What's in the pack?
A closer look at the specs:
A closer look at the quad itself
Unfortunately like most other crazybee boards released at this time, this board ship with a nightly 4.0 build of betaflight that is not fully compatible with the latest version of betaflight. I'd recommend updating to a release version of betaflight 4 and transfer the key data in as I've done with my sailfly x here. The only real difference is the board orientation set up and motor mapping which is captured in the diff all files below:
2s flight performance
Straight up this is a quick little quad even on just 2s. It feels about as fast as a good 2.5 inch on 3s, easily. But the speed isn't even the best part. Control is something else. To me micros have always lacked the control feel of a 5 inch quad, you feel less connected but the Sailfly-X feels a lot more predictable. I found myself able to fly more comfortably even on the maiden flight and throttle control tasks like flying close to the ground felt a lot more natural. My guess is something to do with the very low disc loading that may be more in line with a 5 inch.
Better than both of these those is simply stunning efficiency. Other than the 2s battery that shipped with this quad the only batteries I had immediately available with a standard connector were GNB and Tattu 2s 300mah batteries. I was astounded that these batteries consistently gave me 4-5 minutes of fairly hard flying, it is difficult to fathom. Bob Roogi talks about the ideal maximum weight of a toothpick build being 72. With a 2s 300mah battery is is 58g which may go some way to explaining the efficiency. From my estimates the current meter is well calibrated and the maximum draw I saw at 100% throttle was just 7A total. So what does this mean? Lots of time in the air and very cheap batteries. Also minimal weight means less damage but more on this in the durability section.
Lack of weight does have one minor disadvantage which seems logical - lack of chuck-ability. When you try to throw a quad over and obstacle or in a split-s or power loop it doesn't seem to hold momentum at zero throttle. You can see this in the DVR above where most of my split-s and power loops look poorly timed. This may be a feel things since I am not used to the format but time will tell.
The tune feels precise which seems surprising given dynamic filters are off. Furthermore there are no oscillations and motors are cool even after 4+ minutes of vigorous flying.
UPDATE: After spending more time on 2s 450mah (which yield a 5-6 minute flight time) I feel the extra weight isn't worth it. My recommendation is to stick with 300mah and staying light if you stick with 2s, I've listed a few options at the bottom of the page
3s flight performance
3s on the HappyModel Sailfly-x is fast, the strong feel of control as mentioned in 2s really comes into play here because 3s really tests your limits (mine anyway). Whereas I feel the 2s suits small to medium parks I feel 3s suits medium to large parks. To use the same analogy as before this feels like a fast 2.5 inch micro on 4s from a speed perspective (like the skystars bolt reviewed here) but with better control due to the lighter weight.
One advantage that 3s cannot maintain over 2s is the crazy efficiency. It feels like the top 20% or so of the throttle on 3s really starts to taper off - whether motors are getting beyond their peak efficiency or motors are starting to flatten out there seems to be more current draw with little improvement in thrust. For this reason I prefer to run a 20% throttle cut on 3s. I got around 3.5 minutes from the stock 3s 300mah battery on average but found the variation on flight time based on throttle management to be larger which makes perfect sense given my earlier thoughts on peak efficiency.
This is the major departure from the Sailfly-x. Firstly the Caddx EOS2 camera which is a fairly well known quantity now really offer just middling performance. It's looks nice in directly light but in many conditions the red hues become super-saturated and look unrealistic. Low light performance is average. My main complaint of this particular cam in the trashcan review when in 16:9 format as it is here was the lack of vertical field of view making it tricky to fly. I've personally since gotten used to this but it is something to be mindful of.
I'm pleased to say however that the VTX does tend to make up for the camera shortcoming in that it does appear to offer a better signal the the 25mW sailfly vtx (most AIO vtxs don't actually put out 25mW) and that at 200mW it is vastly more powerful. For me 100mW feel like a good setting - not a lot of heat but a signifant improvement when flying behind trees. Like any modern VTX all settings can be accessed in betaflight OSD via smart audio control.
Now for the major downside... on first glance the trashcan canopy looks great - it is very lightweight AND offers adjustable camera angle. Firstly the angle isn't really adjustable because all the efforts make to make the profile low means the camera board fouls on the other components. Next the light weight it false economy - either by design or lack of material the canopy vibrates and moves in flight which means jello (wobbly video) during mid to high throttle especially. I can get around the camera but the jello is really off putting. You can fly through it like most things but it does detract from the overall experience.
Conclusions and what next
The Eachine Red Devil is a hard one to pick - it offers wonderful value for money and amazing flight performance but is let down by the FPV experience. Although the frame looks to have been strengthened compared to the sailfly-x there are question marks in my head about the long term durability of the plugs in the way they can rub against the battery - even when protected by foam tape.
As a standalone product I do actually prefer the Sailfly-x... the heavier (uglier!) 3d printed canopy offers a sturdier mount which minimises unwanted movement. This means that even though it has an inferior camera and VTX that the FPV experience is more enjoyable.
This isn't all doom and gloom though - like the sailfly-x pricing is MUCH more competitive that any other offering in the toothpick category but it does offer a distinct advantage: potential. I have already ordered and received several low cost upgrades the will help realise the true potential of this powerful ultralight quad. As a hint:
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Here are all the parts specific to the red devil including my recommended batteries. Click through to take you through to the page
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