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wood spine ratings & tuning

Started by gringol, December 26, 2012, 09:35:00 AM

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gringol

I've noticed that some woods seem to have different dynamic spine when it comes to rated spine and tuning than others.  For example, years ago I shot spruce shafts (65-70#).  I switched to doug fir and I need 80-85# to get good flight.  Has anyone else noticed these kinds of differences between wood species? I ask because doug fir is the only wood I know where 80-85# shafts are easily obtained...

nineworlds9

Have you considered poplar?  Or even hickory?
52" Texas Recurve
58" Two Tracks Ogemaw
60" Toelke Chinook
62" Tall Tines Stickflinger
64" Big Jim Mountain Monarch
64" Poison Dart LB
66" Wes Wallace Royal
            
Horse Creek TAC, GA
TBOF

gringol

I've considered poplar, couldn't find spines around 80#.  I've used hickory, but it's so heavy and hard to keep straight that I didn't like it.  I'd like to go with a lighter arrow, maybe a 400 grain bareshaft and I don't know if the difference I've noticed in spine is real or maybe my form has changed...

nineworlds9

Yeah hickory is heavy.  PM John fletch, he makes warbow arrows with poplar and might have some shafts that'd work for you possibly.  I know he's got 80-90 spine in 3/8", but maybe he has some smaller dia./ lighter ones??  No luck with POC?
52" Texas Recurve
58" Two Tracks Ogemaw
60" Toelke Chinook
62" Tall Tines Stickflinger
64" Big Jim Mountain Monarch
64" Poison Dart LB
66" Wes Wallace Royal
            
Horse Creek TAC, GA
TBOF

gringol

POC is an option...maybe I need to clarify my problem.

Currently I shoot 80-85# doug fir.  My bow is 56#@28, but I'm drawing to almost 30".  I've noticed in the past that some woods appear to require a much stiffer spine than others, but I never did any extensive testing.  So, the question is if that difference in rated spine and effective spine real?  i.e. will a 80-85# doug fir shaft behave the same as a 65-70# spruce shaft?  If so, I can get a test pack problem solved, if not I don't want to bother with a test pack if I'm going to have trouble finding shafts of correct spine anyway.

nineworlds9

Ok I gotcha now.  Experiencing a 10-20# variation in rated/static spine and dynamic I could see how that could be frustrating.  I'm just getting into woodies myself and I've been doing lots of research before I spend too much money..  The word is the bending of an arrow in a spine tester can definitely vary depending on the orientation of the arrow...differences in grain etc will affect the reading as the arrow is rotated...and yeah different woods can have different bending depending on grain density and orientation.  That's why it's so important to get high quality shafts that someone really took the time to select carefully...shafts from lower quality wood that maybe only got measured hastily could cause problems.  Good luck and the REAL experts will probably expound on these couple factoids I mentioned.
52" Texas Recurve
58" Two Tracks Ogemaw
60" Toelke Chinook
62" Tall Tines Stickflinger
64" Big Jim Mountain Monarch
64" Poison Dart LB
66" Wes Wallace Royal
            
Horse Creek TAC, GA
TBOF

Jim now in Kentucky

I get consistent results from spine testing shafts of different woods, but I am careful to orient the growth rings the same way.

I go against the grain, as it were, and put the rings in line with the string. (With plastic nocks, there is no chance that the string will split the shaft, as was the reason self nocks were always placed at 90 degrees from the string.)

Maybe I would not get such consistent results if I were shooting bows as heavy as yours. My heaviest is 50#
"Reparrows save arrows!"

"But without faith it is impossible to please Him, for he that cometh to God must believe that he is and that He is a rewarder of them that diligently seek Him." Hebrews 11:6

Orion

Your static spine readings are likely correct.  Doug fir is physically heavier than Sitka spruce and it doesn't recover as quickly.  That's why you need more static spine in Doug fir. If you were shooting hickory or some other hardwood, you would need more static spine yet.

