Prop Test: APC 8x4.5MR and 8x4.5MRP vs Stock

[rowee]

I have always been impressed with APC propellers so when I go my Phantom I decided to see what APC had that would be similar to the stock configuration of the Phantom. APC markets the the 8x4.5MR and 8x4.5MRP as multi-rotor props. I purchases a set and ran some tests.

http://www.apcprop.com/ProductDetails.asp?ProductCode=LP08045MR
http://www.apcprop.com/ProductDetails.asp?ProductCode=LP08045MRP

The APC propellers are 2 grams heavier per prop than stock and stiffer. The APC props had to be reamed to fit on the Phantom. This stiffness might make them more prone to damage over the stock propellers, but this remains to be seen.

Testing Procedure:
Hover duration test of stock Phantom with GoPro camera installed at 6-8ft altitude until Phantom auto lands. Ran the test twice per prop set (twice for APC props and twice for stock props) using the exact same 2 batteries. Times were gathered using a kitchen time. Density altitude was calculated between test days.

There are more precise ways of testing propeller efficiency. I believe the procedure that I followed offers a real world comparison of the differences to the stock configuration on real hardware in a real usage scenario.

Batteries used:
a pair of Mad Dog RC 2200mah 35c

APC Prop Results:
60F degrees, 29.86in barometric pressure, dew point 52F
Density Altitude = 323ft
Hover durations: 9:45 and 9:33

Stock Prop Results:
59F degrees 30.00in barometric pressure, dew point 47F
Density Altitude = 68ft
Hover Duration: 9:49 and 9:34

Conclusion:
Because of the very slight reduction in density altitude from one set of tests to the other, I would expect a tiny improvement in propeller efficiency from one day to the next; which is exactly what occurred. Also, since I am using a kitchen timer to time these tests, there is a bit of variability in the start/stop times of each test; i.e. my thumb may have been faster on the kitchen timer the second day. I personally do not think there is a significant difference between the prop sets and I consider the prop sets to be identical for all practical purposes.

 

[TomDChi]

Thanks so much for this posting! I literally signed up on this board to compliment this post!

All the crucial data included. Problems with data collection (small differences between times may be explained by limits of the timing system) are identified. Inconclusive results are reported! Fantastic!

It would seem that it should be possible to improve the Phantom's performance (handling and flight times) by using better props than the flimsy things that come with it. But I don't see a consensus out there on which props give which results. Your test doesn't find a winner or looser. It might just point to the possibility that, within reason, the available props don't make that much of a difference. Sometimes a non-result is important.

 

[rilot]

I have to agree with the above. A stock Phantom doesn't seem to really change with different props. It's only when you start adding a lot of weight that different props make a difference. And this is mainly to get more lift and thus keep the motors at their most efficient speed for hover.
This is with the exception of the 8x5 Graupners. My Phantom turned in to an unwieldy beast with them. Graupner 9x5s are much better and fly much like the stock Props. I think this is due to the smaller swept area.

 

[DeweyAXD]

Nice test there and well noted out. As rilot says it is when you add weight that the real differences tend to get seen. I would love to see results of your test done with differing loads.

The test that really counts is one that is very hard to scientifically do with any real accuracy and that is one of flight charteristics e.g climb rate, fall rate etc. Maybe with a Mybusters style red/white height scale and a high speed camera. Start the motors and give the Phantom full throttle then measure the time taken in frames per second to rise over a set distance..... a whole lot of work basically :lol:

 

[rowee]

Thanks for the input. I plan to try these tests again in about a week, after I install a gimbal to see if the added weight makes a difference. If it does not make a difference I will be able to safely say that prop construction makes no difference; one less variable to consider in future tests.

 

[martcerv]

Being similar props you wouldn't expect too much difference in flight times at the same length and pitch angles. The stiffer props will react faster but you may want to try some larger props especially once you get a heavier setup.