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Old Aug 16, 2012, 07:58 PM
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feefo's Avatar
Staffs, UK
Joined Apr 2009
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Quote:
Originally Posted by jackosmeister View Post
feefo, ive never tried a 16/15 on a gearbox before, have been tempted to many times though


16/15/3 will handle 60-70A LMR fine, Id suggest 4S too and see what you can come up with. Start with small props and work up
60-70a...really? Didn't expect that much! I was starting to doubt whether it'd be good enough, thinking a bigger motor would be better.

On 4s the calc is showing really limited prop sizes on anything less than 4:1, 10x 6 max for the 2.5 at 70a, 10x 8 for the 3:1 at 60a, 11x 10 with the 3.5 at 64a. Pitch speeds between @ 80-100, best being the 11x 10.
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Old Aug 16, 2012, 11:21 PM
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Joined Jan 2006
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"What capacity was the pack? "

we used a 4s 2200ma 65C with the 2w23 and
a 4s 2500ma 65C with the 2w25
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Old Aug 17, 2012, 05:17 AM
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AndrésMtnez's Avatar
Madrid, Spain
Joined Dec 2004
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Hi again,

Yesterday I tested the MiniHawk with the CG at 50mm, and it´s obviously much better than the 45-47mm it was at the maiden, but it still is not perfect and I think should be moved backwards

The only "problem" is now if I push the elevator too much it will spin faster than with full ailerons due to the short tail moment, wich sometimes is fun . I had increased the elevator throw but even after coming back to the recommended 3-4mm throw still do it

Has anyone experienced this?

I guess I still need to shorten the elevator throw, but now I´m not sure to move the CG further back....


Rolf, what´s your elevator throw?
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Old Aug 17, 2012, 05:37 AM
What is Highspeed ?
Rolf D.'s Avatar
Germany, BY, Bergen
Joined Feb 2011
512 Posts
Hi Andrez`
if I understand it right you will take a curve with aileron and then pull height on elevator it goes hard around the corner ?

thats normal - you must get a feeling for the elevator and airelons

I have had -5mm and +5mm on elevator

greez
rolf
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Old Aug 17, 2012, 07:43 AM
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Madrid, Spain
Joined Dec 2004
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I think I didn´t explain it correctly

I mean if I try to do a tight loop pulling hard the elevator, it doesn´t perform a loop, but a fast roll, much faster than with full ailerons, the problem is this is without aileron input, just elevator

This is only when I try to check if the wing is as strong as people affirm, not in normal flying
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Old Aug 17, 2012, 07:53 AM
Dir. of Innovation at Alert 5
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United States, FL, Fort Lauderdale
Joined Jul 2011
652 Posts
The tail is flexing, check for cracks in the receiver bay access hole and/or by holding the fuse and gently twist back and forth to feel or hear where the issue is coming from... I had the same issue with a slope plane and it turned out the fuse was twisting during hard, full up maneuvers and she would "barrel roll" rather than loop....
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Old Aug 17, 2012, 10:13 AM
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United Kingdom, Wales, Monmouthshire
Joined Aug 2011
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Andres - I've had exactly the same thing a couple of times. I think it's the aerodynamic instability provoking a flick roll when using a lot of elevator throw combined with a rearward CofG. Rather than a flexing/stiffness of the fuselage issue.

As you say, doesn't occur in 'normal' flight, just something to be aware of.
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Old Aug 18, 2012, 04:52 PM
Livin it UP when Im goin DOWN
Arcteryxxx's Avatar
Norway, Telemark, Skien
Joined Feb 2010
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Quote:
Originally Posted by FlyLT View Post
Today I tried my Scorpion 2221-8 with out the gear box
With 4.75X4.75 APC prop.
I pushed it a bit too far
1400W , ~ 90A on 4S and motor was hot ( 80'C )



