APC Multirotor Propellers

Please bear with me, this is my first review!

Preflight:

Update: I ended up using these propellers on the VX1 project to set a new World Record for the fastest racing drone:

Being curious about APC and Graupner propellers (and not finding much info), I decided to purchase a set of the APC B5x4.5E-B4 multirotor propeller set that is specifically aimed at FPV racing and freestyle. The set includes 2 B5x4.5E props and 2 B5x4.5EP props (P for Pusher) and are a bullnose type prop. They list for $5.96 on the APC website which makes them a bit more expensive than the typical props used for FPV racing/freestyle. Are they worth it?

The first thing I noticed is the shape. The root is extremely beefy with a very high angle of attack. Moving towards the tip, the blade profile thins out and the angle is much less aggressive. I can see that the idea here is to keep the pitch the same at any given cross section along the blade. Since the root of the blade has a lower velocity, the pitch angle needs to be more aggressive while the tip of the blade (having a higher velocity) can have a smaller angle but have the same pitch as the root. All blades that I have flown to this point have a fairly constant cross section angle from root to tip. Understanding (somewhat) about the complexities of the forces involved with propellers, I am impressed by the complex shape as it appears well engineered. APC has a whole page dedicated to their engineering methods and also data spreadsheets for each propeller.

apc-b5x4-5e-b4-and-hq5045

HQ 5045BN compared to the shapely APC B5x4.5EP

The elevation view of the propeller is just as interesting:

brotherhobby-t2

However, at least on the Emax RS2205’s, the blade profile near the root actually interferes with the top of the motor. A small spacer can easily fix this problem. I like to add a spacer anyway to allow the air to pass more freely between the root and motor top. The Brotherhobby T2 doesn’t have this problem since it is tapered (I’m assuming they noticed the same issue I did).

rs2205-with-apc-b5x4-5e-b4

As far as balance goes, all 4 blades needed balancing but it was nothing more than any other blade I have come across.

Weight

A quick note on weight: 4 APC props = 21g. 4 HQ 5045 = 18g. Spacers included for both props.

Up to this point, the physical quality (flash & balance) doesn’t seem any better than other blades I have seen. However, it does appear quite a lot of engineering has been put into the design. Will flight performance be worth the extra money? Or is there a reason I have not found any reviews on flight performance?

Flight Test:

Part 1

Initial flight test did not go as planned. I have 2 identical batteries that I can test between two different props. I did get the first battery with the APC props, but the second battery with the HQ 5045 props (to use as a comparison) ended up in a crash. Project B1 can officially R.I.P.

Although I was not able to do a direct comparison today, it appears that the APC props are more efficient since my batteries didn’t seem as warm as normal (the brotherhobby T2 motors are rough on batteries). I actually saw my max speed get up to 185 kmh (115 mph) but it was kind of windy. As far as the “feel” went, they seemed to handle a lot like the HQ 5045’s. So to sum it up, they seem to be more efficient.

I will hopefully (weather permitting) get a chance to do the comparison on 9/27/16 on the F1 frame with the Emax RS2205 2300kv motors. I will do an acro comparison with go pro video and then a distance comparison by flying in circles…

Part 2

I was finally able to do a side by side comparison of the APC and HQ props. The first part of the comparison involved free flying. Between the two blades, I could not tell any difference. Maybe a more experienced pilot would be able to tell, but they felt identical in speed, acceleration, and responsiveness (they even sounded the same!).

The next part of the comparison is what separated the two: distance flown on a 4s 1300mah lipo (please forgive my clibration on my OSD, it is .2V high). This comparison basically consisted of flying in circles the whole time to conserve energy as much as possible. For the APC props, total distance was 4.822km in a time of 5:33 with a final voltage at 14.7:

apc-b5x4-5e-b4-distance-test

Next were the HQ props. Final results were a total distance of 4.986, 5:09 flight time and voltage of 14.8V. Doing the math, the HQ props ended up with a 3.4% greater distance. It’s almost negligible, but the battery also had .1V greater potential:

hq-5045bn-distance-test

Also note that when calculating the speed, the HQ props were 11.5% faster. I wonder if this has anything to do with the larger elevation profile of the APC props?

From the  distance test, I can conclude that the HQ props are more efficient when it comes to distance flown and being conservative on the throttle. It’s not a very confident conclusion since the margin was still relatively close. Although the APC props didn’t go the distance, the opposite might be true if these props were to compete head on in a race setting. Unfortunately my flying skills aren’t there yet – but once they are, I will have to post an updated review.

Thanks for reading!

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