What spine shaft for 29% FOC in 50# bow?

[tigertrad]

#2824

Currently shooting 400 spine 8.2 gpi Warrior carbon arrows at full length (32″) out of a 50#@28″ recurve (actual drawlength about 27″). Arrows fly fine with 125-grain tips, but I have read Dr. Ashby’s studies and would like to go heavy — thinking 725 grains, with about 29% FOC. Question is this: can I simply (and safely) expect to just put in a 200-grain insert and attach, say, a 225-grain Tuffhead into my existing 400 spine shafts to gain the overall weight and FOC I’m looking for? Also, assuming it’s safe, should I expect good arrow flight or expect to have to cut shafts; or should I order a few screw-in insert weights or washers, etc. for fine tuning. Trying to be as efficient and economical as possible in this

[Bruce Smithhammer]

#13266

Adding that much weight to your existing full-length shafts will weaken the spine significantly. If they are currently flying well with a 125gr. head, you are likely going to have to cut them down to stiffen the spine. The good news is that with a 27″ draw length, you have some room to work with.

I would suggest taking one of your shafts and mounting the desired insert/point weight on it, and then progressively cutting in 1/2″ increments (from the rear of the arrow) until you get good flight. And hopefully it will be that simple, but only you will be able to determine that through experimentation and testing.

Keep us posted!

[Doc Nock]

#13289

I’ve been on the road for 7 days, and SH has given you some succinct and sage advice. I’d likely have been more cryptic in my current state of mind…

The concept of building EFOC arrows is one that can result in highly Efficient arrows is a given, but the “economic” part of your quotient might mean it’s a do or die with your current shafting. (?) That might be a bit hinky!

As SH suggested, cutting strengthens the spine and allows more weight to achieve proper tune.

Shimming out your side plate..thicker material or a toothpic glued behind side plate material can “stiffen” spine some, up to a point. Both approaches (cutting and /or shimming,) “stiffen” a weak shaft!

The shorter your shaft, the more weight I believe (?) required to get a higher EFOC… I draw 28.5 and shoot arrows 29.5″ and get 28% w/ 300 total gr up front with insert and head. My current bow required I bump up from 400 shafts to .340 cause it’s far more efficient limb design for my 47# draw! Go figure!:D

Everyone is different and every BOW and how it’s cut and it’s force curve will change things.

Download the Tuff Head Tuning Guide for bare shafting arrows and follow it to a “T”… it’s not a Chinese take out menu where you can order what you want off the menu and get free egg rolls! Do it by the book! Don’t have the funds? Then shoot what works and save the EFOC for when there are a few more shekels to fun the project properly!

[tigertrad]

#13337

Thanks for the replies SH and Doc. Good to know I might not have to start at square one. I’ll get the inserts and tips and see what happens. If I need to go to 340’s, that’s not a big deal. Hopefully the process will go smoothly enough to get the larger issue (the shooter’s brain) recalibrated to instinctively lob those mortars at live game this season. 🙂

[Doc Nock]

#13360

SH is likely a more reliable tutor than I. I was interested in around 600 gr. total weight.

I’ve since found some “target” type shafts that weigh lighter GPI, to keep my overall arrow weight down while still having higher FOC.

Best of both worlds to my thinking. I’m currently shooting some GT7595’s I was “gifted” and they work, but are around 585gr total.

I like Troy Breeding’s tuning guide on Tuff Head site as it suggests you choose your head weight and insert and trim from the rear on a bare shaft… good stuff, but the type of backstop is important as are each element…or you skew the results and can draw rash conclusions and get all tangled up! Don’t ask! 😮

I have 125’s, 145, 175, 200, 225, 250 qnd 300 gr. field points for testing.

Might be simple stick n string, but there are endless ways to tweak and do things to tune properly….

[David Coulter]

#13519

Hi TT,

My bow is a little lighter, a 46#, but I’m shooting 8.2 grain per inch shafts, Beaman Bowhunter, 400. I’m trimming them to a little over 30″, use a 50 gr insert, 75 gr steel adapter and 225 gr Tuffhead. All assembled they weigh in about 625 and balance at just over 28%. They fly great. I did a paper tune on my field tips, which are the same set up and they punched some nice round holes.

Just a guess, but I bet you could get away with trimming another inch or so off and match your 50#er.

