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Old Aug 04, 2014, 12:43 PM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
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Glad you are pleased with your set and had a good maiden flight
Andy
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Old Aug 04, 2014, 09:57 PM
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I just maidened my Bonsai yesterday.. First few tries were straight into the ground!..

Eventually I maxed the up trim, and managed to fly, while constantly holding elevator up about half way!..
I trimmed it now by moving the servo arm a notch up, but the control sufaces are visibly upwards now.. Is this normal?? I aligned the surfaces with the bottom of the wing at first.. I thought to be neutral that's how it would have to be.

My CG is at 142 .. I have a 2222 Motor with a 500mah batttery, and I had to add a bit of nose weight to move the CG forward..
I tried taking the weight out of the nose so I don't need all that trim, but then it flies very twitchy.

Can someone post a photo of their control surface at "neutral flight"?.. is it supposed to be a few degrees up?
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Old Aug 05, 2014, 03:01 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,037 Posts
My Bonsai's c of g is set at 125-130 depending on pack used so looks like still tail heavy. Mine will still get into a spiral dive if I let the speed drop too much so that's why I fly it at WOT most of the time
Most, if not all, flying wings will need some reflex,up elevator trim to fly correctly. Here's how mine is set up
Andy
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Old Aug 05, 2014, 03:37 AM
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Australia, NSW, Sydney
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Yeah, mine are up a few mm. They will need more reflex the further forward you have the CG. Isn't the CG supposed to be near the back of the battery bay? If in doubt, err towards the nose and be prepared to pull back on the elevator.
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Old Aug 05, 2014, 02:07 PM
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Originally Posted by CelloGuy View Post
Yeah, mine are up a few mm. They will need more reflex the further forward you have the CG. Isn't the CG supposed to be near the back of the battery bay? If in doubt, err towards the nose and be prepared to pull back on the elevator.
Toward the back of the battery?? That's really far forward.
I believe the CG is supposed to be very close toward the motor mount, about 5-10mm forward from it
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Old Aug 05, 2014, 02:10 PM
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Originally Posted by headlessagain View Post
My Bonsai's c of g is set at 125-130 depending on pack used so looks like still tail heavy. Mine will still get into a spiral dive if I let the speed drop too much so that's why I fly it at WOT most of the time
Most, if not all, flying wings will need some reflex,up elevator trim to fly correctly. Here's how mine is set up
Andy
Thanks. That's about how mine looks, definitely up.. I thought it should've been flush with the table.

I stalled mine a few times without any spiraling, but my CG is around 140's .. If you're at 125-130 then that's nose heavy isn't it?.. CG too far forward. Use a lighter battery and you'll be closer to the recommended 135-142. Probably when you stall, the nose starts to dive really quickly on yours because of the forward CG.. You can also put in a heavier motor.

WOT all the time would be insane.. I'm cutting the throttle to 10-20% and drifting around a lot.. Using 2222 motor and generating 250grams of thrust, WOT is too hard to control, so I don't use more than 60-70%.
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Old Aug 05, 2014, 05:42 PM
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Australia, NSW, Sydney
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Sorry, meant to say radio bay, not battery bay. Pretty sure the preferred CG for me was near the back of the radio bay, on both of mine. Will check today.

If Andy is tip stalling and spinning when he goes too slowly then his CG is almost definitely a little aft. That happened on my first Bonsai before I checked the CG and I've seen it on plenty of other planes.

Otter, which 2222 are you running?
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Old Aug 05, 2014, 06:11 PM
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Sorry, meant to say radio bay, not battery bay. Pretty sure the preferred CG for me was near the back of the radio bay, on both of mine. Will check today.

If Andy is tip stalling and spinning when he goes too slowly then his CG is almost definitely a little aft. That happened on my first Bonsai before I checked the CG and I've seen it on plenty of other planes.

Otter, which 2222 are you running?
I got the one from HK: Turnigy Aerodrive C2222 Micro brushless Outrunner 2850kv (15g). The motor is really good and it's not getting warm at all, pulling a max of 5A on 2s with 250 thrust seems pretty good. It says max 10amp in the specs, maybe for higher voltage? I've never had anything more than 2s yet. I'm using the Plush 10amp esc. It just barely fits in the mounting, the left/right screws are right on the edges so I put them in a slight angle.. and the motor has a shaft sticking out the back which I had to cut off with a dremel cutoff wheel because it sticks too far. Also you'll need to enlarge the hole in the middle of the mount a bit.

Yes the CG is right at the rear edge of the radio bay up to + 5mm.. according to the measurements I made and the manual.
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Old Aug 06, 2014, 01:39 AM
Reap the wild wind
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Bristol,UK
Joined Feb 2007
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Originally Posted by otterslide View Post
...WOT all the time would be insane.. I'm cutting the throttle to 10-20% and drifting around a lot.. Using 2222 motor and generating 250grams of thrust, WOT is too hard to control, so I don't use more than 60-70%.
I've been piloting flying wings from my start in this hobby and cut my teeth on a correx Mugi Evo. You will soon become used to the speed that these little wing are capable of.
I gave 2 scratch built mini KFm-4 wing to my fb's who both started out using BW 1700's. It was only a few weeks later that they swapped to the 3000kv set up as they felt the need for speed. Faster than the Bonsai as well. Time to build another one for me!
Depron Mini Wing KFm-4 on 4.75 x 4.75.#16 PK 12Feb12 (3 min 43 sec)

Andy
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Old Aug 06, 2014, 10:25 AM
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I've flown it a few times now.. it's extremely fast to me even at 50%.. you need very fast reflexes. Also I'm not using any curves or dialing back any of the inputs, so I find I'm overcorrecting quite a lot.. It's my first time on a wing.
I think I need to scale the controls to maybe 70% and add some expo. Also I'm just getting used to the roll of a wing, it seems that you need to be going pretty fast to get a good roll rate.. if you're going too slow and try to roll it's too slow to even try.

Quote:
Originally Posted by headlessagain View Post
I've been piloting flying wings from my start in this hobby and cut my teeth on a correx Mugi Evo. You will soon become used to the speed that these little wing are capable of.
I gave 2 scratch built mini KFm-4 wing to my fb's who both started out using BW 1700's. It was only a few weeks later that they swapped to the 3000kv set up as they felt the need for speed. Faster than the Bonsai as well. Time to build another one for me!
https://www.youtube.com/watch?v=R8tv...vlMl3j0EOFb00g
Andy
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Old Aug 17, 2014, 01:10 PM
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Back to report again,

Reinforced it with 3 mm carbonfiber rods in the mainwing and 1 mm carbonfiber in the elevons. Just had my second flight. And what a ride it was! With the new reinforcements it was a bit noseheavy and therefore out of trim. Without the help of my brother I wouldnt have gotten that thing trimmed, if you did let go the stick even for a very short time, it would turn right and down very sharp. And it was sooo fast, holy cow I will make a video of one of the next flights and show it to you guys here. I also want to clock it with one of these phoneapps, so I will atleast have a rough estimate of what the speed actually is.

I think ill drop the idea with the FPV equipment though, since its already quite heavy and will leave that job of the FPV basher in my fleet to my 900 mm popwing.

Good start in the new week!

Moga
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