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Old Oct 29, 2012, 04:58 PM
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United States, NV, Fernley
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I figured out my issue with long rotations. I had installed slightly smaller low bounce wheel set on the mains to help soften the landings at high altitude. The last several flights where taking much longer than normal and getting worse. Turns out that the tire is now rubbing on the oleo when on the ground but not when I was checking it over. The plastic axel insert wore down creating lots of play in the hub. So will go back to the stock ones.
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Old Oct 29, 2012, 06:22 PM
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I have a few planes set up with "Takeoff mode" mixes. To save doing all the stuff real-time, you have it pre-done by the mix. eg Allow, or limit, max throttle (to enforce a slower take-off)... up or down elevator trim..... flaps used, or not etc etc.

So it is possible - likely - that there is a good mix to run the Su-35 at for better grass take-offs.
I would think (I need to get mine flying again!):
1) Mix in a FIXED low TV up angle - a very small amount - a few degrees. eg 1 to 3deg or so
2) Probably a small up elevator angle
3) Some small to medium ???? up or down ???? Flaperon/Spoileron. UP I would guess (spoileron). Say 10 - 15deg.
4) Allow full throttle, of course (Prop warbirds can benefit from notable power limitation so you CANT over-do it)

So all you have to do is build up to 100% throttle stick and steer! LOL
(You can even mix a 'servo slow', if your TX has it, to do the throttle build up for you)

And go test.... re-adjust setup.... as required....
Because you don't really want full TV under your own control, when you don't even KNOW what it will do.... like my maiden suddenly rotated to 45deg 'space shuttle launch', but luckily had enough speed and power to fly up like that anyway!
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Old Oct 30, 2012, 02:04 PM
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Well as a rule, I don't limit throw for takeoff or landing. Limiting force deflection increases the need for a greater speed to generate enough moment force to rotate exacerbating the problem that we're talking about avoiding. Worse if you get a gust that put the attitude where you don't want it, you've limited your ability to recover. That all though requires that the pilot not over steer....

I do an eyeball thing.... most models will take off around 35 km/h+ take off or landing. So regardless of the model, once it seems that its accelerating above this speed, I do a hard snap of both Taileron and TV to force the rotation and get air under the ground effect. During the rotation as the nose lifts and mains look to clear I neutral the pitch immediately so that there is no over rotation and let it settle into a gentle climb.

I almost let go of the stick after the flick...sometimes I do a few flicks if it doesn't let go of the grass but I try to avoid anything that may slow the roll out.

My take offs look like a lot of SU4Evers only his shorter takeoffs.
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Old Oct 30, 2012, 04:55 PM
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The mixes don't prevent user inputs going to max still... they are just move the static baselines to new 'take off' positions.
And one switch flick returns it all back to 'normal' too.
So it doesn't stop you "flicking" more up, if required. It just sets up the planes(s) to auto take-off, when they get to the required speed to achieve that.

Most people are taking off WAY shorter than a real one does. (of any aircraft). So distance is no real issue... except if you don't have it available!
And grass, also depending on ground and grass height etc, would need a different take-off set of mixes than a hard runway. (more up elevator and TV etc)
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Old Oct 30, 2012, 05:47 PM
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Max, that makes sense because I usually make the same stick moves that you have described to take off.

...Unless I completely mess up and make a cobra take off!

Cheers!
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Old Oct 30, 2012, 05:58 PM
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J,

I thought your cobra takeoffs were on purpose and planned
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Old Oct 30, 2012, 06:06 PM
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Getting that 'Up flick" perfect is near impossible. You don't get the feedback time to adjust it very well.... the plane doesn't respond, then DOES, in a split second.

On my Me-262 (twin 70mm) if I NEED to take-off early a slight Up Flick will get it into the air - with that non-perfectable "jump", which you then try to turn into a nice take-off look. This is like approx 20m or so.
If I let it run out further - a fair amount longer, say 40m or more - it can take-off 'normal'. No need for an Up Flick, and suited to a take-off mix. And I would say that the whole speed/distance of that is far more realistic in scale to a real one.
20metres for a 1/6th scale jet.... = 120metres for a real one.... not overly realistic!!
Even 40m isn't, but it is at least looking plausible by then! LOL.
You would probably really need 100m or more! (can get to be impractical)

