On Thu, 07 Aug 2008 19:24:12 -0500, dpb <none@[EMAIL PROTECTED]
> wrote:
>Tom Watson wrote:
>...
>
>> let me ask you a question, Chris.
>>
>> In all the tests that I have seen, although it is true that the glue
>> line does not break, the break is always near the glue line. It does
>> not appear to be the case that the break is in another part of the
>> panel that is away from the glue line.
>>
>> What's up with that?
>...
>
>Every test I've seen the two pieces are the same width so the joint is
>in the middle. When the board is loaded and sup****ted on the edges, the
>point of highest stress is then in the middle; hence unless there is a
>weak point farther towards one edge or another, the most likely place
>for the failure is near the point of highest stress, the middle.
>
>Since as noted, the glue joint actually is generally as strong as or
>stronger than the material, typically it is slightly to one side or the
>other of the joint where the break occurs.
>
>Simply physics of the test geometry is the basic explanation... :)
>
>The more interesting test that is illuminating is the one of the bridle
>joint joint loaded perpendicularly to the grain on one piece -- even
>there it is typically either the wood that breaks or a combination
>rather than a glue-line failure for well machined joints.
>
>--
Tomorrow I'm going to glue up a panel like I would use for a raised
panel door.
I'll let it set up for a day or so and then apply force to the center
of the entire panel, which will not be the same as applying a force to
a single glue line.
I'll be interested to see what happens.
Regards, Tom.
Thos. J. Watson - Cabinetmaker
http://home.comcast.net/~tjwatson1/
tjwatson1ATcomcastDOTnet
|
