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My Bixler 1.1 has a non-successful maiden.


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Looks like a rearward CG issue to me. Personally I would not have started playing with the decalage until I'd tried moving the CG forward, but you've done it now! Anyway, start with some unpowered hand launches over long grass to ensure it's in trim before trying a powered flight again - you are looking for a long, flat glide with trim in the centre.

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Yes, you are probably right. I was a bit quick to modify the tail, though it's only a couple of degs.  I have since that rubbish flight read a few people suggesting the CoG they say to use is wrong and it's more like 25% of chord. I've just added 60 gms of lead at the nose to get that.  We'll see how it goes next time. I really assumed that a kit/model that had been around for several years would fly 'out of the box' right! How wrong can you be? 

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Yes.  Mine was ARTF so I had to add a motor, plus I added u/c.  The RTF has motor installed, maybe it's lighter than the one I used. And with a tailwheel  too it will be more tail heavy.  I  added lead at the nose and it was spot on where they told me to balance it.  

 

I have read of other people having issues with these too. When I was trouble shooting this I saw a guy on another forum had to put a heavy padlock up front to get his to fly well!

 

I'll get there in the end.

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It looked to be nose heavy, over controlled but never had the correct actions taken to be recovered from a series of stalls (the "dolphining"). The initial few seconds showed that it was controllable.

Why mess about altering fuselage to alter tail decalage when adjustment of the elevator would have achieved the same end ?

Why increase the elevator authority ? It's being overcontrolled already.

I suggest trying it as a slope soarer, doing a dive test (with no power) & trimming it for a flat glide then practice using the power for climbs & elevator for speed.

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2 hours ago, EarlyBird said:

Here is one that flew straight out of the box

 

H-King Bixler v2 (1.1) EPO 1400mm Glider (PNF): ESSENTIAL RC FLIGHT TEST - Bing video

 

Loads of fun.

Very competent & entertaining aerobatic performance but it's a pity that for a model being sold as "one of the best beginner RC planes on the market " the trainer virtues weren't demonstrated at all. 

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2 hours ago, PatMc said:

It looked to be nose heavy?, over controlled but never had the correct actions taken to be recovered from a series of stalls (the "dolphining"). The initial few seconds showed that it was controllable.

Why mess about altering fuselage to alter tail decalage when adjustment of the elevator would have achieved the same end ?

Why increase the elevator authority ? It's being overcontrolled already.

I suggest trying it as a slope soarer, doing a dive test (with no power) & trimming it for a flat glide then practice using the power for climbs & elevator for speed.

 

Popular opinion from everyone else (several people on other groups)  is that it was tail heavy not nose heavy and those were the symptoms I saw. I DID trim the elevator down as far as I could, it made no difference whatsoever. Even powered right down and diving and as soon as it had speed was climbing like a nutter.  I've seen other people of forums saying that had exactly the same problem.  Other people on forums have said tail heavy and said the quote CoG is incorrect.

 

Looking at drawings of the Bixler the tail and main wing should be zero zero and mine wasn't.  Maybe it bent went I glued the two fusi haves together.  It was an ARTF not a RTF.  

 

I've been flying RC for maybe 15 years and can usually get some kind of control and get a model back on the  ground, even some of my own design scratch builds,  but that was a real challenge.  You said 'over controlled'?  You weren't flying it mate. It wasn't 'over controlled'  I had little or no control and I've been flying models for years like I said.  You suggest I had control and it was OK?  Ha ha, I just about crashed it in!

 

And I usually do a stall and power off to see how a plane behaves. There was no way I could with that.

 

The ones I've seen that flew 'straight out of the box'  in YT videos have been RTF and no u/c.

 

Stay tuned.  I'll show you soon how this flies with MORE nose weight. NOT tail heavy! ?  And with the right incidences! 

 

and Ron ...

 

Strange that. My brother has one, no U/C and I fly it with him on buddy lead. CofG as per the book, 2200 3s, flies really well with throws dialled back.

 

It may well be the bad tail incidence was the problem with mine, though as I said above if you Google other people have had issues with Bixlers so I'm not the only one! 

 

 

 

Edited by Bonzo Moon
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The uncontrolled climb was simply due to being overpowered. The "dolphining" was caused by PIO

Just reduce the throws, learn to use throttle & elevator as suggested & it will fly like the one in the other video.

Elevators don't have to be in line with the rest of the tailplane which is why I said they could have been adjusted instead of bodging the fuselage.  

