Freewing Su-35 Twin 70mm 12 blade

[xviper]

I'm almost done mine. Did some reinforcement of the battery hold down area, reinforced the little nose strut brace thing and glue in a piece of wood where it comes to rest so as to take up that space. Maybe that brace can actually act as a brace. Did all the mixes for the nozzles and will eventually install an A3-L HobbyEagle gyro, mainly to help with the rudder vector nozzle servo. I may as well hook up the ailerons and elevator, too. All's left is to put in a couple different batteries and mark where they have to sit to achieve the desired CG. Then hang it up till a nice day comes. Winter is almost upon us so may not get to fly it till spring.



And a picture of that rudder decal that's backwards.

[C17loadmaster]

The brace clips in at the strut connector and fits in the rail system where you put the wood. On the strut side you have to drill it out and run a small bolt through where it clips together. If it’s not secured with a bolt and nut it will fall apart before you get airborne. If not then... then definitely on landing. I can post a picture

[C17loadmaster]

There is a picture showing it done on mine.

[xviper]

I put a zip tie around that clip. I'll see if that holds. If not, I'll do the nut and bolt.

[seaviper]

My CG check flight yesterday.

After trying just about everything, and after having numerous aborted takeoffs in thick grass, I have settled on the use of both flaps and TV for takeoff. Hopefully this winter our runway will improve.

Gear are holding up so far. 16 flights.

[seaviper]

just noticed the link above is broken. Su-35 stuff here

https://www.youtube.com/playlist?list=PL_b2Jx8sY5ndfG-HlyAPALvTbRsbWtfNA

[Sam CB]

Hi guys! Thank you for starting this post. My second SU on its way from MotionRC and scheduled delivery on Monday, Oct 8.

Unfortunately my formation flight didn't go so well. We weren't flying jets, just ww2 birds but, still pretty cool video. My P47 went up in the air the next day, minimal damage, my buddies Spitfire broke in half.on impact and took some work. He had no control after we collided because my p47 cut his elevator linkage.

https://www.youtube.com/watch?v=kMyS8DLkuV8

(This is my friend's channel btw.)

Regarding SU, i wrecked my first model this summer, in fact, the 4th flight took place just 2 weeks ago. This time, it will be a winter project as it sustained significant damage, basically my front end is gone along with intakes. Stalled on failed landing and took a nose dive in to the pavement..
After watching hours of videos on youtube, i realized my mistakes. I wish i would have done this before my last flight... oh well, lesson learned.
One thing that i still can't get a grip on is that all surfaces were aligned by the book, TV aligned by the factory marks. Elevator at 11mm. CG was at 155mm (with gear down). Also, i noticed that my servo travel on the elevators were different. Left had more travel than right. During my first flight, i noticed that i have insane amount of "down thrust", i attempted to trim (was not using TV on first flight). After trimming elevator, i tested flaps, deployed flaps and nearly hit the ground as it had strong nose down effect. At the time i didn't know that i would get this kind of response from the plane. I am used to flying ww2 birds and normally on flaps down aircraft flares up.. not down lol. So, now i know that jets have reversed effect on flaps down. One thing for sure, why do i get so much down thrust (not talking about flap effect, just standard in-flight with flaps fully retracted)? Is that normal and what is the workaround?
By the way, viper, you mentioned ratio flaps to elevator, sorry i can't find it right now but, as i recall it was 5% and 3%. Please correct me if i am wrong and does that mean you have 5% at full flap which is how many mm down? and 3% at half flap? Are you able to provide measurements please?
When landing, are you in full rate or low rate? I understand i need lots of elevator authority during landing, is that right? I will also reprogram to have flaperons to disable while in flap mode.
What do you use to know if you are balancing at 165mm and is that with gear down or up? I used fishing line to hang the SU and moved the battery until i got it hanging leveled of the ground.
I am also a big fan of FrSky. I fly Taranis X9D+, only i use R9 and EagleTree Vector for FPV. Not planning on flying high or far, just enjoing FPV fixed wing flights very much.
Sorry i am very tired right now and i know i had lots more to ask. I will comeback to it tomorrow with a clear head.
By the way, i moved my stock ESCs into the intakes, had to make cut-outs but worked great. If you want i can share pics.

[xviper]

Also, i noticed that my servo travel on the elevators were different. Left had more travel than right.

During my first flight, i noticed that i have insane amount of "down thrust", i attempted to trim (was not using TV on first flight).

After trimming elevator, i tested flaps, deployed flaps and nearly hit the ground as it had strong nose down effect. At the time i didn't know that i would get this kind of response from the plane. I am used to flying ww2 birds and normally on flaps down aircraft flares up.. not down lol. So, now i know that jets have reversed effect on flaps down. One thing for sure, why do i get so much down thrust (not talking about flap effect, just standard in-flight with flaps fully retracted)? Is that normal and what is the workaround?