I followed Troy’s advice to the letter when I first set these up. His advice was very valuable to me.

Have fun, dwc

[tigertrad]

#14172

Thanks DWC: you’ve done almost exactly what I hope to do, with very close to the same particulars. Glad you can report good results. Great forum here, BTW, with a real depth of knowledge to tap into and a willingness to share.

[David Coulter]

#14461

TT,

My pleasure. Most of us are just passing it on or paying it forward, as it were. The kind folks on this site have been very helpful to me. Keep the questions coming and you’ll be offering advice of your own before long. best, dwc

[tigertrad]

#27792

So it looks like the 400 spine arrows are working in my 50# recurve. The old arrows were 447 grams with a FOC of 15.4% (at 32.5 inches long); the heavyweights (added 100-grain brass insert, plus 75-grain adapter and 225-grain field tip) come in at 679 grams with 28.75% FOC (at 32 inches). Flying pretty well with slightly over 1/2-inch cut off the back and I added a piece of toothpick under the arrow shelf pad. Brain working arc adjustments pretty well up to about 30 yards after shooting 300 – 400 arrows over five or six practice/tuning sessions to date. Thanks for the help y’all!

[David Coulter]

#27953

TT, sounds like you got it. Fun when it works, right? May your arrow find it’s mark this season. best, dwc

[Bruce Smithhammer]

#28589

tigertrad wrote: So it looks like the 400 spine arrows are working in my 50# recurve. The old arrows were 447 grams with a FOC of 15.4% (at 32.5 inches long); the heavyweights (added 100-grain brass insert, plus 75-grain adapter and 225-grain field tip) come in at 679 grams with 28.75% FOC (at 32 inches). Flying pretty well with slightly over 1/2-inch cut off the back and I added a piece of toothpick under the arrow shelf pad. Brain working arc adjustments pretty well up to about 30 yards after shooting 300 – 400 arrows over five or six practice/tuning sessions to date. Thanks for the help y’all!

Nice work. Like DWC said, it’s fun figuring it out and playing around till you find what works. That setup should be capable of taking just about anything you’ll come across.

[tigertrad]

#28910

Yessir, Smith, that’s the plan is to be ready for anything. Plan to shoot a whitetail broadside, but a slight turn could put bone into play; plus, hogs are tough and plentiful in Texas. BTW, I noticed that I wrote GRAMS for the arrow weight when I, of course, meant GRAINS. The arrows aren’t steel rebar. 🙂

[tigertrad]

#30768

Said the arrows were flying “pretty well” above, so I wanted to try and get them flying really well. Realized a possible problem I was forgetting about while reading Doc Nock’s thread in this forum regarding brace height possibly affecting EFOC arrows’ flight. Checked the brace height on my 66″ early ’60s Ben Pearson Javelina recurve, which should be around 8 inches: it was barely 7 inches! Hadn’t noticed the string stretch from leaving it strung for a while and shooting a bunch (wasn’t hitting my wrist). Doc’s thread mentioned erratic flight (think the term used was “squirrely”) as a symptom caused by the front of the fletchings hitting the arrow shelf while the arrow nock is still in contact with the string. Anyway, twisted up string to get brace height at 8″, but forgot to move metal nock while at home and went to range. Flight was improved but not quite consistent. Looked at nocked arrow from side and realized nock point was virtually 90 degrees. Lacking a tool to raise nock, simply nocked arrow above the nock point — probably about 3/8ths” above perpendicular — and started shooting 3 to 4 inch groups flying like darts at 20 yards. Mention all this as a reminder to anyone building heavy arrows to be mindful of proper bow setup when tuning those arrows.

[wojo14]

#25324

I am no expert at this carbon and EFOC thing, but here is what I ended up with for my bow.

I currently shoot a 52# @ 26″ recurve. 26″ is my draw.

My set up is:

Gold Tip Pro Hunters 55/75-400 spine cut end to end 28 7/8″

GT gt nocks. 100g insert, 225 head, and a 25g footing.

Fletched with my own cut 2 1/2″ A & A feathers and turbulator tape.

Total weight of 607g and 28.72% EFOC.

They fly pretty good for my less that perfect form. But I am happy with them right now.

Now I need to get those deer to stop seeing me draw on them!!:x

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