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7 hours ago, Bonzo Moon said:

I've been flying RC for maybe 15 years and can usually get some kind of control and get a model back on the  ground, even some of my own design scratch builds,  but that was a real challenge.  You said 'over controlled'?  You weren't flying it mate. It wasn't 'over controlled'  I had little or no control and I've been flying models for years like I said.  You suggest I had control and it was OK?  Ha ha, I just about crashed it in!

15 years of flying RC, as a novice I can do better than this.

 

I am wondering if this a deliberate demonstration of 'a lack of skill'. What is the motivation behind 'deliberately' crashing is another thought. Curious....

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Thanks for the replies.  Some helpful and some  rather rude. 

 

I was the one flying it,  I know what it was like to fly.  These are supposedly easy to fly, and I can fly RC.  There are plenty of vids on my YT channel of me flying OK.  This  was a flying pig.   

 

It was not POWER, it was porpoising when I shut the throttle.  Anyhow, some of you seem to know better. 

 

deliberate demonstration of 'a lack of skill'.   Is there really any need for this in a friendly forum?  

 

I've read of other people having similar porpoising problems,  I suppose they were all incompetent model flyers too then?

 

If you look at the side elevation drawings of the Bixler THE TAIL INCIDENCE IS SHOWN IN THE SAME INCIDENCE AS THE MAIN SPAR.   MINE WAS A FEW DEGS OUT.

 

There was something wrong with this model and I suspect a combination  tail incidence and CoG  and that's what people being helpful have suggested. 

 

 

15 years of flying RC, as a novice I can do better than this.

 

Steve, you are downright rude.  You weren't flying it.

 

 

   

 

 

 

 

 

 

 

 

 

 

 

Edited by Bonzo Moon
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To try to add some considered analysis, the initial climb out looked in reasonable trim and without any sign of dolphining.  You appeared to eliminate excess power by stating that you'd throttled back so it's probably not a thrust line issue. As the flight progressed, it changed dramatically so any diagnosis needs to apply to what changed.

 

First, did something come loose, move or slip?  Does it use those horrible screw clamp control rod fixings?

 

Slightly long shot otherwise and I don't know your radio's capabilities, but if you can dismiss the possibilities above, could your trims be reversed? This would fit with the increasing need for down trim as the flight and trimming progressed.

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I did notice that too, the fact it appeared to quite suddenly want to climb uncontrollably, hence I gave it a good inspection once on the ground.  I always make sure batteries are very secure, so that wasn't  the issue.  It's velcroed right up front.   Elevator servo worked when I tested pre and post flight?  I am mystified, but it wasn't doing what it should do that's for sure!

 

I'll see what it's like after my CoG change (which as I say is suggested on other forums)  and the tail job I did.  Might even get a chance to try is again today!

 

 

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The only other consideration is the ESC is too close to the RX and caused interference?   I'll add a ferrite ring on the BEC feed.  It's tidy with the ESC  inside but I see Andrew Newton has his outside on his Bixler. Better cooling that way too. Maybe I need to do some butchering which is a shame as it's a nice looking model. 

 

Just checked I had already put on a ferrite ring! 

Edited by Bonzo Moon
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With my (limited to ‘Teacher’ on the buddy lead) flying experience of the Bixler I would say that on full throttle the nose is pushed down (slightly) but, as I said above, it can be very sensitive to control movements so I’ve dialled them right back for when my bro is in control. Previously it was all over the place. As others have suggested, when you next go out with it, get to height then cut the throttle and glide it around, it should float quite nicely.

 

Just seen your post re the esc. I wouldn’t bother changing its current position until you’ve sorted out the general handling issues.

Edited by Ron Gray
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As per my first post, change one variable at a time. There is no need to think about the motor for now. Just do some unpowered test glides over long grass and play with CG and elevator until it is in a good trim; it is designed to glide after all! Once you have done that give it another gentle push (unpowered), and once established in the glide smoothly and gently advance the throttle, watching for any change in trim. If something extreme happens close the throttle and rethink, but if you use this method it is pretty likely to climb away nicely at that point.

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Thanks for the helpful comments Matty.

 

I did get it flying well this afternoon and I will post a full account in a day or two.  I did it step by step, and as you say, including checking the glide .  I usually give my own design models a lob first to see how they glide before I ever try a power fly, though for some reason as this was a kit I wrongly assumed it'd be OK! 

 

For those people who said 'nothing wrong with it, you're just a rubbish RC pilot' , here's a comment on my YT channel today about the Bixler. 

 

'check the incidence angle of the horizontal stab... a dude on my club had that problem with this same aircraft and had to modify the tail's angle.'

 

Which is exactly what I did! 

 

They don't always fly great straight out of the box!

 

Though I have figured what I think was another issue.

 

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