Mavic Mini 2 Colorful Aftermarket Prop Differences

[Dogpilot]

I splurged and bought some novelty high vis props for the Mini 2 the other day. The vendor on Amazon swore they where spec'd for the Mini 2 (they wouldn't fib, would they?). I tried them out yesterday at fairly high altitude, 2400 meters. It was also somewhat breezy. The little bird had no issues with either the altitude or the wind. It did give me a wind warning on the second flight back as it was picking up a bit. I was photographing old secret cliff dwelling nearby that are apparently uncharted in my area. So I was checking something when I got home and my wife noticed the new blades. She thought they where louder. I had noticed a thread back that some folks thought they where quieter, louder, the same. "Wait" I thought, my Apple watch has a decibel meter built in. So I checked it indoors from 3' in a hover. Novelty props 65-66 dB and the stock props 64-65 dB. I didn't notice any real difference in performance one way or the other, first flight ran the battery down to 23%, which was pretty normal duration for that kind of flight with lots of climb to get elevation up to the Horsts the dwellings are on. Normally do this kind of flight with the Pro 2, but I was not actually planning on doing the documentation yesterday, mainly needed the exercise, so I put the Mini in a pouch and brought it along.

Bottom line, look cool, do make it slightly easier to see from some aspects. Not quieter, but noisier, by 1-2 dB. Not really any noticeable performance loss or gain. So if you think they are cool, don't worry about the noise or performance.

 

[DJayI]

(they wouldn't fib, would they?).

Surely not, I cannot even believe you posed the question....?

Seriously though, my concerns from these aftermarket blades would mostly be about balance and material selection. I would be somewhat less concerned about those factors if the blades were branded, say for instance, Master Airscrew.

Thanks for the feedback, now I do not have to wonder.

 

[Yogi053]

Altitude 2400 metres?

 

[Dogpilot]

Yes, I live in the mountains, right next to a ski area, which the top run is at 3248 meters and the mountain tops out at 3957 meters. It is an ex-strato volcano. I was hiking on the adjacent lava dome, which the close ridge on that hike is 2895 meters. There is snow on the ground during the hike and we just got a bunch more this last evening. Nice thing is I don't have to climb much to get to cruising altitude in my aircraft. Saves tons of fuel. Downside, the mountain has swatted its share of aircraft out of the sky. One of the interesting summer hikes is to a splatted B24 Liberator Bomber during WWII. Surprisingly large pieces survived, including its large red painted rudders. We have a ski run named after it, "Red Tail."

 

[Yogi053]

Yes, I live in the mountains, right next to a ski area, which the top run is at 3248 meters and the mountain tops out at 3957 meters. It is an ex-strato volcano. I was hiking on the adjacent lava dome, which the close ridge on that hike is 2895 meters. There is snow on the ground during the hike and we just got a bunch more this last evening. Nice thing is I don't have to climb much to get to cruising altitude in my aircraft. Saves tons of fuel. Downside, the mountain has swatted its share of aircraft out of the sky. One of the interesting summer hikes is to a splatted B24 Liberator Bomber during WWII. Surprisingly large pieces survived, including its large red painted rudders. We have a ski run named after it, "Red Tail."

View attachment 126184

Thank you for the explanation. It certainly looks a cool place to live. (Pun intended).
Stay safe!

 

[Peshoa]

I do not believe that this producer produce better props than the originals. You cannot be sure in the balance, profile, weight, material....what is the point here to risk this nice bird with non safety props?

 

[Peterson]

I would be more concerned that my wife could detect one dB difference in prop noise.

 

[Dogpilot]

My wife, she has the hearing of a bat. The boys learned that ages ago. Not too terribly worried about the props. The material actually seems to be quite durable, a bit more flexible than the originals. Balance seems good. I could go all analytic on them. I actually have the credentials I do have a federal license as an engineer and did test fly helicopters and fixed wing aircraft in the service. I was an AEDO, Aviation Engineering Duty Officer and oversaw and tested 75 helicopters and fixed wing aircraft rebuild and crash damage repairs a month at the Naval Air Rework Facility in North Island. If I only had my Chadwick Helmuth track and balance rig. I could hook it up and check the track with the strobe and the balance on the aircraft, if I didn't die laughing while hooking it all up.

