Freewing Su-35 Twin 70mm 12 blade

[C17loadmaster]

Hi all,

new on this forum, first message.
I bought the SU-35 about 4 years ago, second-hand, from a guy that was afraid to fly it. I find it ironic that he sold it to a woman that's not afraid of flying it :-)
It did take me a while too before I dared committing it to the skies, but once I maidened it, I was really impressed with it. First few flights went great, first landing (before the cameras of national television, no less) was textbook, as if there was nothing to it. This is such a great flyer.
But on the tenth flight or so, I made a huge mistake when turing downwind with too little airspeed, and down she went, right into a tree.
At first sight, I thought it was a total loss, but I took all winter to restore it completely (the inlet ducts had to to be rebuilt from scratch), and now she's in full flight status again.
I did upgrade the motor, keeping the original 6-blade EDF units, and I almost get a 1:1 thrust-to-weight ratio now.
Great to find some more SU-35 fans here, I'll be reading up on this thread first.

Welcome to the thread:Cool:
I read your blog about this plane, your maiden, crash and repair. I don’t know where, I just remember your story. Your repair was pretty cool. I have learned a lot of repair techniques working on this plane. I have repaired 2 fuselages that I also thought were destroyed (That’s how I saw yours). The Fuselage is very weak forward of the mains, to be as light as possible, but I like the way it flies heavier anyway so I strengthen mine. I fill the entire open space with spray foam insulation. It’s probably the most efficient and quick way to add support. Though once it’s in, it’s not coming out. I’ll add a pic of the test fuselages
I don’t know how you guys use TV on takeoff from grass. That’s why I have so many wrecked fuselages. Once I had TV selectable on a switch, I have had great luck. I think most of us use F-15 gear on this thread, which are awesome. If you land hard or a high AoA they will compress low enough that the wooden strakes will contact the ground, though it doesn’t hurt anything on grass. I added intake inlets as well, but tried to have it more scale. I don’t know if they actually add thrust in flight haha.

Viper-
If you want to swap planes I have a spare in the box. I would end up repainting it anyway. The only issue is shipping cost...

Also, if anyone on here needs parts let me know. I sold 2 complete power systems already but I have a bunch of random parts.

[HangarQueen]

I use TV to get out of the grass easily. On landing though, I prefer to have TV off as is adds some pitch sensitivity. Sadly I recently lost this bird while flying formation and trying to land short. I had a hard landing which wrecked just about everything. I do have the yellow / tan camo one in the box though. I may go ahead and build it.

Bummer!
Don't get put off by this mishap...this model flies far too well to keep one in the box.
I have no idea about the damage, but I thought mine was a total loss too: fuselage broken in 3 pieces, one wing ripped off, inlet ducts destroyed, etc, etc. But she flies again!

I found the TV to be a great added value, I leave it on all the time. I found coming in steep enough and with enough AoA (nose up attitude) makes landings a breeze. The only time I got into trouble during the approach I described above, was not due to TV (it saved me from this mess), but from coming in way too shallow an getting nervous on the controls.

Did you check the thrustline of the nozzles during flight?

[xviper]

I use TV to get out of the grass easily. On landing though, I prefer to have TV off as is adds some pitch sensitivity. Sadly I recently lost this bird while flying formation and trying to land short. I had a hard landing which wrecked just about everything. I do have the yellow / tan camo one in the box though. I may go ahead and build it.

Like you, I need the TV on high rates to get off the grass. When I land I just flip the ELE to low rates and keep the TV on. Doesn't seem to be a problem.
Love those back flips. You ain't gonna do those without TV.

[seaviper]

I use TV to get out of the grass easily. On landing though, I prefer to have TV off as is adds some pitch sensitivity. Sadly I recently lost this bird while flying formation and trying to land short. I had a hard landing which wrecked just about everything. I do have the yellow / tan camo one in the box though. I may go ahead and build it.

[HangarQueen]

I did a static thrust measurement last year, once with a cold battery, and compared it to a warmed (40°C) battery.
Battery used: Turnigy Nano 65 5000 mAh.
EDF system: stock 6-blade EDF unit with Dr Mad Thrust Series motor B2970 - 2600kv (37 Euro/piece)

Cold (room temperature) battery measurements:
- thrust 3,22 kg, down to 3,17 kg after 5 sec. Current: 130,1A -> 120A after 5 sec.

Warm battery (after 10 minutes in the warmer bag), not recharged (charge at 90%)
- thrust 3,45 kg, down to 3,28 kg after 5 sec. Current: 141A -> 132A after 5 sec

I thus get a thrust increase of 7%, and almost 1:1 thrust-to-weight ratio (AUW is 3,57 kg).

Before the crash, I was afraid to use the TV, but in hindsight, it could have saved me from a crash.
Someone convinced me to keep the TV on at all times, he ensured me that it doesn't give any nasty side-effects. And so I gave it a try for the re-maiden after restoration.
I kept one insurance though, by putting the TV function on/off on a switch, and asked a fellow club member to operate that switch, should I yell in pure panic and horror that I was flying a powerdrill instead of a model. But it wasn't necessary....it flew just wonderfully, just like before, no twitchiness or anything, just "different".
By different, I mean more agile, without being nervous on the controls. This model is an aerodynamic miracle on its own, with a speed envelope unlike any aircraft or model I've ever flown.
Last fall, I mad a terrible mess of my landing approach, and did my best to make it worse as I approached the runway threshold. The TV saved me brilliantly as I pulled the nose up too sharply (to avoid hitting the ground). Luckily, I opened up the throttle, and I saw the model almost hovering above the runway, giving me all the margin I needed to save the day and go around. Wonderful stuff.

Another thing is the main gear.
I had no complaints of it, as long as I operated on a concrete runway (another club), but that runway didn't offer too much of slowing down the model after landing, making me overrun almost every time into the grass.
I decided to add some electric brakes during the restoration. The re-maiden after restoration was in a club closer to my home, and has a grass runway, so that was another unknown for the first flight.
Takeoff went well, albeit with the notorious "jump off the ground" type of rotation.
Being nervous, I landed kind of hot, and I used the brakes for the first time. They sure were effective, stopping the aircraft immediately.
When I swapped the battery and trying to take off again, I had to abort the takeoff. It pulled strongly to the left and didn't really accelerate. Quick inspection showed the both main gear legs were seriously bent and even twisted. This was very surprising, since the landing wasn't really hard on the gear. In hindsight, I'm convinced it was the braking action that put a serious stress on the gear.
I replaced the main gear with the Freewing F15 struts, and removed the brakes (I don't really need them on grass, and they cause more damage than a runway overrun).

Currently, I'm replacing the inlet cheater holes with some 3D-printed grills.

I'll be doing more static thrust measurements to see the difference with the original cheater holes (mine were extremely crude after the restoration).

[Alpha]

Welcome to Hobby Squawk, HangarQueen! Nice to have you here.

The Su-35 remains a good flying bird despite its age. Which motors did you "upgrade" in the original 6B EDFs? Are you flying full TV, partial, or none at all?

[HangarQueen]

Hi all,

new on this forum, first message.
I bought the SU-35 about 4 years ago, second-hand, from a guy that was afraid to fly it. I find it ironic that he sold it to a woman that's not afraid of flying it :-)
It did take me a while too before I dared committing it to the skies, but once I maidened it, I was really impressed with it. First few flights went great, first landing (before the cameras of national television, no less) was textbook, as if there was nothing to it. This is such a great flyer.
But on the tenth flight or so, I made a huge mistake when turing downwind with too little airspeed, and down she went, right into a tree.
At first sight, I thought it was a total loss, but I took all winter to restore it completely (the inlet ducts had to to be rebuilt from scratch), and now she's in full flight status again.
I did upgrade the motor, keeping the original 6-blade EDF units, and I almost get a 1:1 thrust-to-weight ratio now.
Great to find some more SU-35 fans here, I'll be reading up on this thread first.

