wildschwein wrote: I was wondering if anyone here had any ideas as to what spine range a person would need in a 30 inch POC shaft, to get a 200 grain broadhead to fly accurately from a 35# (near center cut) longbow?

I need to ask, is the bow 35# at you draw or is it 35#s at the standard 28″?

3 feathers asks a good question. I’d also ask why you want so heavy a tip? Your bow will at a good efficiency level with about a 350 grain arrow weight but I bet with 200 grains up front you will have a 500 grain + arrow and that may make your bow kind of sluggish.

General rule of thumb is to add 5# of spine rating for every inch over 28″ and another 5# for for every 20 grains over 125 grains. These are “ballpark” estimates that should get you close but you need to answer 3 feather’s question first.

Absolutely your choice! I just suggest that there is a trade off between arrow weight and velocity and to play with it a little so you know that your are getting the best results you can. A really heavy arrow VERY slow may not be as good as a little lighter arrow a little faster.

wildschwein.

It is true that your bow may perform sluggishly with a heavier arrow you have to be the judge of that.

Your thinking is correct however that a heavy arrow will give you more killing power out of your 35# bow.

Playing with the formulas for kenotic energy and momentum found at http://tuffhead.com/education/formulas_momentum.html

You will see the heavy arrow will outperform every time

I used two seniros KE= kenotic energy P= momentum

1. 500 gin arrow with a velocity of 150 ft/sec KE= 24.98 P= 33.3 ft.lbs

2. 400 gin arrow with a velocity of 160ft/sec KE=27.73 M=28.42

Without getting into a lengthy explanation of KE vs P

you can see that reducing the weight of the arrow by 100 gn and increasing the speed 10ft/sec the KE is slightly increased and the P is decreased.

Momentum is what causes penetration .Momentum is what kills.You can play with the formuls until you find a arrow that will perform from your bow with killing power

GOOD LUCK

My guess is that you would get no better than 120 fps with that weight bow, from that weight arrow.

For animals that don’t duck, like pigs(?) that may be acceptable… But for deer, I don’t think that’s enough speed.

Deer can dodge an arrow moving that slowly with no trouble at all.

Everything is a balancing act. For me, the minimum acceptable arrow speed is 150 fps. I try to get the heaviest arrow I can with the most FOC I can that still yields at least 150 fps. And i am not really happy unless I can get 160 fps…

A secondary effect of such a slow arrow is loss of accuracy IMHO. At least for me. And I attribute it to the fact that the arrow is spending so much more time on the bow, which gives me more time to screw up… That and a much more pronounced curve in the trajectory.

Thus a lethal shot has to be 1 part accuracy and 1 part penetration…

Vintage and Steve said it better than I did. When I said “sluggish” I was trying to say that arrow trajectory needs to be part of the equation in order to hit well. A slow looping arc trajectory is harder to hit with than a little faster and straighter trajectory. It doesn’t matter how much penetration is available if hitting is a challenge. There is a happy medium that combines both penetration and trajectory to get the most efficient result form a given bow draw weight.

I would have to agree that accuracy trumps arrow set up ,foc, total arrow weight, , speed…..,ECT,ECT. Arrow set up is designed is to improve the result of the shot after it is delivered accurately

I am not so sure however that a heavy arrow contributes to accuracy problems. In the example that Steve uses at 110 ft/sec less arrow speed the arrow in a 28’ draw would only be on the bow fractions of seconds. Probably enough time to move the bow hand to give decreased accuracy but I feel that accuracy is more a function of form which arguably should be improved using a lighter bow. There are multiple reports that efoc actually improves accuracy for various reasons which I will not get into .

Steve is dead on about deer ducking arrows. I think more times than not though it is the reaction to arrow in flight sound not the sight of the arrow. If you were hunting antelope and shooting long distance that would be different.

Shooting foc arrows may allow an archer to reduce the feather size thus having potential to quiet the arrow and reducing that potential problem.

Every archer has made conclusions about certain subjects based on their own experience and that is the way it will always be. It is pretty hard to argue with proven science. Given the choice between heavy arrows versus a fast light arrow the heavy arrow for killing power wins out every time.Again check out the formulas for kinetic energy and momentum

Give me a extremly fast uefoc arrow and I would really be happy:D:D

[quote=wildschwein]I was wondering if anyone here had any ideas as to what spine range a person would need in a 30 inch POC shaft, to get a 200 grain broadhead to fly accurately from a 35# (near center cut) longbow?

wildschwein

Going back to the original question of what spine you would need the answer will probably be is you will have to experiment.A lot will depend on how much weight you end up with up front.If I would make a guess a spine range of 50 -55.

with 200 grn up front. At least that would be my starting point. Normally s spine for a 35# longbow would be 40-45 the old rule of thumb of use a spin 10# heavier than the bow.

Without going in to any long winded reasoning I would suggest you start with 50/55 and drop down in point weight to around 145 to 160. If you stay with 200 grain point you will be shooting a telephone pole. If the arrow makes it to the mark, it will not have the momentum for optimum penetration. It will not have the speed to go along with it. Everyone that has offered suggestions is spot on and correct in their analogies. You will have to find the balance between speed and weight that works for you. That is where a lot of folks miss the boat. They go overboard with weight not thinking about what has to get the arrow there. Good luck!!:wink:

No offense intended, and ONLY my opinion but “speed” is a moot point within the discussion of deer “ducking” arrows.

NOOOOOOOOOOO trad bow (and IMHO no others either) are “faster” than a deer’s ability to move.

My brother shot a doe at less than 15 yards with a 60lb wheelie and med weight arrows……and shot the OPPOSITE side he was aiming at when the deer spun at the shot and I sat and watched a friend, limited to Xbow use shoot at a buck at 20 yards……that buck was a good 6 feet from where he was when my friend shot when the arrow arrived.

Too much depends on the deer’s alert status. One feeding might drop a bit at a sound, one on full alert (like one that has scented you and LOOKING) will be long gone at the shot.

That said if a “faster” set IS something that gives the archer more self confidence……I’d support him all the way.

They all will work, placed properly with a good head like the Tuffhead and if hunting with a 35lb bow….yep, I’d be shooting something considered “heavy” for the bow weight.

Kinda like my 650 and up grain arrows are out of my 48lber. 😀

IF I MISS…..it’s not “due to the slow arrow”…..it IS due to “ME not shooting enough”…..period. I have to practice JUST as much with a “fast” set up as I do with a “slow” set up, and IMHO “easier is not always better”.

There is no such thing as a “more accurate arrow speed” and accuracy is totally in the hands of the archer and his/her capabilities and dedications to practice. A SLOW arrow is JUST as “accurate” as a super fast one…..aka the CONSISTANCY is there, all other things equal.

Ill take knowing the penetration is going to be on the high end of what my set up can deliver EVERY time over a “better” fps rating.

Before I get bombarded with “you can get too heavy and it wont penetrate” responses……think of a spear, hand thrown, slow as molasses and I do believe they have killed a few things in time.

Doc’s report also has records of a (If I recall right?) a 40 or 42lb LB penetrating a buffalo bone 100 percent of the time WITH a HEAVY arrow, high FOC and good head set up. Odds of that working on a whitetail? Pretty positive.

The “balance” one searches for is for his own personal preference of the choices at hand between the factors of arrow perforance…..trajectory and penetration.

To each their own.

God Bless

Steve Sr.