wood spine ratings & tuning

[WESTBROOK]

Gringol, check with Ted Fry at Raptor archery, I got some 80-85# spruce from him a while back, they were 24/64th.

Eric

[Orion]

Nope:  I'm not saying that weight is a more critical factor than spine, Kelly.  I'm saying that physical weight affects the dynamic spine of an arrow.  And yes, a 480 grain arrow spined the same as a 360 grain arrow of the same material would show dynamically weaker.  Now, you put feathers on those shafts and shoot them and you probably won't notice a difference.  Would likely show up in bare shafting though.

Feathers ameliorate some big discrepencies in arrows.  I, too, often carry a quiver full of arrows that may vary by as much as 100 grains in weight and 20# in spine, and they all shoot well and pretty close to the same spot.

I've found that most bows are pretty tolerant of spine variations.  I over spine by 10-20# on most of my bows intentionally.  I don't doubt that there's an optimal arrow spine and weight for each bow, and a lot of folks spend a lot of time trying to find out what it is.  I don't.  I know the physical and spine weight woodies  that shoot well out of my bows, and as long as I'm in the ball park, and my fletched arrows are flying straight and where I want them to hit, I don't worry about other stuff.  

But over the years, I have learned that physical weight of the shaft, it's diameter, bow string material, the amount of bow centershot, draw length, etc. all affect the dynamic spine of an arrow, i.e., how it behaves coming off the bow., and that, in turn, affects static spine requirements.

[Kelly]

This is not rocket science nor is it complicated. Just put some feathers on shafts that are relatively close to your specs and they will fly just fine.

All bow/archer combos are capable of shooting 15-25# variance in spine with 100-200 grain differences in weight, in any type of shaft material with very good results.

There is no one perfect combination that is the ONLY combination that works in YOUR bow.

Again don't make this more complicated than need be, feathers are on there for a very good reason-steering-so why try to re-invent the wheel by shooting arrows without them!

[Orion]

I agree, Kelly.  I joined this discussion to provide some plausible explanations as to what may have caused the changed spine that Gringol experienced in his shooting.  Lots of possibilities. If I hijacked this thread with my pontifications, I apologize.

[markliep]

Hi all - any advice on bamboo spining? I'm still trying to get the right weighting - most of the shafts I've made so far I've matched to spruce weighting (10-15# over draw weight) but I'm still seeing too many over spined arrows - increasing point weight solves the problem so it looks like the next step is to go lower. Thx - M

[gringol]

Thanks for the thoughts, guys.  I think what I noticed in the past was caused by the difference between static spine and dynamic spine.  Orion's point regarding the overall mass of the arrow changing the dynamic spine seems like a logical explanation.  I'm sure there are other factors involved, but my initial observation between ash and spruce shafts was made on the same day, with the same bow.  Only difference was the shaft...

Kelly, I agree that feathers can fix a lot, and I want you to know that I'm not one of these guys that spends days, weeks, or even months tuning.  I typically get a test kit, shoot one arrow of each rated spine and pick the best one.  The whole process take about 5 minutes...I first started bareshafting because I could not get ash arrows to fly the same as the spruce I was shooting of THE SAME SPINE RATING.  I stripped the feathers off the ash and they flew down range at more than 45 degrees to the target and promptly snapped on impact.  The spruce did not fly perfectly when bareshafted, but they were certainly pointed in the right direction and didn't break on impact. From my experience there is definitely a difference between at least some woods.  

Could sluggish woods (like ash) be less forgiving when the rating spine is too light?  Makes sense to me...

I posted because I'd like to save myself a few $$$.  I don't want to buy materials build a new set of arrows and then have trouble getting BHs to fly...

Mark,  I'm certainly no bamboo expert, but I've heard many times that the spine of bamboo shafts is much, much more forgiving than wood.  So much so that people don't even bother testing the spine of bamboo shafts...Try starting a thread, you'll probably get some more "expert" input.

[Kelly]

Originally posted by gringol:
Thanks for the thoughts, guys.  I think what I noticed in the past was caused by the difference between static spine and dynamic spine.  Orion's point regarding the overall mass of the arrow changing the dynamic spine seems like a logical explanation.  I'm sure there are other factors involved, but my initial observation between ash and spruce shafts was made on the same day, with the same bow.  Only difference was the shaft...

