CFD was used for stability analysis. The only plan to use CFD is to identify any weird drag spots and to verify control surface loading. Stability analysis was done in Excel and then checked with XFLR5, which is wonderful program...that's also free!Interesting design.
About airfoil, it is not necessary to choose symmetrically. Symmetrical is NACA 00xx series.
Also, what CFD model did you use? How many boundaries layers?
Christos, civil engineer
Being a converted Beech Bonanza, the T-34 level of aerobatics is not very high...Rad-dude 1234,
I'm very interested in your design, I'm aiming for a similar mission with a similar design. Please tell us what Riblett Airfoil you select and why. I've selected the 37A 415, but not aiming for T-34 level of Aerobatics, more mild aerobatics and aiming at providing strength of the 6G and the 415 for stall speed on LS.
What airfoils you using for the Tail feathers, an Aeronautical Engineer friend put me onto a good one NACA 0010-64, Symmetrical airfoil -I like it!
Cherokees have NACA airfoils and have a very mild stall. Did a power on stall in a Warrior last week and it didn't do anything...just mushed along.
I would feel better about the Ribblet airfoils if I saw some actual test data and they had more significant digits in the graphs.
Aero engineers I've talked to all say something different. NACA, Riblett, custom, doesn't matter, use only something with test data...and on and on.
I used the Flow Simulation module of Solidworks for some very basic drag estimates. XFLR5 uses the VLM1 method which can be described here: https://engineering.purdue.edu/~aerodyn/AAE333/FALL10/HOMEWORKS/HW13/XFLR5_v6.01_Beta_Win32(2)/Release/Guidelines.pdfI meant the CFD code. Did you run the k-omega SST model or something else, also what about the grid? how many cells and how many boundaries layers and how much thick?
If you used the auto option of your software, just make sure that it takes the correct values for your problem. For example, if it used k-omega SST, check k, omega, kinematic viscosity, y values etc.
Because of a low-quality grid and incorrect equations will give you a non-realistic cd, cl and the most important, stall behaviour, etc.
I like your project. Be careful with NACA 6 series, it is laminar flow airfoils, something excellent for high efficiency, but on the other hand, some of these have poor stall characteristics.
That's awesome!WRT airfoil selection - the symetrical section used on the Hiperbipe was reportedly eyeballed on the hangar floor. TLAR all the way.
In my experience it performed just fine.
So back when I was working on my Mech Eng degree, one of the requirements to graduate was to participate in a group design project during my senior year. Mine just happened to be to design an RC airplane. Anyways, our team spent weeks upon weeks doing exhaustive analysis to pick the perfect airfoil....until the advising professor told us to just pick one so we could get on with our lives....and on and on.
I think Billski's thoughts on inverted performance are well-taken but, otherwise, ... yeah. Don't sweat the airfoil choice on an airplane like this. You can do more to tailor post-stall behavior for a regular positive-G design with wing planform and twist than will be determined by any given airfoil.My point about the Hiperbipe airfoil was meant to illustrate that there is a lot more design work to do before you pick a specific example. This is not a transport category aircraft that needs to eke out the Nth % of efficiency to make or break it's ROI. We're also not iterating to make a specific range on a bomber or tanker with a fixed powerplant. This is a sport plane with literally dozens of well proven, off the shelf airfoils available that will perform so closely together that even an experienced test pilot would struggle to tell a difference. At this point in the design, airfoil selection should be narrowed down to "yes".
I see a lot of holes in statements and opinions here, Pipercruisen's statement is the most correct. It would be wonderful if all if all Airfoils could have the correct test date, other than that probably the closest is Eppler program and it's far from perfect.
Naturally very experienced people can draw a Airfoil on the hanger floor and it may be close enough i.e 'fit for purpose'. I suppose anything will fly with enough power, flat panels have been and still are used in tail feathers - however there is the issue of optimum lift with minimum Drag and beware the stall.
I think it's up to the designer to do the research and live with the decision, I'm no expert but I am following the lead of some very smart, very talented and very experience people.
All I can suggest is do the same and start with "Theory of Wing Sections" by Abbott and Von Doenhoff.
I used the Flow Simulation module of Solidworks for some very basic drag estimates. XFLR5 uses the VLM1 method which can be described here: https://engineering.purdue.edu/~aerodyn/AAE333/FALL10/HOMEWORKS/HW13/XFLR5_v6.01_Beta_Win32(2)/Release/Guidelines.pdf
Even then, I only took very basic values like wing moment, drag, etc and plugged it into an excel sheet developed from an aircraft stability textbook. Basic lift and drag are relatively easy to calculate when compared to figuring out control and stability, especially for a super conventional design such as this one...and it's much more reliable and easier to calculate that stuff based on proven equations rather than rely on CFD.
So back when I was working on my Mech Eng degree, one of the requirements to graduate was to participate in a group design project during my senior year. Mine just happened to be to design an RC airplane. Anyways, our team spent weeks upon weeks doing exhaustive analysis to pick the perfect airfoil....until the advising professor told us to just pick one so we could get on with our lives.
The moral of the story is that unless there are absolute performance goals like speed and range that you must hit, don't lose too much sleep over what airfoil to pick.
For reference, check out the airfoil on this RC model: