arrow spine brace height help

[bucksbuouy]

Ok... still trying to wrap my mind around all this. I have a longbow marked 72@28 and I draw it 29.5 where Stu's calculator puts me at 85. I picked up some hickory shafts from Allegheny spined at 85 and I left them a full 32". But they are not 85 at 32 are they? They are lower right? They would be 85 at 26" or 28"?

Ok.. now. lol. I have these arrows, under-spined so I want a lower brace height? Right?

[bucksbuouy]

also, like I said, Im short drawing the shafts so does that make them perform like 32" or the 29.5" I actually drew it?

[moebow]

Wood shafts are spined at 28".  Subtract 5# for each inch longer than 28.  For a full 32" your arrows will behave as though they are spined for 65#.  That's the rule of thumb for 125 grain points.
Depending on your bow, FF string, center cut etc, if you were to cut to 30" (ya, if you are planning to use broad heads you'll need longer) your arrows will be about 75# spine and in the ball park for your bow.

[bucksbuouy]

Ok well at least I know. What can I expect, performance wise, if I shoot these arrows, under spined at 32"? Also, the weight of the shafts is about 700 grains and the points are 160.

[moebow]

Physical weight of the arrow won't affect spine or arrow flight, just trajectory.  With 160 gr points you will loose another 5# so so of effective spine. So now you'd be down to about 60#.  As shafts get more and more under spined you will find a loss of consistent point of impact -- that is they get "squirrely."

Why do you want them so long? and Why such a heavy point?  If there's a reason OK but you are making life harder than it needs to be.  Wood shafts are not like the aluminum or carbon arrows and my experience with them is to make them as long as necessary but no longer.  That's kind of the reverse of the theory of the other materials.

[bucksbuouy]

That makes sense. They do seem squirrely.

The only reason for leaving them so long is because my natural draw length is about 29.5 or 30, so I would only be cutting an inch or so off anyway, so I figured I would just leave them full length.

My reasons for going so heavy in general is because the bow is so heavy and I figured some extra mass in the arrow would decrease hand shock. You can also get great deals on used bows that are heavy and I figured if I can draw it I might as well. Also, I hunt in a residential area and Im really concerned that I get good penetration and a quick kill before the deer runs into the neighbors yard.

thanks for the help moebow

[moebow]

Even cutting just one inch off and dropping to 125 grain points will get you 10#s of spine back and you'd be right back in the ball park.  You will still have VERY heavy arrows out of a pretty heavy bow and should have penetration out the "wazoo". Good arrow flight is at least as important (if not more) as mass weight of the arrow when it comes to penetration.  Once the arrow is through the deer it's done all it can and more power/penetration won't help with a faster kill.

[bucksbuouy]

Good arrow flight and a pass through is all I can hope for unfortunately I dont have anyone to explain these things to me locally. Im going to cut these arrows down today and see how they feel but I may just end up scrapping them and getting a proper outfit. Thanks again.

[Don Stokes]

Bucksbuouy, I suggest you try some broadheads before you go too far. I think you'll be badly underspined with full length shafts.

[bucksbuouy]

yeah actually I have crunched the numbers and like you said moebow if I just take an inch or two off and go with 125 grain heads Ill be perfect. I feel alot better now. lol.

[Orion]

I assume you're shooting a Hill style longbow, cut 1/8-inch from center with a dacron string.  If so, you're drawing about 78# or more at 29 1/2 inches.  You'll need at least 85# spine to get good arrow flight if you leave the shafts full length and use 160- grain points.  You might get away with 85# if you shorten them one inch and reduce the point weight to 125 grains.

Adding shaft weight has the same (though reduced) effect as adding point weight.  Neither changes the static spine, but both change the dynamic spine of the arrow.  However, adding 25 more grains to the point has a greater effect than adding 25 more grains to the arrow shaft, which is distributed along the entire length of the shaft. Regardless, adding physical weight to the arrow requires more static spine, how much more depends on how much more physical weight is added and where it's added.

In addition, hardwoods are physically heavy and don't recover from flexing around the riser as fast as softwoods like cedar, spruce and fir, and thus require an even heavier spine. With your current set up (arrow length, point-weight, wood choice), 90-95# spine will likely work better, particularly with broadheads.

If my assumptions are incorrect and you're shooting a hybrid, cut to center or past center and a fast flite string, you'll need a lot more spine, probably another 20# or so to 100-105#. That's pretty hard to come by in wood,but possible.

Adjusting the brace is done to find the sweet spot and perhaps final tune the bow to the arrows.  It will only change the draw weight, and thus arrow spine required, by a pound or two. Good luck.    :eek:

[Don Stokes]

Very good summary, Orion.

[bucksbuouy]

My bow is a Bama bow with a 5/16" offset (if I measured correctly)and according to Stu's calculator that drops my dynamic spine from 84 to something like 67 pounds. Ive heard of dropping ten pounds of spine for long bows but not 17. Does that seem extreme?

orion- are you saying if I shorten my shafts Ill get a lower spine? stop me if Im misunderstanding but shortening the shafts and dropping point weight should infact increase spine. These shafts are spined 85@28 but I shoot about 30 and wanted to leave them at 32 where they have a 60# spine. thats the issue.

[bucksbuouy]

orion- never mind bud I got ya

[bucksbuouy]

brain fart