[C17loadmaster]

Yeah, I have them set for slow, thrust vectored flying. I fly off grass with trees surrounding me (golf course). I learned the hard way with using TV on takeoff and gaining altitude after rotation. The TV would put the plane in the air too fast and I would stall 5 feet above the ground and float around with the nose pointing straight up until I finally gave up, pulled the throttle back, and let the nose snap off the fuselage haha.

Now I fly with TV and high rates on a switch that I only select when at the appropriate altitude. Also, it took a good flight or two to realize the control surfaces need hardly any throw. It’s very sensitive to inputs, especially without expo. As far as using rudders as an airbrake, I won’t ever use it on the SU. It lands slow enough... it might be cool just to have, but definitely don’t need it

[xviper]

I think another factor that must be considered is that most of these planes with "linked" AIL/ELE are of the swept back type, where the trailing edge of the main wing is very close to the elevator. In cases like this, the combine deflection of both control surfaces (in the same direction) increases the push on one side of the fulcrum. Now, if you had a more standard wing (more straight), then what you say may indeed be the case. However, in these swept wing planes, applying force with linked control surfaces immediately pitches the plane up, making it a giant airbrake and almost stopping the forward speed. If the control surfaces were not linked, this effect would not be nearly as pronounced and the maneuver not nearly as spectacular. That's when the VT nozzles flip the plane over, doing a stunt that is quite remarkable and very entertaining to see. Even in cases where there is no VT, the effect is still dramatic. Having a couple of these swept back, linked planes, the straight thrust, along with the linked surfaces make for a very entertaining plane. Without the linked surfaces, they are just another very boring plane. Again, it's all about what you want the plane to do and sometimes, this voids the usal ideas of what the aerodynamics of flight might be. Finally, an RC aircraft doesn't always do what you might think a real one would do.
I'm going to have to disagree with the high bank angle turn (flat circle). In the middle of such a circle, if I yank on the ELE hard and fast with linked surfaces, the plane will do a horizontal back flip very quickly without using up any forward distance to speak of and only losing a small amount of altitude, then straighten out and continue the circle. It's the strangest thing to see.
Now, after having said all that, here's a video of some Russian jets doing the cobra maneuver. At about 1:45, you see a real Mig 29 initiating a Cobra. Note that BOTH the ailerons and the elevators are going in the same direction to initiate and continue this maneuver. Right after this, it shows an SU-35 doing the same thing but the video is too fuzzy to see the control surfaces but I have no doubt hey are doing the same thing.

[TangoVector]

Thanks for the response!

There are two different things to talk about. One is the speed-envelope where the wing creates lift, the other one is at very slow speed, where you want the plane to swap ends with the help of TV an inertia.
My thinking was about lift for turning tighter, I guess that what you want is in the low speed, past "turning tighter", and it is about to reduce the drag of the wing when backflipping through the air at right angles. In that case moving the ailerons up with elevators could work.

When it comes to the F8, look at this picture:




The linked ailerons are in the wrong direction. The elevators are trying to increase the angle of attack on the wing, while the ailerons are lowering the AoA, just look at the angle the elevators are at to make it fly. If the ailerons where moving in the other direction they would actually help. In a roll though, they should look like that on one side and opposite (down/down) on the other side.

So for turning tighter with airspeed: Ailerons down / elevators up and vice versa.
For rolling all speeds: Aileron down / taileron down and aileron up / taileron up.
Backflips: Ailerons up / elevators up

[xviper]

If you really want the ailerons to help,

It depends on what it is that you want to "help". Take for example, the latest versions of Freewing 64mm EDF like the Crusader and Thunderchief and the HobbyKing SU-35. All of these are designed to have the ailerons and the elevators connected so that they work in unison. The wing type is set at "elevon". When one goes up, so does the other. This "helps" the planes to do incredible rolls and "helps" to do loops in a very tight space. These are planes where the ailerons and elevators are quite close to each other along the length of the plane. My SebArt Mig 29, with thrust vectoring but NO linked ailerons and elevators can do a loop in a very tight circle. If it also had the ailerons and elevators linked, I'm sure the Mig could do a loop within its own body length. It looks like the thing does a back flip or a front summersault. My HobbyKing SU-35 is a mid-prop pusher and it can do a loop almost within its own length. I believe that's what these fellas are trying to do with their SU's. Even without linked control surfaces, my Freewing SU-35 can almost do a back flip with the TV alone. Linking the surfaces would make it insane. Having the ailerons and elevators work in opposition would fight the TV nozzles in trying to do a back flip.

