T-mount propellers are those that are based on a 1.5mm diameter centre shaft secured by a 2mm screw either side. They have been the only mounting option for 2-2.5 inch props but are now becoming more popular for 3" due to the weight they save over a 5mm single shaft prop mount. There are only 4 different types of t-mount 3" prop currently available so I've compared them all plus the new HQ 2 blade which is due for imminent release plus a darkhorse prop in a smaller size to make up the numbers. Please note this is a subjective comparison based on my opinion but my help as a startpoint for your decision. This is based on real world feel, light time and bitter experience with motors I've burnt out.
Emax Avan 3 inch tri-blade
This is the first modern design 3 inch prop designed for a t-mount which was released with the 3" Babyhawk R (reviewed here).
HQ 3x3x3 v1s tri-blade
HQ props have the newest 3" t-mount prop design at present. This has been chosen as the stock propeller for the Full Speed Leader 3 (initial review here and flights here)
Gemfan 3035 triblade
This is quite an old prop and can be hard to find but is still suprisingly relevant.
Gemfan 3025 bi-blade
This is the original 3" t-mount prop and so can be found for sale in weird and wonderful places
HQ 3x3x2 v1s bi-blade
Just released at the time of writing: as per the 3x3x3 above but bi-blade rather than triblade. Disclaimer: I have not tested yet and below information based on assumptions from comparing bi-blades and tri-blades in general. Will update once mine arrive and I've tested.
Dark horse to consider...
Gemfan 2540 flash triblade
Yes this is a 2.5" prop but objectively it is so good it is worth considering downsizing. You can find an earlier review I did on these here and a review on the Skystars Bolt X120 which uses these on 4s here
Please note the King Kong 2840 propeller was not included here because I found the Gemfan 2540 superior in every way. Also I have not include the Rotor X 3044 because it is difficult to source where I am based. The feedback that I have had is that it is more aggressive in pitch than any of the above props and probably only suitable for for stator sizes 13xx and up.
The Leader 3 (SE) is a follow up to the hugely successful Leader 120 which I have reviewed and documented modification extensively, most recently with a summary here. Both are available from Fullspeedrc.com This has been a highly anticipated release not least of which because there has been no releases from Full Speed since last years' Beebee 66 light. The good news is that a big chunk of that wait has been spent working on the Leader 3. FYI two of the main guys are pilots from Full Speed RC are pilots and do a lot of work testing before release which is a welcome change in this hobby compared to many models that come out half-baked.
Firstly the Leader is available in 2 variants. The standard model (Leader 3) can be seen below and weighs 87g with regualar standoffs. The Leader 3 SE is exclusive to Fullspeedrc.com and comes with a 3d printed canopy instead of the standoffs. It is 6g heavier but offers several benefits that I'll cover a little later on.
A run through the components
First the frame. Like the Leader 120 the base plate of the frame is 3mm thick although it has been stretched to 130mm motor to motor diagonally rather than 120mm This means it is capable of accepting a true 3" propeller rather than 2.8" maximum on the Leader 120. The frame is most definitely still a 'deadcat' shape meaning the two motors are further apart (107mm) than the 2 rear motors (98mm). Additionally it is a 'squashed-x' compared to a 'stretched-x' meaning the front and rear motors on the same side are closer together. This means it should be more stable in the roll vs. pitch axis but modern flight software somewhat negates this. Compared to the leader 120, sideplates have increased from 2mm to 3mm thick which should aid durability. More imporatantly a 19mm gap rather than 17-18mm means the leader 3/SE now natively fits a 19mm micro cam. It's worth nothing that the baseplate is only 1 piece so you cannot replace single arms. Personally I think replaceable arms are unnecessary on any quad size less than 4" since there is much less leverage for breaking on a smaller quad. The frame can be purchased separately here.
The canopy (Leader 3SE only). When I first saw the canopy I wasn't keen because it adds 8g weight however I think the functionality may just offset that - jury is out until I fly it some more. The 3d TPU print is of very high quality available in black,white, red, purple, blue or yellow and performs the following functions:
The motors are 1106 4500kv which is the same specs as those found on the Emax Babyhawk R 3 inch and the Skystars X120. They are not open bottom and have mounting holes for regular t-mount props and the emax 2.3" avan props. Most importantly they are rated for up to 4s.
Like the original Leader 120, build quailty is excellent. Solder is clean, wires are cut to length. Not much more to say here, it is well beyond my ability! With the quad assembled there is plenty of room behind the camera to adjust tilt (45° and beyond are capable) and the receiver is mounted in this void. with plenty of room left yet. This is speculation but I'd like to address anyway since it seems like a common thread: my best guess is the caddx turtles HD FPV/DVR (not yet released at time of writing) will fit but not without a little modification. My reasoning is that there seems to be 2-3mm 'spare' room between each stack layer. If these standoffs are trimmed by this amount you will be able to save 6-9mm in height which should be enought to fit the turtles board. It will require some fine wire management and a steady hand to trim the standoff but I do think it may be physically possible - a project for another day. That being said, the double stack of the runcam split micro definitely will not fit.
