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DX5e with EPP Bonsai - Limited Throws

colorex

Rotor Riot!
Mentor
#1
Okay, so my friend Nick (The only one of my friends who flies, but lives eight hours away) got himself an EPP Bonsai from HobbyKing. He has 2 DX5e's but no programmable radios, as he gave me the 72MHz Tx I'm using now.

But he has an issue - the servos won't do full throws when using elevon mixing. Reading on the web about this, I found that Spektrum limits it's throws to prevent the radio from breaking the servos. So it limits throws to 50% so that the throw only goes to 100% when doing full aileron and full elevator.

He already adjusted his throws physically, as much as possible, but it's not helping much. I suggested he drill another hole closer to the control surface, or extend the servo arms.

Anyway, I wanted to ask you if you had any other ideas to solve this problem (without using a v-tail mixe as suggested in a youtube video)

Thanks,

colorex
 

Ak Flyer

Fly the wings off
Mentor
#2
So when you are getting the combined elevator and aileron for 100% servo travel, you still don't have enough throw? If you have everything the servo will give you then you have to change the mechanical ratio like you said. I don't think there's much else to do that you haven't said unless he gets a better radio.
 

Mike oxbig

15% nitro is my cologne
#3
What kind of servos are we talking about? And how long are the servo arms? Are the throws close to the listed specs or are they way out?
 

colorex

Rotor Riot!
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#4
He said he had half an inch of throw on single inputs - and he's using MG servos so I think it's OK to make the servo arms longer.
 

pgerts

Old age member
Mentor
#5
The problem you describe is (was?) also an issue with DX6i.
Another problem might be the servos. Some servos has much less throw than others. I have experienced this with metal gear servos.
Is half inch to little? Wings are normally fast to roll. Are there any up deflection on the rudders in neutral? Wings (zagi type) normally have about 1/8" or more up to fly level.
 

jetpackninja

More combat please...
Mentor
#6
half inch should be PLENTY of throw for single input-
just to be clear, from neutral to full back on the stick the elevons should move around 3/8 of an inch...
too much throw on a flying wing and it will snap roll when you try to do a loop and can easily stall into a turn.
 

jetpackninja

More combat please...
Mentor
#7
+1 on what gerts says

The mixing algorithims the DX6i (and likely the DX5e) uses is flawed.
We get around this on our combat wings by adding differential mechanically in the setup.
This can be done by placing the servo arms rotated onto the servos a couple of teeth toward the front of the plane.
Here's a picture of one of my wings setup, servos centered and trimmed for level flight.
a4764743-53-DSC04976.jpg
 

colorex

Rotor Riot!
Mentor
#8
half inch should be PLENTY of throw for single input-
just to be clear, from neutral to full back on the stick the elevons should move around 3/8 of an inch...
too much throw on a flying wing and it will snap roll when you try to do a loop and can easily stall into a turn.
So if half an inch is enough throw for a bonsai, then I guess I'll have to judge my friend's flying skills. He also seemed to have trouble with the prop facing the wrong direction.

As I said he is very far away so I can't tell what's wrong. He just told me on skype that he didn't get it to work.
 

jetpackninja

More combat please...
Mentor
#9
What is the problem that he is having? Trouble launching?

If he has the prop on backwards it will not generate enough thrust and he will very likely have a difficult time even launching the plane.

CG is also very important to get right. I'm not sure where the Bonsai should balance. It's easy to get a flying wing tail heavy and unfortunately almost impossible to fly them if they are tail heavy.

Good luck helping your friend long distance ;) Difficult but not impossible.

These are the most common issues that we see new flying wing flyers struggle with the most:
CG issues (especially tail heavy)-
Prop on backwards-
Too much throw-
Sloppy linkages, flexing control rods-
 
#10
On the DX6i or DX7/8 or any other programmable radio you can do 2 mixes\: ail-ail 125% and elev-elev 125%. This is the way that you can get round the elevon mix decreased throw issue but you don't necessarily need that much. I just have it this way with a lot of EXPO so I have full deflection if I need it.
 

pgerts

Old age member
Mentor
#11
So if half an inch is enough throw for a bonsai, ..
As I said he is very far away so I can't tell what's wrong. He just told me on skype that he didn't get it to work.
One thing i always do with a glider or wing is to launch it without the motor on (power on) to get the glide correct.
The "plane" shall glide straight at least 10 meters without any radio input after a throw. You will of course give a little up just when it is to land.
Example of how to launch a wing:
and perhaps not to-----
 
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colorex

Rotor Riot!
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#12
Thanks! I'll contact him when I can with this info. I'm looking into the correct CG for this plane. Does the CG point vary with the setup?
 

jetpackninja

More combat please...
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#13
Thanks! I'll contact him when I can with this info. I'm looking into the correct CG for this plane. Does the CG point vary with the setup?
Yes, different batteries, ESCs, servos and motors can vary greatly. Even the type and how much adhesive used can make a difference.
 

colorex

Rotor Riot!
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#14
Yes, different batteries, ESCs, servos and motors can vary greatly. Even the type and how much adhesive used can make a difference.
Yes, I know that the weight of stuff can change, but even if I put a 1Kg motor and 1Kg battery on it, it should still be balanced on the same spot, right?
 

jetpackninja

More combat please...
Mentor
#15
No
On most flying wings the motor is much closer to the CG than where the battery will be placed so the 1kg battery will affect the cg more than the 1 kg motor

The amount of influence each item may have on the CG will have more effect on the CG as they are placed farther away, think of leverage. It's really immaterial at this point unless you know where the recommended CG is for the wing. Does any of the documentation that comes with the bonsai suggest where to start with the CG?

Most of the wings that I use don't have any pre cut slot for the electrics. I go as far as decorating the wing even, before I start finalizing the location for the electrics. I cut the battery slot dead last in hopes of getting the plane to balance in the right spot without adding any weight.
 

colorex

Rotor Riot!
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#16
No
On most flying wings the motor is much closer to the CG than where the battery will be placed so the 1kg battery will affect the cg more than the 1 kg motor
I see, but the recommended CG spot doesn't change after that, right? The point where it should be balanced?
 

teflyer

Full Circle
#19
Yep, I believe so :)
but have your friend do a glide test anyway to make sure as pgerts suggested. No electronics on it, just chucking it and then use some sort of weight (I personally use paper clips - about 5 grams per paper clip :D ) to add on until it flies perfectly level.

EDIT: 1cm back from the back wall of the electronics compartment
 
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colorex

Rotor Riot!
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#20
Yep, I believe so :)
but have your friend do a glide test anyway to make sure as pgerts suggested. No electronics on it, just chucking it and then use some sort of weight (I personally use paper clips - about 5 grams per paper clip :D ) to add on until it flies perfectly level.

EDIT: 1cm back from the back wall of the electronics compartment
OK, I must have missed that part - the glide test - I'll call him up to see what he says.