I'm still working on this part as I have kids thus time is always an issue... However I'm always open to creative suggestions. Question: So what would you be looking for in a fin?

Side Note: I plan on slimming down a few of the parts to reduce mass. Biggest area being the front bumper (Hammer-Head) which could see a few tweaks here and there.

functionally a fin ensures that if you crash upside down you can turtle mode out with more ease as you should at least have 2 props not touching the ground.
a fin adds weight, induces bad quad behavior in the wind, and affects negatively agility.

nowadays fins are replaced by rods.

i have a 2.5 massive droner that I dismantled because it was too heavy. I drilled it to convert it to 16mm stack and even then it cant compete with toothpicks.

@ dafunk

A toothpick build is a bit like a dragster in the sense that it's build for speed with no accommodations made for durability. Just by running with the Droner frame your at a disadvantage even if the rest of the hardware is identical. That being said, at least the Droner will survive to fly another day, while the toothpick will need rebuilding.

Now as for the Fin what I got so far...

• It needs to be tall enough to keep the rear props clear of the ground but not so tall as to create handling problems.
• Must be light as possible and have a very slim head-on profile.
• If possible remove as much of the Aero (side) surfaces as possible to limit the effects of wind.
• Modular design to allow it to be removed or replaced as needed.

Side Bar (1): With whats listed above, realistically we could setup the VTX antenna to perform the same function. Yet without all the extra fluff of actually installing a fin. Easiest route would be to insert the antenna through a Capri Sun drink box straw. Then leave the Omi hanging at the end of the straw. Another possibility would be to heatshrink the antenna to the outside of the straw, which would allow for easier assembly. This would only use the Straw as support to keep the antenna stiff and thus allow the antenna to hold up the rear motors easily.

Side Bar (2): We could 3D-print the Droners side & support pieces and really go skinny with it. This would save 2-4 grams at most as well as allow parts of the frame the be quickly replaceable. You'd still need the CF frame of coarse as it wouldn't go over well with CMW if i produced the entire frame.

Hello,

2 additional things come to my mind
1- make sure the fin is rigid enough to hold the quad weight upside down
2- decide if you want to be able to pinch the fin to hold the quad in which case the center of gravity relative to the fin will matter

@dafunk

The original idea was to place the Fin where the rear spacer is now. However it with would require an internal M2 aluminum spacer through the Fin to maintain structural support. Otherwise the side CF pieces would be very prone to flex. At worst, this could make the copters integrity suspect and at best the Gyro / Camera could feel the flexing as the copter made high-G turns. Just pushing screws into the TPU wouldn't work as the print material isn't capable of supporting the screw threads under load. (Too fluffy) Rather the hole the screw sits in would become stripped in a short period of time, if not immediately.

Look at this older project I did 1-2 years back: https://www.thingiverse.com/thing:3571841
It shows the hinged door with an M3 aluminum spacer inside the hinge. With the M3 screws first going through the side panels into the printed hinge and then into aluminum spacer. This saved weight as it allowed me to use a smaller spacer (5 mm) while still keeping the frame very stiff. Yes, that Bicopter flies rather well after 1 year of tuning but is still scary as all hell to fly though... (Think flying guillotine)

About your suggestions

1) Is pretty simple to do by controlling the material thickness in key areas...

2) Is quite a bit harder as this would require Fin placement on top the Canopy to match the CG (Center of Gravity) for easier pickup. Also consider that printing it AIO (All in One) wouldn't be possible using TPU. Simply put, it would be prone to print-related warping and you'd end up with a lot of waste material from the print supports. Thus it would have to be printed / attached separately to ensure high quality prints. The upside of this is that the Fin would be hot-swappable without requiring the removal of the Canopy. Please keep in mind that the canopy thickness is only 1.5 mm in many places. Thus it may require beefing up to properly support the Fin's load in flight / crash.

Edit
I laid the quad upside down on my desk and can clearly see that the props have around 1" + of clearance. It appears to self-level on the flat part of the canopy which is nice. Even thumping or pushing the quad around, it returns to the flat position. Adding a fin would raise the clearance but make the quad prone to sitting at an odd angle. Not sure if a Fin would really add value here unless the copter crashed in tall grass. Even then, you'd most likely not be able to flip back over in such a situation.

Our discussion here is quite good and constructive!

