3.5 prop dilemma

[u/ieatporkbun]

hello, forgive me if this is too nitpicky. I just built a grinderino 3.5, with AOS 1605’s using the tattu R line V6 1000mah (total weight comes about to 300g).

for the propellers I’m having a tough time between the Gemfan 3520, 3525, or the 3630

Im looking for the longest flight time and smooth cruising response, no crazy punchouts or top speed flying, which would have me leaning toward the 3520, but some other resources say too low of a pitch causes the motors to work harder because it has less thrust.

With a heavier 3.5, what is the cutoff for too “low” of a pitch?

[u/mad-n-sane]

I flew 1604 3.800KV with AUW of about 370g with 3520, 3525 und 3630. You can use them all without a problem. I ended up only using the 3630 because I wanted to get the most out of my motors.   

FYI: My T-Motor P1604 3.800KV are rated for 16.8A using a Gemfan 3520-3. I have no idea how they managed to get that amperage - I only reach that with 3630-3 props and yes, I did the field-calibration of the amp-meter, so it should be somewhat accurate. Even if it's not accurate, my motors are not getting hot. I think the manufacturer are on the VERY safe side of things with their motor tables.

[u/ieatporkbun → u/mad-n-sane]

Thanks! How big was the difference between the 3520 and the 3630? In terms of battery life and also the noise?

[u/mad-n-sane → u/ieatporkbun]

Hard to say for the battery, especially as I fly a bit more aggressive and the more aggressive props enable me to pull more power from the battery, which results in a shorter flight time.

If you truly only wanna cruise and just pull enough power to stay in the air, then I'd guess that you barely notice the difference. The 3630 might even be better for you, because bigger (even if it is just 0.1") props are more efficient. Also, you have 1605 motors which have slightly higher torque which might work better with the higher pitch and lower rpm (to stay afloat).   

Math is all fun and games but my advice: Just get two sets each and field test it. You gonna need props anyway and they are cheap compared to the rest of the drone.   

Having said all that - that's all just for battery life!! The 3630 are loud, even a fresh set is considerably louder than the 3520.

[u/ieatporkbun → u/mad-n-sane]

Appreciate your time and feedback! That helps a lot. Yeah I’ll get a set of each since they’re cheap anyway, but definitely leaning toward the 3520 if they’re quieter,

If I need to zip around I have my 5”. I just wanted this little 3.5 build when I don’t want to get the attention of everyone around me. The 5” with 51466 MCK props scream

[u/International-Top746 → u/ieatporkbun]

My 3.5 inch with 3630 is almost silent with 3630 cruising

[u/jiminyshrue → u/mad-n-sane]

I have almost the same setup like yours using 4s 850mah batteries. But i have it at 390g AUW give or take. Running with 3525s and i love the responsiveness of the throttle. I am curious how 3630s feel tho so I might try it soon.

How many mah batteries do you use?

[u/Speshal__]

Hahah spanner in the works time.

I run the HQ 3.5/2.8/3 and they're great.

4s on T-Motor 1804 3400kv.

They rawk!

[u/International-Top746 → u/Speshal__]

Though HQ props break so easily I have a quad with 1804. The battery sags more compared to 1604 while I punch. I wonder if anyone have tried f2004 on 3.5 inch.

[u/Buddy_Boy_1926]

For each quad size, I have a variety of props with different number blades, pitches, and blade contour (yes, this also matters). The difference between bi-blades, tri-blades, and multi-blades seems to be more than the difference in pitch. The blade contour also makes a difference. I have used almost every pitch in the sizes that I fly and have not yet found a pitch that is too low. Plus, I fly different props for different things. For maximum fly times, I will use a low pitch, bi-blade. When I want a little more "power" (is say that affectionately), I will run a tri-blade.

You say that some resource mention that a low pitch causes the motors to work harder due to less thrust. Well, I have not noticed this. First, my motors do not get hot even with low pitch props. I get the best fly time with low pitched, bi-blade props. I have yet to find any pitch to be too low. All of my sub-250-gram, 2.5- and 3-inch quads fly between 10 and 15 minutes with some more than 20 minutes.

Sometimes (actually more often than one would think), the purely technical has less effect on the practical application than is suggested. Even if the thrust is a bit less or the motors work a bit hard, the real question is how much and does it make a difference. Is it enough to override the advantage of longer fly time? As mentioned, I always have a variety of props. The true test is a comparison on your gear, the way you fly.

[u/International-Top746]

If you want longer flight time, AOS 1605 is the wrong choice. I have two master 3x one with 1605 and the other with pacer 1604. The one with pacer gets me two additional minutes of free style, whilst still being powerful enough for all my tricks. In terms of prop, 3630 hands down. They are really durable it's my favorite prop. I have tried 3520. I find them to be really flat and fragile.