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Old Apr 15, 2012, 09:29 AM
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props props props. and multicopter (naza)

I've been doing lot of research into flight behavior and props on multicopter. Some just affirmed the old ideas and found some new ones.

This whole enterprise started with report of DJI 10" props breaking in air and trying to find alternative. Graupners are the best by all account and would have gotten the set, except for their current lack of availability precluded that for myself. So, I started testing props

The anecdotal evidence has always been to use light weight props, and this has always been old standby APC SF and EPP props. I've also had some hobby king 10x6 set on hand (they are very affordable) and purchased a set of 9x4.5 APC EP props. (figuring that they are similiar to graupner e props)

after testing, I find that APC EP props are not suitable for multicopter. they do work, but I could not get rid of wobble due to their weight. wobble was not big, but it existed in all condition and could not be tuned out. may be they would work better with slightly bigger motor, but not with stock DJI 920kv motor. also, I could not get 9x5 GWS 3bladed props to work well with naza. bit of wobble. could be due to balance issue as I could see at least 1 prop badly out of balance. (but again, 10x6 had at least as bad a balance on 1 prop and flew well) it is interesting, as gary had good luck with GWS and heavy loading. the motors do stay cool with gws 9x5. gary did have trouble getting rid of all vibration with gws, so not great for AP.

DJI sf props besides breaking also tend to wobble in fast descent/high wind. this is due to blade flexing. of course 10" is much worse than 8". 8" seems to be durable compared to 10" (no report of it failing in air) with 8" at 1.5kg (goprop and 4S4400 plus LG extension) it flies really solid, but without the floaty feeling.

now, cheap 10x6 HK props at 3.50 for 6 . these were real surprise find. they are really out of balance, so you need to balance them. (I sanded the bottom) but they really are performed well on my 450. almost no wobble in fast descent and great power. 8" still flies better on my dji450, but these flies better than 10" dji props. smooth power too. i setup my 550 with these since I don't have graupners. after some flights, the motors do get too hot. so , i went and put on the 8" dji props. man, both of my 450 and 550 loves these 8". for lighter weight setup, 8" are hard to beat.

I have some 9x4.5 gemfan carbon reinforced blades coming, and will get graupners when they become available again and will post comparison. I've heard that they work well, so I am hoping they will be my solution for heavier load.



basic conclusion:

for bests stability, you want to use light stiff blade. for best control, you also want high disk loading. I am figuring 32oz/sqft disk loading as a good starting point for. this do go against efficiency though. so, if you want longer flight, you want lighter loading/bigger blade. but this is the compromise that you have to choose based on your need.

for AP/AV, the choice is clear. light weight EP prop like graupners are the best (and why they are most popular) we need APC and others to step up and make light EP props for us multicopter users.
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Old Apr 18, 2012, 02:47 PM
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well, I got my gemfans. I had to drill them out to 8mm (step drill then reamed using 5/16", which are .313 instead of .315 that 8mm is. close enough. they were pretty well balanced out of package. very little sanding to balance them. and they are smooth. light/rigid blade, just what the doctor ordered.


motors come down just luke warm. (at 2.6kg hexa) I think these will handle upto 3kg no problem. I am a happy camper in finding them "GEMs" lol. they are perfect match for the DJI 920kv motor.

remember though, drilling and reaming is a percision job. take care and do it slow.
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Old Apr 21, 2012, 03:20 PM
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Thanks, didn't realize the prop choice could be so important
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Old Sep 12, 2012, 05:04 PM
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To update: I've been using zingers and I have never been happier. larger props does take more effort to balance though once done, you are golden. under 10" is very easy to balance, over 10" and hub balancing gets really important.
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Old Apr 24, 2013, 01:34 AM
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Quote:
Originally Posted by askman View Post

for bests stability, you want to use light stiff blade. for best control, you also want high disk loading. I am figuring 32oz/sqft disk loading as a good starting point for. this do go against efficiency though. so, if you want longer flight, you want lighter loading/bigger blade. but this is the compromise that you have to choose based on your need.

for AP/AV, the choice is clear. light weight EP prop like graupners are the best (and why they are most popular) we need APC and others to step up and make light EP props for us multicopter users.
Isn't that contrary to your last post?! I would think, that the Zinger props are stiff but not light?! Does that mean you changed your conclusion?1 Just wondering as I am trying to decide on what props to get...

thanks,

kmd
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Old Apr 24, 2013, 02:18 PM
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this was generality and still holds true, but in the end, you have to test it. woodies are extremely stiff and they tend to work pretty well, especially in wind. I think part of the reason is the fact that they are bit less efficient as well due to simpler profile. Some also had some good luck with graupner clone Carbon props in 11-12" size from china.

also, different controller will behave bit differently with different props.

I use zinger because, affordable, available and performs well in wind. beyond that, they are bit safer as they will break on contact with ground and not cut you as bad. the CF and plastic props are much more vicious in terms of cut.
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Old Apr 25, 2013, 01:47 AM
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Quote:
Originally Posted by askman View Post
this was generality and still holds true, but in the end, you have to test it. woodies are extremely stiff and they tend to work pretty well, especially in wind. I think part of the reason is the fact that they are bit less efficient as well due to simpler profile. Some also had some good luck with graupner clone Carbon props in 11-12" size from china.

also, different controller will behave bit differently with different props.

I use zinger because, affordable, available and performs well in wind. beyond that, they are bit safer as they will break on contact with ground and not cut you as bad. the CF and plastic props are much more vicious in terms of cut.
Thanks for the fast reply and the great info! Appreciate it! I just ordered some GemFan Wooden props today. Cannot wait to get them and try them! I choose because of what you said and the fact that others said pretty much the same thing!
I hope I will never find out, how vicious props can be! Is anyone wearing special gloved when dealing with multirotors?!

thanks,

kmd
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