Thank you!

Formula-1 look...
Yes, Its possible to do this with the front bumper but I'm not sure how it would print. The current design was a PiTa to print and had to be refined to allow it to work. I think I went through 40 + iterations and maybe a dozen or so prints to get the various parts to both fit right and the print to an acceptable level of quality.

Question: So how exactly does the print need to be to achieve the correct Formula-1 look?

u made my day with your bicopter !!
seriously when I clicked the link my expectations were not that high.

reading your edit shows the fin adds weight without adding functionality... if I were in your shoes I would set a goal in battery time per flight and start removing decorations until that goal is met.

Glad you liked the Bi-copter! It's been a pet project of mine since David released the initial build to the public. Unfortunately RCE closed shop and thus the development of the Bi-copter has all but stopped. (Not counting my endless tinkering) On the upside, I've been able to solve the reverse flight instability (oscillation) issue the original design had by adding motor filtering. Betaflight's not really made for non-quads so tuning has been much fun! (Sarc)

Only thing I've yet to work out is how to add a "tail" to the Bi-copter while still preserving the spirit of the original design. Reason I want to add a tail (Inverted V-Tail) is to improve Yaw / Pitch stability at high speeds to address stability issues encountered. Example... I'm hauling arse and then try to turn without slowing down. This results in the nose suddenly dropping if the Yaw rate becomes too great. I'm guessing that the extra lift / drag from the body isn't enough to compensate for when the servos tilt to Yaw. It's like running sideways and expecting to be able to maintain a sprint.... Ain't happening! Its possible that by adding a tail that the added drag will help stabilize the Pitch axis during a hard Yaw, keeping the nose up. Alternatively, I have considered decoupling the Yaw from the main rotors and adding a small rotor just aft of the main body. Being that brush-less motors are bi-directional capable, it should be able to use a tiny-whoop motor to act as a Yaw rotor. If thats possible, then all the Servos would have to manage would be Pitch control. (Motor speed controls Roll) Yes I know this would basically become a Tricopter...

Anyways back on topic...

I could have most of the Massive Droner frame 3D printed from Nylon-CF as I've a friend in Frankfurt with some serious printing tech. This is the same material used for the Bi-copter yet at most this would lower the flight weigh 3- 5 grams. I'm thinking this may not be worth the costs (20-40 Euros) or effort involved for such a small gain. Otherwise, the best way to increase the flight times would be to run a 3S LiPo, lower KV motors (mounted inverted) with 3" bi-bladed propellers. This would lower the prop losses significantly while allowing for 20 - 30% increase in available mAh from the LiPo. Maybe even ditch the side CF panels / motor braces altogether while building up the frame pretending it were a toothpick quad instead. This would drop nearly 20 grams from the build but the durability would suffer as a result.

Actually what I had in mind is to minimize the the 3d printed parts. the droner rigidity makes it fly better relative to a toothpick.
I don't think you should get rid of any original part. In my opinion, you have the perfect kv, as I have the exact same motors and they are not particularly power hungry.

Also from personal experience, toothpicks are not fragile at all. their lightweight makes them endure a lot of abuse. I find myself damaging a lot of motor and I know it sounds wrong but I wish props for this category were less durable to save motors.

Question: Can you share your BF settings? I've been looking and there is next to nothing on-line for the Droner.

diff all

version

Betaflight / STM32F411 (S411) 4.2.0 Jun 14 2020 / 03:04:43 (8f2d21460) MSP API: 1.43

config: manufacturer_id: IFRC, board_name: IFLIGHT_F411_PRO, version: bc19b7dc, date: 2020-04-01T04:37:12Z

start the command batch

batch start

reset configuration to default settings

defaults nosave

board_name IFLIGHT_F411_PRO
manufacturer_id IFRC
mcu_id 0056000f3439510f38313437
signature

name: MASSIVE droner

feature

feature -RX_PARALLEL_PWM
feature -AIRMODE
feature RX_SERIAL

map

map TAER1234

serial

serial 0 8192 115200 57600 0 115200
serial 1 64 115200 57600 0 115200

aux

aux 0 0 0 1800 2100 0 0
aux 1 1 1 1300 1700 0 0
aux 2 13 2 1800 2100 0 0
aux 3 28 1 900 1100 0 0
aux 4 31 4 1900 2100 0 0
aux 5 35 4 1800 2100 0 0
aux 6 47 1 1800 2100 0 0