My only concern is the supplied screws. They did seem to have loosened a bit on the 4 flights I have done rigorous testing on. So I will most likely put a dab of blue locktite on them today. The Mini 2 is a nice piece of kit. I got mine absurdly cheap, Cragslist is quite the resource and I do travel about quite a bit in my work. So yes awful things can happen if they fail but unlike my minimum wage job in the service, I won't die (don't ever figure the hours spent flying on and off the carrier and all the other time on that dumpster then rationalize it vs your salary, its pathetic. Even worse for the enlisted, it criminal). One must realize that its total value is 10 pizzas from our local excellent pizza establishment. Like Spacex, one can learn from the mistakes, if the pockets are deep enough.

So the little bird remains very steady, without and shaking or visible harmonics from out of balance situations. I did test H46's transition to kevlar blades. So like that program, I shall do the: go fly them and see what happens. Pull them off after 10 or so flights. I do have an absurdly expensive and elaborate pair of microscopes I use in my work as a geologist (after the service last thing I wanted to do was fly for a living, I only fly now to get someplace or do sensor runs). I also have a dye penetrant kit for my aircraft, but I think the penetrant may melt the blades...

So I am going to risk it, until something better comes along or the Mini has some other related disaster, ending its tiny cute life. I only got it for its entertainment value and ease of transport. I have a 2 pro and a zoom. Both excellent and very capable. I am not going to carry them around much the entire kit is somewhat heavy. I can also bring this little bird along on trips abroad to do a bit of work and if it is confiscated I shall not drop to the ground wailing. I would not do anything serious with it. I have better ones for that. Besides the colorful blades enhance its "toy" classification. Making it easier to explain to the wannabe Minister of Small Animals giving you grief in Zambia.

 

[Dogpilot]

Really awful weather here today. I did manage to suffer through some skiing in the morning, but the WX quickly turned to full on tempest. So end of skiing, now sitting at home. So wishing I still had my track & balance rig, well not really, big bulky very expensive box. I was thinking how to check these tiny props in flight? The question nagged at the back of my mind so somehow I had to come up with a solution. Ding! Small light went off in my brain. Quite noticeable, since my skull is fairly empty. I have a super high speed flash setup. Fast enough to stop a supersonic bullet in flight, 1/41,600 of a second.

So I setup near the expansive windows so the critter could get a decent GPS signal, wich is fairly close. I have the windows coated with a nickel film since UV is wicked up at this altitude. The beast said it got a 'weak' signal and could hover. I then took, static and dynamic pics with both sets installed. Conclusion: while the profile looks different in static, they appear nearly identical in dynamic mode. Not much coning going on in either set, so stability is dependent on the software, not aerodynamics.

You may have noticed, I got some of the colorful engine caps as well. The critter is becoming quite festive in appearance. All this came in roughly the same time and cost almost pennies. Apparently Neptune and Earth are at a close approach so shipping time was within my lifetime. Now I suppose the burning question with all the drone police out there. Did all these mods make it go over the 250 gram limit? Nope, mine weighs out at 244 grams with the stuff installed. BTW, I will see if the engine caps wreak havoc on the engine temps. I just need a day when I can fly outdoors and horse the beast around and then check it with my FLIR camera. Not happening today.

Static:




Dynamic:

 

[rehkram]

Thanks for that very interesting test. It's great baseline data.

But what happens during the way we tend to fly? I mean fast climbs and descents (including rotor vortex ring state situations), tight banked turns, and so on. Also the buffeting effect of winds from various angles.

That would be very hard to measure obviously, but they are the flight modes where the props are exercised the most.

Nice job with HSF, I needed one for my temporary obsession with hummingbird photography when I lived in Austin TX, where you had to beat them off with a stick. But even if I could've afforded one my camera couldn't sync with a flash that fast. And still can't.

Interested to know what camera and flash you used there. Thanks again.

