The Build

The purpose of this build is to reduce the noise of the Shendrone Squirt v2. Most of the props that I have tried sound very similar, with an annoying deep beehive droning sound. I was very happy with my last Squirt v2 build by achieving longer flight times. But now, I want to it sound less intimidating.

My initial thoughts were to get bigger motors to spin props that can produce more thrust. I have been hearing a lot of good thing about the HQ 76MMX8 props and I wanted to give it a try, because it might be exactly what I need.

I wanted to keep the build as light as possible because the FPV Cycle 2203 motors (~20 grams) are heavier than the 1407 motors (~15 grams). So, I use the standard 2 wall and 15% Infill Gyroid settings for all my 3D printed parts with some exceptions where I added more infill or walls for extra strength. In Cura, it is really easy to make those modifications when you are slicing it.

I am very grateful that DroneCOproductions (https://www.dronecoproductions.com/) for sharing the awesome Slammed Squirt 3D printed parts, because it looks awesome! However, I did make some minor changes to fit my build. Here is breakdown about the files I remixed and could be found on thingiverse (https://www.thingiverse.com/thing:4780861)

Antenna mount in the rear of the quad (SQUIRT_VISTA__ANTENNA_MOUNT_v2.stl). If you mount the caddx vista at the very end of the squirt v2 frame with the existing M2 20x20 holes, the Caddx Air Unit sits very close to the rear standoff. It is so close that there is no room for the antenna mount to slide far enough down for ducts to stack on top of. So, I remixed it by cutting a 3mm notch to allow it to slide down a little further.

Next up are the ducts (MiniDucts_Slammed_v5.stl). The hole where the 25mm standoff goes through in the front is too thick. It is fine until I put the carbon fiber top plate on. So, I removed 2mm off two holes that goes in the 25mm standoff.

Finially, the GoPro 7 case. The GoPro mount that DroneCOproductions created did not have enough protection for my taste so I used my favorite case and remixed it to fit this build. I am willing to take on the extra weight to give the GoPro 7 more protection.

I am not sure what quad is Gemfan and HQ are designing their props for, but it is NOT for the Shendron Squirt v2, because all the new design props never fit! They are all slightly too big, so I need to trim all the props with a Dremel. These HQ Prop Ducted 76MMX8 might be the worst one of all because there are 8 blades on each prop.

Betaflight

My original Squirt v2 Mini Duct build is running an older Betaflight firmware (v4.1.5) with Robert Moss tunes. But I am curious to see how it will do with BF 4.2.8 and the Cinematic Presets. I have been using default PIDs and use only Betaflight presets with BiDirectionalDshot and RPM filtering for all my new builds. For the most part it works very well for all my 5” builds and even a 2”. But for the Squirt, it does not seem to do too well. I am getting lots of prop wash, especially when I fly close to the ground and the get noticeable lower flight times too. Then I rolled my firmware back too v4.1.5 with Robert Moss’s tunes and the 2203 motors squirt is happy again. I am very sure you can get the same results if not better with BF 4.2.8. But right now, I do not have the time to PID tune it.

Initial Tests

To make a long story short…. Are the HQ Prop Ducted 76MMX8 less noisy? Yes, it is. I do not think it is a huge difference, but it is noticeable. It is possible that the lower frequency sounds from a 3 blade prop travels further so it may appear to be louder. Whereas the 8-blade prop has a higher pitch sound. Overall, I think the HQ Prop Ducted 76MMX8 do sound better, but with the cost of lower efficiency.

Here is a breakdown using a DeciBel (dB) meter to measure the sounds at variouse points for each prop. Look at the youtube video desrciption to use the quick links.

HQ 76MMX8 Props:
0:13 - 5 Feet Away 73dB
0:22 - Across the Street 51dB
0:52 - Up Close 84dB
1:14 - Punch Out - 75dB

iFlight Nazgul Cine 3040 Props:
2:58 - 5 Feet Away - 72.9dB
3:11 - Across the Street 51dB
3:49 - Up Close 83dB
4:19 - Punch Out 73dB

Here is the bottom line with the props. If you want better sounds with a slight flight time reduction, then go with the HQ 76MMX8 Props (8 Blade). You lose only 1 min of flight time, so that is not too bad if you usually get about 7 - 8 mins. But if you want to do some freestyle flying with it, switch back to the 3 blade props because the 8 blade props are very sluggish. I think all those blades acts like wings and catch a lot of air as you move faster. You seem to glide into corners and dives. You need to put a lot of stick input to get it to move. As for the motors.... 2203 vs 1407. If you are doing slow cinematic flights, there is no noticeable difference except for efficiency. The 1407 motors are more efficient, so you will get longer flight times. But if you plan to do some freestyle flying, that is where the 2203 motors start to shine. You can feel the extra power from the 2203 motors especially coming out of the dive and the quad is some stable without the props wash wiggles. The 2203 motors are a lot smoother when you are flying it hard.

Multi Color TPU (July 10, 2021)

I built two Squirts with the same TPU color theme because I like the theme. You can find more details about the multi color TPU here: https://rotorbuilds.com/build/27601

The only downside about the new TPU is the weight. In the previous version (black and red theme) I used a 98A shore hardness TPU and that allowed me to print with 2 walls and still maintain a firm print.

But with the 95A shore hardness TPU I had to print with 3 wall or the ducts would be too soft and flexible. Also keep in mind that I am only using 15% (gyroid) infill so the wall count makes a big difference. In the end, the new TPU parts gained 20 grams. I also switch to an iFlight Nazgul 3040 props because the original red props did not match.

Windy Day Test - 18mph / 38mph gusts
GoPro 7 Black w/ Hypersmooth

Same video as above but with the DJI DVR.