Tapio wrote,
<<Tsk tsk. I might get insulted of that. Please remember that it was
my
first F1D, >>
And please remember that it was necessary for you to ask the CG
question twice to trigger any responses, two so far.
<<I might get insulted> I was afraid that you would see it as an
insult instead of an ISSUE. Perhaps many others here could have been
more diplomatic, but they didn't answer. So please consider all the
below more "strong medicine," not insults. Unfortunately, everything
in print seems more severe than the same words in person.
<<but after some flying I have noticed how overly-rugged it is. >>
This is a important step, to notice that.
<<I just would not
want to spend months of struggling with findinf a proper CG location<<
Months of struggle with CG? I'm sorry if that was necessary on your
first model, but this is probably part of the bigger issue I
am "insulting you" about. I think Mr. Bailey was likewise implying
that being close to weight will begin to reduce the CG problem as
being anything close to overwhelming (months of struggle.)
BBailey wrote,
<<As you bring the weight down, the pitch inertia will also come down
and will improve the stability as a result. This means you may then
be able to move the CG back a little>>
Tapio wrote,
_after_ I reach the magic goal of building to weight, but would
rather get
to the goal of properly flying models sooner rather than later.
>>
The Big Square article, which you refer to, has complete component
weights, down to the density of each spar, and I recall those
published weights were WITH VP. You've made nice looking F1Ms, which
I remember seeing at West Baden 04. F1ds are not rocket science! I
imagine the problems with anyone trying "lightweight models" should
be in the handling of model parts, and launching, but not in the
building, which ought to be a simpler matter of believing what is
written. It's all easier upon seeing one at a contest, and how they
should handle.
<<Well yeah, quite a big margin though as my first attempt flies at
100%,
and Hunt's model shows 75%. OK, I compromise, aiming at 80 to 85% on
the
next one.>>
So, the Big Square article recommended 75%, you set your current
model at 100% or even behind TE IIRC, yet you lament that "F1d plans
fail to list CG location." The Big Square has a relatively low tail
volume (area of tail X distance from wing) which naturally goes
together with *relatively* forward CG positions. Some flyers today
are running further back CG, but with big tails and long models, a
few even near 50% wing area, 34" long models. But in the case of Big
Square it would be better to follow what a good designer directs than
to be tempted by what others are currently doing with different
designs, IMO. BTW, current "new" 55 cm rules were a reflection of
Mr. Hunt's first Big Square, and not vice versa, I am told by a
couple authorities! So it had better fly!
<< Would like to have my next model into 1.2 grams,
and NOT make it then overweight by having to move the wing to and fro
on>>
Moving two wingposts should not make model "overweight." We're
talking two strong joints (top) and two weak joints (bottom.) Maybe
a .005 g glue pick up, at worst. I just don't like poking too many
holes in motortube. (Plugging the old ones is optional.)
<<Would like to have my next model into 1.2 grams,
and NOT make it then overweight by having to move the wing to and
fro>>
Another trick that I have tried in order to have instant "CG
portability" is to have several lengths of rear half tailbooms, all
interchangeable, but built to different lengths, say one that makes a
model 31" one for 32" , 33", whatever. But it's not easy to end up
with a series of rear half-booms having same weights, similar
stiffness. In general, interchangeability is great in theory, but
can become its own kind of nightmare, especially at contests. Props
however should be interchangeable!
HTH,
Mark F1diddler
Received on Mon Dec 17 2007 - 07:31:20 CET