Primitive Archer

Main Discussion Area => Bows => Topic started by: arachnid on June 07, 2015, 02:35:56 pm

Title: A thing I don`t get about grain run-offs
Post by: arachnid on June 07, 2015, 02:35:56 pm

HI guys.

I was wondering this for a long time now- when I pick a board with straight grain and the cut the bow shape out of it, doesn`t the width taper technicly create grain run-offs on the bow`s back?
I draw this crappy looking drawing to explain myself:
(https://lh3.googleusercontent.com/z8y_gFkd3UM9ZMQsPT0iV3DOQNLu0n9e4_9HVjPKXKE=w672-h554-no)

The image to the right is the board. The middle one is the shape of the bow (on this case a pyramid but is can be anything) marked on the board and the left one is the bow cut of the board. I marked with a blue circuls the spots that are supposebly run-offs.
And yet- this is the way to go and it works! How come the bow doesn`t break at these spots?

I`ll be more the happy to know...

Thanks,
Dor

Title: Re: A thing I don`t get about grain run-offs
Post by: J05H on June 07, 2015, 02:44:12 pm

I can't see the picture, but I can say the goal is to minimize run-off. We can't fully eliminate run-off be cause it's present any time we taper the width. As long as we keep it to an absolute minimum, we give the bow the best possible chance to survive.

Title: Re: A thing I don`t get about grain run-offs
Post by: aaron on June 07, 2015, 04:10:56 pm

because the run offs are on the side rather than the back, they are not under much stress. Runoffs on the belly and sides are ok, but runoffs on the back are a problem- that's why we follow a growth ring on the back..

Title: Re: A thing I don`t get about grain run-offs
Post by: Badger on June 07, 2015, 04:46:00 pm

  Dor, you are correct, mos of our side tapers are pretty low angles and that seems to minmise the effects of the grain running out at those points. On occassion it will lift a splinter in areas that taper but no often. Rounding the corners will usually be all that is needed to reduce the risk.

  Aaron, the growth rings and grain lines run opposite directions. On board bows we always wrongly refler to the growth ring lines as grain and it gets confusing.

Title: Re: A thing I don`t get about grain run-offs
Post by: arachnid on June 07, 2015, 04:53:47 pm

Thanks Steve.
That been said, will rounding the edges reduce the risk of a lift splinter on a higher angle runoff?

Title: Re: A thing I don`t get about grain run-offs
Post by: George Tsoukalas on June 08, 2015, 09:30:21 am

The fibers are straight tip to tip. Those really are not run offs.
Jawge

Title: Re: A thing I don`t get about grain run-offs
Post by: PatM on June 08, 2015, 09:49:37 am

Quote from: George Tsoukalas on June 08, 2015, 09:30:21 am

The fibers are straight tip to tip. Those really are not run offs.
Jawge

They still are effectively if the width is tapered through the lines.