Hi Bill,
Very interesting. Do you or anyone else have a
theory to explain what you have observed?
I would have expected the solid wing to have a
better sink rate because the airfoil is more
accurately shaped and does not flex or change shape
like a plastic covered wing does. So that observation
I think can be explained and is expected. What I can't
explain is the observation of the solid wing needing
more torque to fly.
Did the model have a large velocity difference
between the sink rate test and the torque test? Maybe
the airfoil shape (4% arc) is a better airfoil at the
velocity where the torque testing was done and the
airfoil NACA4702 is a better airfoil at the velocity
where the sink rate was measured?
Thanks,
Kurt
--- Bill Gowen <b.gowen_at_earthlink.net> wrote:
> Kurt
> The wood wing is pretty much like a giant Cat I
> glider wing. Of course it doesn't need the strength
> of a glider wing and it doesn't have to flex. I
> think the front part was made from .040 wood and the
> rear part from .030. I used a few ribs to shape the
> airfoil. The top surface is a very close
> approximation of an NACA 4702 - 4% camber, 70% high
> point and 2% thick. The built up wing has a 4% arc
> airfoil with 1/16 sq. spars.
>
> I tested the model as a glider while ballasted up to
> 9 grams without a prop. The wood wing had a
> significantly better sink rate. I expected that it
> would fly on less torque than the built-up wing, but
> it didn't work out that way.
>
> The wood wing has been lying around my shop for
> several months now and wasn't as straight as I would
> have liked. I still expected it to perform a lot
> better than it did.
>
> ----- Original Message -----
> From: Kurt Krempetz
> To: Indoor_Construction_at_yahoogroups.com
> Sent: Saturday, December 02, 2006 9:48 PM
> Subject: Re: [Indoor_Construction] LittleSquare
> finally earns its wings!
>
>
> Hi Bill,
> Thanks for reporting your testing of your
> LittleSquare. Could you clairify what the
> difference
> was between the built-up wing that turned 3:25 and
> the
> wing that turned 3:04.
>
> Thanks,
> Kurt
>
> --- Bill Gowen <b.gowen_at_earthlink.net> wrote:
>
> > Yep - I finally got to actually fly LittleSquare
> > today. The model was
> > set up with the wood wing so I flew it that way
> > first. After hitting
> > everything possible on something like 6 or 8
> flights
> > I finally got
> > one clean flight of 3:04. This was on 5/99
> rubber
> > about .092". All of
> > the other flights were over 2 minutes.
> >
> > Then I switched to the built up wing, retrimmed
> the
> > model and
> > launched a full wind flight on the same motor
> and at
> > the same torque.
> > It climbed much faster and smacked the ceiling
> and
> > hung. This was not
> > really the expected result! On the next flight I
> > dropped the launch
> > torque considerably and got a clean flight of
> 3:25.
> >
> > The model is so ultra-stable that I think some
> CG
> > adjusting might be
> > in order to get the flight time a little higher.
> I
> > wasn't able to do
> > that today.
> >
> > The most important thing I learned about the
> design
> > today is that it
> > is absolutely and positively rock solid in the
> air.
> > Every flight made
> > was picture perfect until some obstruction got
> in
> > the way. If you
> > build one of these according to the plan it
> should
> > do what it's
> > supposed to do.
> >
> >
> >
>
> Kurt Krempetz
>
>
>
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>
> [Non-text portions of this message have been
> removed]
>
>
Kurt Krempetz
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Received on Sat Dec 02 2006 - 21:02:49 CET