May 05, 2011, 06:15 AM
Registered User
Vienna, Austria
Joined Apr 2007
2,542 Posts
Quote:
 Originally Posted by Jurgen Heilig Hi Clemens, actually, some sleek models do reach the theroretical (geometrical) pitch speeds, because all those drive calculators never consider that the prop blades are profiled. You are assuming that the top speed was reached with an 9x6", when the recommended folder is actually 8x7". I would assume, that the voltage under load at top speed is closer to 11.5V than 10.5V. 11.5V x 1350U/V x 1/60 x 0.1778m (=7") = 46m/s = 165.6kph = 103mph Jürgen
Hi Jürgen, I agree that the 8x7 folder would be much better (in the SEFF videos there I see APC props though - could be the 8x8 and then it would make sense), in my last post I also commented that the prop airfoil might allow a plane to reach the theoretical pitch speed, and I also agree that good high C batteries might even provide 11,5 V under considerable load when they are full - but just like tdriedger before you also calculate pitch speed as if the motor experiences no load (idle speed at 11,5V) - see my last post.
I do not doubt that the recommended motor at 600W+ would get the Dogfighter up to around 100mph level with the right prop.
cheers
Clemens
Last edited by mopetista; May 06, 2011 at 06:47 AM.
May 05, 2011, 06:52 AM
Registered User
53859 Niederkassel, Germany
Joined Sep 2000
18,828 Posts
Quote:
 Originally Posted by mopetista ... you also calculate pitch speed as if the motor experiences no load (idle speed at 11,5V) - see my last post. ...
Hi Clemens,

I know that this is very simplified, but I am pretty sure that the motor will get to such speeds and hold them in a horizontal line - at least for a while.

I am sure MPX checked their speed claims with telemetry.

Jürgen
May 05, 2011, 10:12 AM
WCRC Skyhawks
Greenville, SC
Joined Jul 2008
43 Posts
This is a theoretical (no-load) approach, you should consider a rpm drop under load (factor ~0.8 to be safe) => 82mph

Quote:
 Originally Posted by Jurgen Heilig Hi Clemens, actually, some sleek models do reach the theroretical (geometrical) pitch speeds, because all those drive calculators never consider that the prop blades are profiled. You are assuming that the top speed was reached with an 9x6", when the recommended folder is actually 8x7". I would assume, that the voltage under load at top speed is closer to 11.5V than 10.5V. 11.5V x 1350U/V x 1/60 x 0.1778m (=7") = 46m/s = 165.6kph = 103mph Jürgen
 May 05, 2011, 02:20 PM Hitec/Multiplex USA San Diego Joined Dec 2005 174 Posts We flew it with the 1350 KV Motor on the 10x7 Prop at SEFF. According to the GPS we got a ground Speed of 103 MPH with no wind. The battery was a TP 65C 2700Mah 3S. There is a pretty good chance the 1350 KV motor and 10x7 prop end up being the final specs for the U.S. Power package. On the windiest of days we recorded a Ground Speed of 133Mph and yes it was blowing at about 30mph. Shawn
May 05, 2011, 03:06 PM
Registered User
USA, CA, San Carlos
Joined Apr 2003
422 Posts
Quote:
 Originally Posted by sspiker We flew it with the 1350 KV Motor on the 10x7 Prop at SEFF. According to the GPS we got a ground Speed of 103 MPH with no wind. The battery was a TP 65C 2700Mah 3S. There is a pretty good chance the 1350 KV motor and 10x7 prop end up being the final specs for the U.S. Power package. On the windiest of days we recorded a Ground Speed of 133Mph and yes it was blowing at about 30mph. Shawn
At least now we have some numbers that make some sense...

11.5v x 1350kv = 15525rpm @ 7in pitch = 102.9 mph pitch speed

I'll let someone else comment on airframe drag, motor efficiency, and prop unloading.
May 06, 2011, 12:06 AM
Registered User
53859 Niederkassel, Germany
Joined Sep 2000
18,828 Posts
Quote:
 Originally Posted by tdriedger At least now we have some numbers that make some sense... 11.5v x 1350kv = 15525rpm @ 7in pitch = 102.9 mph pitch speed ...

http://www.rcgroups.com/forums/showp...4&postcount=90

And the chances are much higher to reach those rpm figures with an 8x7" rather than a 10x7" prop.

Jürgen
 May 06, 2011, 01:24 AM Registered User United States, CA, Sacramento Joined Jan 2010 3,283 Posts Can't wait for the dogfighter! here are some quick imperial conversions: 25.4mm = 1" 12" = 1'(foot) 5280' = 1 mi Think that is retarded? At least we don't use Rods, Furlongs, Fathoms, Chains and Links anymore! Last edited by restlessswind; May 06, 2011 at 01:37 AM.
May 09, 2011, 05:12 PM
Registered User
Vienna, Austria
Joined Apr 2007
2,542 Posts
What the Dogfighter will look like in the air

- similar to the Midget Mustang I would think

Thanks to J Barnes for the great video of the Midget Mustang. The Dogfighter videos lack this feel of speed but with the right setup the experience should be similar

 PlaneAdrenalinRC's Mini-Midget Mustang (5 min 56 sec)

If I wanted to sell a plane I'd get some good videos done - but that's just me, I am no marketing buff, probably they know better at Multiplex

cheers
Clemens
 May 17, 2011, 11:10 AM JOHN 3:16 STILL APPLIES Central Ohio Joined Feb 2008 7,261 Posts So is this thing coming to the USA this year, or.........? Do we know the price yet?
 May 17, 2011, 02:22 PM Owner - Flying Models United States, CT Joined Aug 2003 2,464 Posts yes \$129.99
May 17, 2011, 04:27 PM
Registered User
United States, CT
Joined Aug 2005
1,980 Posts
Quote:
 Originally Posted by Thayer yes \$129.99
Sounds about right...kit only, of course.
If it wasn't MPX we would tell them to pound sand.

Any dates yet?
May 23, 2011, 11:47 PM
Registered User
53859 Niederkassel, Germany
Joined Sep 2000
18,828 Posts
Dogfighter in Action ...

video from last weekend:

 FMC Dietzenbach 2011 - Multiplex DogFighter (3 min 50 sec)

Jürgen
 May 24, 2011, 03:44 AM Making mischief in the air Berkshire UK Joined Jan 2008 903 Posts thats more like it . good video ! looking forward to getting mine now (the waiting is the worst part huh) - looks like it also has good slow speed manners as well ..
 May 24, 2011, 03:52 AM Registered User Tampere, Finland Joined Nov 2004 4,463 Posts It does look good, whatever the top speed is exactly. Sounds OK too. What did that one have for power?
May 24, 2011, 03:58 AM
Registered User
53859 Niederkassel, Germany
Joined Sep 2000
18,828 Posts
Quote:
 Originally Posted by perttime It does look good, whatever the top speed is exactly. Sounds OK too. What did that one have for power?
MPX Dogfighter Ultra Li-Batt Set.

Jürgen