On Thu, Nov 6, 2008 at 12:23 AM, Ron Jensen <[EMAIL PROTECTED]> wrote:
> Hmm... I've been playing with xfoil a little trying to hone my
> aerodynamics knowledge... I've also been working with DATCOM+ a bit for
> the same purpose, but DATCOM isn't good for low reynolds numbers, so I
> don't know what it would do in this application... What Reynolds number
> are we looking at? Somewhere between 5e6 and 1.5e7?
I've never sat down to see how Reynolds numbers are computed. Is this based
on wing area, wing loading, wing span?
I was thinking the other day, that it might be really interesting to have a
couple new aeromatic modes for generating numbers appropriate for small
model aircraft that are often used in UAS research.
> Remember, I modeled the Oscar Sette... And followed the mission on the
> blog...
Sorry didn't mean to imply that if I did ... Since we are on the mailing
list I was thinking about a wider audience.
> Duplicating your flight control system in JSBSim is what I'm most
> interested in... You only have one control surface per wing so I assume
> they must function as elevons (both elevators and ailerons). Do you
> simply sum the aileron input and elevator input? Is pure elevator or
> pure aileron input capable of driving the elevon to full deflection?
Right. We do this very simply. The autopilot still thinks in terms of
elevator and aileron, but the surface positions are summed before they are
sent to the actual servos. (If the autopilot is configured for flying wing
mode.)
In terms of maximum throw, the RC transmitter can only get to full servo
deflection when you have your transmitter stick in the corner (max elevator
+ max aileron) so I think it mixes in 50% of each. That's something you can
actually adjust on the transmitter, but I've gone with the defaults and
they've worked out well for this airframe.
The autopilot itself is capable of driving the elevator or aileron
individually to the full extreme, but in my autopilot configuration, I have
greatly constrained the maximum throws, so the autopilot never actually gets
close to any of the extremes.
Not that I've actually seen this personally, but even on very low throws
(maybe 10-20% of the maximum possible range), my wing will to a pretty tight
loop if the elevator is configured to go the wrong direction. :-)
> Hopefully that doesn't make design too super-secret.
It's the combination of all the components and the experience from several
smart people and a large amount of effort and time (and research and
contributions from a wide variety of public sources) that goes into the
whole package and makes it interesting and useful. (And in our case, our
experience with making electronics and other systems work in a marine
environment adds to the value of this particular package.) We don't have
any stunning aerodynamics break throughs, no stunning development in
materials or construction techniques. No cloaking device, no tachyon beams,
no dylithium crystals (yet).
It looks like a fairly simple model... But none of your pictures has
> anything I can use for scale... Any hints like root chord, tip cord and
> semi-span (the length of the removable wing panel). Maybe body width
> and length...
Let me see if I can get you some detailed information if you are interested
in playing around with this. I know that flying wings are a very popular
platform in the small UAS world, so I'd love to have more examples of these
in FlightGear.
> The better the flight model, the better the autopilot, right?
Yes, it all feeds on each other, hopefully in an upwards cycle. :-)
> I solved that problem... I have two dogs!
We are down to one after this summer. :-( We lost our big dog, Kenai ... he
was almost 13 so I guess that's not a bad run for such a big dog.
--
Curtis Olson: http://baron.flightgear.org/~curt/
-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Flightgear-devel mailing list
Flightgear-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/flightgear-devel
