Spine Question

[Kip]

I cant remember what number of stupid question Im on, so I wont number this one.
When they measure spine, is there a certain position the arrow has to be on the tester?
Does the grain of the arrow have to be horizontal/vertical, or doesnt it matter?

It seems to me, that if you spine test an arrow with the grain going like this=====, you would get a different measurement if you tested it again with the grain like this ||||||.
Does this make any sense, or do I need to find something else to think about?

[LBR]

It does make a difference, but I'm not sure which way you spine them--I think against the grain (looking straight down you see the lines side by side==============). That's why I buy shafts that are hand spined--when they are machine spined, they are spined just whichever way they land.

Chad

[Lilhunter]

Kip,

Your grain should be l l l l

not =====

on your spine tester.


That said, check the spine on both lllll sides to find where it spines out. Good shafts will be more consistent as you rotate the shaft.

[Arthur P]

Wood arrows are spined by resting the arrow over supports 26" apart and suspending a 2-pound weight in the center of the shaft, then measuring the deflection or amount of bend. Shafts are stiffest on the edge grain side of the shaft. Arrows should be made up so the edge grain is against the sight window with the 'points' of the face grain facing forward along the top side of the shaft. So, spine should be tested on the edge grain side of the shaft.

The reason the points of the face grain should be running forward on the top of the shaft is for safety. Wood usually splits and breaks along the grain line. If the points are facing forward along the bottom of the shaft, and you don't notice a crack in the arrow, the arrow could break on release and force the back end of the shaft down into your wrist. With the points running forward on the top of the shaft, the back end of the arrow will likely be forced UP, away from your wrist, if the arrow breaks.

[PineLander]

Very nice post Arthur, very visual indeed.
Couldn't have said it any better, all info is right on the money.

I believe this is the most important part....
"Arrows should be made up so the edge grain is against the sight window"
so... spine them the same way with weight against the edge grain.

It's conceivable that a person could take a mismatched set and spine them 'against' or 'with' the grain, to come up with a somewhat close group. But I wouldn't recommended it, as some would end up with the weak side of grain against the riser... not very safe as continual flexing on the weak side may cause failure.

[CAJUNBOWHNTR]

So looking at the nock end of the shaft should the grain lines be vertical or horizontal????

CB

[Ossage]

horizontal. Perp to the string.

Arthur is totaly correct about the rising falling grain thing. However, a better option is to have straight grain from one end to the other, rather than relying on what happens when the shaft breaks. It's perfectly possible to get straight grain.

[Lilhunter]

the edge grain lays perpendicular to your bow as you hold your bow striaght up and down.

On a spine tester, this edge grain will be straight up and down vs side to side when nocked on a bow string.

so with a nock, the edge grain is perpendicular to your string or paralell to your string groove in your nock.