Freewing Su-35 (Vendor-independent; please read 1st post and stay on-topic) - Page 322 - RC Groups
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Nov 02, 2012, 11:08 PM
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fredmdbud's Avatar
That's the fun of tweaking and flying. You don't have to be able to explain it - if it works, it works. The Chinese modellers did all the hard work for you, just assemble and hit the throttle!
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Nov 02, 2012, 11:28 PM
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Something PeterVRC said bring back what I was doing when setting up the vectors. I started with the first one in the instructions (vector 1 mixing to Rudder channel) only one of the nozzles would move. Going to set up the vectors with a Rx battery. Trouble maybe one of the vector servos
Nov 02, 2012, 11:28 PM
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acesimmer's Avatar
Holy Crap Batman!.... I saw less technical crap when flying the real jets. Good to see though
Nov 02, 2012, 11:55 PM
You are a "go" for reentry
Maxthrottle's Avatar
Well Fred I stand corrected. My read up was it initially had in only certain plains and limited conditions not near the suite we see today. I'll go back and look at my research. That still doesn't change much though. Many of the carrier aircraft in the late 70s early 80 using flapperons pre FBW of the F-16, did so manually as does civil aircraft today. Its still not special magic to set the lift condition of the wing and control with the tailerons.

After all as I said the turbine guys are doing it all the time.
Nov 03, 2012, 12:07 AM
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What has any lift co-efficient got to do with the discussion about pitch angle caused by flaps and/or slats?
(Plus you can see how slats are quite different to leading edge extensions angling downwards a quite a sharp angle - 30 to 40deg)

If you take a wing and add 'slats' - or rather, whatever the Su-35 has and are called, but I will call them slats - the wing takes on a new chord, and chord line. The chord line now runs (approx) from the bottom edge of the slat, to the trailing edge of the wing. That is a greater downwards angle than it was before the slats.
The wing can't operate at the normal AoA it had before slats, so it will pitch up to the equilibrium point of the new chord. This is whether the slats runs full length on the wing or not - it will all just equalise somewhere, of at least some level of pitch upwards.
The elevator may not even need to be moved at all... or it might need to be... in the grand total of this new balance. Whatever that flight dynamics balance ends up, that is what it is.

If you take a wing and only add flaps... or long aileron/flaperons, the reverse happens. A new chord line runs from the wings leading edge, to the flaps trailing edge - which is lower down now. The wing now needs to pitch DOWNWARDS to operate correctly.
So the aircrafts AoA will be more negative than before.

Throw in both slats and flaps, and the end result depends on the angle/area of both sets. Of course they would design and test the whole system to do as they require - not just a willy nilly addition of size/area.

Those pics showed the Su-35 coming in to land (or slow pass-by flight, which uses the same process anyway) and the elvator is at is "fuselage neautral' point. (not the line of flight tneutral).
That doesn't actually mean anything much in terms of what aerodynamics 'must' cause what really, it is just the result of the balance of all factors. And in another aircraft design it might need up elevator, or even down, for the final balances all to be as desired.
It just so happens (not impossible it is all part of the design, and they test and change etc to get it all optimal) that the balances of the slats, flaps, airspeed required for landing... all aspects of the plane... end up that it flies at that angle, and is maintained at that angle fine by neutral elevator in the Su-35 case.
One thing it does show is the slats and flaps are the ones responsible for this balanced attitude outcome - because there are no other 'new' aspects introduced, and the elevators are neutral so they did not do it.
The plane could also fly that same AoA and manner, for eg, if up elevator was used, possibly with TV, and no flaps or slats... basically a high alpha process.
Flaps will not cause this positive AoA resultant - they would cause pitch DOWN.
So the slats would have to be the biggest factor (and their pitch UP resultant due to their input into a 'new' chord line) in this balance, as they would have to be for the plane's 'equilibrium' upwards pitch to offset the flaps dowwards pitch input.
As mentioned above, there are NO other inputs in play that are different to other than the slats and flaps being in operation now... so they must be the dominant inputs to the result.

