Wood for spars
CVG stands for clear vertical grain. Clear means free of knots or
defects. Vertical grain means that the annual rings are at right angles to
the surface on the widest side of a board. It eliminates checking and
twisting. You should also try to get structural select grade lumber if
possible for spars. Structural select will have no pitch pockets or grain
runout. Lumbermen just refer to it as struc select cvg. Douglas fir is best
if you have it available locally. I wouldn't think that it would be worth
the expense to get aircraft grade Sitka spruce. Probably it will be
impossible to get struc select cvg so you will just have to get the best you
can find at your local retailer. Just pick through a pile and do the best
you can. You should watch for grain run out and knots. Also watch out for
pitch pockets or sticky pitchy wood. Both can cause a spar failure.
good luck
Phil
defects. Vertical grain means that the annual rings are at right angles to
the surface on the widest side of a board. It eliminates checking and
twisting. You should also try to get structural select grade lumber if
possible for spars. Structural select will have no pitch pockets or grain
runout. Lumbermen just refer to it as struc select cvg. Douglas fir is best
if you have it available locally. I wouldn't think that it would be worth
the expense to get aircraft grade Sitka spruce. Probably it will be
impossible to get struc select cvg so you will just have to get the best you
can find at your local retailer. Just pick through a pile and do the best
you can. You should watch for grain run out and knots. Also watch out for
pitch pockets or sticky pitchy wood. Both can cause a spar failure.
good luck
Phil