 

[Dogpilot]

I would not be terribly concerned with vortex rings. We did some fairly extensive studies with the CH53E since settling with power was kind of an issue when you had 18 tonnes on the sling. You need several factors to come into effect at the same time. Never personally could get it to settle, since I needed a hotter higher density altitude, coupled with just the right wind, than we could come up with at North Island/ Imperial Beach (where we kept the huge blocks of concrete to test with). It was the poor Marine pilots up at 29 stumps had more issues and one of my buds had it coming onto a carrier in the Red Sea in an RH53D, loaded. Lucky for him he could just slide off to the side and now had 65' to get some forward speed. Didn't really crop up in the dual tandems, in my experience. To make up for it we had this weird ground resonance thing could cause us to literally disintegrate on the ground if we where on matting or just the right surface.

How to high speed sync your hummers. Don't know what system you use so instruction is going to be generic. First off your not syncing, your just running the exposure off the flash output. Darker is better, so just the flash is giving your illumination. Set the f-stop to give your exposure for the scene. The flash will stop the bird in flight and if you set the correct f-stop, it will be properly lit. Nikon SB-800 set to 1/128th will give you 1/40,000. Cannons not so fast, top out at 1/20,000 for most of the speedlites. Bottom line is experiment, set your camera to the highest sync speed you can get (1/60- 1/200 depending on make) and set the stops for flash. Do this in manual.

 

[rehkram]

I'm currently stuck on a Nikon D600, which does not get good reviews for handling this kind of stuff, and probably couldn't cope with the SB-800. But I'll look into it, thank you!

Re. vortex ring states, I can demo it at will on my MM v.1- fly high, full left stick down. I admit it doesn't exactly drop out of the air but it can get pretty crazy if you keep pushing it. Forward stick will fly you out of it but even if you don't the system's landing algorithm will prevent a CFIT, which is nice.

 

[Dogpilot]

Actually it will work with the D600. The SB-800 is fully compatible. Again, your really not depending on the camera to much more than fire the flash and open and close the shutter. Just shoot it in manual. SB-800's are cheap as well, since they are older. Funny part about them, they are more powerful and faster than the newer flashes and do more sync option along with slave options than the new ones.

I think your settling is more a software thing. The mini 2 simply will not do anything lower than around 20". Then it just settles into the landing mode. Vortex ring issues are an issue in the more directly vertical with no wind to move the mass of downward air away from your influence area. Tim said it was quite terrifying when it happened to him. H53's in general have an irrational amount of power, they do eventually run out of pedal. If you pull on the collective they always have loads of grunt to get you out of trouble. These little things are not that heavy and don't displace nearly as much air as a heavy in a proportional basis. Then there is the scale issue. Your interaction with air is different as you scale down. Insects are literally rowing in the air as it interacts more like a viscous medium than a gas on their scale. Fruit flies, for example make their wings meet overhead and create a vacuum as they pull them apart, literally drawing their body up to the pocket of vacuum (or being pushed into it) created by the wing separation. Of course they are really tiny, but you see how it scales down.

The other factor, these quads are not really flying like a helicopter does as you scale up. The blades don't change their angle of attack, your change in lift is done by RPM. This would cause issues in forward flight with advancing and retreating blades eventually stalling out on the backside. Kind of why compound helicopters slow their blades down and rely on thrust from either a prop or jet for forward speed. Slow your blades down or "droop" on a regular helicopter your in for a world of trouble. Blade stall at high speed makes the bird start to roll to the stall as you lose lift. I just loved doing the helicopter part of the program, they just where so much more interesting than the fixed wing ones.

Hummingbird shot, notice there is the blur and a stopped image, since their was too much ambient light in the shot and I let the flash choose the output speed:

 

[rehkram]

Thanks Dogpilot, all very interesting. I'll look into that flash. I also appreciate your contrasts on how full size choppers fly vs fixed rotor pitch drones. You get a10 point bonus for the fruit flies thing, that's fascinating.

We get the occasional flurries of hummingbirds up here on our porch in NYS, and I'd like to get back into the pursuit of the perfect hummingbird shot.

Yeah, that highlight on the bird's left neck just slowed the shutter speed enough to not freeze the shot, nice as it is anyway, actually. As good as it is, Nikon's matrix metering still needs work. And I still need to study.

 

[Adolf]

Thank You for sharing. Good info.