[thumperX]

If 2 arrows weight the same, but have a 2% difference on FOC will they hit in the same spot on a target??? or will it be differnet enough to notice??

 

[xXxSABERxXx]

the outside diameter will determine that for the most part. you can have a bow that shoots a large arrow weighing maybe 250grns more and a small arrow and have them hit the same spot bc of the way they are on the rest.

 

[BowRegards]

Good question. Bump.

 

[Archersteve]

I assume that the question is more one of theory, and not reality.

So, in theory, if all things were the same other than foc, including total weight, total diameter, total fletch size and orientation, etc., etc., etc., then the greater foc would be more consistent, but on a wind free day they would indeed hit the same spot.

Now, how do you get the same arrow with a different foc? It can be done with wraps, etc., but it takes some work to do it.:wink:

 

[BowRegards]

But, does the arrow with the lower foc fly with the point higher? If so, will the point strike the target higher?

 

[michihunter]

Heavier Fletchings lighter tips and vica versa Steve.:wink:

 

[nuts&bolts]

If 2 arrows weight the same, but have a 2% difference on FOC will they hit in the same spot on a target??? or will it be differnet enough to notice??

I had someone ask me a very similar question.

Brand X was a medium outside diameter shaft,
with a weight of 8 grains per inch, let's say.

Brand Y was a large diameter shaft,
also with a weight of 8 grains per inch.

The question was were these two shafts interchangeable.

Answer = No.

Brand X was a 0.400 spine shaft.
Brand Y was a 0.340 spine shaft.

So, even though the unit weight for both shafts
are the same,
you still need to evaluate the spine (stiffness) rating.

Unit weight does not provide information about the stiffness.

So, if two shafts are at the same unit weight,
and the FOC is within 2%,
all that means is that one of the shafts has a slightly heavier broadhead.

One must still evaluate
the spine rating of the two arrows,
to completely hypothesize about the probable point of impact.

 

[nuts&bolts]

But, does the arrow with the lower foc fly with the point higher? If so, will the point strike the target higher?

With a 2% difference in FOC,
you would easily notice at 90 meters (100 yds).

At 20 yds, any difference in point of impact
would most likely be due to the shooter,
rather than the arrow.

 

[TMan51]

I have found that arrows of similar spine will often group quite closely out to 20-25 yds, irrespective of weight.

An example of that is the fact that my 70lb Cybertec & Ultramag shoot quite well with GT 75/95's, Beman ICS 340's and CX Terminator 4075's, with 100 or 125gr tips My Protec shoots Beman ICS 500's and GTUL 400's into the same spot @ 50lbs, at all distances, (They weigh the same within a grain or two), but the same combo from my 60lb Razortec does not.

My guess is that 2% difference in FOC, or quite a bit more difference in weight, is not significant at least over 2-30yds, but spine, and especially dynamic spine, probably is.

 

[Archersteve]

But, does the arrow with the lower foc fly with the point higher? If so, will the point strike the target higher?

The acceleration due to gravity is constant for all items, so unless you think air has a boyant effect, the points would fly the same.

 

[Archersteve]

Heavier Fletchings lighter tips and vica versa Steve.:wink:

"It can be done with wraps, etc., but it takes some work to do it."

Most tips have 15 or 25 grain differences between weights. Most fletch differences will be in 5 to 7 grains for three fletch. Good try, but I'll stick with my first claim.:wink: :zip: :tongue:

 

[Archersteve]

With a 2% difference in FOC,
you would easily notice at 90 meters (100 yds).

At 20 yds, any difference in point of impact
would most likely be due to the shooter,
rather than the arrow.

It is not often that I and lug nut do not agree, so log this in your journal as perhaps the only time this has happened.

My physics knowledge and my personal experience say that only the consistency would be observed at 90 meters, not the specific point of impact; assuming again that all other things were equal.

 

[thumperX]

alot of response

Thank for the responses, wasnt sure if I get any anwsers... now Ill try and give more detail...
Both arrows are the same, Redline 410's, and same lenght.. the differnce is in the wraps, fletching and tips... arrow1 has a full 7" wrap and 3 AAE 4" fletchings and a 90gr tip...Arrow2 has a 5" wrap with 3 2.5in quick spin fletchings and a 100gr point.. all the arrows weight with 5 grs of each other...
I shoot a spot hogg pin sight and in 3D shoot mostly hunter class, because of the pin sight. Want to play around with open class, although I feel at a disadvantage with the pin sight and believe you need the scope and adjustable sight to zero in on longer yardage shots..Some of the local shoots they dont care what arrows you shoot (not sure if I agree with that) but want to shoot the quick spins instead of them just laying around till I get a differnet sight...

 

[cmbhunter]

The acceleration due to gravity is constant for all items...

That is true but... if you are considering the "nose over" effect the acceleration of gravity is acting on the CoM of the arrow and has greater mechanical advantage or moment about the geometric center of the arrow with a higher FOC. This would tend to make the arrow rotate "nose down" and loose altitued faster. I agree that the difference would be negligable at 20yds but I believe the higher FOC would impact lower at 90m.