If you can find POC in the same spine and physical weight as the spruce, it should fly the same. The lightest Doug fir shafts at a given spine weigh pretty close to the heaviest Sitka spruce shafts at the same spine.  Thus, if your Doug fir supplier can supply you with very light (for the species) Doug fir shafts, you should be able to use them in a spine pretty close to what you're using in Sitka spruce.  Hope all this makes some sense.

The short of it is that as you increase physical weight and reduce elasticity, you need to go up in static spine, and vice-versa.  Good luck.

Fletcher

I've shot both Sitka and Doug Fir quite a bit and haven't noticed any difference in dynamic spine between the two; if my bow shoots a 60 lb fir, I can shoot a 60 lb Sitka, same length and point weight, from the same bow.  Of all the arrow woods, fir is my favorite.  I find the fir to be a "snappier" wood and it seems to me to recover quicker than any other wood.

I don't know what bow you are shooting, but 56@28 drawn to 30" is 60-62 lb and with a 31" BOP arrow, 80-85 spine seems right in line.  Has your bow or form has changed from your Sitka Spruce days?
Good judgement comes from experience.  Experience comes from bad judgement.

"The next best thing to playing and winning is playing and losing."

"An archer doesn't have to be a bowhunter, but a bowhunter should be an archer."

gringol

fletcher,
my form has changed a bit.  I'm drawing about 2" longer now.  In my spruce days I was shooting a 70# bow (mild R/D, D-shaped longbow) and 65-70# spruce with 160 up front.  I never bareshafted those, but they flew great even with 4" fletches.

I love fir arrows, but I'd like to have the option of shooting spruce (or even POC) because it's lighter, but it's not easy finding 80-85# shafts in those woods...

nineworlds9

Cool.  I knew we'd get some good info soon on this thread.  I chimed in to keep it at the top, learned a couple things.  Love Tradgang.
52" Texas Recurve
58" Two Tracks Ogemaw
60" Toelke Chinook
62" Tall Tines Stickflinger
64" Big Jim Mountain Monarch
64" Poison Dart LB
66" Wes Wallace Royal
            
Horse Creek TAC, GA
TBOF

Orion

Rick: Your experience is what I was getting at in my second paragraph.  At the same physical weight, Doug fir and Sitka spruce of the same spine should shoot the same.  But unless one specifies the physical weight when ordering shafts, the Doug firs are likely to be physically heavier than Sitka spruce. I'm assumed that was Gringol's initial situation.

I haven't shot enough Doug fir side by side with spruce to say it's springier.  I have shot a lot of it along side of POC, and I think cedar has the edge there. Regardless, the differences are small. I think physical weight plays a bigger role than the wood's elasticity in having to bump up static spine a little.

Fletcher

Hildebrand has been the main supplier of Sitka for quite a while and they have stopped doweling 23/64, likely due to lack of demand; 23/64 can be a hard sell these days.  Sitka just doesn't have the spine of D Fir.  Fir does vary in weight quite a bit and you should be able to find some in the low 400's if you went direct to Surewood.
Good judgement comes from experience.  Experience comes from bad judgement.

"The next best thing to playing and winning is playing and losing."

"An archer doesn't have to be a bowhunter, but a bowhunter should be an archer."

gringol

Thanks for the help, guys.  After your answers and a conversation with Hildebrand, it seems it is possible to find both lighter doug firs @80-85# and 80-85# spruce.  You just have to make some phone calls, and then snatch them up when they are available.  Since I haven't tried either yet, I don't know which way is more reliable...

Personally I prefer 23/64.  I guess I'm a bit weird.  It just seems easier to put a self-nock and then a back taper on a fat shaft...

Kelly

QuoteOriginally posted by gringol:
I've noticed that some woods seem to have different dynamic spine when it comes to rated spine and tuning than others.  For example, years ago I shot spruce shafts (65-70#).  I switched to doug fir and I need 80-85# to get good flight.  Has anyone else noticed these kinds of differences between wood species? I ask because doug fir is the only wood I know where 80-85# shafts are easily obtained...
NO, no difference in spine needed between woods-POC, Sitka Spruce, Douglas Fir, Lodgepole Pine, Western Hemlock, Ash, etc. at least in my 40+ years of making/selling arrows I've not noticed a difference.

