Grain run-out and steam bending

[nedL]

The question of grain run-out in wood used for steam bending has come up a number of times and it sometimes seems difficult to convey the concept to new folks here. Considering I had a couple of examples on hand that I could photograph I thought I'd post some pictures in hopes they might help clarify things.

http://www.imagestation.com/picture/sraid181/p0145a3f8b963c8223487fd24daaedb8f/f2d5af2d.jpg
Here is an obvious example of what happens when the grain run-out is to severe for the bend. The wood splits along the grain. In this case I think the split is something like 6" - 8" long. So in the straight piece before bending one would have been able to see that in about 6"-8" of length the grain moved about 2/3 of the way across the rib.
http://www.imagestation.com/picture/sraid182/p825ab5de1de4b10019219cfa85041cd7/f2bfa153.jpg
This is toward the other end of the same rib, it bent just fine as the grain was parallel to the rib.
This is why you buy more stock & rip more ribs than are needed. If I had tried to put this rib in another location in the boat where the bend was not as sever It would probably have been fine.

http://www.imagestation.com/picture/sraid181/p892dd9b2dd955d50df98a527b2576049/f2d5ae8c.jpg
And with a real nice piece you can have fun making oak knots. :D

[ 08-19-2005, 12:51 PM: Message edited by: nedL ]

[Bob Cleek]

And, as I expect you know, a metal strap clamped on the outside of the bend will go a long way towards preventing such breaks.

[nedL]

Very true Bob. In my case I'm re-ribbing & when pushing them down on the inside of the hull (& working alone) its a bit tougher to use a backing strap & keep it in place. Out of 25 or so ribs I lost only a few that I thought had to much run-out to begin with.