The Happymodel Mobula7 (reviewed here), Eachine Trashcan (reviewed here) and many other brushless whoops use generic 4 bladed 40mm props that are cheap and readily available but are they the best? Simply put, no. They are from a toy grade mould and we have accepted them because when these brushless whoops were first released there was simply nothing else available. Fast forward to the present day with the growth in popularity of these models there are a lot more options, some readily available internationally, some not so much. In this article I'll give you my experiences on what I found to be my favourite prop and the justification of why (what it is I look for in a propeller).
This is the sixth article in my series of HappyModel Mobula7 upgrades, many of which can be used for the Trashcan too. Also to come are:
What props are available?
If you're in North America probably the full list of what is below. I'm not in North America though so I was limited to what was locally available and what had low (or no) international shipping cost. Therefore this is not an exhaustive test, my approach was more on of pragmatism.
I'll compare all my findings back to a baseline result of the stock props for simplicity
Gemfan 1636 (4 blade)
I used these when I was running the v3/trashcan frame which I blogged about here. These were a direct improvement over the stock props in all aspects but were a little more amp-hungry. Grip and speed was improved and control felt better. Props are well balanced but heavier than stock. They are extremely durable especially when you consider the protection afforded by the ducts. You will achieve hover at very low throttle
These props are a good upgrade but not my personal favourite.
Note: These are more like 41mm than 40mm and frustratingly don't quite fit in the ducts of of the v3/trashcan frame - the ones you see above were painstakingly sanded down and even then still rubbed every now and then. I hear TBS props have the same issue
Happymodel cut down to 2 blade
Frustrated with the fit of the gemfan props and wanting to try something a bit faster an moe efficient I cut down the standard 4 bladed props to a 2-blade using nail clippers. Try to cut as close to the hub as possible but "good enough" is ok because any difference in cut has less impact the closer the variation is to the hub. Anyway I really liked the performance - they had a high top speed than the gemfan and a lower current draw but they did feel a bit looser than I would have liked given the substatial drop in useful blade area. More throttle was needed to hover for the same reason. I'd recommend giving these a try if you have a spare set floating around. I liked these for outdoor but felt a bit sloppy inside.
Gemfan 1635 (3 blade)
I got fed up with trimming the gemfan 1636 to fit the v3/trashcan frame I actually switched back to an original mobula frame. I know it's not as durable but I really wanted to try the Gemfan 1635 unadulterated. I'm glad I did as these are the props I've been looking for all along. They felt the fastest of all 4 props I've tried and I still managed a good 3:30 on my old turnigy nanotech 2s 300mah batteries. Control/grip felt at least as good as the stock 4-bladed props and only slightly less grip than the 4-bladed 1636. Like the 1636 they are well balanced and very durable. These are my favourite all round propeller for the Mobula7 and trashcan.
Alongside the reduced durability, the original mobula 7 frame is designed for 1s batteries. I have made a simple mod as below to allow any battery. It's not beautiful but is very functional and adds only a tiny amount of weight (would be less if I used a lighter rubber band).
Firstly none of these props get rid of yaw washout in dirty (propwash) air - this is just a limitation of ducted frames. Some say it can be tuned out but results I've seen have not be repeatable. The best fix is to adapt your flying style to suit.
Funnily the props I've reviewed handle different situations in different ways, meaning a horses for courses approach. My favourite is the Gemfan 1635 3-blade which is something of an allrounder. To summarise:
If I get some energy I'm quite keen to try the Gemfan 1636 as a 2-bladed prop - I think it would be a speed demon outdoor but then again I'd probably choose to fly the Sailfly-x which is faster, better control with more battery life.
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