Plenty to talk about here although most can be foundin commentary of the Betaflight screens below. If you don't choose to read these however:
Final thoughts pre-flight
As you can see from above this looks to be a very well thought out quad and not something slapped together from a spare parts bin. The Babyhawk R and Skystars bolt X120 have both shown that 1106 4500kV motors perform well on 4s in 2.5" and 3" so I am excited to see what the Leader 3SE will add here with all the work that has gone into development from a hardware and software perspective. On paper this looks to have the edge on both of those models in terms of weight, VTX capability and ESC current overhead however the real test will come in flight - stay tuned for part 2 of this review where I will cover flight in full - I already have 3s and 4s batteries charged for tomorrow :)
The Fullspeed RC Leader 3/SE can be bought directly from Fullspeedrc.com and is also available at other retailers however buying from the source is your best chance to get your hands on one quickly.
This is part 2 of the review. In part 1 I discuss an overview and setup (including betaflight settings from factory) are covered in detail: Part 1 review
Firstly a very important correction. In the first review I showed a picture of the quadcopter minus battery sitting on a set of scales at 65g. I took this for granted and after measuring on my own scales got 84g. I don't usually trust weight in text but seeing it was sitting on digital scales I did not measure myself. Disappointing as this is misleading so I updated Gearbest immediately. To their credit they promptly took the image down and corrected the weight in the description - see below.
Preparing for flight
Just some minor housekeeping prior to the first flight. XM receiver was fixed in place on top of the VTX as it was dangling free when I received it. Antenna was fixed in place with a cable tie off the rear arm and heatshrink to secure. VTX antenna got the same treatment off the rear upper-deck of the frame. Lastly I replaced the rubbish battery strap with one from RJX hobbies (review here). Although a buckled strap was included as well as the one picture above, it was much too long? Weird.
Flight performance on 2s
Just because the Bolt X120 *can* fly on 2s doesn't mean you *should* fly on 2s. I used my Turnigy Nanotech 2s 950mah (47g) pack and needed about 40% throttle to hover. I could fly but performance was lacklustre and I got bored. I did get about 4 minutes flight time but won't say any more.
Flight performance on 3s
After my initial disappointment on the weight, performance on 3s 450mah turnigy nanotech was better than I had expected. It felt controlled with enough speed to be enjoyable. I had to switch to default betaflight 3.3 PIDs though since the customised PIDs look more like a 4s tune and felt sloppy as a result. I did manage to get good flight times on these little batteries of approximately 2.5 - 3.0 coming down at 3.75 volts and had fun doing so. Given then power of the quad I'd probably pefer a 650mah 3s for another minute or so of flight and would have less concern about sagging on big throttle punches. For the places I usually enjoy micros the most (tight with small trees) I found 3s the most fun.
Quick update: compared back to back on same batteries with my Leader 120 which is lighter (68g vs 84g) with 'smaller' motors (1104 7500kV vs. 1106 4500kV). I found it was similar speed with comparable handling and I actually got as good if not slightly better flight time on the Skystars Bolt - the extra stator size was negated by the lower kV from an efficiency standpoint. The leader however cannot do 4s...
When I went from 3s to 4s on the BabyHawk R 3" (review here) I got a reasonable increase in speed but not 33% as you'd probably expect. Given the same motor size (1106 4500kV) I was expecting something similar here but got a complete shock here - This thing ABSOLUTELY SCREAMS on 4s. I've always liked the Gemfan 2540 props (review here) but have never tried them on 4s and boy, they sure hold up and deliver on the extra power, it was like a different quad altogether. The speed was like nothing I'd felt on a micro and I had real trouble managing in a tight area. This probably wasn't helped by the fact I was using a CNHL Ministar 4s 650mah battery which weighs 87g so I was really blowing out on corners, even with a lot of extra throttle. It reminded my of running a heavy 4s 3 inch with 1408 motors - super fast but handled like a brick. I'd dare say 450mah 4s at around 62g would be a better option for weight control. at the cost of some flight time. As it stood I was getting 4 - 4.5 minutes on the 650mah battery. I've since moved to betaflight 3.4.0 and have got the tune tighter without oscillations but it is still a handful. For my piloting ability running this quad on 4s requires a bigger area akin to my 4 and 5 inch quads but that kind of deafeats the purpose of this micro. For my money and ability I actually prefer this on 3s - It is much quieter and handles better with the lower weight which is better suited to small parks. The noise alone on 4s makes people more wary of this one.
Rather than trying to recommend how many cells you should run I've merely stated my opinions on what I want from a micro. The most important thing here is that this Skystars Bolt X120 is well and truly capable of comfortably running 3s or 4s depending on where you are flying or how you are feeling on a particular day. The new throttle limiting feature on betaflight is a great way of limiting power to fly on 4s if for example you want to stick with just this battery size with power more akin to 3s. I've written a full tutorial on this here including how to assign to an AUX switch.
Although I alluded to the similarities to the original Leader 120 (review here) it is clearly a different quadcopter with a different feel and different capabilities - it has a much better camera and VTX but is much heavier and designed to run on more cells which make it heavier again for a different flight feel. A better comparison is perhaps the BabyHawk R 3 inch which I find handles better but lacks the speed of this model, particularly on 4s. Images below on a scale for all of these for comparison.
The Skystars bolt can be bought exclusively from Gearbest in several different formats - an unbuilt kit with no receiver (PNF), a built quad with no receiver, or as a built quad with FRSKY or Flysky receivers.
Check on my discounts page regularly for specials but at the time of writing the unbuilt kit is available for $117 and the FRSKY BNF as seen here is available for $134