As i replaced the F4 aio in my Cinelog 25 with a F7 recently i had a spare Geprc F411 35A AIO. So lets build another small whoop.
Am still super happy with my 1st mobigital 7 build, even with a Runcam Thumb Pro, but i wanted something inbetween thus so 85mm it is ;-)
Using similar build concept as my mobigotal, but then with a carbon frame to get better stiffness and less or no jello , which was a battle i was not going to win on the plastic frame of the mobigtal.

One of the key focus points on my build was to keep a super low profile for a DJI build , even with a thumb pro on top. On most builds it goes sky high when using canopies (so super bad for balance and small gap cearance) . But by using an 85 mm frame and 40mm props (typicaly used only for 74mm frames) you get some space between the front props to drop the camera in line with the props. So you dont need a high canopy and on top a thumb pro, but the thumb pro can be mounted straight on the stack. 

Name : DigiTwig V1

------ Parts list ------
Frame - Twiglet mini 2' carbon frame (selected as can hold happymodel type 3 screw mounts but also 4 screw larger motors so future flexible)
PropGuards - Cut off prop guards from mobilite 7 v3 frame (cleaned up with dremmel and spray painted with Plasti Dip 'Black & Blue')
FC/ESC - GEPRC F411 35A AIO (running BF 4.4 , esc on Bluejay 48khz)
Motors - Happymodel 1102 10000kv
VTX - Caddix Vista (un-dressed )
CAM - Caddix polar nano
RX - TBS crossfire nano rx
Antenne - Mini Immortal T and a Small UFL antenna
Props - Gemfan 40mm 3 bladed props
Mounting stuff 
    - Cam mount, standoffs, thumb pro mount all custom TPU
    - AIO gummies and some rubber o-rings here and there.
    - metal 4x m2x30mm screws for the stack column and some nuts/washers
    - metal 12x m1.6x5mm longer screws to mount motors 
Bat grip - ummagrip for nice snug lipo on bottom (hold lipo without strap) and some random strap
Noise - buzzer(micro)
BlingBling - led strip (missing in action in the mail still)

Total build weight - ex bat 60gram.
Fav Lipos sofar - Flywoo explorer 750Mah HV 2s and Tattu 450Mah 3s (with motor output limit at 80%)








The AIO and Vista mounting holes where all widened to fit in a column mount as all slightly different. So a bit of drilling/squeezing/filing/bending to make it all fit nicely.
Motor screws longer to fit carbon + prop guard.
Lots of TPU standoffs to make it all fit nicely. 
Cam holder has (slighly) adjustable angle to fit my style 
Squeezed TBS crossfire nano rx between AIO and frame
Created a simple TPU holder for my Runcam Thumb Pro

Other than that nothing special in the build process.

Software wise i copied all my settings from my Mobigital 75mm whoop (running BF4.4 betas) as same AIO and connections etc. So only adjusting the tune with some slider action

Maiden flights in my appartement did show that (with roughly)  identical weight as my Mobigital , it needs higher throttle so lower flight time with same battery. Likely due to more obstructed airflow from the carbon frame arms below.  Its compensated by zero jello and almost no vibrations (compared the Mobigital) because of the more rigid build.
Also the slightly wider wheelbase makes if feel more stable around the roll axis with the camera mounted on top. Super smooth small gap camera stuff , so exactly what i was looking for. And a super low profile of 30mm due to the low stack position and camera mount.
Flies great at 2S and 3s . 3s better with the camera on top.
I may at some point flip the build and make it a pusher to see if unrestricted airflow makes it a better whoop overall. Probably also going to play with different motors in the future just for the fun of it.
Anyway, some tuning and fun flying to do ;-)

edit: see later post for pusher version DigiTwig V2 which final version ended up looking like this


edit 2 : and again later here DigiTwig V3 which is the final version i settled with after a long road of modifications until i was happy. This version has front 40mm and back 2' props

That red on black looks great!

(14-Oct-2022, 07:38 PM)Lemonyleprosy Wrote: That red on black looks great!

Thanks. Bit hard to see , but its very dark blue and not black. The spray paint was called "Black & Blue" but it is a nice dark blue shade.

Hi Fpvapnea,

Very interesting build. GOOD JOB. 

Very genius to cut off the whoops and use with the Twiglet CF frame.  

Using an "Undressed" or "Naked" Vista unit is also interesting. 

What is the dry weight (without battery) ??

What batteries are you useing ??