Just my $0.02, correct me if I'm wrong.

 

[Archersteve]

Thank for the responses, wasnt sure if I get any anwsers... now Ill try and give more detail...
Both arrows are the same, Redline 410's, and same lenght.. the differnce is in the wraps, fletching and tips... arrow1 has a full 7" wrap and 3 AAE 4" fletchings and a 90gr tip...Arrow2 has a 5" wrap with 3 2.5in quick spin fletchings and a 100gr point.. all the arrows weight with 5 grs of each other...
I shoot a spot hogg pin sight and in 3D shoot mostly hunter class, because of the pin sight. Want to play around with open class, although I feel at a disadvantage with the pin sight and believe you need the scope and adjustable sight to zero in on longer yardage shots..Some of the local shoots they dont care what arrows you shoot (not sure if I agree with that) but want to shoot the quick spins instead of them just laying around till I get a differnet sight...

OK, now we have something to work with.

Your issue will now be "is there a difference beteen the arrows due to the different components". The difference in fletching will cause the fletch with the higher air resistance to fall lower. I believe that you will find that the quick spins will have more "down range" resistance and will drop quicker (slower therefore more time in flight therefore more time for gravity to affect them). You should not see much of a difference until perhaps 50 or 60 yards, depending on your skill level. Also, 5 grains can slow the arrow down (initially) enough to show up at longer ranges as well.

Personally, I would not worry to much about it unless you see a problem at the practice range. I suggest that once you know your arrows, you can just hold a little over.

 

[Archersteve]

That is true but... if you are considering the "nose over" effect the acceleration of gravity is acting on the CoM of the arrow and has greater mechanical advantage or moment about the geometric center of the arrow with a higher FOC. This would tend to make the arrow rotate "nose down" and loose altitued faster. I agree that the difference would be negligable at 20yds but I believe the higher FOC would impact lower at 90m.

Just my $0.02, correct me if I'm wrong.

OK, you are corrected.:wink:

I have tried to write something that would be clear on AT a dozen times, and I am now understanding that without a sketch pad, a free body diagram, or at least a black board, it is not going to happen. Meet me in Darrington next year at the NFAA Nationals and we can continue this discussion.

We agree with the COM (center of mass), we agree on greater mechanical advantage (the reason a higher FOC will be more consistent at long range or with broadheads), but we do not agree on a "nose over" effect.

I guess for now we will just need to agree to disagree on this one.

 

[cmbhunter]

The above was only my interpretation of how it would work. I'm not that familiar with the "nose over" effect and honestly not 100% convinced it is even an effect.

I agree that I was disagreed with. Still awaiting correction:wink:
Since I don't shoot NFAA and live nowhere near WA, please post FBDs as attachement to PM. Always up for a good proof, especially from a guy who's avitar looks like Einstein.

 

[michihunter]

"It can be done with wraps, etc., but it takes some work to do it."

Most tips have 15 or 25 grain differences between weights. Most fletch differences will be in 5 to 7 grains for three fletch. Good try, but I'll stick with my first claim.:wink: :zip: :tongue:

5" Vanes weigh approx 36gr. Blazers weigh 15 gr. Assuming 3 fletches. Feathers weigh less. First claim nonwithstanding.:wink: :tongue:

 

[Archersteve]

The above was only my interpretation of how it would work. I'm not that familiar with the "nose over" effect and honestly not 100% convinced it is even an effect.

I agree that I was disagreed with. Still awaiting correction:wink:
Since I don't shoot NFAA and live nowhere near WA, please post FBDs as attachement to PM. Always up for a good proof, especially from a guy who's avitar looks like Einstein.

Initial PM sent.

By the way, my oldest daughter did the Avitar, complaining about or removing it would land me in the dog house forever.:zip:

 

[Archersteve]

5" Vanes weigh approx 36gr. Blazers weigh 15 gr. Assuming 3 fletches. Feathers weigh less. First claim nonwithstanding.:wink: :tongue:

The drag of 5" vanes, compared to feathers of any size, or compared to Blazers, would change the total equation.

All other things can now be disregarded because drag is not the same. My experience indicates that standard Blazers have the same stability as 4" vanes, but have less drag, so I would guess the drag would be something like this.

Standard Blazers, lowest drag out of these compared.
4" vanes, next lowest.
5" vanes, next lowest.
4" feathers, next lowest.
5" feathers, highest.

Even that comparrison is not "linear" because at initial speeds the feathers fold down and you do not have more drag. At longer distances, the feathers are like little parachutes.

So michihunter, throw me another hard ball, I think I nocked (hehehe) that one out of the park.:wink: :wink: :wink:

At the risk of quoting myself, "I assume that the question is more one of theory, and not reality.

So, in theory, if all things were the same other than foc, including total weight, total diameter, total fletch size and orientation, etc., etc., etc., then the greater foc would be more consistent, but on a wind free day they would indeed hit the same spot."