By the way, viper, you mentioned ratio flaps to elevator, sorry i can't find it right now but, as i recall it was 5% and 3%. Please correct me if i am wrong and does that mean you have 5% at full flap which is how many mm down? and 3% at half flap? Are you able to provide measurements please?

When landing, are you in full rate or low rate? I understand i need lots of elevator authority during landing, is that right? I will also reprogram to have flaperons to disable while in flap mode.

What do you use to know if you are balancing at 165mm and is that with gear down or up? I used fishing line to hang the SU and moved the battery until i got it hanging leveled of the ground.

You covered quite a lot of stuff. I'll try to answer as best I can from my own opinion and perspective.

On planes with two elevator servos, it's not always possible to have the arms at exactly 90 degrees when centered. You'll usually notice that one side will be slightly different than the other side. This is because the teeth on the mounting cog aren't small enough to do a fine enough adjustment so that both sides are exactly the same. You can compensate for this to some extent by putting each elevator servo on separate channels so you can do a minor "sub-trim" but even then, it's not going to be exact from one side to the other. You'll max out one side before the other and that's why the travel can be different. This happens more when you are at "full stick". You can minimize this by not going full stick. Try reducing the travel by 5% or 10%.

By "down thrust", are you meaning the nozzles are pointed up so as to push the tail down, making the plane pitch up? If it's too much, try using sub-trim on each nozzle to get them to a more desirable angle. If you use the marks on the nozzles, that should make them where they ought to be. If you're talking about the elevator setting, this too, can be trimmed better either via the TX or manually by adjusting each rod.

I'm a little confused when you say "flaps". This plane has no flaps. Are you talking about flaperons? Also, if you are using flaperons, slowing down the deployment to 3 to 4 seconds per step will reduce the tendency for the plane to change attitude.

It's wrong to assume that jets have the reverse affect on "flaps down". This is not always true. Each jet has its own characteristics and those with actual flaps can "balloon" or they can nose dive. It all depends on the shape of the wing. This SU does NOT have actually flaps. Programming flaperons can be a bit dangerous if you don't watch out for how much flaps you dial in. Since they are also used as ailerons, you can easily over-drive those servos and strip them.

It wasn't me who mentioned about flaps to elevator mixing since I've never used flaperons on this plane. Again, you must be careful. You said your plane nose dives when you deploy "flaps". In that case you do NOT want any down elevator compensation as this will aggravate the nose dive. On a Spektrum Tx, possitive % on the elevator - flap mix is down elevator as this is to counter a ballooning effect. If your plane is nose diving, then you want negative % for the compensation, if it were a Spektrum Tx. I can't speak for FrSky.

Each person is different. I land most of my planes (prop or jets) in low or medium rates. I don't recall that this SU needs a lot of elevator authority to land. If it's trimmed properly, it should be quite controllable during landing on low to mid rates. Remember, you've got those nozzles to vector. These can come into play when landing if you so desire.

You have to ask yourself if this is a "high wing" plane or a "low wing" plane.

(See my post #90 for an edit to this point.)

---

As for balancing with wheels down or up, my logic says ........................ "Do you fly the bulk of your flight with the wheels up or down?" I want my plane to be well balanced and trimmed during flight so I balance with wheels up. When taking off or landing, I'm more on the sticks flying the thing to control it better during those "delicate" times. When it's flying around with the wheels up, I want it to be able to fly "hands off" (neutral) most of the time. It won't do that if you've balanced it with wheels down. But each to their own.

[seaviper]

Hi Sam,

Thanks for posting on the thread. Xviper covered most everything. But I would like to add that on mine I do in fact use flaps. I have it programmed such that when flaps go down, either notch 1 or notch 2 (3 way switch), the ailerons no longer function and the tailerons take over. I found that flaperons did not do a good job of rolling the aircraft when flaps were out. But tailerons did.My aircraft did have a slight nose down tendency with flaps. I just added a very small amount, like 1 and 2% I think, of elevator to flap mixing. In my CG check video and in the Flaps Test video, you can see she makes a fine power-off landing. I was basically gliding all the way in. You can see in the CG video, on the first and last screens, the flight controls on landing. It takes very little elevator to hold the nose up.

Now, as for CG, I think the manual screwed up. Just my opinion. I think they should have measured along the joint where the wing panel meets the fuselage. The book shows something a little different. It doesn't matter though. You want your elevator in that range of 10-13mm. Mine is at 11mm. My CG is 165mm from the point in the book. But it's about 145mm measured at the joint. I will make a video on that. My Admiral 5000 rides all the way fwd to the bulkhead. The Turnigy 5000 rides 1" aft of the bulkhead.

