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Old Nov 07, 2006, 05:00 AM
Registered User
Perth, Western Australia
Joined Mar 2006
366 Posts
I've just read all 100 pages and one question I haven't seen yet is about the motor thrust angle:
does down thrust mean the motor is pointing down at the front and therefore lifting the angle of attack -----/
or is it down at the back, lowering the attitude? -----\

Thought it might be worth my checking before the maiden flight
Thanks.
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Old Nov 07, 2006, 05:27 AM
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ModelTony's Avatar
Irvine, Scotland
Joined Jun 2004
636 Posts
[QUOTE=utilman]And a Typhoon 15/10 with 6x4 or 7x5 prop?

Voltage: 7,2 - 12V
KV: 1500
Max: 200Watt
Maximale efficientie: 78%
Cont: 22A.
Max: 35A.
Size: 34x29,2mm (excl. as)
Weight: 76gram[/QUOT

This a useful page for this motor:
http://www.airmedia.se/Typhoon-15-10-test.htm

Tony
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Old Nov 07, 2006, 05:30 AM
More props are better than One
TaSaJaRa's Avatar
Joined Nov 2004
2,118 Posts
Down thrust means the motor is pointing down at the back where your prop is, thus making the nose go downward in flight. It is the same effect as an elevator.
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Old Nov 07, 2006, 10:38 PM
Registered User
Perth, Western Australia
Joined Mar 2006
366 Posts
Really? Ok, I guessed it was the other way.

Thanks for that.
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Old Nov 08, 2006, 06:42 AM
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Perth, Western Australia
Joined Mar 2006
366 Posts
Wow, what a nice plane!

It was my first time with anything jet-like but this is a tame little beast that seems more than happy to float around with no throttle. The initial drop after launch still scared me even though I knew to expect it.

I'm running a 7x5e that makes 700gm static on the kitchen scales (no Watt meter).
If I go with a faster prop that makes only say 400gm static, can I expect the thrust to actually improve over the static measurement once in the air? This would obviously be because of prop stall at zero airspeed so I am trying to work out if it will climb better than the calculated figures suggest.
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Old Nov 08, 2006, 08:13 AM
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Rochester, Great Britain (UK)
Joined Oct 2004
287 Posts
Quote:
Originally Posted by gt35r
Wow, what a nice plane!

It was my first time with anything jet-like but this is a tame little beast that seems more than happy to float around with no throttle. The initial drop after launch still scared me even though I knew to expect it.

I'm running a 7x5e that makes 700gm static on the kitchen scales (no Watt meter).
If I go with a faster prop that makes only say 400gm static, can I expect the thrust to actually improve over the static measurement once in the air? This would obviously be because of prop stall at zero airspeed so I am trying to work out if it will climb better than the calculated figures suggest.
Need more info on your setup up.
A shot in the dark!
A 7*5 apc-e 700 grams thrust, 13,000 rpm 60mph pitch speed for about 20 amps on 3 cells.
A 4.5*4.1 410 grams thrust, 23,000 rpm 95 mph pitch speed for 20 amps.
I have used the low thrust setup it needs a good toss in the air to get it going but if speed is your thing its good fun.
You do need a watt meter puff up 1 set of cells and it would have been paid for. The meter is good for charging cells as well.

Rob
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Old Nov 08, 2006, 03:01 PM
so i rewired it...
xorbe's Avatar
Mountain View CA USA
Joined Jun 2006
898 Posts
Quote:
Originally Posted by Rob1953
As a point of interest your speed was around 125 km per Hour. (80mph)


Rob
I see you updated. We got the radar gun on it at lunch today and got 83 mph. Only got one reading out of several passes.
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Old Nov 08, 2006, 07:01 PM
Altivolus per Aquila
Soar Master's Avatar
United States, CT, Naugatuck
Joined Sep 2006
325 Posts
My friend put a Multiplex 480 4D in his FunJet. It had to be going 100 mph or so. It sounds so cool.

Go to rccyberflyer.com and register to use the forums. You will recieve a free t-shirt and hat.

