News:


  • April 19, 2024, 01:37:49 AM

Login with username, password and session length

Author Topic: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?  (Read 1490 times)

Offline Frank Imbriaco

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 912
  • At the 69 Willow Grove NATS with J.D. FALCON II
ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« on: July 14, 2018, 06:24:29 AM »
APC has a nice line of pusher and tractor props for multi-rotors. They are  "in-between"  thin electric series and slow flier series as far as construction and blade . There are more size choices, too, in the multi-rotor line.
The hubs on the thin electric and multi-rotor are similar and for the most part, so is the blade profile. Multi-rotor props are a bit lighter which is a good thing because they demand less current which theoretically, should keep the ESC happier and less likely to go into shut down or RPM limitation from load.

That said, the RPM limit is 105,000 divided by prop size (8 ", 9" , etc.) on multi-rotor as opposed to an RPM limit of 145,000 divided by prop size on thin electric.  A definite negative . So, peak RPM MUST be monitored.

What I'd like to know if anyone is using multi-rotor props on their e-ships , what RPM differential exists between them and electric thin, and general experiences.

With prudent use, we shouldn't toss blades .

Offline jfv

  • 24 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 634
Re: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« Reply #1 on: July 14, 2018, 10:12:10 AM »
I have a carbon fiber 12x4 that is very thin but has a reasonable hub and is very stiff.  I only tried it once as the bite it took reduced my lap time by about 0.8 seconds.  Couldn't slow my motor down enough get the lap speed down.  I plan on trying it again when I have a setup that will give me an appropriate RPM.
Jim Vigani

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12808
Re: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« Reply #2 on: July 14, 2018, 10:37:45 AM »
Kenny Stevens ran them at the World's in 2014.  He broke a blade off on a tuft of grass, which caused the nose to come off in a subsequent flight.  Here's part of the story.  Someone may have a better one to tell.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Frank Imbriaco

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 912
  • At the 69 Willow Grove NATS with J.D. FALCON II
Re: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« Reply #3 on: July 14, 2018, 11:03:39 AM »
 As I recall... but Kenny would have to be the one to tell us if it was a "tuft of grass" as you assert or a  turf prop strike.

Offline Dennis Adamisin

  • 2019 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4340
Re: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« Reply #4 on: July 14, 2018, 11:50:04 AM »
Matt Neumann tried some of the carbon multirotor props and failed them at the hub.  Thankfully they only got flexible and did not separate.

APC rates their multirotor props with MUCH lower max RPM than their regular electric props, so much so that they are not suitable for our use.
Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12808
Re: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« Reply #5 on: July 15, 2018, 08:55:50 AM »
As I recall... but Kenny would have to be the one to tell us if it was a "tuft of grass" as you assert or a  turf prop strike.

I may indeed have that wrong.  There was an extensive discussion/report about that here when it happened, but I couldn't find it -- the best I could do was that post by Kenny that I shared a link to.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 740
Re: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« Reply #6 on: August 20, 2018, 12:26:56 PM »
Hello everybody,
I have used different 2 blade MR APC props for my electric models.

The main reason: they were lighter then equivalent "normal" props. The hub was less bulky and the transition between the hub and the blades was thinner.

Unfortunately, they were also less stiff than the "normal" props in the out-of-the plane of rotation direction. Simply put: the blades were more flexible. When I started flying sharp corners, the gyroscopic moment was bending the blades and I could hear the very well audible "bzzz" sound exiting the corners when the blades rebounded.

I have replaced the MP APC 2 blade props with Igor's 11x5x3 carbon composite electric and the "bzzzz" sound disappeared.

Happy Flying,
Matt

Online Peter Germann

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 400
Re: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« Reply #7 on: August 21, 2018, 03:02:09 AM »
June 2016: Symmetria, Aeronaut Cam Carbon light 14 x 6 Pusher at 8’974 RPM:

Sequence:

1.   Prop noise in outside loops
2.   More prop noise in outside corners
3.   Sudden disintegration of fuselage nose in flight, immediate crash
4.   Found both blades broken at the root, inside the 57 mm spinner
5.   No blades found at place of impact

Peter Germann

Offline TDM

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 844
Re: ANYONE WITH EXPERIENCE USING MULTI-ROTOR PROPS ?
« Reply #8 on: August 21, 2018, 06:12:47 AM »
I was inquiring about the same thing and found out that they are not rated for the kind of RPMs we are running. They might go up to 6500RPM if that.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi


Advertise Here
Tags:
 


Advertise Here