As far as rates go, I don't do rates unless flight testing. I run about 40% expo and full travel on most surfaces unless flight testing shows that I shouldn't. On the nose wheel steering I run full travel (separate channel) and 70% expo. It softens up the center but gives me full throw for that turnaround at the end of the runway.

I have another SU-35, the yellow one, in the box. I am doing a complete build, tuning, and Taranis programming video series on it. I will also take it to the field and discuss flight tuning. This is coming up over the next few months. Maybe that will help you have success on the next one. Xviper, myself, and C-17 have all tuned and flown these things. You came to the right place.

Have a nice day <Salute>

Edit: Loved the video.Nice flying!. Can you fix the P-47?

[xviper]

Edit to post #88 regarding balancing right side up or upside down........................

I just looked at my SU and my marks are on the top, which means I balanced it upside down. (With 44 planes, I forgot how I did this one). This plane is more of a "mid wing", so when I tested which way provided the best stability (less teeter totter effect) when held at the marks. I guess for this plane it was upside down because I felt more of the plane's mass was above the wings.

[xviper]

Regarding "flaperons" ..............................
Of the planes that I own or have owned, 3 do not have actual flaps and those 3 I found needed them. First was my 90mm F-16. I programmed flaperons and tailerons. This helped shorten the take off run and slowed it down a bit for the landing. The second one is the 70mm F-16. This one has standard elevators for an RC model, so tailerons would not have worked well since the elevator control surface is small. I kept the flaperon deployment smaller. Finally, on my FlexJet, flaperons really helped to slow it down for landing. Take offs weren't a problem as it has plenty of power to get off the ground easily. I will, over the winter, cut actual flaps into the very long ailerons. I don't like flaperons on a plane for the reason I gave earlier. On all these planes, flap deployment is quite slow (around 3 to 4 seconds) and there are no adverse pitching when deployed and any small effects are easily dealt with manually. Just remember to slow the plane down a bit first as you deploy. Slamming them on at speed with no deployment slow down, will generally always cause an upset in pitch.

[seaviper]

I agree on the flaps.I always use a 3 second deployment on flaps. But in this case, since I was disengaging ailerons and engaging tailerons too, things didn't jive. So I just didn't use any slow-down on the flaps. My Su-35 flies fine. I don't see any pitch change with flaps. Gear cause a little nose down I think. Most folks who have a problem with flaps are deploying them at mach 2.

The flaperons on this bird, by themselves, don't provide a very nice roll. It's more of a weird dutch roll kind of thing. The tailerons cleared that right up.

It really doesn't matter whether you balance right side up or upside down. Just use whichever method is easier to balance without dropping the bird. Full scales are just weighed at each wheel. It all works out the same. The gear on this one moves back a little when extended. So I like to balance these kinds of birds with the gear down. That way I know that the CG I am seeing is the farthest aft it will be. When they retract, the CG moves fwd a little. This bird is like the F-15. It has such a large CG range that I doubt you will get in trouble with CG.

As for the thrust vector alignment, take your time and make sure that thing is right dead smack on the edge of those marks. Look all around the gimbal and make sure all marks are right on the money. I also add in about 40% expo on the TV.

Maybe I will get to fly her again tomorrow. We just got a new Sony 4k video camera. So hopefully the video will be better than the last time. We will see.

[C17loadmaster]

Regarding "flaperons" ..............................
Of the planes that I own or have owned, 3 do not have actual flaps and those 3 I found needed them. First was my 90mm F-16. I programmed flaperons and tailerons. This helped shorten the take off run and slowed it down a bit for the landing. The second one is the 70mm F-16. This one has standard elevators for an RC model, so tailerons would not have worked well since the elevator control surface is small. I kept the flaperon deployment smaller. Finally, on my FlexJet, flaperons really helped to slow it down for landing. Take offs weren't a problem as it has plenty of power to get off the ground easily. I will, over the winter, cut actual flaps into the very long ailerons. I don't like flaperons on a plane for the reason I gave earlier. On all these planes, flap deployment is quite slow (around 3 to 4 seconds) and there are no adverse pitching when deployed and any small effects are easily dealt with manually. Just remember to slow the plane down a bit first as you deploy. Slamming them on at speed with no deployment slow down, will generally always cause an upset in pitch.

I have the same exact setup for 90 and 70mm F-16s and they work well. On the SU-35 I also use flaperons but in order for them to be effective enough without tailerons, I have to switch to HIGH rates when I get setup for landing. So I actually have to select 3 different switches to get the plane in landing configuration. It slows down to a good landing speed and just floats in with little throttle.

I am using a 10 channel receiver and each of the TV servos take up channels so I have one spare channel. It could be the other elevator for taileron use, or a gyro on/off. I have it hooked up to a HobbyEagle A3S3 gyro. All I need is one more open channel to be able to set it up the way I would prefer.

