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Friday, April 11, 2014

SU35 MK2 TEST BED SLOW FLYING/HIGH ALPHA TESTING

Hi Everyone -

I got out yesterday morning and blasted through almost every lipo I have in my Su35 of all sizes, 1600/1800 and 2200.  Fourteen flights on it in total... :)

Fortunately it was relatively calm for the first couple hours, so I was able to get a much better feel for the plane without the wind.

I remember when I did the flyoff originally between the Su35 and Su37 how I had described the Su37 as smooth and the Su35 as aggressive.  Well now with these mods, the Su35 is smooth and more precise than anything else.  It will snap in and out of maneuvers when I want it to by slamming the sticks around, but for the most part when I am flying around or doing scale type aerobatics, it just feels so precise with the smaller control surfaces and everything else that is going on.

To see if the reduced ailerons and elevons had any big impact on slower speed cruising, I spent one flight just cruising at 50% throttle just like I normally used to with the stock surfaces.  It actually performed better because when I went into a turn, loop or roll, I didn't have as much surface area being dragged through the slipstream.  I also cruised around as best I could at about 40% throttle without aid of any high lift devices (flaps, spoilers, etc) and even then it was very responsive.  I had to be a little smoother with the inputs so as not to stall, but that is normal for any plane as it slows down I think.

I could get a bit of high alpha with it, but definitely nowhere near where I can get with my F18.  I started off with about half inch travel on the flaps, etc.  I tried all the configurations flaps, spoilers, flaperons and spoilerons and as soon as I got up about 25 degrees AOA, wing rock would come on and then if I tried to ease it up just a little higher..wow, wing rock came on pretty violently to the point where I had less than about 3 seconds to drop the nose and fly away or I would end up inverted!

So I tried another configuration, less flap, etc like down to as low as 1/4" travel and that softened it a bit, but not by much.  I also found that I had to have the extra weight of a 2200 battery to get any kind of stability in a nose high attitude, anything lighter and it was like trying to put a feral cat on a leash...not fun!

With straight flaps (not flaperons) I could actually fly around level at about 30% throttle, it gave me that extra lift, but it was a bit of a razor's edge, too much bank or just a bit too slow and bang, it would stall.  It behaved like a tip stall, but not sure if it was that or just the low wing stalling in a turn, either way it made for some interesting recoveries...or lack thereof...as you can see in the picture below I got a little bit of a battle scar, but now it has more character!  Just some dirt, fortunately not one bit of structural damage.  I tried a couple approaches and landings with flaps, but in all honesty, I don't really need them now, this plane glides so much more stable and smooth than the stock Su35, flaps are not really a requirement.



So next calm day I might trying to go down just a bit more on the flaps, etc to see if that helps.  I think that this is not really a high alpha model, which is fine, I know folks get good high alpha with the Su37 when they play around with canards, but I prefer the profile of the Su35 MK2, so I'll live with that.

So back to the good news again.... :)  I have my throws down around 70% still in the roll and pitch and would not go any higher than that.  Even with the reduced elevons and ailerons at 70% throws it does non scale flip loops and rifle bullet rolls, so it definitely doesn't need more.  I had thought about reducing the throws even more, but then sometimes with slow maneuvers I want that extra bit of throw just to get me over the top or around the corner.  

The rudders are very effective for special aerobatics, but I need to tone them down a bit for slow speed flying and high alpha, they are a bit too big for my liking.  I tried a couple of hammerhead stall turns today though and they worked well for that and the plane stayed true in the roll axis, the old Su35 would try to do an inside roll if I tried just kicking the rudders when I was approaching stall in the vertical, so I think that dihedral effect of the vert stabs helps with the stability in the yaw even when kicking some pretty hard rudder.

So like I said earlier, precision is what is really impressing me about this plane with these mods, it just carves beautifully in and out of turns, staying true and solid all the way through, very smooth through loops and it rolls true on it's axis very smoothly and precisely.


Cheers,

Scott

Wednesday, April 9, 2014

FRC SU35 MK2 TESTBED MAIDEN COMPLETE! :)

Hi everyone -

After waiting out the weather, I managed to get some flying in with my Su35 MK2!

This plane in this configuration flies rock solid awesome!  In all speed regimes (especially top speed) it just tracks like it is on rails even in a wind.  I detected no torque roll once I go the trim sorted out.  Anytime I just flew thumbs off straight and level, it just stayed going exactly where I pointed it with negligible wobble or bad habits.

The smaller elevons still gave plenty of authority, but I had less "washout" or "fishtailing" in crosswind turns.  With ailerons and elevons working together, rolls and turns were crisp and scale, even with only 70% throws.  I found I preferred the ailerons and elevons working together when the wind was up as I had just that extra authority and stability.  The main thing I did like was that with the smaller surfaces and other stability factors going on I was able to drop the expo down on both the roll and pitch by about 20% each and ended up with a better "feel" for my plane.

In my excitement to get flying I forgot to take any 2200 batteries to give me that extra wind stability, but I didn't really need them.  I found this Su35 with this configuration flew as well in the wind as my stock one did with the extra weight of a 2200 battery and empty this plane and my old one are identical in weight.  Unfortunately I no longer have my old one as too many "gonks" forced it into retirement.

It also felt much more stable and smooth in another very important phase of flight...approach to landing, very smooth and stable even with a wind.

The extended Kfs and kicked out vertical stabs might be causing a tiny bit of drag, but I will take a small loss of top speed for increased stability any day!

I noticed no problems with tip stalls or thrust vectoring stalls, the two areas where I tended to get myself into trouble with my old stock Su35 MK2, so I am very happy with that.

I have a lot going on here with all these mods and after only 9 flights it is tough to tell "what is doing what", but no matter, all these changes just work so darn well together, if I never figure it out, I'm not worried, it just works!

I have considerably more testing I want to do, but mostly different control surface configurations with the aileron being used as spoilers, flaps, spoilerons and flaperons, better to do those on a calmer day perhaps.

So lots of fun to test out a few different things on this amazing plane and nice to be able to soften and stabilize it a bit to allow me to keep up with it a little better... :)

Here is a walkaround and maiden flight video I shot yesterday.  The flight portion is not the best, mostly white plane gets washed out against a white/grey sky quite a bit... :/


Cheers,

Scott

Friday, April 4, 2014

FRC SU35 MK2 TEST BED PLANE COMPLETE... :)

Hi everyone -

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







Thursday, April 3, 2014

300th FLIGHT OF MY RC POWERS F18 V3... :)

Hi everyone -

Special day at the field today, I flew the 300th flight on my RC Powers F18 V3!  A year and a half ago when I first started building and flying RC parkjets, I wasn't sure I would get to 300 flights total, never mind having one plane that has 300 flights!  Much of my early parkjet career was build, fly, crash, repair, fly, crash, build another one, fly crash and....repeat!

Zero flights -


300 flights -


She is definitely showing a little wear and tear and isn't the prettiest plane in my hangar, but she just flies so darn good!  Although the Mig29 V3 is my favorite parkjet of all time for it's versatility in weight, wing loading, power setups, aerobatics and low and high speed stability, it is the F18 V3 that truly allowed me to take my flying skills and confidence to a new level.  As I mention in the video below I fly this plane lower and tighter to myself than any other plane I have ever flown and those skills and confidence have bled over into how I can fly all my other planes as well.

I shot some flight footage to commemorate the occasion 



I hope to continue to have many more enjoyable flights with this amazing plane, love the RC Powers F18 V3!

Cheers,

Scott