Thanks.
Dryweight is 60 grams. I fly 2s with my favorite sofar the Flywoo 750Mah HV explorer 2s.
They give me serious power and 5,5-6 minutes of flytime.
For 3s i stick with tattu 450Mah, not too big/heavy and extra oumph when the Thumb pro is on top.
Waiting desperate to test some of these GNB batteries but a nightmare to get here in NL and already waiting 2 months for a batch from china (expected arrival moved up to end of november grrrrrrrrr)
Just finished the build yesterday so more testing to do what is the best balance of weight vs flytime with and without camera on too.
But before i went to bed last night i flew 3 packs of the flywoo's , had the throttle dialed in , then a few of the tattu 3s with power limit ar 80% not to launch it through my ceiling to jupiter and was looooooooving it. Dare i say it flew even with more fun than my beloved mobigital. Somehow you feel its a little wider and waaaaay stiffer when banking through the corners at high speed. Feels more like a fighter jet and an actual quad than a little speedy toy ?✌️

p.s. regarding the cut of propguards, i did not like the typical 'just stick carbon under whoop frame' approach in an efford to make it stiffer and fight jello for the 4k camera footage but wanted full carbon response but with just the protection of the guards. These little props can be nasty razorblades if they hit a painting or other delicate stuff (or my skin)

I am soooo going to love this thing.

(15-Oct-2022, 09:01 AM)fpvapnea Wrote: These little props can be nasty razorblades if they hit a painting or other delicate stuff (or my skin)

When I first started and bought my Beta85, I decided to test it in my room, while not wearing a t-shirt and after some beer.  It promptly flew up and hit my chest (read that as nipple) and chewed it up before I could disarm.  That was with propguards, which seemed to make it worse in one sense, but without it would have definitely drawn blood. 

Lesson learned.  Wear clothing when testing your new 2S drone.

(I did laugh afterwards)

While reading i felt that one. Aaawwwwwggghhhhhh

Quoting myself "I may at some point flip the build and make it a pusher to see if unrestricted airflow makes it a better whoop overall."

DigiTwig V2

As i had an extra Twiglet mini frame (i ordered 2) I ripped my mobigital 7 apart and transplanted its guts into this frame but now in a pusher setup.
So now i have 2 quads with identical components and tune and weight (1g diff) one puller and one pusher to be able to compare apples to apples.
And WOW. Same battery (flywoo 2s 750Mah HV) ~1.5 minutes longer (about 7+ mins).
Hovers at 10-15% lower throttle.
Does make a hell of a lot more and more irritating noise though , not sure why with better airflow and have to investigate. 

Originaly when i dropped flight time compared to the mobigital , i suspected the more disturbed airflow of the carbon frame in the path of the air to be the main culprit as could not explain it any other way. In a pusher that is no longer there anymore and indeed flight times return to expected with same motors/props/weight.
Wil do more comparisons coming weekend on fly feel etc.

That’s an awesome experiment!
Do they have any differences in flight characteristics, or is it primarily just the longer flight and louder noise?

(18-Oct-2022, 10:30 PM)Lemonyleprosy Wrote: That’s an awesome experiment!
Do they have any differences in flight characteristics, or is it primarily just the longer flight and louder noise?

I have not tested that properly as almost midnight here and just did some hover and back and forth testing etc before going to bed to confirm my suspicion. 
Will report back when i have a good idea if and what is the diff in flight behavior/feeling.
It will likely fly a bit different and may require some adjustments in tuning etc. Will see when i have more time.
Back to my dayjob for now ;-)

Hi fpvapnea,

First, I like your pusher.  Cool   GOOD JOB 

Very ineresting. I have always thought that it should work that way, but
never bothered to try what you have done; that is, to compare the FLY
TIMES with two identical quads except for one being a pusher and one 
a standard configuration. 

I have one 4 inch open prop pusher. Although I don't have a lot of air time
on this one, flights have averaged about 16 minutes with a 3S 1100 mAh
battery. Thing is, I generally get about 15-16 minutes with any one of my
standard 4 inch quads using the same battery. Also, note that none of my
4 inch quads are the same and don't even weigh the same, so not as close
of a comparison as yours. 

I do believe that the whoops with multiple struts disrupt the airflow more 
than just the arm of an open prop quad...so, there might not be as much 
fly time differential on 4 inch open prop quads.

When I get some time, I should do some additional comparison testing with 
the pusher compared to my other 4 inch rigs. I might even add some payload 
to the lighter ones to even out the weight which should level the playing field 
a bit.


 

Yeah my first instinct would normaly also be the strust from the whoop prop guards.
But the thing is (before i build this pusher) i compared the build with the Mobigital build.
It has same struts/propguards, same motors, same props, same AIO.
Diff is only the carbon frame and (which is the unclear factor) and the slighly wider wheelbase (85 vs 75 mm), wich i have been thinking about as well how this would affect airflow etc.
The few grams weight diff i compensated with some dead weight.
And still i had 10-15% higher hover throttle between the 2 pullers, which over the duration of the flight causes the lower flight time.
So only one of the 2 diffs could cause the sudden drop in flight time between these 2 models.