[seaviper]

Hi guys! Thank you for starting this post. My second SU on its way from MotionRC and scheduled delivery on Monday, Oct 8.

What do you use to know if you are balancing at 165mm and is that with gear down or up? I used fishing line to hang the SU and moved the battery until i got it hanging leveled of the ground.

I just read where you used fishing line to hang the model. Not necessary.

Look in the manual. They show you where to measure CG. Then just use your fingers. That's all I do. It's worked for me for many years.

I use a tape measure and a pencil to mark the point, then use my fingers to balance. Simple and easy CG machine. After the first flight you can start fine tuning your CG. The goal is to have zero trim and the elevators practically neutral. All models are a little different though. In the case of the Su-35, they want the elevators between 10 and 13mm LE deflection because of the long LERX (leading edge root extension). You could neutralize the elevator completely and move the CG even further back. But you might find she pops up on you because of that LERX. Mine flies real good where I have her balanced. And that is right on that wire channel. But the CG is not critical on this bird. You can go way up or back from there.

https://www.hobbysquawk.com/forum/rc-airplanes/jets-and-edfs/150680-freewing-su-35-twin-70mm-12-blade?p=153997#post153997

[C17loadmaster]

As far as CG, I just put the battery as far forward as I can, like Sea viper, and have my receiver in the same place (behind the battery tray). I didn’t need to do anything else to adjust the CG, but my ESCs are in the normal spot. I use both 5000 and 6000mah packs weighing 725 and 810 grams. The plane flies fine on both, but lands a lot easier with the bigger 6000s. I have seen where people have cutt open the bottom of the nose (just forward of the nose gear bay) and added 100g of weight.

[xviper]

As far as CG, I just put the battery as far forward as I can, like Sea viper, and have my receiver in the same place (behind the battery tray). I didn’t need to do anything else to adjust the CG, but my ESCs are in the normal spot. I use both 5000 and 6000mah packs weighing 725 and 810 grams. The plane flies fine on both, but lands a lot easier with the bigger 6000s. I have seen where people have cutt open the bottom of the nose (just forward of the nose gear bay) and added 100g of weight.

That is interesting information. I will likely use the Turnigy heavy duty 5000's. I guess the 4000's won't balance right without more weight added. I think my hopes of hovering this plane is out the window. It's already a very heavy plane and with a big battery in it, it's going to struggle to hold its own weight up.

[seaviper]

Yeah Xviper I'm sorry man. I don't think you can hover her. Maybe at the beginning of the flight with a lightweight Admiral 4000. I don't know. But I have my CG setup where the 5000 goes all the way forward. Doubt a 4000 would get you anywhere.

On a happy note...I did get to fly mine today. She hit 99mph and I wasn't even trying. And she flew so smooth. I love the Su-35. Hopefully we got some usable footage with the new 4k video camera. If the footage is ok, I will post it.
Maidened the L-39 today. Man what a sweet bird that is. film in the can

[C17loadmaster]

Yeah Xviper I'm sorry man. I don't think you can hover her. Maybe at the beginning of the flight with a lightweight Admiral 4000. I don't know. But I have my CG setup where the 5000 goes all the way forward. Doubt a 4000 would get you anywhere.

On a happy note...I did get to fly mine today. She hit 99mph and I wasn't even trying. And she flew so smooth. I love the Su-35. Hopefully we got some usable footage with the new 4k video camera. If the footage is ok, I will post it.
Maidened the L-39 today. Man what a sweet bird that is. film in the can

I’m curious to see how the new FW EDF units feel. I have purchased 3 so far but have yet to fly (too many projects) they are the same weight as the last generation of fans but produce significantly improved thrust at the same amp draw.

I read to be very careful using 4000s in the SU... yeah it will be lighter, but many have said the plane becomes almost un-flyable. Way too tail heavy

[C17loadmaster]

I am almost ready to maiden my SU-35 project plane... I have 2. This one has the 2210kV Inrunners and twin 80a ESCs. I have been working on it slowly to reinforce the weak areas of the fuselage and overall making it as awesome and reliable as I can. I will only use 6000mah batteries on this one so I can get the same flight time as if it were stock. I will have my wife record the maiden. I lost my "flying field" yesterday because too many people were complaining of the noise. I fly almost daily from the golf course that's 1/10 of a mile from my house via golf cart. There are literally no areas close for me to fly... There is an awful pavement only flying club where I work an hour away but its always very windy and the runway is an old unmaintained neighborhood road on a closed section of Beale AFB. Its actually on the RealFlight simulator as "Beale Blackbirds" as an option for flying the simulator.

[seaviper]

Good luck on the maiden. Take it easy and bring her back safe