UEFOC by double inserting, where's the truth??

[olddogrib]

I don't usually double post on multiple forums but there's an EFOC post here that's directly related to an issue I brought up elsewhere and I don't want to hijack either of those threads.  Jason S. has an interesting video here where he achieved ungodly high EFOC numbers by double inserting combined with heavy broadheads. This indicates what some have been claiming for some time, that insert weight does not have the same spine-weakening effect as pure tip weight, i.e a 100 gr. insert with a 125 gr. tip is not going to shoot the same as 225 gr. tip(w/a std. light aluminum insert). Those in this camp have said that longer inserts have the same effect as footing a shaft and thereby stiffen spine, not weaken it as additional tip weight would. Jason's achieving something 30% FOC with something like 400 out of 700 gr. on the front. I dare say Stu's charts would class these weaker than porridge(and Jason concedes that), but they shoot well for him.(excluding his garage casualty)  It's time to clear this up(and revise the charts, if necessary), it can't work both ways. A respondent on the other site says wheelie shooters have been use multiple weighted inserts as a FOC tool, the additional internal weight has negligible affect on spine. Where's the truth...inquiring minds want to know?

[BowDiddle]

Any footing you add, whether internal or external that extends beyond the inside end of a standard insert actually shortens the flexible length of the arrow, thereby stiffening it's dynamic spine.

It's the same thing as shortening the arrow, so using this method to get higher foc allows you to do so without weakening the spine as much as it would if you stack all the weight directly on the front.

[gonefishing600]

Originally posted by BowDiddle:
Any footing you add, whether internal or external that extends beyond the inside end of a standard insert actually shortens the flexible length of the arrow, thereby stiffening it's dynamic spine.

It's the same thing as shortening the arrow, so using this method to get higher foc allows you to do so without weakening the spine as much as it would if you stack all the weight directly on the front.

Very well put, I think it's just common sense.

[Orion]

Agreed.  And it's really not new info.  Used to be lots of discussions to that effect when O.L. and Doc Ashby still posted here.

[olddogrib]

Okay, maybe I've been in a coma and missed the obvious, let me restate  the issue. I just ran a hypothetical .400 grain 29" arrow with 11.4 grain nocks and 250 grain heads through Stu's calculator two ways. One with a 12 grain insert (typical standard aluminum) and a 238 gr. hypothetical head and the other with a 100 grain (typical brass, weighted) insert and a 150 grain head. The results are essentially the same (within 2lbs dynamic spine).  You guys are saying no way and everybody on here is aware of it.  I'm saying I keep seeing advice to that effect (corroborating the chart) all the time.  What gives?

[gonefishing600]

Correct me if I'm wrong, but on your first post you said double inserts, and BowDiddle stated that "Any footing you add, whether internal or external that extends beyond the inside end of a standard insert"

EXTENDS BEYOND THE INSIDE END OF A STANDARD INSERT!

Now your comparing a 100gr. insert to a aluminum insert of the same length. That's a whole different ballgame.

[olddogrib]

I'm sure I'm not aware of all the styles, but the arrows that I've been familiar with that had the option of offering heavier inserts, brass may have gotten you to 50 gr. in a standard length, but I think most were longer if you went with a 100 gr. option. Double/single issue aside, the question is when you get up into the 250-300 gr. plus range, will an aluminum insert heavy point combo have the same effect on spine as a combo where approx. 50% of the wait is internal and comes from a heavy brass insert. The consensus used to be it made no difference(the chart still does), now I'm hearing differently. I don't make this stuff up, lol!

The 100gr brass inserts I use are .7" longer than the standard aluminum insert.

And the answer to your question is NO! It will not be the same but will not be enough different to make a hill of beans difference (this is for one brass insert. I have never tried two, so don't know how much difference that extra inside the shaft would make).

In the big picture, it really does not make any difference. Either way is going to yield high FOC values, so whichever you get tuned for you will work just fine.

Bisch

[Orion]

OK, I think I understand what you're saying.  There's almost no noticeable difference between a heavy head and aluminum insert vs a lighter head and brass insert, given that the overall front weight is the same and both the inserts are the same standard length, about one inch. If one broad head or insert is slightly longer than the other, it could change the dynamic spine a smidgeon one wayh or the other, but we probably don't have equipment sensitive enough t measure it, and certainly most aren't good enough to detect it in their shooting.

I thought you were talking about a 3-5-inch or longer internal or external footings, which some folks put into/on their arrows.  Though the extra weight leans toward softening the dynamic spine, the long footing prevents the shaft from bending there, thus stiffing the spine.  In this case, the stiffening effect is greater than the softening effect.  Actually, this is just a more extreme example of what Gone Fisin said initially.

The longer the insert, the more it stiffens the dynamic spine.  The more the broad head weighs and the longer it is, i.e., the more itsticks out the front of the arrow, the more it reduces the dynamic spine.  Which one wins out depends on what the combinations happen to be.

[Sapcut]

What you do is forget about the stinkin chart or calculator.  Anything of substance that you add whether against the inside or against the outside of the shaft will stiffen the spine.  The chart just hasn't learned that yet.

But more advantages to adding to the outside than the inside.

