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Mar 03, 2021, 06:16 PM
I Love Tea!
Husky2000's Avatar
Quote:
Originally Posted by paultbg
Maybe you should try to launch inverted ? It looks like always want to go the other way....
I think that's about the only thing I didn't try.
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Mar 03, 2021, 06:26 PM
I Love Tea!
Husky2000's Avatar
Quote:
Originally Posted by ChilternFlyer
Fun video.

That's a real surprise.
My Dart 250 is easy to launch and flies like a pussy cat. (It doesn't have a flight controller in it either).
I use 850 mah 3s in mine (it weighs 80g).

It looks like you're putting far too much aileron control input into it making it uncontrollable.
Either that or you have a huge battery in it pushing the wing loading too high for it to cope with..
Have you tried reducing your rates and adding more expo to it? (I put 25% - 30% on my wings)
The Dart 250 is very light so doesn't really need much input at all. ( It also doesn't like the wind much either).

I put started with a mix of 10% (on a switch) up elevator on mine, but now that I've got it trimmed I don't need it for launching.
2/3 throttle and toss it like a chuck glider is all it should need.
Yes from the videos I've seen these little things seem easy to launch so I was surprised I had so much trouble.

It is a bit overweight at around 300g as it has a 1000mah 3 cell lipo and I managed to stuff a dji air unit in there too (a bit brave for a maiden flight admittedly). It should easily cope with that though, there seems to be many setups around at that weight or over. At least that's what I thought.

You are right about the throws, there is a huge amount of travel and that's definitely one of the problems but it seems I need full left aileron at launch to stop that ridiculous torque roll, if that's what it is. So reducing the throws may make the launch even more difficult but would certainly be much better once its in the air.

Steps to try will include reducing throws, adding some expo as you suggest, swapping the 2 blade prop for the 3 blade in the hope of reducing torque roll, and removing the air unit at least temporarily to reduce the weight. See if that helps.
Mar 03, 2021, 06:30 PM
I Love Tea!
Husky2000's Avatar
Quote:
Originally Posted by OMEGOOLIEBIRD
Looks like it has a ton of static right elevon up deflection. Also rolls right every time. May be a simple setup adjustment required.
It's a whole lot of left up elevon you can see in the vid, at the point where I'm checking CG. Even with that much left it still rolls right. I'm baffled!
Mar 04, 2021, 04:53 AM
312mph FPV
OMEGOOLIEBIRD's Avatar
Quote:
Originally Posted by Husky2000
It's a whole lot of left up elevon you can see in the vid, at the point where I'm checking CG. Even with that much left it still rolls right. I'm baffled!
Well, if the gyros are definitely the right way, i'm baffled too!
Mar 04, 2021, 04:50 PM
Happy Days
mudlark's Avatar
Quote:
Originally Posted by Husky2000
It was maiden day recently for my Zohd Dart 250g. It could have gone better! Here's 1.5 minutes of your life you'll never get back:

https://www.youtube.com/watch?v=bQlLnRtdMKU
Weird??
Mine is easy to launch on 2s. Flies like a dream with no FC
Good video though
Mar 05, 2021, 03:54 AM
Fly,crash,glue,repeat!
Jake Bullit's Avatar
Quote:
Originally Posted by Husky2000
It was maiden day recently for my Zohd Dart 250g. It could have gone better! Here's 1.5 minutes of your life you'll never get back:

https://www.youtube.com/watch?v=bQlLnRtdMKU
Prop facing correct way?

Launch with less throttle?

Ailerons binding?

Lowest hole on servo arm ,and highest on aileron horn?

Servo arm slipping?

Lack of talent?

Mar 05, 2021, 05:51 PM
I Love Tea!
Husky2000's Avatar
Quote:
Originally Posted by mudlark
Weird??
Mine is easy to launch on 2s. Flies like a dream with no FC
Good video though
Weird indeed. Much jiggery pokery ahead for this one I fear!

Quote:
Originally Posted by Jake Bullit
Prop facing correct way?
Yup!

Launch with less throttle?
Tried that, same difference

Ailerons binding?
Hmmm, I don't think so but it's worth a check

Lowest hole on servo arm ,and highest on aileron horn?
I''ve definately got far too much aileron travel. I'll reduce it!

Servo arm slipping?
Dunno but I'll check it

Lack of talent?
No comment!

Mar 05, 2021, 06:17 PM
Still flying a desk..
ChilternFlyer's Avatar
Quote:
Originally Posted by OMEGOOLIEBIRD
Looks like it has a ton of static right elevon up deflection. Also rolls right every time. May be a simple setup adjustment required.
Torque roll usually makes it roll to the left not the right. Something doesn't seem right
Mar 05, 2021, 06:21 PM
Still flying a desk..
ChilternFlyer's Avatar
Quote:
Originally Posted by Husky2000
Yes from the videos I've seen these little things seem easy to launch so I was surprised I had so much trouble.

It is a bit overweight at around 300g as it has a 1000mah 3 cell lipo and I managed to stuff a dji air unit in there too (a bit brave for a maiden flight admittedly). It should easily cope with that though, there seems to be many setups around at that weight or over. At least that's what I thought.

