Hi folks...
A friend suggested I join here and so I am very new to this group....
I have been flying the FX79 Buffalo for a few months now and have a bit of an issue....
A few weeks ago I found myself quite high so I pointed it down into a moderate dive and very quickly, she started to "flap her wings!" I did pull out of it ok but it ended up in a crash... not too bad but I would say it was 80% my fault and 20% due to damage caused my the extreme flutter...???? maybe???
Anyway, the plane is flying again and what I want to know is....
Has anyone else experienced this and how can I fix it?
I was planning on laminating the wing but it was suggested to insert extra carbon spares into the outer wing section to add rigidity???
Any ideas???
I get the same effect on the X8 - one of them can't sustain WOT on level flight without the wings starting to go.
I've reinforced one by fiberglassing it, will be experimenting to see how it's worked, but the overall fix is just to stiffen the airframe up.
Aileron and or elevon flutter is normally caused by either too much slop in the linkages, control surface hinges either breaking or loose or servo not man enough for the stress and bouncing between neutral point. The most likely is hinge failure. I am never 100% happy with the EPP foam type of hinge. I prefer to separate the surface in the build stage and use a different system for hinges. Robart or even fuzzy Mylar, any hinge method to take the slop out.
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Thanks for the replies guys....
The servos are HiTec HS 56HB's I'm sure they are way better than the standard???
This even happens when I turn into moderate wind and keep the ground speed up....
From the ground, it looks like the the wins "flap" up and down maybe a foot???
Here's a video... look at 2:30-ish...
https://www.youtube.com/watch?v=NL-SiqbBhWQ (https://www.youtube.com/watch?v=NL-SiqbBhWQ)
It was a very gusty day so probably shouldn't have flown....
dig some small grooves into the wing and hot glue some fibreglass rod in there. 3mm will be fine. I would put a couple on the top and a couple on the bottom of each wing. you will be surprised how much it stiffens them up. just make sure they are smooth to the wing surface.
if needs be you could insert a diagonal one as a bonus.
test this you will be fine. but if you want to laminate after you can.
but be aware you have the wrong plane if you want to do steep dives and lots of aerobatics and agility stuff. Any of the ritewing planes are much more suitable for this sort of stuff.
Quote from: Billy_boy_2010 on June 01, 2016, 01:23:44 PM
dig some small grooves into the wing and hot glue some fibreglass rod in there. 3mm will be fine. I would put a couple on the top and a couple on the bottom of each wing. you will be surprised how much it stiffens them up. just make sure they are smooth to the wing surface.
if needs be you could insert a diagonal one as a bonus.
test this you will be fine. but if you want to laminate after you can.
but be aware you have the wrong plane if you want to do steep dives and lots of aerobatics and agility stuff. Any of the ritewing planes are much more suitable for this sort of stuff.
Thanks BillyBoy...
The steep dive I did was just that I was thinking I was too high and wanted to scrub off some altitude...
I have some carbon strips so I think that's the way I'm going????
Had this happen with an old wing - the wings warped so much that they themselves became elevons making the plane uncontrollable.
Now I fly grandma planes :)
Quote from: Steve W on June 01, 2016, 01:45:13 PM
Had this happen with an old wing - the wings warped so much that they themselves became elevons making the plane uncontrollable.
Now I fly grandma planes :)
I was surprised the wing didn't brake up in the air! I had a huge deflection and maybe that was the beginning....
I'd don't know???
It's flying again, I just wanna add some rigidity to the outer panels....
Quote from: KillerDave on June 01, 2016, 10:41:50 PM
I was surprised the wing didn't brake up in the air! I had a huge deflection and maybe that was the beginning....
I'd don't know???
It's flying again, I just wanna add some rigidity to the outer panels....
Basic principal of flight is that altitude is governed by the throttle not the elevator. You should have just closed the throttle a bit and descended by bleeding of height. A power dive like that could pull the wings off.
