The way I do is take the stab area and divide by the span to get an
average chord. Then you have to figure out where the average chord
location is to get the correct "length of the model". For example if you
have a 3" mean chord and the stab root chord is a 4" wide chord, and the
stab is say an elliptical planform, then the effective model length is
1/2" shorter because the mean stab chord is 3" not the physical 4" of
the center rib and the 3" is centered on the 4" rib so 4"-3 = 1 " chord
difference and half of that difference is in front to the mean chord and
half behind so the model is 0.5" shorter in the spreadsheet than it
physically measures. The Coslik stabs are straight trailing edge (if I
recall correctly) so the mean chord will also have its trailing edge
coincide with the end of the tailboom in that case.
An easy way to measure your stab area on a complex curve is to cut the
stab out of a sheet of paper, weight the paper stab then weight a square
piece of paper to get the unit weight per sq inch then divide the weight
of the paper stab by the unit weight /sq in then you will know your stab
sq inches, then just divide by the span to get your mean chord.
Don
>
>
> Don,
>
> Long time listener first time caller...
>
> In the design spreadsheet, how do we deal with the "mean tailchord"
> entry? For example, the maximum tail chord on my f1d is 5.25" but
> when I average the chord at the center and tip (since my stab is swept
> like a Coslick ezb stab) I get something like 3.8". Then when I try
> both of these values, I get a large difference in the static margin.
> My concern is that when I try the smaller "average" value, my static
> margin becomes negative.
>
> How should I deal with the stab geometry in the spreadsheet?
>
> Thanks,
>
> Brett Sanborn
>
>
Received on Fri Jan 14 2011 - 16:46:23 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:46 CET