[damascusdave]

I always wonder what you are planning to hunt with those arrows...if you do not need them for the game you are hunting why even bother...none of us are shooting hypothetical arrows...if the information is all that important to you why not spend the time and money to find out and share your findings with the rest of us...I shoot arrows that weigh over 900 grains with 75 grain inserts and 250 grain points at 155 fps...if I wanted to make them into 950 grain arrows all I would have to do is shorten them a bit and use 300 grain screw in points which are readily available...or I could shorten them a bit more and use a 300 glue on Tuffhead with a 100 grain screw in adapter and they would be 1050 grains...and I sincerely doubt there is any animal in North America that I cannot get a pass through on if I hit them right at a reasonable range with those arrows...if I hit them wrong those arrows will still not penetrate very well at all...if you want to shoot through the thick part of a scapula you better be using a rifle...it is not rocket science to get heavy arrows...just takes a bunch of time and money...and I have a hard time believing that once an arrow reaches that sort of total weight the FOC really needs to be more than the 15 to 20 percent those arrows achieve...I am doing all that with a bow that is about 60 to 62 pounds at my 30 inch draw length so well within reach of anyone who wants to work a bit at draw weight...I just turned 63 and am not in all the great physical condition

DDave

[BowDiddle]

The chart I have of Stu's calculator does have an area to enter the length and weight of footing. It calculates the footing length against the added weight real good, and gives a real good overall dynamic spine of the arrow.

Is it dead on all the time? NO, but it is always close enough to give me a workable shaft.

[BowDiddle]

I just did a calculation adding 50gr of front load on an arrow using a .300 spine arrow at 31" as the base.

50gr added in point weight dropped the dynamic spine by 16#

50gr added as a 2" footing only dropped the dynamic spine by 3.5#

Both increased the FOC by the same amount.

This shows that the footing can and will increase the FOC the same as point weight, but will offset the loss of spine from the added weight, and my experience in shooting/tuning these type arrows holds true to what this shows.

[Tedd]

This in interesting. Currently heavy inserts are brass. In theory, could a long insert be made of a material that increased arrow weight with no affect on spine? Example…an aluminum 100 grain insert. Say it's two inches long and  stiffens the arrow with the exact amount that it weakens the arrow from adding weight?
Or maybe you just want to stiffen and shaft? By using a long but light insert?
Does stiffening the front few inches of a shaft, give the shaft similar properties as tapered shaft?
I usually use tapered shafts but often try parallel setups and find them finicky. It seems others find the parallel shafts finicky also to be considering small small changes such as internal footing vs point weight.
Tedd

[Tedd]

This in interesting. Currently heavy inserts are brass. In theory, could a long insert be made of a material that increased arrow weight with no affect on spine? Example…an aluminum 100 grain insert. Say it's two inches long and  stiffens the arrow with the exact amount that it weakens the arrow from adding weight?
Or maybe you just want to stiffen and shaft? By using a long but light insert?
Does stiffening the front few inches of a shaft, give the shaft similar properties as tapered shaft?
I usually use tapered shafts but often try parallel setups and find them finicky. It seems others find the parallel shafts finicky also to be considering small small changes such as internal footing vs point weight.
Tedd

[olddogrib]

BowDiddle, thanks that helps.  I did not think to try entering a non-standard length insert( or double one for that matter) as a footing. (would you enter the weight in both fields?).  Best I remember, when heavy inserts became an option for skinny shafts they had break-off sections to choose your weight/lengths and were definitely longer than standard inserts.  I'm not trying to belabor the point, but as long as I've been at this game I can imagine the frustration of a newbie trying to pick an arrow combo when it's not clear if  he's going to weaken spine with additional tip weight or stiffen it because he happened to chose a longer than standard heavy insert so he could use the broadheads he has on hand, but that actually did the opposite of what he wanted to accomplish.

Originally posted by BowDiddle:
I just did a calculation adding 50gr of front load on an arrow using a .300 spine arrow at 31" as the base.

50gr added in point weight dropped the dynamic spine by 16#

50gr added as a 2" footing only dropped the dynamic spine by 3.5#

Both increased the FOC by the same amount.

This shows that the footing can and will increase the FOC the same as point weight, but will offset the loss of spine from the added weight, and my experience in shooting/tuning these type arrows holds true to what this shows.

It makes no sense to me how weight inside the shaft could increase the FOC the same amount as that same weight in front of the shaft?????? I don't see any way possible that can be correct.

Bisch

[BowDiddle]

[/qb][/QUOTE]It makes no sense to me how weight inside the shaft could increase the FOC the same amount as that same weight in front of the shaft?????? I don't see any way possible that can be correct.

Bisch [/QB][/QUOTE]

Well you are right to a point.

The FOC won't be exactly the same, but the difference is so small (were talking less than 1%), that Stu's calculator does not change it.

At any rate, when talking adding weight spanned over a 2 to 3 inch distance from the front of the shaft, or all the weight stacked right on the end of the shaft, the difference in FOC will be so slight as to be insignificant, but doing it with the footing helps avoid coming up with a significantly under spine arrow.

[Orion]

BowDiddle:  How do you figure they both increased the FOC the same amount.  If the weight is farther forward, i.e., in the point vs the footing, it has to move the balance point/FOC farther forward. Me thinks there's something amiss with the formula. Though the dynamic spine relationships are in the direction we theorize, we really have no way of knowing if the percentages are accurate.

Oops. I should have read Bisch's query more closely.  He's saying the same thing.

[BowDiddle]

Originally posted by Orion:
BowDiddle:  How do you figure they both increased the FOC the same amount.  If the weight is farther forward, i.e., in the point vs the footing, it has to move the balance point/FOC farther forward. Me thinks there's something amiss with the formula. Though the dynamic spine relationships are in the direction we theorize, we really have no way of knowing if the percentages are accurate.

Read my response to Bish.