Kelly, I agree that feathers can fix a lot, and I want you to know that I'm not one of these guys that spends days, weeks, or even months tuning.  I typically get a test kit, shoot one arrow of each rated spine and pick the best one.  The whole process take about 5 minutes...I first started bareshafting because I could not get ash arrows to fly the same as the spruce I was shooting of THE SAME SPINE RATING.  I stripped the feathers off the ash and they flew down range at more than 45 degrees to the target and promptly snapped on impact.  The spruce did not fly perfectly when bareshafted, but they were certainly pointed in the right direction and didn't break on impact. From my experience there is definitely a difference between at least some woods.  

Could sluggish woods (like ash) be less forgiving when the rating spine is too light?  Makes sense to me...

I posted because I'd like to save myself a few $$$.  I don't want to buy materials build a new set of arrows and then have trouble getting BHs to fly...

Mark,  I'm certainly no bamboo expert, but I've heard many times that the spine of bamboo shafts is much, much more forgiving than wood.  So much so that people don't even bother testing the spine of bamboo shafts...Try starting a thread, you'll probably get some more "expert" input.

Feathers are not meant to fix anything-they are to steer the broadhead tipped arrow. Without sufficient steering by the fletchings the blades of the broadhead will do the steering.

Now when talking about bareshaft testing one does not use broadheads so there is no steering mechanism. In order to get a somewhat straight flying bare shaft one needs to increase the spine to nullify paradox as much as possible to steer the arrow hence why so many results of bareshaft testing need such stiffer spined arrows-20# or more than really needed. If bareshaft testing is so great and such a perfect way to find ones "perfect" spine then why does one then put feathers on these perfect bareshafts? I suggest it is to steer the broadhead-so why not start here instead.

Agree that the difficulty in tuning/spine is with broadheads and that is why myself and many others, including everyone from the old days find their arrow spine by shooting broadheads first. If broadheads fly perfect then any other point one uses thereafter will fly perfect. Why take all the time trying to find spine with field points and then still not know if it is correct with broadheads-rather tune with broadheads first.

That said there still is not one perfect spine per bow/archer combination. Rather several-10-20# variance and still have perfect flying broadheads. It just is not that critical because we as archers are not machines since all bows are capable of far better accuracy in the machines hands than the archers. If it was that critical the archer would have good and bad flying arrows(even though they are identical in every way) depending upon uniformity and repeatibility of the archers form, or not. There is built in flexibility in the equipment we use to accomidate our flexibility of form. Sure we all strive to repeat/perfect the from process as close as possible in each and every shot but we are not machines.

Regarding grain weight it has been my experience that heavier grain weight broadhead tipped arrows are easier to control than really lightweight ones given all else is identical, spine, diameter, fletching, etc. plus no changes on the archer end including the same bow, draw, etc. Same reason why heavier arrows reduce string noise and bow vibration/recoil/shock.

Regarding your original question-re douglas fir compared to Sitka Spruce. Each wood has a grain weight variance within the same spine group of 100 grains and more-even more with Douglas Fir. That said, the light end of douglas fir is very close to the mid range end of Sitka Spruce so the difference does not need to be that great. If you know the grain weight of your spruce then tell Neil or Roxanne at Hildebrand what that grain weight is and they will get as close as possible.

I'm guessing that your spruce may be on the light side, spinewise since you said they didn't bareshaft very well either so an increase in spine will probably be good for you anyway. Tell Neil and Roxanne about your equipment and what you want to accomplish in your finished broadhead tipped arrow and they'll help you get the right spine-they've had a good teacher. If in doubt, always err on the high side. And if the required spine is not available but the next 5# spine group below is just use longer feathers or 4 fletch over 3-either ow which will have the effect of the next higher spine group, or maybe one can use a shorter arrow-sometimes even 1/2" could be enough if on the edge of spine.

Sorry for being so long winded here-this is my last post on this subject. Enjoy the flight of the arrow!