Daniel Burleson

Ok. Thanks for looking into this, André. I was initially investigating the relationship between Vx and Vz because I was looking to optimize the plane to have Vz = 0 at aoa = 0, so that the plane would maintain constant altitude while flying horizontally. I see now that the type 4 analysis is more suited towards investigating critical Reynolds numbers. Thanks again Daniel

Hmm ok. But in the analysis definition, it says Type 4 (fixed aoa), and then I ran the analysis from 0 m/s to 25 m/s at 0 aoa. So using a type 4 analysis for my plane, it seems that I am indeed changing the total speed. If i graph V vs aoa, it is a vertical line at aoa = 0, ranging from V = 0 m/s to V = 25 m/s, which makes sense, but it does seem that with this analysis, the total speed is changing. Sorry if I am misunderstanding something here.

Hello, I performed a type 4 analysis to investigate the relationship between Vx and Vz. When I plot Vx vs Fz, I can see that as Vx increases from 0 m/s at 0 aoa, Fz increases, which makes sense since this is how the plane will takeoff. However, if I plot Vx vs Vz, as Vx increases, Vz decreases, which does not make sense. Near Vx = 0 m/s, how can there be any postive value of Vz? Furthermore, since the lift force and the weight are the only vertical forces at 0 aoa, how is it possible that if Fz (lift)...

Thanks for the reply André! I've got one more question today. I have been reading the guidelines, and I'm a little confused on the difference between Cl and CL. I am able to plot a polar of Cl vs CL for my plane, but what exactly is Cl? From this link http://web.mit.edu/aeroutil_v1.0/xfoil_doc.txt, it states "the XFOIL force coefficients CL, CD, CM are obtained by normalizing the forces and moment with only the freestream dynamic pressure....the conventional and XFOIL definitions differ only by the...

Hello, I was taking a look at the derivation of the tail volume from this link http://www.xflr5.com/docs/XFLR5_and_Stability_analysis.pdf. On page 11, it sums the moments about the quarter chord point, but I am wondering why the center of gravity was not taken into account. Since the cog is not necessarily at the quarter chord point, shouldn't it be considered in the sum of moments? Am I missing something obvious? I could not find much material on tail volume online, so that is why I am asking here...

Hello, I was taking a look at the derivation of the tail volume from this link http://www.xflr5.com/docs/XFLR5_and_Stability_analysis.pdf. On page 11, it sums the moments about the quarter chord point, but I am wondering why the center of gravity was not taken into account. Since the cog is not necessarily at the quarter chord point, shouldn't it be considered in the sum of moments? Am I missing something obvious? I could not find much material on tail volume online, so that is why I am asking here...

Hello, I am currently working on my first RC plane project, and have just begun using xflr5. After reading the section explaining the NCrit and forced trip location parameters from this document http://web.mit.edu/drela/Public/web/xfoil/xfoil_doc.txt, I'm wondering if and when it is necessary to change the forced trip location values. The document explains what NCrit values are appropriate, but I'm still a little confused as to when the forced trip locations must be considered. Thanks, Daniel B.