Hi Kevin.
Oddly enough I was looking at this again while eating breakfast this morning and my eyes caught the (radians) notation. I didn't work out the math exactly, but it would be much closer to what he indicated.
When I installed qprop to my c: drive, the directory is c:\qprop\runs and the file is kagan.
There are a couple of f1d examples there too.
Regards.
Mike Kirda
--- In Indoor_Construction_at_yahoogroups.com, Kevin Lamers <kevin.lamers@...> wrote:
>
> Hi Mike,
>
> I saw your question at RC groups as well (
> http://www.rcgroups.com/forums/showthread.php?t=2023310). Your number for
> CL_a is wrong because you use alpha in degrees, not in radians.
> For example if you only look at the first linear part of your graph (from 0
> to 5 degree) you can see an increase in CL of roughly 0.48. The 5 degree
> change in alpha should be converted to radians (devide by 180/PI=57.3),
> thus 5/57.3=0.0872.
> Now CL_a (actually the change in CL due to a change in alpha) is
> 0.48/0.0872=5.5.
>
> The rest of the differences are probably due to a slightly different input
> in Xfoil/xflr5.
>
> BTW, where can I find the example you used?
>
> Best wishes,
> Kevin
>
>
> 2013/10/23 mkirda_at_... <mkirda@...>
>
> > **
> >
> >
> > Greetings.
> >
> > I've been looking at this program on and off for a year or so.
> >
> > Dr. Drela included some example files for F1D props, specifically John
> > Kagan's.
> >
> > Silly me, I like to understand things. So I follow the documentation and
> > after computing the polars for a 3% arc file (as generic as it gets for
> > prop airfoils), I try comparing to the examples.
> >
> > And as you might guess, nothing matches. Some things are close, however I
> > cannot understand how he got the numbers in the example files using the
> > polar at Re5000 as indicated.
> >
> > Is there anyone on-line that I might work with offline a bit to understand
> > this a bit better? I have to assume I am doing something wrong...
> >
> > Regards.
> > Mike Kirda
> >
> >
> >
>
Received on Mon Oct 28 2013 - 07:50:24 CET