (representing the tension on the band), Vp remains the same. The percentage of energy waste will be Vf/(Vf+Vp). If Vp is constant, then this ratio will increase as Vf increases, asymptotically approaching 1 in the limit, or 100%. Unless the force from the bands goes up very dramatically with their stretch length, it will not outweigh the energy loss. However I must say that I do not know a decent mathematical description of how force from a rubber band is related to its degree of stretch, but I suspect that within the limits of the band it is linear.

As for the flip hypothesis, it is easy to test with a crossbow slingshot ... where there is no flip, or some fixed amount depending on how you set up the crossbow. Set up the crossbow with bands attached to sliding points along a forward prod. Set the fork separation to minimal, take 10 shots. Set the fork separation a little more, take 10 shots. Etc. That should produce a decent curve of the effect of fork separation on velocity at a fixed draw length, independent of flip.

Cheers ....... Charles


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## dgui (Jan 12, 2010)

One or more things are being omitted here. Is the pouch releasing the projectile at the identical same point on both forks? 

Which slingshot has the advantage of having a longer pull on the bands that should provide greater speed?


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## dgui (Jan 12, 2010)

As far as the flip goes. There was a statement that I read on some Dankung slingshot shooter and he claims if the flip is done correctly you can gain a third increase in fps. Now I do not flip shoot and I noticed while comparing the PFS which is 2 1/8 inch wide outside and a Pocket Shooter that is 3 1/2 inch outside measurements with the same pouch and identical bands and shooting 5/8 marbles and at 23 feet and there was a very noticeable difference in impact so I went to steel and the 3/8 with the PFS went through a bean can but only dented the can with the wider shooter. I would equate this to the difference in shooting flat bands that are 1/2 inch and then shooting bands that are 5/8 inch wide and mind you there is only 1/8 inch difference but it does change the impact.


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## Jacktrevally (Feb 14, 2011)

DGui, I doubt that 1\8 of an inch will do much difference in the resultant force!

Even 2 inches isn't going to make much difference either!

There are extreme calculation and assumption made in this thread! I would suggest that, REALISTIC values are taken and calculated!

Again, Dayhiker made a point!


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## Bill Hays (Aug 9, 2010)

You can and do naturally pull back further with narrower forks. Mount different fork widths to a slingshot rifle, so you get the exact same draw length, and your results will be quite a bit different... not nearly so dramatic.

The trick is to find the correct mix of accuracy and speed... accuracy is mainly affected in a narrower fork setup by the type of pouch and band length and whether it holds on to the ball a little at the point of release where the bands are collapsing.

I can be just as accurate with one of my Son's little slingshots as I am with one of my big slingshots... so long as the correct band, pouch and ammo setups are used.


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## dgui (Jan 12, 2010)

Jacktrevally said:


> DGui, I doubt that 1\8 of an inch will do much difference in the resultant force!
> 
> Even 2 inches isn't going to make much difference either!
> 
> ...


Give it a try, there are times when a little change makes the difference.


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## NaturalFork (Jan 21, 2010)

Wide vs narrow makes sense. If the fork is wide the bands retract both outwards and forwards, with a narrow fork they only retract forwards, generating more fps. At least that is my theory.


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## slingshotwannabe (Oct 17, 2011)

dgui said:


> DGui, I doubt that 1\8 of an inch will do much difference in the resultant force!
> 
> Even 2 inches isn't going to make much difference either!
> 
> ...


Give it a try, there are times when a little change makes the difference.
[/quote]








with dgui


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## toxophool (Nov 22, 2011)

So I guess "speed freaks" should all be shooting stickshots, eh? ;-)


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## Charles (Aug 26, 2010)

toxophool said:


> So I guess "speed freaks" should all be shooting stickshots, eh? ;-)


Theoretically, wider forks should shoot more slowly ... but whether the difference is significant is still open to more rigorous empirical test. I hope to set up a test bed with fixed draw length, mechanical release, and variable width forks after the holidays.

The stick shot is slightly complicated, as the bands tend to interfere with each other on a stick shot. But perhaps I will be able to test that as well.

Cheers ..... Charles


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