I'm a scientist by training so not usually one to use hyperbole (especially where it feels click-baity in titles) but I really do mean it here: This is the best value quad I've reviewed so far this year. It is not the best long range, it is not the best free-style and it is not the best racer. But for those occasions where you are looking to fly in a small to medium park, empty office or commercial area out from your back yard which is 90% of my fling, this is the ideal tool for the job.
The HappyModel Sailfly-x is a "toothpick class" ultralight micro quadcopter. It has an all up weight of 38g without battery and can take 1s, 2s or 3s batteries. It is available with onboard FRSKY, FlySky or DSM reveivers or without a receiver where you can add crossfire or anything else. It is a fairly complete kit (see below) and is available for just $88 at full retail. Availability seems to be somewhat limited to Banggood at time of writing but my guess is that many retailers will pick this one up.
For this review I'll break down what is included, the specs, document differences from the stock betaflight and then cover off in the actual review performance on 2s, 3s, FPV performance and close with a summary and my recommendations. I'll also list spares and upgrade parts as the become available.
Specs and what this means
Bad news/good news scenario. The bad news is this is a nighly build version of betaflight 4.0 meaning the latest version of configurator (10.5.1) is not 100% compatible at time of writing - it will crash when entering aux switch adjustments or OSD. CLI is fully functional however. The good news is the settings are customised and really good out of the box. I've captured the customisations in screen grabs below so it is easy enough to update to a release version of betaflight and re-apply these customisations. As usual, click to embiggen.
Last things to cover off before flights
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.
Although this is generally considered to be one of the better All In One (AIO) cameras from a light handling perspective (check out my night flight on the Mobula7 with the same camera), it is still inferior to many separated cam/vtxs option both from a picture and signal transmission perspective. This has been done for 2 good reasons though: weight and cost; both of which are reasons that make this especially compelling. No doubt people will be updating their sailfly-x with better (and heavier) cameras and VTXs but this can really have a negative impact on performance. Example 1: Although the Eachine Traschan has a better camera and vtx, the increase in weight really hurts the flight dynamics meaning it is less fun to fly than the mobula7. Perhaps more relevant is the direct comparison of the sailfly-x to the fullspeed toothpick: the fullspeed model clearly has a better picture and signal but I find myself wanting to fly the sailfly-x more due to superior flight characteristics.
Discussion aside image is pretty clear if a little low in resolution and pretty good light handling although perhaps a bit washed out. VTX power is limited to 25mW which is fine for close-by flying and even reasonable distance if you have good google antennas but it can get a little ropey which trying to get the signal to penetrate foliage.
Given how ridiculously durable I've found this to be I'd call this a 'tank' but it's not - the extreme durability comes as a result of the light weight. You can see below I've made a simple crash compilation video and although early days, not one has even bent a prob. Yes I don't fly over concrete for the most part but If I'd crashed a more conventional micro like this it would be bent props at a minimum. This is an excellent improvement over the Mobula 7 which was widely criticised for it's weak frame and also over the trashcan for it's finicky canopy. Both frame and canopy on the Sailfly are VERY sturdy given the all up weight.
Summary and recommendations
The Sailfly-X is a very low cost "toothpick-class" micro brushless quadcopter from Happymodel, the same company that released the popular Snapper7 and Mobula7 micro quadcopters. It is well equipped with propellers, flight battery and even a spare canopy. It is ultralight meaning it can achieve high performance even with small batteries.
The quad is very well balanced component-wise and offers excellent control and power on 2s and outstanding power on 3s. The light weight comes about from the simplified components namely the main board which includes flight controller, 4xescs and a receiver plus an all-in-one vtx-camera. Being lightweight it has excellent durability from my testing so far. A further advantage of the low weight and high thrust is the exceptional flight time - a low cost 2s 300mah battery offered strong performance for 4-5 minutes of flying time.
This is a very easy quad to recommend - it offers breathtaking performance given the size, is extremely durable and offers exceptional flight time. This is even before we consider the price which around $88 at full retail which is remarkable and worth buying just for components to use on you own build (components which are not often discounted at time of review...). One of the sacrifices made to keep the weight down was the use of an all-in-one camera which has a comparatively low resolution at 700TVL and only offers up to 25mW. That said this is one of the better AIO cameras and offers surprisingly good low light performance.
I can see this being a good seller for Happymodel so long as they can keep their QC and customer service in check. Personally I've had no failures but have heard many stories of poor QC on the Mobula7HD. Hopefully they have learnt their lesson and 30-40 packs in I have had no issues at all.
As I mentioned in the first paragraph of this review I tend to avoid using hyperbole and making direct recommendations but if it is anything to go by one of the first things I did was tell a local retailer that he must stock this model - the performance per $ is just too great to ignore.
Quick update: Use the code Aff7off to get the sailfly-x for just $80-$82. This and other specials over on my coupons and discount page.
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Spare parts and upgrades
As parts become available I'll list them here.