Originally Posted by
flywilly
Hi Alex,
As usual, fantastic engineering and craftsmanship. I'm curious about your design philosophy. F3A seems to have 3 design trends: 1) more wings; biplanes and triplanes; 2) aerodynamic aids like the T-canalizer, SFGs (side force generators), and fuselage strakes; 3) bigger fuselages which increases the side area and fuselage volume. There are, of course, combinations, as well, like Naruke's Advatage monoplane which has a moderately large fuselage and a small T-can with wing SFGs. How did you arrive at your Vortex design? I like the simplicity of one wing and no aerodynamic gadgets.
Thanks,
Will
Thank you Will, you are too kind
The biplanes are really nice and maybe I’ll design one someday, but at the moment my goal was to develop the monoplane as much as possible before moving on to something completely different.
When designing the Vortex I had a list of things to improve from my previous design Audax (build thread
here), so it’s an evolution even if it looks quite different. Audax was designed in 2012, so by the end of 2016 it was a small plane compared to the BJ Craft Invitation or other current designs. For Vortex the fuselage side area was increased massively to improve the rolling and knife edge performance needed for the latest F schedule; also the distribution of the side area was changed and fuselage pressure center moved forward for better handling in crosswinds.
Audax had very narrow wingtips and snap-rolled beautifully but faster than I could move my fingers so I thought I can afford trading some snap roll performance for more predictable spin entries and improved handling in bad weather. That’s why the Vortex wingtips are wider with increased leading edge radius.
The purpose of the canalizer is to improve the knife edge performance. I tested one on my old Radiance design and the knife edge performance was significantly better but at the same time the canalizer induced a strong pull to canopy in horizontal knife edge flight. I tried to adjust the canalizer incidence or move the CG backwards, but nothing really helped so in the end I just gave up on using it. I know other pilots use canalizers with great success but as described a while go in my Airflow Visualization thread, I found other ways to improve knife edge flight:
http://www.rcuniverse.com/forum/rc-p...isation-3.html
I would say the effect of using the 2 fin fences was roughly equal to the canalizer and I received good reports from other pilots that tested them. There was even an article about this in Kfactor magazine (May 2014 issue) and the author’s conclusion was that the fin fences compared favorably to the canalizer:
may14.pdf
So if I’m ever going to need more knife edge performance for Vortex, I will just use the fin fences. The weight is only a few grams and I couldn’t see any disadvantage in using them.