Wood Arrow Spine Adjustment Question

[ItzaKen]

Hello!
Yes, I've made my own spine tester w/ a plunger dial guage, so I'm looking for ultra-fine tuning advice for those who've had experience in making/adjusting their own arrow shafts.
AND, if this question belongs on a diff forum, please tell me!!

I have some spruce shafts which are tapered for 10" at the nock end; some shaft makers taper them for 6".

Does/would the 5" of fletch actually stiffen the arrow in that region and affect the spine and behavior of flight?

Should the area of flex really be greatest below the fletch?  Here's my thinking....
An "untapered arrow flexes the full length and so, the oscillation would be the full length, compared to a "tapered" arrow, where just that section is doing most of the oscillation, while the point end and the fletch end would flex less.

Have any of you played with this and sanded your arrows accordingly and tested them?

Thanks!
Ken

[ItzaKen]

Reply from McDave:

Yes, the fletching stiffens the dynamic spine of the arrow.  That's the reason I fletch my bare shafts and then cut off the feathers down to the quill.  The feathers I cut off also stiffen the shaft to some degree, but cutting them off down to the quill is the best compromise I can come up with if I want to bare shaft tune.

I know that tapered shafts are considered more desirable than straight shafts, but I don't know all the reasons why.  One reason is that tapering at the nock end reduces the chance that there will be quill contact with the shelf or strike plate.  I suppose it also increases the FOC to a minor degree.

Your thought that tapering would increase the degree of flex in the tapered area makes sense.  However, I haven't heard of anyone worrying about this (and I’ve read people in this forum, including myself, worry about just about everything).

Well, that just about exhausts my knowledge on this subject, except that you should post equipment related questions in PowWow.  Maybe some moderator will move it over there, so you'll know where to look if it disappears from here.

[ItzaKen]

Great tips!
I'm happy to know that someone else has been down this trail....  I've not heard of anyone bare shafting with quills, but it makes sense, as it seems they would act as "braces".

Related:  I was going to ask a question on PaleoPlanet, but perhaps here/on PowWow...
I'm wanting to make some Ocean Spray(Holodiscus discolor) arrows; the Kalapuya people, here in the Willamette Valley of Oregon, used very small points, often misinterpreted/confused as "bird points".  They were wider than the shaft and that's all that mattered, 'cuz a piece of glass in the lungs makes for a bad day for a deer, or anything, for that matter.


Anyway, I was wondering if there were a need to scrape the shafts to parallel, or just leave the fat end forward, giving a good FOC/weight forward, for good flight, tapering the front only enough to make a nice transition to the arrowhead.

[Orion]

First a partial reply to your initial post.  Yes, fletching stiffens the dynamic spine a very little bit through the addition of weight to the rear of the arrow.  However, for three 5-inch feathers, that's only about 15-20 grains, and I don't know very many stick bow shooters who could tell the difference. 

A rear taper helps a wood arrow recover faster. I'm not entirely sure how it does that, except perhaps to increase the FOC of the arrow by a percentage or two, moving the balance point of the arrow forward a bit.  The longer taper (9-10 inches) just removes more material than a shorter taper. In my experience, a 9-inch taper will take off about 20 grains of weight, plus or minus a little depending on initial shaft diameter, amount of taper and wood species. I don't think the tapered part of the shaft flexes noticeably more than the untapered front end of the arrow.  Most of the arrow flex occures nearer the center of the shaft.

Any additional feather clearance tapering might yield is negligible.  For example, if a 11/32 shaft is tapered to 5/16, that's a reduction in the diamter of 1/32 -- which has to be halved (1/64-inch) because it occurs all around the shaft so to speak.  That is, the outside of the shaft is decreased by only 1/64 of an inch with any orientation toward the bow's side plate.  Commercial feather height varies more than 1/64-inch within the same batch of feathers. Regardless, if the arrow is tuned properly to the bow, the feathers should not come nearly that close to the riser as they pass.

Regarding making Ocean Spray arrows.  I'm not familiar with the wood/shrub species you're talking about, but if it's naturally tapered, there would be no reason to make the front end of the shaft parallel before starting the point taper.  The full length taper is one of the strong points of bamboo shafting.  It contributes to good arrow flight.

If you plan on using your small points for hunting, do check the regulations in your area.  Most regs specify a minimum arrow point/broadhead width. Good luck.


 

[ItzaKen]

Very detailed answer!.. Thank you.

The idea of sanding the taper in front of the fletch is less about the taper/shaft diameter and more about putting the flex there, so that that's the oscillation point and prevents the entire shaft from oscillating so much.  Just an idea.  I guess I'll have to waste an arrow and play with it, this Spring/Summer.

You are most correct about blade width; Oregon's minimum is 7/8" and unbarbed.