Foc

[SonofDixie]

My list of Questions is growing smaller! Lol. Thanks for all the advice yall have been helping me out with.

But now and then with more research and practice, i come across something else....

FOC.....

Could someone help understand what this is and why i need to understand it? Thanks guys.

[Mike_W]

Weight front of center, this is crucial for proper arrow flight and penetration. You want the front of your arrow to have 10+% for best arrow flight and penetration because the front of your arrow is what you are shooting and the back /fletching are only there to "steer".

[45-70sapper]

I understand it as putting the weight forward of the center point of the arrow for proper arrow flight. I imagined it as a tractor trailer. The tractor is pulling the trailer and it goes in a straight line. If you put the tractor behind and tried to push the trailer, it would go all over the place. The heavy foc drags the arrow behind it. But I'm no expert, just how I understood it.

[LA_bowhunter]

Here is a shortcut to some common archery calculators for FOC, KE, Momentum etc. Also a link to archery report where some of these concepts are explained.


http://archerycalculator.com/arrow-f...oc-calculator/

http://archeryreport.com/

Rick

[L.O.S.T.Arrow]

For example why I still use 125 gr broadheads...adds to FOC

Neil

[nekred]

FOC is a balance like everything else....

there are trade-offs.... you start adding pint weight to get FOC and spine weakens....

To me you tailor the arrow for spine.... to get more FOC you go to a heavier broadhead and now you have to shorten arrow to stiffen it.... FOC is expressed as percentage ahead of center for the balance point.... Think of it as a teeter totter and you shorten one end you have to add more weight to balance it or tip it .....

so you have a 26" arrow with 125 grain head or a 29" arrow with 75 grain head.... which one has more FOC?

FOC is a conversion measurement..... meaning because it is expressed as a percentage it does not tell the whole story.....

I have an arrow with a 300 grain point for target but that is to get the spine I want and it is my 20 yard indoor arrow... it does not fly nearly as nice at long range as my skinny carbon arrow with 100 grain points for 90m FITA....

For me there are more variables to think about than FOC....

Most important is Spine.... then FOC is also important as well as arrow drag as distance increases I want to reduce drag and get optimum FOC..... also balanced with initial velocity.....which is affected by point weight as well...

For each game I play I have an optimum arrow built for the purpose.

For Indoor target I want a fat heavy arrow built like a truck that gets me about 240 fps which allows bow to cycle fast enough to help reduce errors, but slow enough to not be twitchy....and fat to catch more scoring lines

For Outdoor target I want a relatively heavy arrow with good sectional density and less surface area for decreased drag (skinny arrow) with a higher FOC... more like 15%

However for 3D arrow I want light fast and don't need so much FOC.... as velocity is more important and as long as FOC is not -ve all is good....

etc....

BUT ALL HAVE TO HAVE PROPER SPINE

[Mike_W]

Originally Posted by nekred

FOC is a balance like everything else....

there are trade-offs.... you start adding pint weight to get FOC and spine weakens....

To me you tailor the arrow for spine.... to get more FOC you go to a heavier broadhead and now you have to shorten arrow to stiffen it.... FOC is expressed as percentage ahead of center for the balance point.... Think of it as a teeter totter and you shorten one end you have to add more weight to balance it or tip it .....

so you have a 26" arrow with 125 grain head or a 29" arrow with 75 grain head.... which one has more FOC?

FOC is a conversion measurement..... meaning because it is expressed as a percentage it does not tell the whole story.....

I have an arrow with a 300 grain point for target but that is to get the spine I want and it is my 20 yard indoor arrow... it does not fly nearly as nice at long range as my skinny carbon arrow with 100 grain points for 90m FITA....

For me there are more variables to think about than FOC....

Most important is Spine.... then FOC is also important as well as arrow drag as distance increases I want to reduce drag and get optimum FOC..... also balanced with initial velocity.....which is affected by point weight as well...

For each game I play I have an optimum arrow built for the purpose.

For Indoor target I want a fat heavy arrow built like a truck that gets me about 240 fps which allows bow to cycle fast enough to help reduce errors, but slow enough to not be twitchy....and fat to catch more scoring lines

For Outdoor target I want a relatively heavy arrow with good sectional density and less surface area for decreased drag (skinny arrow) with a higher FOC... more like 15%

However for 3D arrow I want light fast and don't need so much FOC.... as velocity is more important and as long as FOC is not -ve all is good....

etc....

BUT ALL HAVE TO HAVE PROPER SPINE

Wow talk about blowing his head up info overload for a guy that didn't know what FOC meant.
Good info though and all true it's a balancing act to get an arrow just right and there are programs to help you in finding the proper spine of arrow and a good foc.

The most common issue I see in new archers is arrows that are far too long 5-6" past the rest ... Sure this helps with foc but won't help with spine/tuning.

[ThreeD]

Originally Posted by L.O.S.T.Arrow

For example why I still use 125 gr broadheads...adds to FOC

Neil

Ditto.

[petew]

Originally Posted by Mike_W

Wow talk about blowing his head up info overload for a guy that didn't know what FOC meant.
Good info though and all true it's a balancing act to get an arrow just right and there are programs to help you in finding the proper spine of arrow and a good foc.

The most common issue I see in new archers is arrows that are far too long 5-6" past the rest ... Sure this helps with foc but won't help with spine/tuning.

Actualy it may help lots with spine and tuning.

[Mike_W]

Not considering 99% of those are a 32 inch 340 or 300 spine being shot out of 70lb bows

[nekred]

Originally Posted by Mike_W

Wow talk about blowing his head up info overload for a guy that didn't know what FOC meant.
Good info though and all true it's a balancing act to get an arrow just right and there are programs to help you in finding the proper spine of arrow and a good foc.

The most common issue I see in new archers is arrows that are far too long 5-6" past the rest ... Sure this helps with foc but won't help with spine/tuning.

Arrow length affects spine.... I had a junior archer that wanted fat arrows and the only way I could get them to spine is run as heavy of a tip as I could find and leave them long.... Then they went into an archery shop that is no longer in business and they cut 4" off "because they were too long".... which made them way too stiff... After that I instructed any of my students to let NO ONE touch their arrows... For example to get 2712's to spine to 60 lb compound one needs 300 grains up front and for me they have to be 32" long!.... They stick way out in front....

Another little know tuning method is also node tuning..... arrows undergoing the shot cycle flex and this flex is a wave form with a certain frequency and amplitude.... that really is what spine is and why there is a term like tuning... with any wave there are crests, troughs and nodes.... nodes are like the pivot point.... and as the arrow moves forward this node moves along the arrow.... at same speed arrow is moving forward if spine is ideal.... having the rest situated at this node point helps as well.... especially with spring rests and ugly cookies...

[nekred]

on my trad bow I can go with a 500 spine arrow and cut it short or with a 400 spine and leave it longer... which I like better as it moves point out further and assists with peripheral aiming....