I Thought Gemfan Was Supposed To Be Good Props

[fengshuidrone]

Bought 2 pairs of 11 x 4.7 slow fly style Gemfan from Heli Direct. First off,let me say that I use a DuBro prop balancer. 3 of the 4 props balanced up fairly easily as most props do. Only one other one needed the hub balanced as well as the blades. But that fourth one......It will NOT balance and shows signs that the center hole is actually slightly off. No amount of hub balancing will bring the prop in. It will blade balance perfectly on the light side of the hub but flip the prop over and it ALWAYS returns heavy side of the hub down. I even put a huge glob of hot glue on the light side that had to weigh 1/4 gram and it still swings back to the heavy side of the hub. That is an off center hole. I am not happy with what I supposed was a high quality prop. I have never had this problem even with cheap, scrape the bottom of the barrel props from China!!! Anyone else have a problem with the quality of their Gemfans??

 

[Old Man]

In that size and type of prop I always stick with APC. Never tried the Gemfan line.

 

[fengshuidrone]

The gemfans were just a couple bucks cheaper. APC was my second choice unfortunately. Upon closer examination I see signs of the injection mold's incomplete filling of the mold cavity, what with little sunken in areas near the hub where the plastic should be solid and smooth. I used to supervise inspectors as well as personally inspect plastic door parts for a contractor that made them for Ford. I know incomplete cavity filling when I see it. That part should have been a reject. Just my luck I guess. I will avoid Gemfans from now on. The other one of the same rotation was fine. Must have come from two different injection molding machines or one of the sprues was partially clogged (because there are probably multiple blades made from each injection.)

 

[Old Man]

Just an information reference thing but APC props are used exclusively on a small UAV. In many thousands of props I have yet to see a bad one. Been using them in RC sport and RC giant scale racing in various sizes for over a decade with the same defect rate, which is why I go to them first in the 10" to 12" size range when an output shaft is used.

 

[SamaraMedia]

I've found HQ props to be pretty well balanced straight from the package, 9"-12".

 

[Aerialmediaone]

I have had decent luck with gemfan Carbon props, but generally speaking gemfan is not a "quality prop"


Sent from my iPhone using Tapatalk

 

[Motopreserve]

I've found HQ props to be pretty well balanced straight from the package, 9"-12".

+1. Wish I could try some larger ones. Unfortunately, the wood props they came out with were nowhere near the quality of their composite props.

 

[Pumpkinguy]

I tried a gemfan 10" on a 355mm sized quad with 2212-900 motors and had a prop failure mid air. broke right off at the hub. All others had stress marks on either side of the hub. (where the plastic turns white) From here forward I only use them on my mini quad.

 

[fengshuidrone]

On a more positive side I was able to reduce my throttle mid point down from 75% to 70%. Not so sure the vibration won't be an issue yet. They make a lot of noise. They must have a little more thrust than my 10" props did at mid throttle or I wouldn't be able to hover at half throttle with the lower throttle mid setting.

 

[Motopreserve]

On a more positive side I was able to reduce my throttle mid point down from 75% to 70%. Not so sure the vibration won't be an issue yet. They make a lot of noise. They must have a little more thrust than my 10" props did at mid throttle or I wouldn't be able to hover at half throttle with the lower throttle mid setting.

Are you hovering at 70% or adjusting your mid point?

 

[fengshuidrone]

Are you hovering at 70% or adjusting your mid point?

In my PID tuning section of my FC I can set my throttle stick position to make my quad hover perfectly at mid stick, no matter how much actual power it takes. Lets say my quad is a little heavy (and it is.) When my FC throttle mid PID is set at 50% my quad is just getting off the ground and struggling to fly with my stick at mid throttle. When I move the stick to about 70% of it's travel, my quad finally hovers. If I set this this PID to reflect the 70% it takes to hover, the quad now hovers at mid stick. It was taking 75% before switching to 11" props. With the 11" props I am getting 5% more lift at 50% throttle. Yes, I know,this means that there is only a 30% power reserve beyond mid stick. I only ever do slow flying and AP with this quad so that is plenty of reserve beyond hover and even more now than there was with 10" props. The 11" props boost the thrust at full throttle by 90 grams (x 4 motors) adding up to 360 more grams thrust at full power than the ten inch props. All tests and PID changes done with craft at full AUW including payload.