ball park cedar spine question

[Mike Spaulding]

Hi all,

I'm setting up a new to me Dwyer Dauntless for cedars and would like to get a ball park suggestion for correct spine.  I would buy one of 3River's test groups, but I'm not sure any of them are heavy enough after running the numbers through the dynamic spine calc.

61#'s @ 29", I draw 27.5".  I'd like to use a 29" arrow and using a 150gr tip.  I'm assuming 13gr/" or so. it says I need a 85 - 90 spine.  the bow is cut -1/8" from center and shooting fast flight.  does this sound correct to you?  The calculator has never let me down in the past, but this just seems heavy!  thanks for the input!

-Mike

[Orion]

You'll be drawing about 57-58#.  Add about 5# each for a heavy point and ff string and you're at 68#.  65-70# would probably work, I'd go with 70-75# just because I like to overspine a little. That weight isn't real common in 11/32 POC, but they are available, and I'd recommend them.  I've shot some of Dave's bows, though not a Dauntless, and I've been shooting cedars for about 40 years.

[frank bullitt]

Mike, I'm with Jerry on the spine!  I've not shot cedar as long as he has, but long enough!

Don't always go by the numbers posted. Longbows on the norm, will shoot closer spine weight to "Drawn" weight, most time. Reason being, shelf past center and paradox. Also, the shooters style will dictate alot.

I've seen some longbows, like Hill style, that shot better alittle underspined!

Wish I had some cedar at 70lbs to send to you to try! Ask around someone might. Does it have to be cedar? Pine or fir, Ramin, maybe?

[Bjorn]

The spine calc is right on I think. You can get Fir or Spruce from Raptor in 11/32 and your spine requirement.

[Mike Spaulding]

Thanks all!  also, is there a reason your recommending 11/32 as opposed to the 23/64.  I used to shoot 23/64 out of my GN's.  I've found you can get them in heavier spines easier if required.  thanks again, the knowledge on this site is priceless!

[frank bullitt]

I don't think there is a problem with them. I have shot them, and if you can get them tapered, even better.  

[Mike Spaulding]

Thanks for all the help again, very much appreciated!

[Danny Rowan]

At a 27.5 draw you are pulling about 57#, so go up one spine group=65#, add 5 for ff=70#, add 5 for point over 145=75#, add 5 for every inch over 28" of arrow=80#, if cut to center add another 5# if not subtract 5#. I would say 80/85 will be pretty close.

[Hud]

According to 3Rivers Wood Shafting, which I find pretty accurate.

Modern Longbow with 125 Gr. Pt. & Fast Flight
55-60# (yours 57#), & 29" arrow = 65-70# then,
Add 5 gr for 150 gr.pt. = 70-75#.

My reasoning, unless your bow is designed to shoot 13 gr/in, you have a heavy arrow. I'll shoot POC, Fir or Spruce, tapered shafts 28 1/4" to back of the head, and 590-620 gr. arrow from a R&D Robertson Purist 62" longbow, 63# and shoot either 65-70#, or 70-75# equally well, allowing for Fast Flight, and 160 gr. pt. It is 1/8" from center. At 13gr/in. your arrow weight is about 741 gr. with 150 gr. point. Are you using a laminated birch shaft to get that weight? It is going to be slower than you think without a high FOC.

[lpcjon2]

Check the classified's as well,good deals to be had on wood arrows.

[Fletcher]

Mike, is your Dauntless shelf cut 1/8" out from center or past center.  I didn't think Dave cut his bows past center.  The 70-74's sound close to me, too.  With a fir shaft you can get these in either 11/32 or 23/64.

I should have some test arrows in that range and length if you want to shoot some.

[Orion]

Frank:  I prefer the 11/32 over the23/64 because the center of the arrow is a little closer to the center of the bow.  A very tiny bit.  By comparison, using a 23/64 has the same effect as building out the shelf ever so slightly.  With a 23/64 shaft the same physical weight as a 11/32, you could probably drop spine 5#.  I also think11/32 have a very slight edge over 23/64 in increasing penetration, just as 5/16 and smaller diameter carbons have an even greater advantage.  Either shaft will work, of course.  Folks drawing heavy bows and/or with long draws usually don't have a choice.  They need to go to 23/64 to get sufficient spine.

[Mike Spaulding]

Thanks all again for all the info!  It looks like I'm just going to have to try a few different shafts to see what the bow likes, but seems like the 70 - 85 or so is the arrow groups I'll need to try.  

Fletcher, the bow is cut 1/8" out from center not past, so that would mean a stiffer spine correct?

thanks again everyone!

[Orion]

No, it means a softer spine because the arrow is pointed more outward and has to bend more to get around the riser.  That's part of what I was trying to explain in the post immediately above yours.

[Mike Spaulding]

ahh, got it, thanks Orion!

[Fletcher]

Orion has it right on the shelf thing.  I prefer 11/32 as well, but I don't see any appreciable difference between shooting 11/32 and 23/64.  The radial difference is less than .008"; the hair on your head is .003".  Doing the math, .008" works out to about 1/2 pound spine.  The 23/64 shaft has the advantage of a bit more strength and weight, if you're looking for it.