I'm about get into building my own arrows. Up until now I haven't given FOC, vane type and total weight an excessive amount of thought due to the fine details being largely out of my control. My goal is 8 grains per pound of draw weight or 480 total grains. Here's what I have: Beman Centershot shaft 10.3 gpi 29" long Easton H brass insert 50/75 grain Vane Tec Vmax 3" vanes with right helical (I'm thinking 3 degrees) Easton H nock at 9 grains. 100 grain tip All added up, I come up with either 475 or 500 total weight depending on how I use the insert. Share your thoughts on which weight I should go with, any guesstimate on foc (the arrows are 29" long) and any thoughts on my vane choice. All advice from experienced builders is appreciated.
With a arrow that heavy, you'd be fine with between 10-15% FOC . Will not have a problem with penetration, imo
That arrow will pound through a deer no problem. Almost 185 grains up front means it will have good FOC and solid penetration.
With 100 grain tips that setup with the 50 grain inserts would finish out at 484 grains with 12.60% FOC. Assuming based on the numbers provided above you are shooting 60 pounds. This setup would yield 8.06 grains per pound. With the 75 grain insert it would finish out at 509 grains with 14.39% FOC. Again, assuming 60 pounds draw weight this would yield 8.48 grains per pound. However, based on your bows IBO rating and assuming a 29 inch draw length and 60 pounds draw weight, I would not recommend the 340 arrow spine but rather the 400's. Even with the high FOC (extra weight up front) of either of these arrows with the 50 grain inserts they are on the very high side of stiff spine. The 75 grain inserts are a bit stiff as well. The 75 grain setup would be borderline OK to use, but feel they are just to heavy for your current setup. Your bow would be shooting around 225 FPS with this set up.
With the arrows of your choice, for optimal spine the numbers show (assuming 60 pounds and 29 inch DL): 400 spine centershot arrows 28 inches long 50 grain inserts 100 grain tips Your nock and vane choices from above Yields 237 FPS 7.56 grains per pound 454 grains arrow weight 13.40% FOC 56.64 KE
Thanks for all the comments so far. I've always used 340 spine arrows. Never could get 400s to tune well for me, always got weak spine indicators . With extra weight up front that would make the 400 even worse. For what it's worth, I'm shooting 29 inches for draw length and my draw weight is 60ish pounds. I adjusted it to where I feel most comfortable but haven't measured it yet.
What weak spine indicators did you get? I find it very difficult to see an IBO rated bow of 302 FPS shooting 60 pounds under spined with .400 deflection. Based on your original arrow setup preferences from above (29 inch shaft your vane and nock choice) with the 50 grain inserts the optimal shaft spine for your bow (assuming 29 inch DL) is .390 deflection. Again based on your arrow preferences above (29 inch shaft your vane and nock choice) but with the 75 grain inserts the optimal shaft spine for your bow is .375 deflection. Do what you want. Good luck this fall.
Broadheads always hit right of my field points when broadhead tuning with 400 spine 29 inch arrows. Switched to 340 spine 29 inch and it tuned right up. I know that all the charts call for me to use 400 spine but I figure it is what it is. Besides, as long as they shoot straight I like having the extra weight and extra spine in case I want to turn the pounds back up.
Buy a couple loose arrows of both spines and play around with the combinations and see how they compare.
There is two different measures of spine. Static spine and dynamic spine. Static spine is the rating an arrow achieves via measured deflection. The deflection is measured by finding the center point of an arrow and then measuring 14 inches to the left and 14 inches to the right. The arrow is then supported at these two locations and a 1.94 pound weight is hung from the exact center of the arrow. How far the arrow bends (deflects) from this hanging weight is measured in 1/1000's of an inch. A 500 spine arrow deflected .500's of an inch, a 400 spine arrow .400's of an inch and so on. Static spine only takes the deflection of the arrow into consideration. It takes nothing else into consideration. Dynamic spine however is more of a "living" thing. Dynamic spine is how your arrow actually reacts when it is shot from your bow. It takes into consideration EVERYTHING. The aggressiveness of your cams, the bows let off percentage, your draw weight, draw length, weight of the accessories on your bow string, (peep, D loop, string silencers etc) the length of the arrow, the weight of your insert, points, nock, fletching, literally everything. Changing any of the above will directly impact your dynamic spine.
Whatever my dynamic spine requirements are, they seem to be met best with a 340 shaft. Anybody have any thoughts to share about selecting vanes? Straight fletch, Blazer style is all I've used before on factory fletched arrows. There seems to be an endless amount of other choices in materials, styles and lengths
I am not trying to change your mind on your arrow selection. I listed what mathematically yielded the best match for your setup earlier, do with it as you please. I have since only been sharing info with you as you are a new arrow builder. Dynamic spine is a little complex to understand at first. With it you can easily setup up a 400 spine arrow to be as stiff or stiffer than a 340. For example... With all things being equal: Same arrow selection, insert, tip weight, vanes and nocks.... A 29 inch Gold Tip Velocity 340 shaft and a 25 inch 400 shaft exhibit the same dynamic spine (using this as an example as I shoot the Velocity 340's). Using heavier vanes or arrow wraps or lighted nocks will all increase dynamic spine. In essence adding weight to the back of your arrow, increases dynamic spine. So obviously lighter vanes and nocks decreases dynamic spine. Just the opposite up front. Heavier inserts and points decrease dynamic spine, lighter increases dynamic spine. As for vanes, my first choice is the NAP quickspins (not the twister) and second choice is Bohning Blazer vanes. Both are great choices, I feel the quickspins are more forgiving in the event of any sort of vane contact in flight as they are not as rigid and have a little less of a profile.
I appreciate all the advise and I certainly don't mean to debate a topic I know little about. I guess that I'm just trying to ease my way into it. Using my 29" Bowhunter 340 arrows as a base line, I'm really not changing anything but the tip weight. The shaft is slightly heavier but I'm keeping with the same spine for now and will see how it performs for me. I'll play with shaft length and spine next round. I also need to get my draw weight measured before I start trying to micro manage my arrow spine. I could actually be closer to 65 pounds than 60. I just don't have a scale at home that can measure it.