In the higher up 'somewhat simplistic' outline of a new chordline, I just said "the bottom edge" of the flap, or slat. In reality is it somewhere from the leading edge to the slat lower edge, and the same for the flap - somewhere from standard trailing edge, to the lower flap edge now. So when the slats and flaps are both down, the line is "somewhere" from that front start, to the rear edge end. It is actually an "effective chordline" and for eg it could run from the very lower edge of the slat, to just one third down the flap/aileron - it doesn't have to be a the bottom of the flap/aileron edge. A complex mix of all the aerodynamics will set where this 'effective chordline' really is. So even though the slat are smaller, they can still input more than the flaps to the new chordline, and thus pitch end result.
Last edited by PeterVRC; Nov 03, 2012 at 12:28 AM.
Nov 03, 2012, 12:19 AM
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Whiskey Whiskey: You're on to something. Reason only one nozzle moved was number one vector labeled lead was not repeat was not servo for moving both nozzles at once. All vector servo's are working.
Nov 03, 2012, 12:38 AM
You are a "go" for reentry
Maxthrottle's Avatar
Originally Posted by R. Mike Neely
Set the voltage????? I believed this to be a plug and play unit. May go to hobby shop and buy another one, will ask them to set voltage to what? Wish I could sent picture, have equipment, not the skills to do it. Rx alright. Removed main retracts and plug directly into reciever, no worky.
The CC Becs are programmable to 10V. But then what battery did you connect to the BEC? They can't generate more volts than what is supplied. And CC BECs handle 6S (Min 5v, max 25.2v) unless you greatly over volt your 6S. They default supply 4.8V.
But if you didn't change that .....
I've plugged in the FW servos and retracts on the wrong polarity many times on my Hitec servo programmer at 6V not paying attention to which way I placed the male radio wire. So even if you switch polarity, I wouldn't expect it to suddenly burn them up let along several of them even at 6V.

Did you have anything plugged into the other side of the RX like the ESC BECs.... Just trying to help you figure out what to look for but until we can tell how you wired it its a guessing game. I love a mystery.
Nov 03, 2012, 12:49 AM
Should've, Would've, Could've
v8truckin's Avatar
Originally Posted by R. Mike Neely
For what it's worth. While trying to set up for thrust vetoring I lost power to receiver. It was suggested that the BEC in the ESC had stop working. Removing the red wirer from the thottle to receiver and adding a small nimh battery and all was well. To save weight deceided to put in a castlecreation 10 amp peak BEC. As soon as I plugged in the unit the cc bec sparked and smoked. Unplug immediately. Now one elevator servo not working, retracts not working gear door not working. Told my sad story to the fellows at our flying field and one said he was told that CC BEC will not work with some of these Chinese servos. I am still planning to get this plane flying. ( for what its worth)
Did you remove the nimh battery before you plugged in the bec?

What size lipo did you use?

Was your bec installed/soldered such as the diagram on the back of the cc bec instructions? Correct polarity?

Did you remove the red wire from the escs y-cable? If not, did you remove it from both escs wires instead as to not have one escs bec still active?

I to have plugged in hitec servos in reverse and have never had a esc, servo, or bec fry. Pictures speak a thousand words and will help a lot. Hope we can help.
Nov 03, 2012, 01:10 AM
You are a "go" for reentry
Maxthrottle's Avatar
Originally Posted by PeterVRC
What has any lift co-efficient got to do with the discussion about pitch angle caused by flaps and/or slats?.....
Sorry I didn't even read everything you wrote because of your first premise.
The tailerons undoes all that seems to be concerning you. So even if a design has any moment influence its AoA is dictated by the stab angle.
I just read some of what you wrote. Again remembe what the approach profile is doing. The entire aircrafts settles into a AoA and as the speed slows what you are correcting with the Stabs is less and throttle management starts to take up both altitude and attitude influence. The datum line the big arrow is trim neutral. But because the approach already has the tail weight low that itself is countering any pitch moment that the flaps may induce. And the LE flaps droop even when the flapperons don't by the way.

A foil shaped wing with LE and TE flaps deployed is simply taking the shape and aerodynamic characteristics of the under camber foil. As such it increases the lift coefficient of the foil and thus slows the aircrafts flight profile. Many think air breaking but just like a under cambered foil, they are high drag high lift. That's all you are doing by flap/flapperons and LE left devices.

