I recently reviewed the STPHobby Armor 5C FPV Drone, it’s a BNF 5-inch drone with lots of heavy accessories. It flies fine but I think it has so much potential for better flight performance, so I decided to document my process of making it fly better by reducing some weight. Same principle should apply to all types of FPV drones.
After you’ve built or bought an FPV Drone, there are two ways to make it fly better:
- Tune it better (filter, PID and rates)
- Make it lighter – when a quad is lighter, it accelerates and decelerates faster, hence more responsive to the sticks and less prone to prop wash
Take a look at this post how to tune your quad, in this post I will focus on how to make it lighter.
This is what I am working on, the STPHobby Armor 5C.
To build a light weight FPV drone you should use lighter parts such as motors, frame, FC/ESC stack, etc. But since I don’t want to rebuilt the quad and try to keep the original parts, I will be looking for ways to shave off some weight.
Table of Contents
Removing unnecessary accessories
First thing is to take away all those plastic side plates. Apart from looking cool, for me they do pretty much nothing. And they weigh 14g total! Unbelievable.
You should remove any devices you are not using on the quad.
The Armor 5C comes with GPS, but I don’t plan to fly long range with it just freestyle, so I will be removing the GPS and its TPU mount. The weight saving is almost 11g! But I’d have to move the RX antenna elsewhere, I will be mounting it under one of the arms.
Going to the extreme, I even removed those plastic tubes on the arms. They are supposed to provide protection to the motor wires in case they get cut by propellers. But since I don’t plan to crash often, it shouldn’t matter much (I am a risk taker). Saving only 2 grams, but every gram counts :)
Cloth tape is awesome for securing motor wires, get some here: https://amzn.to/3DgTb70.
Using lighter screws
Warning: By using lighter/weaker screws can potentially reduce the strength and durability of your drone. Understand the risk before proceeding.
Titanium screws are much more expensive than steel ones, and generally aren’t as strong. However titanium screws are only about half the weight of steel! That’s why they are great for premium builds and racers where weight is critical.
The relatively cheaper Grade2 titanium screws are not as tough as steel screws though, so I’d still use steel wherever strength matters. There are different grades of titanium screws, you can learn more here.
I got mine from AliExpress for about $3 per pack of 10 screws, 2-week shipping to the UK.
I replaced most of the frame screws with titanium, but left the front ones steel as they usually take the most impacts.
And I replaced the stack screws too (original are 28mm steel) with titanium (26mm seem to work fine). Because they are slightly shorter, I had to remove the tiny little 1mm rubber spacer between the FC and ESC. Weight saving = 2.6g .
Removing motor skids
Because of those skids, longer screws are needed. By removing those motor skids and using fewer and shorter steel screws, I can save over 12 grams total! And because that weight is at the very edge of the quad, it has an even more profound benefit! The quad should be more snappy and responsive due to the smaller moment of inertia.
When using fewer motor screws, you MUST use threadlocker or they are more likely to come loose over time due to motor vibration.
I will be replacing those M2 hardware for mounting the Vista with a couple of 2mm zip ties (with double sided foam tape under the Vista). This can save about 1.5g.
Using a lighter antenna
I replaced the long VTX antenna with a shorter one. Not only the original antenna weighs more, long antennas also tend to vibrate more and might cause noise issue. By using a shorter antenna, I saved around 2g.
Taking away GoPro mount
The GoPro mount weighs 13 grams! I don’t even fly with a GoPro on this quad, so I will be leaving it out.
Using TPU FPV camera standoff mounts
3D printed TPU standoff mounts for FPV camera can be lighter than those carbon fibre camera plates for sure. But I couldn’t find a suitable design for the standoffs in my build (nor did I have time to design/test one), so I just left it as it is.
Another great tip is to shorten all electrical wires on the build, especially motor wires and the thick XT60 lead.
How much weight did I save?
Over 60 grams of weight saving! Without spending money on titanium screws and a lighter VTX antenna, you can probably still get the weight down at least 40g for free on this build.
Only after making your quad as light as possible, then tune it properly may unleash all of its potential and performance. This quad is going to fly so amazing :)
Using lighter props
After you have shaved off all the dead weight, consider trying some lighter props. This is the cheapest way to improve performance of your quad. Lighter props allow for faster RPM changes and improve acceleration/deceleration, making your quad more responsive, potentially allows for higher PID gains as well and better propwash handling.
Retune your quad
Since this has completely changed the weight distribution and performance of your quad, you should definitely retune it after all these changes. Follow this filter and PID tuning guide for instructions.