spine for a wood bow

[deermaster1]

i am making my first wood bow so it will not be cut to center. i have never used arrows in a non-center cut bow.  what spine of port orford should i get for a 50 lb bow at 28" draw lenght ? i will use a 125gr head. thanks for any info

[PV]

10# over draw weight has been  good starting point for my wood bows.I leave them long to start and cut them down as needed.

[aromakr]

deermaster:
Will your bow have a shelf? The important part is the distance from the center of the limb to the strike plate. On a bow that say is 1/4" I would start at 5# under bow weight, unless the arrow will be 29" BOP then go bow weight. for every 1/16" over 1/4" subtract another 5#.
Bob

[cvarcher]

You didnt say what your draw length was.Even though the bow is 50lbs at 28" if your only pulling 26" it would be down to say 45lbs.So heres what you do. Mark where you draw your arrow comfortably and find your draw length. Say its 26" . OK from a brace of 6.5inches to 28" is 21.5inches right. Now take that 50lbs and divide it by 21.5 and youll get the tillered weight per inch.(2.3lbs/inch. Multiply that by your 2inch loss (4.6lbs) Now subtract that from the 50lbs and you have a close weight of about 45 lbs your holding at your draw. Your arrows spine should match that with the common target tip (125gr) and so it would be 45-50lb spine.If you then add a broadhead it could weaken the spine a little so you up that by another 5lbs.

[NorthShoreLB]

In my experiance, I would start with a spine 10# less than whatever bow poundage you pull, with a 125gr head, than you can cut them back to stiffen them a bit

[Yellowsnake]

If the bow"s shelf is not center cut then I would start with 5-10# less than what you will be pulling.  Also, I've found that with bows that have non-center cut shelves(or no shelf at all)a longer arrow tends to be more accurate.

[Minuteman]

Long arrows act like they are spined lower because theres more wood there to bend around the handle,more mass up front to make the arrow bend more, diminishing the spine.
 I shoot full length 58# spine woodies out of my center shot, 50# ,fg recurve and they fy great. Got some 58# arrows from another bow that are cut down and they don't fly worth a hoot , hit left every time.
 All that being said theres alot of variables in a self bow so you gotta test out some arrows and see how they fly.I'd say 10# less than yer draw weight to start.

[PV]

Interesting. I found the lighter spines  shot left for me. Lefty shooter and 1/4 shelf cut in.Seeing the consensus here I'll be trying the lighter spine again.

[aromakr]

PV:

If you are a left hand shooter, light spines will shoot left! Everything is reversed for the lefty.
Minuteman:
Longer shafts don't act like they are spined lower, they are spined lower! The spine standard is 28" and every inch longer than that will decrease in spine 5#, it has nothing to do with more mass up front, a longer shaft is more limber. Keep in mind the arrow is pushed from the nock end, when the bows energy is transfered to the arrow a longer arrow will bend more in the middle than a shorter arrow of the same spine between 26" centers.
 Bob

[Shawn Leonard]

A full length shaft 32 or 33"s whatever are still spined the same as no matter what. If ya cut it to 30"s it will still spine the same as when it was 33" on a spine tester. The shaft just acts weaker as it is longer and more arrow to bend and makes it act limber. Aromaker is right on with his assesment. Shawn

[George Tsoukalas]

deermaster, I draw 26 inches and cut my shafts at  30 inches for a finished and pointed arrow of around 29 inches bop. Most of my bows want arrows at bow weight or 5# below for a spine.   You could leave the arrows full length and cut them down if they behave like they are overspined. See Selfbow Care and Tuning on my site. If you want to continue making bows,  I recommend that you buy a test kit of 2 or 3 spines from someone and fletch up the shafts cut to the length you like and choose the best flying arrow. BTW "best  flying" means you should see nothing but fletching as the arrow heads to target. More on my site.
 http://mysite.verizon.net/georgeandjoni/archer.html
Jawge

[aromakr]

Geroge:
How can you cut down an overspine shaft and make it shoot correct?
Bob

[George Tsoukalas]

Thanks, Bob. Good pick up. I meant to say "underspined". Jawge

[PV]

aromaker:

  I shoot 5-10# overweight spine out of my wood bows because the underspined arrows were showing weak for me.Guess everthing is reversed for lefty's.  :rolleyes:

[George Tsoukalas]

PV, is the arrow leaving the bow silently or do you hear it whacking the side of your bow? What is your draw length and how  long are your arrows? What is the width of at the handle pass? I figure aromakr would ask these questions anyway.    Jawge

[LBR]

I don't think there is an accurate formula--evenin getting in a ball-park will be hit or miss.  It's going to depend on the shelf (how close or far from center), the design, the type wood, the individual piece of wood, etc. etc. etc.  My current selfbow is 65@30, and full length 45-50# spine fly great from it.

Chad