FOC, weight, spine?

[timbermoose]

i got some woodies for christmas and finally got around to checking the foc and they are at 8%.  they are spined at 55-60, full length(i have 31" draw). and currently have 125gr tips. figure i could use woodie weights to increase the FOC, but wont that change the spine? this is for my small game/ stump shooting setup. i have to figure somthing else out for my big game set up. what would you all recomend for a 70#@30" and a 80#@30"? 80# is for our moose.

[Stumpkiller]

IMHO you don't have to worry about FOC with wood shafts as they are of a proper weight by default.  Get the proper spine and tune your bow so they fly well.  A metal head on a wood shaft with fletching at the rear will have form stability and mass for penetration.  Plenty of moose have been killed with 125 gr broadheads.  My suggestion might be to go with a Douglas Fir or laminated birch shaft and toss out the FOC tables.

[Jim Wright]

You are correct, simply adding weight to the front will turn your properly spined set-up weak. To increase f.o.c. you can increase your point weight by approximately 25 grains for each spine range increase. For example if you wanted to use the woody weights as you mention in your 1st set-up you could go with the 75 gr. woody weight and the same 125 gr. points for a total of 200 grains, you would then increase your spine range to 70-75 lbs. Also f.o.c. can be increased by shortning arrow lenth while increasing point weight but you are handi-capped here because of your long draw.

[Fletcher]

The Woody Weights won't change the shaft's static spine, but they will change the dynamic spine and how much static spine you will need.  You could just try some 160 or 190 gr points.  Cheaper and easier than the WW, but will up your FOC.  They will still change the dynamic spine of the arrows; about 5 and 10 pounds respectively.  

125 gr heads and low FOC's have been killing things for many years, but that doesn't mean we can't do better.  The Ashby studies have shown irrefutable evidence that higher FOC's improve arrow penetration and performance.

Tell us more your 70 and 80 lb bows; make, model, string, depth of shelf.  We should be able to get you pretty close.  Doug Fir shafts should serve you very well.

[Stumpkiller]

The Ashby studies have shown irrefutable evidence that higher FOC's improve arrow penetration and performance.

 

. . . .this is for my small game/ stump shooting setup.  

How dead does a stump or bunny have to be?
       

For his moose - there is still a school that says the bigger the game the smaller the head to insure penetration.  Dr. Ashby has done outstanding work and if I ever get to go to Africa I'll be all over his writings.

[timbermoose]

the 70#er will be a 70" howard hill big 5, when i get my tax return. the 80#er is a 72" homemade longbow made from solid hickory. has a flemish string and the shelf is about 1/4 before center. borrowed some alluminum arrows from a buddy and she shoots fast. but i would like to have some woodies for her.

[Fletcher]

At 31" you should be drawing 73-74 lb.  A Hill bow will generally shoot a bit below draw weight with a 28" arrow and a 125 gr point.  Add 15 lb for the 31" arrow and another 5 for a heavier point if you want.  That's a 90-94 lb spine.  With this much adjustment, I'd recommend some test arrows to be sure you get what you need.  With a 31" draw and arrow, you don't have much room to play around.  By playing with point taper length I can usually get 31.25" - 31.5" BOP  You might want to consider using some Reparrow foots to give you a longer arrow shaft.  If you are lucky, both bows may shoot the same arrow.  I think they will be close.