When I used the Su on a road, I would say it was about a 50m take off run (could have been more - just trying to guesstimate land mark points there), with no TV or Up Flick. It was getting to the verge of 'scarey' (sort of) because that is a fair way away and getting smaller and smaller by then. But really, it was all fine and did just fly off - probably also a lot more like watching real one disappear down the runway! They get 'small' as they get half way or more down it too! hehe
But that was road.....
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Old Oct 30, 2012, 06:16 PM
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It would certainly help if everyone who discusses take off rolls would provide field altitude. Otherwise its not that relevant to others. I'm at 4200 ft with long roll. InVegas at 2000 ft it was much better for taking off and also landing compared to my home field in Reno area.
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Old Oct 30, 2012, 06:28 PM
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I don't know Pete. I don't have a problem doing it repeatedly. I occasionally do a jack in the box but SU4Ever demo'd smooth lift offs in several videos. So no not impossible.
Limiting throw I'm referring also to the TV. The idea of setting up a snap roll to instead be a ROG is doable though I wouldn't. I never use snap roll programming because I'd rather just keep my thumbs on the sticks to learn to fly my way through changing situations.

None of that may change the original issue though why even after a number of attempts he couldn't get the model off the ground. I had the same issue with the Euro early on. It was the 3mm rod that connected the strut to the retract. It would bend too easily and bog the nose gear down slowing just enough to prevent rotation.
I changed it and had little issue thereafter. Thus why I asked about the other conditions since I was able to take off at time in such short distances.

And Pete this is not a scale flight forum. So a pilot doesn't have to fly scale especially if he neither has a long enough run way to, nor favours the model being a tiny dot by the time they pull. You do know BTW they fly its cousin the SU-33 without catapult off shorter Soviet carriers up a slight ramp. Nothing wrong getting the model to do what it can controllably do.
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Old Oct 30, 2012, 06:41 PM
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Quote:
Originally Posted by acesimmer View Post
It would certainly help if everyone who discusses take off rolls would provide field altitude. Otherwise its not that relevant to others. I'm at 4200 ft with long roll. InVegas at 2000 ft it was much better for taking off and also landing compared to my home field in Reno area.
I have no idea what altitude that I'm at But with the decreased density it only means you have no choice but to have a longer roll out and a higher ROG speed. You get used to the average lift point compared to other models in your experience since the SU-35 doesn't have special considerations compared to other models. That's why my answers are a little vague because conditions vary.

Not sure if its an altitude off grass issue that may be keeping him earth bound.
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Old Oct 30, 2012, 06:48 PM
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I received my SU-35 from Banana Hobby and have been very happy till today. I have not flown it, getting it ready. Setting throws and was trying to setup thrust vetoring when I seem to have lost one or both ESC's. Plug in battery( big spark, a little scrary) and I have no power to receiver. Put five cell NiMH battery in receiver without throttle and everything works.(ali,elev and rud) Now the QUESTION, how do I trouble shoot the ESC?
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Old Oct 30, 2012, 07:12 PM
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Have you ruled out the BEC as the problem?
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Old Oct 30, 2012, 08:02 PM
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Mine did that. I installed an external BEC, and all was right in the world. The ESC's could provide enough currect for one, maybe two, servos, but more than that and the voltage dropped to <3, and my Rx dropped out.

For the guys 'flicking' elevator to rotate - funnily enough, that's exactly how a normal (full size) takeoff is done. Difference is, you can feel nose wheel liftoff, so you can release the backstick and control the pitch rate.
I've often wondered how we can get the look of nose wheel liftoff, then mainwheel of takeoff, and hold the nose up on landing. Everything seems to happen far too quickly for my fingers!
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Old Oct 30, 2012, 08:10 PM
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Yep it is all too quick in models, as they are so light and wing loading riduculously low. So real ones MUST take-off slow and inertia changes are readable by a pilot in plenty of time.... though I expect they are using FBW also, so the pilot may not even do anything at all special. He just 'pulls back' and the FBW controls surfaces a required to get a perfect take-off!
They probably have a 'take-off' mode they set too! (Like mixing your TX to help you does)

Taking off 'properly'.. flying 'properly'.. landing 'properly'... behaving 'properly'.... is why pretty well all of my models are well over the weight others typically use. It doesn't stop them taking off.......
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Old Oct 30, 2012, 08:20 PM
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fredmdbud---have not ruled out BEC because i don't have much knowledge concerning the electrical end of our hobby. Odysis said he fixed his with an external BEC and I will try to do that. Put an external BEC in hobby lobbies B-25, never knew if it was working or not. how big of BEC should I get?
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