You will get an e-mail the following day asking your shirt size, etc. You can choose either 3D flyer or Quiet Flyer shirt and hat.
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Old Nov 08, 2006, 07:11 PM
Registered User
Perth, Western Australia
Joined Mar 2006
366 Posts
Quote:
Originally Posted by Rob1953
Need more info on your setup up.
A shot in the dark!
A 7*5 apc-e 700 grams thrust, 13,000 rpm 60mph pitch speed for about 20 amps on 3 cells.
A 4.5*4.1 410 grams thrust, 23,000 rpm 95 mph pitch speed for 20 amps.
I have used the low thrust setup it needs a good toss in the air to get it going but if speed is your thing its good fun.
You do need a watt meter puff up 1 set of cells and it would have been paid for. The meter is good for charging cells as well.

Rob
Thanks for that,

yeah I guessed about 20A in putting out 150W, the motor is an ebay china outrunner of 1600kV that fits inside the mount. I'm guessing it does about 80kmh, but I don't think a smaller prop would draw enough current.
The only other motor I have that would fit is a Warp4 3 turn and I bought a 5.5x2.5e prop for that, might not be any faster though as I wanted it around 20A for the 1500 15C 3cell battery. One difference might be that it has more thrust in flight.
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Old Nov 08, 2006, 07:45 PM
fast,,,, faster
FASTBEN's Avatar
KELLER TEXAS
Joined Feb 2002
3,373 Posts
well at last got around the FJ way to much projects,going DF,
wemo 480
mega 16/15/3
3s1p 2100 prolite
i have moded the rear end and now its sloped from top and the bottom to provide better air for the DF unit,the fan is instaled at the rear in the mid section,im hopping to achive 100+ mils with this setup also it will be glassed with 1/4 oz and minwax.
ben
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Old Nov 08, 2006, 09:16 PM
Registered User
Joined May 2006
8,113 Posts
Cool! post some pictures when you can please.
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Old Nov 09, 2006, 04:12 AM
Registered User
Rochester, Great Britain (UK)
Joined Oct 2004
287 Posts
Quote:
Originally Posted by xorbe
I see you updated. We got the radar gun on it at lunch today and got 83 mph. Only got one reading out of several passes.
Thanks for the reply the Doppler speed measurement is not far off then.

Rob
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Old Nov 10, 2006, 12:12 PM
fast,,,, faster
FASTBEN's Avatar
KELLER TEXAS
Joined Feb 2002
3,373 Posts
FJ edf

Quote:
Originally Posted by Socomon
Cool! post some pictures when you can please.
some pics of progress,i started the glassing to day.
ben
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Old Nov 10, 2006, 04:56 PM
so i rewired it...
xorbe's Avatar
Mountain View CA USA
Joined Jun 2006
898 Posts
@fastben - wow you're going all out...

Flew the FJ with the 500SH with TP2070-4SX on a 4.75x4.5C -- not recommened for that 300W motor @ ~650W. Was careful to use WOT only in short bursts. It sure screams! I think it had unlimited vertical, unlike 5x5 on 3s. Need to use the radar of course, but it felt only just a bit faster than 3s on 5x5 -- the prop is just too small. Oh but the sound is lovely. Need to get a DPR-100 to find out what the real power is in the air. Ran a separate ParkBEC 6V just in case something fried.

Here's a useless video of static testing 4s on my FunJet with tachometer:
134mph prop pitch speed (0 min 14 sec)


I picked up an Eagle Tree MicroPower data recorder, temp and rpm sensors... curiosity is killing the cat!
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Last edited by xorbe; Nov 11, 2006 at 05:26 PM.
Old Nov 11, 2006, 07:17 PM
so i rewired it...
xorbe's Avatar
Mountain View CA USA
Joined Jun 2006
898 Posts
Peak watts on the ground has not much to do with sustained watts in the air.
My log indicates that sustained is a good 200W less than what WattsUp peak is:
http://www.rcgroups.com/forums/showt...2999&p=6371980
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