You are right about the throws, there is a huge amount of travel and that's definitely one of the problems but it seems I need full left aileron at launch to stop that ridiculous torque roll, if that's what it is. So reducing the throws may make the launch even more difficult but would certainly be much better once its in the air.

Steps to try will include reducing throws, adding some expo as you suggest, swapping the 2 blade prop for the 3 blade in the hope of reducing torque roll, and removing the air unit at least temporarily to reduce the weight. See if that helps.
The air unit is making it too heavy.
You haven't put the air unit on the right hand wing have you?
mine weighs 238G with the battery. (no FPV yet)
Mar 06, 2021, 03:58 AM
Registered User
Quote:
Originally Posted by ChilternFlyer
Torque roll usually makes it roll to the left not the right. Something doesn't seem right
Depends on direction of prop rotation. Could roll either way. Left with CCW conventional prop or right with CW pusher prop

Malc
Mar 06, 2021, 04:32 AM
Still flying a desk..
ChilternFlyer's Avatar
Quote:
Originally Posted by highviz
Depends on direction of prop rotation. Could roll either way. Left with CCW conventional prop or right with CW pusher prop

Malc
Yeah, I know that but he could have the wrong prop on the motor (that is currently spinning in the opposite direction to what a normal prop expects)
Mar 06, 2021, 07:33 AM
312mph FPV
OMEGOOLIEBIRD's Avatar
It's got the look of gyros the wrong way... or uncalibrated Gyro/Accelerometers or something.

The other possibility is CG combined with extra weight. The static up elevon will act counterintuitively, because it will actually reduce the likelyhood of that wing stalling, making the other wing drop first when it stalls. You can get this type of stall when it is too nose heavy, effectively increasing the wing loading when combined with up elevator trying to hold the nose up. Also, similar when nose light, it will be naturally increasing it's angle of attack, inducing an early stall, which will effect the wing with static up elevon last.. I hope that makes sense!

I find that as the weight increases on an airframe, the CG needs to move forwards, considerably in some cases. The HK Vampire for example ended up nearly an inch further forward than it flew on a lighter slower setup. Funjet can need move forward around 15-20mm when getting up to 2.2kg or so. However, other airframes with different wing sections may have a fairly static CG over quite a wide weight range. I find that a swept leading edge will make the need for CG change more profound than most other shapes.
Last edited by OMEGOOLIEBIRD; Mar 06, 2021 at 07:54 AM.
Mar 06, 2021, 07:41 AM
Registered User
Quote:
Originally Posted by OMEGOOLIEBIRD
It's got the look of gyros the wrong way... or uncalibrated Gyro/Accelerometers or something.
Crash video ends with the caption 'time to add a flight controller' - so I'm guessing there are not too many gyro/ accelerometers to calibrate at the moment Looks to me like just too much movement / control inputs which are stalling the wing.
Mar 06, 2021, 04:39 PM
I Love Tea!
Husky2000's Avatar
Yeah there is currently no FC or gyros in this thing. In nearly 40 years of flying RC I have always flown and trimmed a plane in full manual and never found a plane I couldn't fly successfully manually. So this is very frustrating and admittedly comical.

The CG is spot on although Omegooliebird makes a good point on moving it forwards with weight. I don't think that's it though, and it is well balanced nose to tail too, that air unit is central!

The up elevator visible in the vid where I'm checking CG was only there for about 3 launches, just to see the effect, it wasn't that deflected most of the time so that's not to blame either.

Torque roll. Yep, that's part of the problem. See the pic below. Prop goes CCW, plane goes CW, in other words it rolls to the right. However this is the stock motor and prop so I would expect things to be reasonably matched in that respect. Part of the problem, but not the whole problem!

Control surface travel - yes there is far too much which makes it squirrelly to say the least, once it's in the air. But having attempted launches with all sorts of deflection, including neutral / little bit of reflex I am confident the launch problems are not caused by this. Dodgy controllability yes, launch problems no.

It's overweight at 298g but that's nowhere near the weight of some successful models on the 250g thread. One guy flies at well over 400g and it launches beautifully.

I have added an air scoop to force air down to the air unit but surely that can't be it! see the pic.

If you have a Dart 250 when you get 5 mins could you check the motor mount. Mine has a slight offset to the right, pic below. How is your mount? perfectly straight?
Last edited by Husky2000; Mar 06, 2021 at 06:03 PM.
Mar 07, 2021, 07:09 AM
I Like Popcorn
flylite's Avatar
Afternoon you lot
I'm doing some retro build vids to chart the history of FPV - its advancements and how a lot of this started.
I'm looking for really old PCB's - Alex's Paris boards etc so putting it out there if any of you lot still have these boards kicking about, if you do could you let me know - happy to pay for them and cover shipping.
Will need a few vids of people tuning out and flying these also if you would like to share.
Do let me know, I'm sure many of you have something in the back of a box/draw/someplace.

Aim is to have a vid series on YT covering FC's and development up to where we are now.

Hope you are all ok and getting at least a few packs flown this weekend.

James



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