Spine Question??

[Guru]

With my newly finished selfbow, I plan on shooting some Doug Campbell damascus trade points that weight 190grs....so far it looks like about 60# spine is what I need for them.

The other points I want to shoot are 300gr. Woody Blackwell stone points.


Here's my question: being as the stones are so much heavier, any educated guess' on how much I would need to go up in spine??  70#???

It's not like there's a 300gr FP availible(at least that I know of), and I don't want to shoot the head  more than a couple times....I need to be close right off the bat.


keep in mind this is a far from center shot selfbow, that I draw a solid 28"...
Thanx

[PEARL DRUMS]

I have about zero knowledge with self bows. But when I glue on a 125 or 160 grain tip onto my arrows, they fly the same, sound the same and hit the same. Thats ony 35 grains and your talking 110 gr. I would guess a 70# spine is close. Plus you have the hafting (sp?) and "glue" holding it together to add more wt.

[JimB]

I don't have a lot of experience changing point weights on woods but on other arrows,I see about 18-25 grs of point weight equalling 5# of spine-bows 50-55#.

I think I would be tempted to go with at least 20# more spine weight.

Would it be feasible to play around with a heavy field point first to get in the ballpark?You could make up a point using a 100 gr Woody Weight and a 190 gr glue on.You could even add lead shot up in the ferrule to exactly match your stone point weight.#6 shot is 2 grs per pellet.You can usually get 6 or 7 of them up in the end of the ferrule.

I recently made up a set of heavy field points using the Woody weights.I just couldn't get there any other way.You have to be careful with tip alignment since you are dealing with 2 glue joints.

[steadman]

Tough one Curt. If you need some 70-75# arrows to try let me know, I also have some 190 gr points. I would try the woody weights to get the 300 grains as well. Let me know and good luck.

[Pat B]

Curt, as you may have already found out a selfbow is a different animal than a center shot bow. The end results can be the same but a bit of different thinking is necessary.
  As with all wood arrows the spine value of an arrow is determined for a 28" shaft with a 125gr point measured between uprights spaced 26" apart and a 2# weight hung from the center. You can adjust the actual spine by changing the length of the shaft(5# per inch, increased by shortening, decreased by lengthening)and I have found longer arrows seem to fly better from selfbows. I shoot 29" arrows with my 26" draw. Also the spine can be changed by changing the point weight. The standard is for a 125 gr point so the more weight forward the less the actual spine will be.
  I shoot mostly cane or hardwood shoot arrows that have a natural taper. This taper automatically reduces the measured spine because of the natural weight forward but also the narrow tail end(natural taper) of the shaft gets around the bow easier so a tapered shaft shoots like an arrow that is 10# spine weight lighter. Here is an example of this...My selfbow pulls 55#@26" and I shoot 29" arrows. The natural taper of this arrow allows me to shoot 65# spined arrow. The extra 1" over 28" allows for a 70# spined arrow from my 55# bow. This is with an arrow with a full length taper.
   When I shoot cedars they are 29" for my 26" draw also. you can reduce the measured spine by 5# because it is 1" over the standard 28".
  I'm not sure of the actual values but anything over the 125gr point weight will decrease the spine weight so arrows with heavier spine weight needed for heavier points.
  Art Butner(artcher1) is more articulate with this explanation than I am. I can make arrows that shoot well from my selfbows but I have a hard time explaining it.
  My attempted explanation has probably confused you more! d;^)

[Art B]

How about giving us a better idea of your setup Curt. Bow weight at your draw length and a close estimate of the offset at your arrow pass. Preferred arrow length would help also.

Going from the standard 125 gr point as Pat metioned to a 190 gr will cause four spine changes IMO. That's an extra 20# of needed spine.

So, using a 300gr head I'll bet you'll need something in the neighborhood of 100#+. And that's probably using parallel (vs naturally tapered shafts like cane) shafts.  

Several variables as you can see, then you throw in the shooter.

[Art B]

You might want to contact Charles (Stringstretcher) and compare notes. He made up some bamboo arrows here a while back and used 300 gr stone heads also. ART B

[Shawn Leonard]

Ya could take a 308 case cut it off at the shoulder and add lead shot and glue til ya get to 300 grains. That said If ya leave the woodie 30"s I would say you will need at least 75# spine maybe a tad more. I have some real good wood(hothaps stuff) that is 77#s on the button. Shawn

[Guru]

Thanx for all the help guys....

Looks like I need to get some of those WW's and 190 fp's...

The bow is about 55#'s at my draw....I prefer to keep my arrows no longer than needed. I normally cut them right at 29"

The thing with these Woody stone points it that they're very long, so might factor in as well.

I;m dyin' to get some arrows together for this bow, but it looks like I'll really have to take my time and do it right.