Compression blocks and spine

pinecrest · August 31, 2008, 11:36:00 AM

Iwant to try and make some poplar shafts.I need 85-90# spine,32'' arrow.Can I get this from poplar and if I use a block how much do they reduce spine?

Ray Hammond · August 31, 2008, 12:30:00 PM

pinecrest, I would think a compression block would INCREASE spine, not decrease it.

pinecrest · August 31, 2008, 12:38:00 PM

The 3rivers catalog says it decreases spine.

donw · August 31, 2008, 12:54:00 PM

try it and see...

i would agree that compressing should INCREASE spine and if i remember correctly there used to be an arrow called the 'forgewood' that was compressed and they were very stiff spined.

maybe the use of heat is the determining factor.

dino · August 31, 2008, 01:06:00 PM

Anybody that I've ever talked to that has used the compression block has reported a LOSS is spine. I know it sounds backwards. About 6 lbs on a POC from 11/32 to 5/16 is what I remember. Search some archived threads. Might find more there. I've used some 3/8 Poplar dowels and many of them spined in the 90+ range so you shouldn't have much problem finding that heavy of a spine in them, but your going to have to run some thru the compression block to find out exactly how much they will loose. dino

Stone Knife · August 31, 2008, 02:06:00 PM

I lost from 3 to 5 pounds on cedar, going from 11/32 to 5/16.

SlowBowinMO · August 31, 2008, 02:06:00 PM

You are both altering (crushing) the outer wood as well as reducing diameter, both of which affect strength negatively, which reduces spine.

pinecrest · August 31, 2008, 02:47:00 PM

I think I''ll skip the block and leave them 3/8 as I need the spine.Thanks for the input.

Ray Hammond · August 31, 2008, 03:33:00 PM

Then it must not really compress the shaft..the only compressed shafts I ever used were true Bill Sweetland forgewoods....and they were made smaller and denser by compression..and increased in spine and dropped in diameter, significantly.

It must the the lack of heat- and the compression block must only be like "boning" a baseball bat...it just hardens the skin..rather than compressing the shaft?

aromakr · August 31, 2008, 04:23:00 PM

Ray:
Your talking about apples and oranges. The sweetland shafts were truly compressed. The growth rings were compressed "BEFORE" the wood was doweled. the "Compression block" is nothing more that a highly burnished shaft. Does it reduce its diameter, yes but its not compressed in the true since of the word. Only a small portion of the shaft's outer surface is compressed.
Bob

O.L. Adcock · August 31, 2008, 08:07:00 PM

Spine goes up by the cube of the diameter so a tiny decrease in diameter makes a huge decrease in spine no matter the material. Bob's right, forgewoods can be high spine for their diameter but larger diameter forgewoods are stiffer still....O.L.

Ray Hammond · August 31, 2008, 08:50:00 PM

Right, as I suspected, its nothing more than when you 'bone' a newly made baseball bat to harden the exterior skin of the wood...no real compression except cosmetic.

Jeremy · September 01, 2008, 12:54:00 PM

I was wondering if there'd be a run on compression blocks from 3Rivers after the last TBM

The Veritas 3/8" dowel cutter does work very well, but I'd recommend sawing your blanks oversize by at least a 1/16" of an inch, especially if you're doweling doug fir, pine, or poplar. You'll get a much cleaner cut. Veritas actually recommends a 1/2" blank.