Then we move on to the pusher and the flight time between this and the mobigital disappears. So somehow the pusher compensates/negates the initial cause of this diff.
On larger frames the percentual size of the prop airflow blocked by the carbon frame is much smaller , but on this tiny whoop style builds its a large percentage (check the pictures) . Also larger motors probably care less about such a relatively small blockage. But tiny motors and tiny props is a different ballgame. So i am leaning strongly that this is the biggest factor. Cant think of anything else.

p.s. Probably wont have much time for any more tests this week , but this weekend will dive in deeper.
Its nice to have such an apples to apples situation as i can play with all kins of small things and do a direct comparison to the effect.
The louder noise is an unclear by product i still have no explanation for. Have to check the build carefully for anything loose/touching/rubbing etc as also have some vibrations in the low frequencies so maybe some loose nuts/washers etc when i slapped this quickly together. But they at least dont affect flight time ;-)

Had a quick flight in my lunch brake and besides the 1.5 minutes flight time diff and the sound diff, they fly pretty similar. Slight advantage for pusher which seems to fly a little more on rails (hitting gaps super clean) while the puller feels a little less stable. But only slightly not enough to give it a big heads up on flight performance and could just as easily be slight different tuning requirements . (angle mode only btw as not good enough for acro mode indoors, but with super low force (25) to get as close to acro as possible)

Regarding the sound. Its less then yesterday after redoing all the motor attachements with a few washers here and there to make sure i dont hit the windings. I held it down on the table and in turtle mode push full throttle on each separate motor or in pairs and i feel and hear vibrations from the back motors . So props and or motors suspect on the rear. Very well possible as been changing props a lot and the force it takes each time can easily bend shaft and or props. Will get some new motors in next months so wil just replace all and think it should clean up large part of the wierd sound.

I just remembered i had some 1102 9000Kv Uruav motors in some drawer that came in last week.
So i replaced (all soldered of course so an open hart surgery yet again) all motors , put new props on, betaflight remap/direction...............
Crap....
One motor D.O.A... Nice bangoods (aliexpress, slow but always good sofar, bangoods fast but hit and miss).

Anyway, test within a test (fpv inception....) i replaced the broken 9000Kv URUAV with a 10000kv Happymodel and just see what happens.
3,2,1.... no explosion and it flies . No problem apparently . Interesting but makes sense as every motor is driven with its own esc so why not ;-)
Then again if you google skitzo frankenquad , this is peanuts ....

Anywaaaaay. Sound is better, but still way louder than in puller mode.
I tested with props on (yeah i dont care anymore at this point ) in betaflight and one motor at a time , smooth as a baby bottom sounding like a sowing machine.
2 motors at the same time , sound level goes up and becomes screeeky and you feel vibrations between the 2 on the frame arms.
So i think its just the forces on the frame getting all sort of interference vibrations between the engines.
Apparently bending away from the center stack (pusher) generates different and stronger vibrations than towards the center stack (puller).
The aio (gyro) does not pick them up at least not that i can see , likely due to hanging in soft mounting, which is nice. In betaflight with my hand on the frame i feel the vibrations when i open up the throttle , but the curves in the betaflight gyro scope stays nice and flat.
Same for blackbox. Nothing funky and all clean, specially after filters (which explains the long flight time and smooth flying).

Going to ignore it , it flies great , who cares at this point hahaha. Waiting for my new designed thumb pro mount for this pusher to get back from the 3d print shop (dont own a 3d printer....one step at a time with this crazy hobby) and then testing in "cinematic flying" mode, but will be fine as my mcGuyvered contraption to do a quick test showed it flies great also with heavy payload. What its main purpose is in the end. Small gaps filming where my cinelog 25 with naked gopro cant get in.

Hmmmm, something interesting i had not noticed when i quickly checked blackbox logs yesterday (as was looking for something else) and i still see today.
Seems like most of the work is done by just 2 motors on 1 diagonal axis (left bottom to right top) while the other axis is doing maybe 25%-40%. On a hover....

That could definately explain the noise as 2 motors on super high rpms.
So something is fishy and stinks here  and not just a small balance thing or something. And no it is not that one different motor as seen this same thing when it was all running on 10000kv. Not sure what it is. But too many factor at play as also running latest nightly and working with latest nightly configurator that has issues . So maybe my whole bf config is f'ed up on this build.
I think i am going to flash this back to something stable like 4.3 .....
Something for another day. Have had enough  experimenting for the day


edit: could not let it rest. BF4.3 flashed with some default and presets to exclude my own crap.
On hover in angle mode still same. Wierd crap...
Any ideas ??