http://www.youtube.com/watch?v=j2m1hRwXI_A&hd=1
Just re-read this post an watched the video a handful times. This is awesome! Have you got any doppler readings yet?
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Old Aug 18, 2012, 05:32 PM
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Earth
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Quote:
Originally Posted by Arcteryxxx View Post
Just re-read this post an watched the video a handful times. This is awesome! Have you got any doppler readings yet?
I tried today with 4.5x4.5 prop and it sounded faster,but It was windy and I could not do nice low and level pass.
The best pass against the wind was 220km/h
I think it looks faster,than it really is
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Old Aug 18, 2012, 05:44 PM
Livin it UP when Im goin DOWN
Arcteryxxx's Avatar
Norway, Telemark, Skien
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Quote:
Originally Posted by FlyLT View Post
I tried today with 4.5x4.5 prop and it sounded faster,but It was windy and I could not do nice low and level pass.
The best pass against the wind was 220km/h
I think it looks faster,than it really is
Hm.......
Got an envelope with new props for the speeder today. 6x5.5 exchanged for the 5.25x6.25 on the Mega 16/25/2EC and 4S LiPo. Higher pitch speed and less thrust for sure. The 6x5.5 is a great prop, but I do think a lot of energy is waisted on excess thrust in this airframe. At the speeds we are talking about anyway.
FlyLT: I do believe the 4.5 is a bit to small for getting the miniHawk up to speed. Churning too much pitch speed under lack of thrust.
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Old Aug 18, 2012, 11:47 PM
Lloyd Robinson
fishboy77's Avatar
USA, MO, St Louis
Joined Jun 2007
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Quote:
Originally Posted by Arcteryxxx View Post
Hm.......
Got an envelope with new props for the speeder today. 6x5.5 exchanged for the 5.25x6.25 on the Mega 16/25/2EC and 4S LiPo. Higher pitch speed and less thrust for sure. The 6x5.5 is a great prop, but I do think a lot of energy is waisted on excess thrust in this airframe. At the speeds we are talking about anyway.
FlyLT: I do believe the 4.5 is a bit to small for getting the miniHawk up to speed. Churning too much pitch speed under lack of thrust.
+1. I tried the 4.5x4.1 on the 16/25/2 on 4s and it was weak in terms of both thrust and top speed. The 4.75x4.75 is a lot better, but the 5.25x4.75 is better still. The top end between the 4.75x4.75 and the 5.25x4.75 is pretty close, but the 5.25x4.75 has much better vertical performance. That's my favorite prop for the Reverb right now.
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Old Aug 19, 2012, 04:26 AM
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FlyLT's Avatar
Earth
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Quote:
Originally Posted by Arcteryxxx View Post
Hm.......
Got an envelope with new props for the speeder today. 6x5.5 exchanged for the 5.25x6.25 on the Mega 16/25/2EC and 4S LiPo. Higher pitch speed and less thrust for sure. The 6x5.5 is a great prop, but I do think a lot of energy is waisted on excess thrust in this airframe. At the speeds we are talking about anyway.
FlyLT: I do believe the 4.5 is a bit to small for getting the miniHawk up to speed. Churning too much pitch speed under lack of thrust.
I agree ,but the 4.75x4.75 looks too big for this motor.
I couldn't touch the motor, it was so hot. Even with 4.5x4.5 it was quite hot,but not like that.
To keep it cool I would have to do 2-3 passes only and then just fly around or land it
Normally I do speed pass ,then I fly a circle slowly and again speed pass,so I dont push it constantly. But still the CC 100 data log gave me 180F temperature )
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Old Aug 19, 2012, 06:04 AM
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Staffs, UK
Joined Apr 2009
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Have you got a heatsink on your motor or is the space too tight? Have you opened up the air holes in the fuse with a dremel or left them closed? Better would be to have holes in the motor mount to allow air through the motor, although the spinner will stop a lot of air getting through, coolnose spinner would help too.

Don't want to upset you....but if your motor's got that hot you may have damaged it, even if it still seems ok. I burnt the windings on my 16/25/2CE F5D prop testing and had to send it back for a rewind (only had it a couple of weeks...). Give your motor a smell (don't let the Mrs catch you doing this, they tend to think you're losing the plot/ take the p s/tell your mates who don't fly who take the p s). If you can smell a burnt odour, soz, you've damaged it.
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Old Aug 19, 2012, 06:09 AM
Livin it UP when Im goin DOWN
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Norway, Telemark, Skien
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He is running an outrunner (2221) - heatsink no option

Btw: Scorpion andertises it can take 180 degC.....
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Old Aug 19, 2012, 06:24 AM
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FlyLT's Avatar
Earth
Joined Oct 2009
349 Posts
Quote:
Originally Posted by feefo View Post
Have you got a heatsink on your motor or is the space too tight? Have you opened up the air holes in the fuse with a dremel or left them closed? Better would be to have holes in the motor mount to allow air through the motor, although the spinner will stop a lot of air getting through, coolnose spinner would help too.

Don't want to upset you....but if your motor's got that hot you may have damaged it, even if it still seems ok. I burnt the windings on my 16/25/2CE F5D prop testing and had to send it back for a rewind (only had it a couple of weeks...). Give your motor a smell (don't let the Mrs catch you doing this, they tend to think you're losing the plot/ take the p s/tell your mates who don't fly who take the p s). If you can smell a burnt odour, soz, you've damaged it.
Yes I have opened those air holes and there are holes in the motormount,but as you said the spinner stops a lot of air.
This is outrunrer motor,so no heatsink here . Thats why I like inrunners
I have checked the motor and I think I can smell something.. not quite sure its burnt odour,but what else could it be?
Anyway if its already damaged,I put it on my foamy Funjet to see how long it will last.
And for my little Hawk I will go for the Mega 16 25 2
Thank You
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