adjrange

adjrange 0 0 1 900 2100 12 1 0 0

vtxtable

vtxtable bands 6
vtxtable channels 8
vtxtable band 1 BOSCAM_A A CUSTOM 5865 5845 5825 5805 5785 5765 5745 5725
vtxtable band 2 BOSCAM_B B CUSTOM 5733 5752 5771 5790 5809 5828 5847 5866
vtxtable band 3 BOSCAM_E E CUSTOM 5705 5685 5665 5645 5885 5905 5925 5945
vtxtable band 4 FATSHARK F CUSTOM 5740 5760 5780 5800 5820 5840 5860 5880
vtxtable band 5 RACEBAND R CUSTOM 5658 5695 5732 5769 5806 5843 5880 5917
vtxtable band 6 BAND_D D CUSTOM 5362 5399 5436 5473 5510 5547 5584 5621
vtxtable powerlevels 3
vtxtable powervalues 25 100 200
vtxtable powerlabels 25 100 200

master

set gyro_lowpass2_hz = 375
set dyn_notch_width_percent = 0
set dyn_notch_q = 250
set dyn_notch_min_hz = 70
set dyn_notch_max_hz = 350
set dyn_lpf_gyro_min_hz = 300
set dyn_lpf_gyro_max_hz = 750
set acc_calibration = 179,24,-389,1
set rc_smoothing_auto_smoothness = 20
set serialrx_provider = SBUS
set blackbox_p_ratio = 64
set dshot_bidir = ON
set motor_pwm_protocol = DSHOT300
set motor_poles = 12
set yaw_motors_reversed = ON
set osd_rssi_pos = 2092
set osd_tim_2_pos = 2516
set osd_current_pos = 2081
set osd_mah_drawn_pos = 2507
set osd_gps_speed_pos = 52
set osd_gps_lon_pos = 66
set osd_gps_lat_pos = 81
set osd_gps_sats_pos = 48
set osd_home_dir_pos = 47
set osd_home_dist_pos = 56
set osd_avg_cell_voltage_pos = 2498
set debug_mode = GYRO_SCALED
set vtx_band = 5
set vtx_channel = 1
set vtx_power = 2
set vtx_freq = 5658
set gyro_rpm_notch_q = 800
set name = MASSIVE droner

profile 0

profile 0

set dyn_lpf_dterm_min_hz = 105
set dyn_lpf_dterm_max_hz = 255
set dyn_lpf_dterm_curve_expo = 7
set dterm_lowpass2_hz = 225
set feedforward_transition = 40
set iterm_relax_cutoff = 10
set yaw_lowpass_hz = 70
set throttle_boost_cutoff = 10
set ff_interpolate_sp = AVERAGED_4
set ff_spike_limit = 55
set ff_smooth_factor = 40
set ff_boost = 0

profile 1

profile 2

restore original profile selection

profile 0

rateprofile 0

rateprofile 0

set rates_type = ACTUAL
set roll_rc_rate = 20
set pitch_rc_rate = 20
set yaw_rc_rate = 20
set roll_expo = 40
set pitch_expo = 40
set yaw_expo = 40
set roll_srate = 72
set pitch_srate = 72
set yaw_srate = 67

rateprofile 1

rateprofile 1

set rates_type = ACTUAL
set roll_rc_rate = 10
set pitch_rc_rate = 10
set yaw_rc_rate = 10
set roll_expo = 54
set pitch_expo = 54
set yaw_expo = 54
set roll_srate = 72
set pitch_srate = 72
set yaw_srate = 67

rateprofile 2

rateprofile 3

rateprofile 4

rateprofile 5

restore original rateprofile selection

rateprofile 0

save configuration

save

i could share a blackbox file if you are ok to share your email or other mean of file transfer. its a hover flight on 1204 xing 4500kv ... as i said before I didnt fly it much because it didnt fly long enough. i could not tune it properly on 1107 toa 4s (16mm stack) but i have the blackbox and config for it.
I declared it not worthy of flying on 20mm stack because of short flight times (although the handling felt perfect).

If I was to rebuild it again I would use these settings https://theuavtech.com/presets/ => with the filtering of a toothpick and the pid tune of a 5" freestyle