My Su35 MK2 test bed plane is complete.
I didn't spend a lot of time on a fancy paint job since there could be the potential of cutting things up to fine tune my mods as well as tape that will be going along the trailing edge of the Kfs to test that effect. So just a quick magic marker job so I can keep track of it in the sky and we are ready to "kick the tires and light the fires"!
My build is essentially the same as my previous builds, 6mm depron, 4mm paperless dollar store foam for Kf airfoils, mostly Foam Tac glue with hot glue, epoxy, 3M Super 77 spray adhesive where needed. Power setup is the Focal Price 2700 motor with a 6x3 EMP prop and Turnigy Plush 40A ESC, 6 servos for elevons, rudders and ailerons which will also be switch selectable as spoileron and flaperons. Overall weight with a 1600 battery is 535 grams/18.9 oz.
The Su35 MK2 is a great little plane, I had about 100 flights on my previous one before I had to recycle it due to too many "gonks". However, when I get myself into trouble with it, it is normally at slow speed and I sometimes get caught in thrust vectoring or tip stalls. Also, just to fly it around within my skill level without scaring myself with it, I have my expos up pretty high, 65% in the pitch and 80% in the roll.
Fortunately, my great new friend Stephan (sgmoran from the RC Powers forums) was also starting some mods on the Mig29 V3 to get it to do some better knife edges, so rudder mods and he has also been playing with aileron size and tapering off the trailing edge of Kfs (he used painter tape for the testing). So he has been very gracious in sharing his research and his findings and we have been bouncing lots of ideas back and forth on the cause and effects of different mods. Not because the planes are bad, but rather to fine tune an already good design to fly more in sync with our flying styles. You can read about Stephan's amazing research, testing and conclusions to the mods he made on his RCP Mig29 V3 here http://rcpowers.com/community/threads/mig-29-v3-the-%E2%80%9Cfastest%E2%80%9D.15553/page-56 at posts #1111 and #1121.
I did considerable research and study, watched lots of video of Su35s flying, studied plan views (I know, I need to get a life... :/) to get an idea of some scale size mods I could possibly make without taking all the aggressiveness and aerobatic finesse out of the Su35 MK2.
So, since I was building another FRC Su35 MK2 anyway, I thought it would be a perfect opportunity to try out a few mods and a few different build and finish techniques that Stephan had shared with me to see what impact they would have on the Su35.
Starting at the front of the plane, I decided to run the top airfoil forward along the leading edge extension, so that it is one continuous piece flowing into the wing.
I have used this type of airfoil on an RCP F22 V1, T50 V1 and it is the stock Kf setup on the FRC F15 MK2 and I found it gives great added stability to those three planes. It does come with a bit of a drag cost due to the thicker leading edge, but I will trade more stability for lost speed in this situation.
I reduced the size of the ailerons almost by half and put them inboard, more in the position where flaps might be. I am hoping this will reduce some of the sensitivity in the roll, reduce possibility of tip stalls and from what Stephan has tested, it works great for high alpha as well when they are deployed as spoilerons. I am also going to set them up as flaps to see what impact that might have to make approach and landing a little more relaxed.
With Scott Lott's permission (the main designer from RC Powers), I borrowed the idea of angling out (from front to back) the vertical stabilizers. This technique was introduced on the RC Powers Mig29 V3 and RCP is so happy with it, all the V4s will have a similar "wedge" type design to the their vertical stabs. To prevent interference with the prop slot, this meant widening the back deck of the plane 1.2 cm. Hopefully you can see the slight deflection in this picture, they are each deflected out 2 degrees from stock.
I reduced the size of the elevons and played around a little bit with the scale look of the TV vanes.
So, they do look a little more scale as I fashioned a "drag chute" boom between the engine nozzles, but that little bit is longer than the stock TV vanes and I only reduced the surface area of the TV vanes from stock by 1/2 a sq inch. So I am not sure this will help or hurt with the possibility of TV stalls. I will test fly it with this setup and see what happens, but if I find little to no difference, I will sacrifice the scale look for performance and cut off the "boom" which will then reduce the TV vane area by almost 3 sq inches.
Other techniques I used which I haven't tried before are that I tapered the trailing edge of the wing/ailerons, the vert stabs/rudders and the elevons. I also placed my rudder hinge bevel on the outside and ran all my rudder servos and linkage on the outside as well to make the prop wash area as clean as possible. I am hoping both these techniques will help make for a smoother ride and performance.
Another test I will be doing at the field is to fly the Kfs with the standard trailing edge first, then I will tape them over to reduce/remove the vacuum effect behind the Kf step to see how different the plane handles and feels.
So lots do to once I get to the field and I am excited to get going with it once I get over a nasty cold and the weather gets better... :)
Stay tuned for more reports from the field testing... :)
Cheers,
Scott
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