At ~0.55 in this video, you can just make out one of those tight loops on my Mig 29. Near the top of the loop, the plane almost stops flying and completes the loop with very little airspeed. If it had the ailerons and elevators linked, it could have done a back flip virtually dead in the air.

[TangoVector]

On my flying SU I swapped out the RX from 10 to 12. Now I have it programmed to function the way I wanted it to. Including tailerons that active on flaps and in “demo mode” with TV. I also have the ailerons both move up together when pulling up the elevator and both moving down in conjunction with down elevator.

If you really want the ailerons to help, they should be the other way around. When dropping the ailerons like flaps, they increase the wings angle of attack, which is what you do with the up elevator. Having the ailerons going up decreases the AoA and is counterproductive when pulling up in the same way as ailerons going down is not helping when pushing down.

My SU is still in the box, for a little while longer, but when it comes out, I think tailerons is on the list and maybe airbrake rudders. Have you tried having the rudders deflect outward as an airbrake?

/Tobias

[C17loadmaster]

I am still working on my unflown SU. I’ve been distracted with other planes and I don’t want any mistakes. It’s taken way longer than I thought. I couldn’t tell how much work has been done until I pulled out my flying version and compared the two. I’m about done with paint and moving on to assembly.

On my flying SU I swapped out the RX from 10 to 12. Now I have it programmed to function the way I wanted it to. Including tailerons that active on flaps and in “demo mode” with TV. I also have the ailerons both move up together when pulling up the elevator and both moving down in conjunction with down elevator. It should be able to do things that I will never be able to master. I can’t wait get it out and fly it.

Ill post pics when I’m done with the Inrunner version.

[C17loadmaster]

I have pitot airspeed, dual rpm and temp sensors (one for each motor/esc), altitude, lipo sensor, and RSSI. I also programmed a switch on the transmitter to take a screenshot of the telemetry screen for logging purposes.
I forgot to do the screenshot on that flight. I imagine she would do about 110+ flat out.

I remember that now. That’s pretty cool

[seaviper]

I have pitot airspeed, dual rpm and temp sensors (one for each motor/esc), altitude, lipo sensor, and RSSI. I also programmed a switch on the transmitter to take a screenshot of the telemetry screen for logging purposes.
I forgot to do the screenshot on that flight. I imagine she would do about 110+ flat out.

[C17loadmaster]

You have speed telemetry? I saw previous posts of your telemetry data, I'll take a closer look. I have a GPS speedometer but that will give you the highest speed attained... So in order to get a good "level flight" reading I would have to take off, climb, do a speed run in level flight without descending, deploy flaperons, and land haha

[seaviper]

Yes she has stock power. I forgot to take a screen shot of the telemetry. But her previous high speed was 107. Yesterday she did 109. I still did not fully open her up. I know she can go faster.

[C17loadmaster]

On the stock power system? I didn’t know that the stock outrunners should be using 80a ESCs

[seaviper]

Flew the Su-35 today three times. Hit 109 mph. Not bad.

[seaviper]

I didnt do supports on the verticals. Mine are sturdy enough i think.

On the l39 and the su35 i prefer the heavier batteries. Right now i am flying with the turnigy heavy duty batts. That twin 70 will eat batteries for lunch. I keep the su35 to 3 mins or less. The flights are short but still a lot of fun.

i have the yellow one in the box. Its for sale. But if it doesnt sell i will use it for spares.

hopefully i can fly mine this weekend