On Aug 17, 2:50 am, Charles Vincent wrote:
Fortunat1 wrote:
"Rich S." wrote in
:

"Fortunat1" wrote in message
...
Well, obviously I'd protect it, but I'm not going to rely on epoxy to
bear a load. If I can't get the holes 100% I'll bush them....

...So I guess I'l just be as careful as I can cutting the holes. Just
looking through Bengelis' book, I see he recommends using a twist drill to
cut the holes, presumably to their final size,...

I would test that theory first. Reamers may or may not give a good
finish on wood. That was one of the reasons I quoted the study I did.
The twist drill gave the best hole finish.


Bits made for wood, high quality brad-point or forstner bits,
may give you a cleaner hole than a twist drill made for metal.
Cheap bits are crap-they'll burn their way through the wood.

As a rule of thumb, when working wood, use tools made for
woodworking. Duh!

Wood expands and contracts with changes in humidity and
it does so anisotropically. E.g. a flat-sawn board will
have the highest expansion rate accross it's width, less through
its thickness, and minimal along it's length. Quarter sawn or
vertically grained wood, which is what you usually want for
a spar cap, will have those first two rates reversed.

What this means is that if you drill a perfectly circular hole
in a piece of wood, as soon as the humidity changes it
becomes an oval hole. The same is true of a wooden dowel.

Wood finishes slow the rate at which wood absorbs or
releases moisture to the air so as to prevent moisture
gradients through the interior of the wood, which minimizes
e warpage. But all wood finishes are permeable to some
degree to water vapor.

So don't get too crazy about making the hole perfect. I think
the epoxy approach is a good idea.

--

FF