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Quote from: BigT on June 01, 2016, 10:48:45 PM
Basic principal of flight is that altitude is governed by the throttle not the elevator. You should have just closed the throttle a bit and descended by bleeding of height. A power dive like that could pull the wings off.
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Yeah, I just wasn't thinking.... :-[
My FX61 did that on it's maiden. It was due to too higher gains on the elevon's.
I use an FY-41 lite fc and once the gains were dialed down it behaved much better.
I still get a little in a fierce dive which I think IS due to wing flex although it is laminated. :)
Maybe a spin would have been a better idea to lose height.
Quote from: KillerDave on June 01, 2016, 01:35:22 PM
Thanks BillyBoy...
The steep dive I did was just that I was thinking I was too high and wanted to scrub off some altitude...
I have some carbon strips so I think that's the way I'm going????
carbon strips will work. Probably better if anything. just be sure you insert them in such a way that their direction resists the flapping.
only reason I suggested fibreglass was because it doesn't block rf signal. carbon does. so if it's an ultra long range plane fibreglass will still be better.
it will never be an agile plane though. buy a ZII for that:) Or a mini drak in a year when they are avaliable.
Quote from: Chris in Kabul on June 02, 2016, 05:21:28 PM
Maybe a spin would have been a better idea to lose height.
A tight spiral works well.... ;D
Quote from: Billy_boy_2010 on June 02, 2016, 08:11:50 PM
carbon strips will work. Probably better if anything. just be sure you insert them in such a way that their direction resists the flapping.
only reason I suggested fibreglass was because it doesn't block rf signal. carbon does. so if it's an ultra long range plane fibreglass will still be better.
it will never be an agile plane though. buy a ZII for that:) Or a mini drak in a year when they are avaliable.
I realise it is a cruiser and it does fly real nice on a good day but this flapping happened at a speed I would never have expected... even turning into a strong-ish wind was enough to get it going...
And there was me thinking it was just me who had the 'flappy wing' version of the fx-79.
Been wondering how to get a bit more rigidity into the wing without adding too much weight.
Currently looking an extending the carbon tubes in the wing extensions so it goes further into fuselage, and as suggest here running some carbon tubes into the wing for added stability.
But the issue I always seem to have, is crosswinds and turning too sharply. As there's very little washout on the wing it tends to stall, and then pitch up.
Glad to see others have had the same issues.
Quote from: joolski on June 21, 2016, 04:34:36 PM
And there was me thinking it was just me who had the 'flappy wing' version of the fx-79.
Been wondering how to get a bit more rigidity into the wing without adding too much weight.
Currently looking an extending the carbon tubes in the wing extensions so it goes further into fuselage, and as suggest here running some carbon tubes into the wing for added stability.
But the issue I always seem to have, is crosswinds and turning too sharply. As there's very little washout on the wing it tends to stall, and then pitch up.
Glad to see others have had the same issues.
Sorry I didn't reply sooner....
Did you get yours sorted?
I fitted additional carbon strips into the outer wing sections.
one fitted into a slot cut 15-20mm behind the LE and another 10-15mm ahead of the elevons.
I do believe the connection between the wings could be much stronger but I am not kind to my plane and have broken it a few times! >:(
If I could move and store the FX-79 in one piece, I would fix them permanently!
Went out today and set-up my MFD AP!
Still a little to do but in STB mode she flies great! Steady as a rock with quite changeable wind conditions!
Next stop, FPV! :D
I can now confirm that the mod's I made, do in fact work!
Well over 100kph dive and rock solid!
It flies awesomely!
is this what you mean
https://www.youtube.com/watch?v=UMlQpFyKpkA (https://www.youtube.com/watch?v=UMlQpFyKpkA)
Quote from: wayneuk on October 29, 2016, 05:11:22 PM
is this what you mean
https://youtu.be/UMlQpFyKpkA?t=1m12s
Hi wayne,
Yes, that is what mine did... I think you controlled that well...
Are you saying you want to fly my FX?
Where are you?