My guess is something else changed from"years ago" to the present.
>>>>============>

Enjoy the flight of an arrow amongst Mother Nature's Glory!

Once one opens the mind to the plausible, the unbelievable becomes possible!

>>>>============>

Yours for better bowhunting, Kelly

gringol

kelly,  
while I was still shooting spruce I made a switch to ash and I noticed a huge difference.  I could not get decent flight with ash of the same spine rating as the spruce unless I used 6" native-cut feathers on the ash.  At the time I was shooting spruce with 4" shields...

So, remembering that experience I thought there might be a similar difference between fir a spruce...

Orion

Kelly:  I would agree with you as long as the shafts are the same physical weight and the same diameter.  However, often they are not.  On average, Doug fir runs 50-75 grains heavier than POC.  Now, the lightest Doug fir might come out about the same as the heavier/heaviest POC, but unless one stipulates the physical weight when one ordersshafts, one is likely to get the middle weight or whatever the vendor happens to have a lot of.  

A more extreme example might illustrate this. A 700 grain hickory shaft spined at 50# does not shoot the same as a 500 grain POC shaft spined at 50#. It takes more of the bow's energy to get the 700 grain arrow moving, and that additional arrow weight causes the arrow to flex more, i.e., show a weaker dynamic spine.  If we want that 700 grtain arrow to shoot/act like the 500 grain arrow, we need to increase its static spine.

In short, changing the weight of the arrow changes the dynamic spine required and thus the static spine required to achieve it. That's what folks are doing with carbon arrows all the time in adding or taking weight off the point.
 
Arrow diameter also affects static spine. Gringol, your arrows initially may have been 11/32, and those you're shooting now may be 23/64.  11/32 shafts of the same spine will act stiffer on the bow compared to 23/64 shafts because they ride closer to the center of the bow. Thus, a lighter spine 11/32 spine will shoot the same as a heavier spine 23/64.  Add in the physical weight differences between the two diameter shafts, and it becomes pretty clear that more spine could be needed.

It's possible, too, of course, that the arrow shelf on the bow you're shooting today is not cut to the same depth as the bow you were shooting some years ago. If the bow you're shooting now is cut further from center, it would require more spine.

All these things are cumulative.  A heavier arrow, thicker arrow and sight window cut proud of center all require an increase in static spine. If you're shooting a fast flite string now, drawing longer, etc., they, too, would require more spine. Together,these factors could easily account for the difference you're seeing with your present set up vis a vis what you shot years ago.

mncarphntr

So, I'm thinking of building some Doug Fir arrows. Is it a waste of money to get a POC test kit to find the right spine shaft?

WESTBROOK


Kelly

All things being equal with your bow setup and your draw length one should not see any differences between different woods of the same spine regardless of weight.

All types of wood used for shaft material will have a given 100-150 grain weight variance from highest to lowest in the same 5# spine group/same diameter. Some like Douglas Fir may have 200 grains or more variance and others like Sitka Spruce are closer to the 100/120 grain variance in a given spine group of the same diameter.

If weight was a more critical factor than spine then the 480 grain 60-64# spine POC would  be weaker than the 360 grain 60-64# spine POC-is that what I'm hearing from your point of view, Orion?

I have been known to have arrows of various grain weights in my quiver, various woods and sometimes 10-20# spine difference and they all fly the same-perfect. Sure the heavier arrow will drop more but we are talking arrow flight here and it will still fly straight if spined the same as the lighter one.
>>>>============>

Enjoy the flight of an arrow amongst Mother Nature's Glory!

Once one opens the mind to the plausible, the unbelievable becomes possible!

>>>>============>

Yours for better bowhunting, Kelly


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