Nothing complex about it. You keep looking at the potential foil moment and intense analysis but regardless of what it is, by design, the tailerons/stabilators undoes it. Look at it another way. Even the wings foil itself without the stab creates a pitch moment. Look at a flying wing. The TE has a up turned TE to counter the pitch moment. But on a tailed aircraft the stab takes the roll of countering that. So regardless if you have flap only, TE flap with LE droop flap or even just LE droop flap, what ever it induces the stab is on the tail to set the desired attitude. It was in the glider example and you see it in the determination of any AR.

I'm gonna stop talking cause from what you said you don't even have the plane to try it. So this conversations isn't even for you to actually utilize anything that we're talking about and I'm tired of hijacking this thread.
Last edited by Maxthrottle; Nov 03, 2012 at 01:23 AM.
Nov 03, 2012, 01:12 AM
You are a "go" for reentry
Maxthrottle's Avatar
Originally Posted by v8truckin
...Did you remove the red wire from the escs y-cable? If not, did you remove it from both escs wires instead as to not have one escs bec still active?....
That too is key:
5. Can the CC BECs be run in parallel for very high current applications?

No, switching regulators like the CC BEC will fight each other if used in parallel. A separate component is needed to isolate them from each other. Castle is looking into creating something that will allow you to do this. Stay tuned!
Nov 03, 2012, 02:20 AM
Registered User
I resumed repairs....

I put in the main 'box frame' parts - using epoxy - and it is STRONG. I have not even put in the bulkheads, and might not even use them!
I stopped at the nose gear bay front firewall, to leave some 'weakness' ahead of that. But from there rearwards, to the end of the ESC bay, it is very very strong. So there will be far more to worry about than the 'wing to nose area' if any crash causes detriment because of that strength! It will deal with all 'normal' level stresses, and a bit above, and after that you would be in a serious damage state anyway.

Next, on to the filling and surface finishing.....
And a new better looking, and better scaled, pilot.
I will investigate making it into a single front gear bay door also. The FW pair seem to be a wide opeing, so that might make a single door too big and then it would look amiss.

Nov 03, 2012, 10:39 AM
Registered User
There's a possibility that our retract units are still working. I found this thread just a moment ago:

It could explain why the gear door sequencer was putting out 5V to 0V between the signal and ground terminals during my trouble shooting, while normal servo outputs are in the millivolt range.

Still doesn't explain why they wouldn't work when all connected through the sequencer though...

I have to go to the monthly club meeting before I can research more.

*edit* the sequencer and all three retracts were bad.
Last edited by Whiskey Whiskey; Nov 14, 2012 at 08:53 PM.
Nov 03, 2012, 08:18 PM
Life begins at transition
Not really. The retracts still work on the normal 1520us signal any other servo does.

If they work on a servo tester, or straight on the Rx, it's your sequencer.
If they won't work on any device, it's the retract.
Nov 03, 2012, 08:31 PM
dro56595@bigpo's Avatar
Another two flights this morning. Captured some on-board video from the first flight. Unfortunately, the video file is reporting as corrupt on both my Mac and PC. Am running it through some conversion programmes to see if I can recover something ...

Odysis, you'll be pleased to know that my nose is now scale too. Lost the ADP somewhere.
Will post some video showing flight with the missiles on board (if I can recover the file).

My ESC cooling mods helped a little, but only put off the overheat rpm modulation until very late in the first flight.

Second flight I just zoomed about, keeping plenty of forward speed, and there were no problems. If I want to do a lot of Viff'ing, it'll need better cooling.


Nov 03, 2012, 09:14 PM
Registered User
Originally Posted by Odysis
Not really. The retracts still work on the normal 1520us signal any other servo does.

If they work on a servo tester, or straight on the Rx, it's your sequencer.
If they won't work on any device, it's the retract.
Well, neither of the 3 retracts will oprate individually with a receiver nor a servo tester. So either all 3 are bad, or they require a special signal from the sequencer. Can anyone verify that yes the retracts can be tested by normal means without the sequencer? I find it hard to believe all 3 retracts are bad.

The sequencer is definately bad as I read 5V between the ground and signal pins regardless of gear switch position on my transmitter.

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