Const. question from Phil Alvirez

From: Mark <f1diddler_at_yahoo.com>
Date: Thu, 10 Aug 2006 18:21:23 -0000

Subject: Stiffness tests for balsa.
Anybody : Do you have, (or know where to get), stiffness tests for
all
parts (with figures) for the light weight categories such as F1d,
Intermediate Stick, Limited and regular Pennyplanes, Mini-Sticks, and
the
like?
I mean, something like what Larry Coslick did on that article
published
(twice) in the INAV about E C B (notice that I don't say "Easy B"-
it's
simple, very few pieces, but a hell to build and fly) in which he
provides
the modeler with an easy way to test every single piece before
building
the
model , so there are no surprises after finishing it. That could be
helpful
to bring new people into this dying hobby of ours.
With balsa wood getting more scarce every day (ARF's are the way most
guys
fly nowadays), how do you expect anybody finding the way to build to
weight-or build light-if he doesn't have points of comparison? And
it's
frustrating to build just to learn that all the effort was for
nothing,
even
if you build to weight, as the plane is too flexible. I can tell you
from
my own experience!
Besides Larry's data, the only other time I have seen anybody telling
you
how to test something for stiffness on a practical way (with
figures)
is
what Doug McLean mentioned in his article about a bipe Penny,
published
in
the Model Builder (Sept 76 issue) for the selection of the wing spars
(as a
coincidence, it was in the same issue that an article about a
control-line
plane designed by yours truly appeared-in those days I was into that,
but
not yet into indoor). McLean tells us precisely what to seek: For a
given
spar size, let the spar protrude 4-1/2", hang a weight of 2 grams
from
the
tip, and the deflection shouldn't be more than 3/8". That's what we
need to
know!
So, please, tell us if you have figures like those.
Regards
Phil Alvirez
Received on Thu Aug 10 2006 - 11:21:33 CEST