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Old Feb 08, 2012, 12:25 AM
The stalling italian
gionir's Avatar
France, RA, Lyon
Joined Jan 2011
297 Posts
Quote:
Originally Posted by gionir View Post
Guys, I finally received my hawk kit from HK.
As I don't have the manual, could someone please post the position of the CG?

Many thanks!

G
Anyone? Pleeeease?
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Old Feb 08, 2012, 12:54 AM
easily confused
mu2freighter's Avatar
Nashville Metro, Tennessee, United States
Joined Sep 2003
2,183 Posts
Quote:
Originally Posted by gionir View Post
Anyone? Pleeeease?
Sure thing, here's the scan from the manual. CG's 24mm back from the leading edge at the root intersecting the intake.
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Old Feb 08, 2012, 01:55 AM
The stalling italian
gionir's Avatar
France, RA, Lyon
Joined Jan 2011
297 Posts
Quote:
Originally Posted by mu2freighter View Post
Sure thing, here's the scan from the manual. CG's 24mm back from the leading edge at the root intersecting the intake.
Thanks mate, much appreciated. Can't wait to maiden it now!

Cheers

EDIT: good thing that my hundredth post goes out to thank you!
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Old Feb 08, 2012, 03:11 PM
Electric flyer
fly time's Avatar
Renton, WA, US
Joined Oct 2007
1,291 Posts
Quote:
Originally Posted by mu2freighter View Post
Sure thing, here's the scan from the manual. CG's 24mm back from the leading edge at the root intersecting the intake.
I've found the recommended CG for the Hawk is difficult to achieve with even the lightest of batteries (my 350 mAh Sky Lipo weighs in at just 25 grams).

My CG is forward of the recommended position by probably 10 mm. It flies fine under throttle, but it is impossible to flair the nose up when you slow it to landing speed. Because of that, my last flight ended with a cracked fuselage

Before I fly next, I will increase the elevator throws to see if that will help.
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Old Feb 08, 2012, 04:04 PM
The stalling italian
gionir's Avatar
France, RA, Lyon
Joined Jan 2011
297 Posts
Quote:
Originally Posted by fly time View Post
I've found the recommended CG for the Hawk is difficult to achieve with even the lightest of batteries (my 350 mAh Sky Lipo weighs in at just 25 grams).

My CG is forward of the recommended position by probably 10 mm. It flies fine under throttle, but it is impossible to flair the nose up when you slow it to landing speed. Because of that, my last flight ended with a cracked fuselage

Before I fly next, I will increase the elevator throws to see if that will help.
You got me thinking here:
At the beginning I thought that it's too nose heavy, therefore you need light batts to achieve the cg.
Then, if I am right, you cannot really change the cg of a plane, as it derives from the design and the weight of all the parts combined, but don't quote me on that.
She may balance in a different point from the one on the manual, but in the end she'll fly weird.
Have you tried with a small weight in the tail to see if you can get her to balance properly?
Mi opinion is that bigger throws might help but it doesn't solve the real problem.
Unless, of course, they made a design mistake and the specified CG is wrong.
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Old Feb 08, 2012, 05:38 PM
Electric flyer
fly time's Avatar
Renton, WA, US
Joined Oct 2007
1,291 Posts
Quote:
Originally Posted by gionir View Post
You got me thinking here:
At the beginning I thought that it's too nose heavy, therefore you need light batts to achieve the cg.
Then, if I am right, you cannot really change the cg of a plane, as it derives from the design and the weight of all the parts combined, but don't quote me on that.
She may balance in a different point from the one on the manual, but in the end she'll fly weird.
Have you tried with a small weight in the tail to see if you can get her to balance properly?
Mi opinion is that bigger throws might help but it doesn't solve the real problem.
Unless, of course, they made a design mistake and the specified CG is wrong.
It's a neat little jet, but not perfectly engineered

It probably would fly a little better with the CG at 24mm, but I was not able to find a battery any lighter than the one that I have (maybe I did not look hard enough), and I did not want to add weight (though if it were all the way back, it probably would not take much). You probably could move the electronics or fan back some, but as small as everything is it seemed like a pain to even try. So I flew it with the CG forward, and found that it flew fine all the way up to having to land the thing. With the throttle off, the nose drops as soon as you try to slow down. My first 5 "crash landings" did no damage, but the 6th one cracked the fuse just a little. I think with a little more elevator authority I could hold the nose a little higher. We shall see.

The most important thing with these micros is to keep the weight as light as possible! A few grams makes a difference in performance, so don't add weight to balance it unless you have to.
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Old Feb 08, 2012, 05:51 PM
The stalling italian
gionir's Avatar
France, RA, Lyon
Joined Jan 2011
297 Posts
Quote:
Originally Posted by fly time View Post
It's a neat little jet, but not perfectly engineered

It probably would fly a little better with the CG at 24mm, but I was not able to find a battery any lighter than the one that I have (maybe I did not look hard enough), and I did not want to add weight (though if it were all the way back, it probably would not take much). You probably could move the electronics or fan back some, but as small as everything is it seemed like a pain to even try. So I flew it with the CG forward, and found that it flew fine all the way up to having to land the thing. With the throttle off, the nose drops as soon as you try to slow down. My first 5 "crash landings" did no damage, but the 6th one cracked the fuse just a little. I think with a little more elevator authority I could hold the nose a little higher. We shall see.

The most important thing with these micros is to keep the weight as light as possible! A few grams makes a difference in performance, so don't add weight to balance it unless you have to.
You are certainly right, both my Sabre and MiG 15 are very sensible to every gram I add. Although the authority of 3S compensate the extra weight.
Your post made me think that those four batteries I bought for her, 500 mAh 3S, 69 grams, won't be as good as I thought.
I think I'll give her a try with the cg at 24mm and take it from there..
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Old Feb 08, 2012, 06:13 PM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
1,372 Posts
I saw somewhere, probably earlier in this thread, Nitrocharged modded his by moving the complete fan assembly back in the airframe a bit to help achieve correct CG to accomodate the battery.
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Old Feb 08, 2012, 06:41 PM
Not enough hours in the day
Slaanesh's Avatar
Melbourne
Joined Feb 2009
2,427 Posts
What a pain - so the Hawk is no good either? I don't want to have to move components around though it looks necessary.

I think a better option would be to relocate the elevator servo and place the battery in this area instead? This would be easy enough to do if you have the unassemble "spare-parts" version

I really want to keep my Hawk at the recommended 95g weight even on a 3S system.
Considering it's tiny wing area, you want this one to be as light as possible.
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Old Feb 08, 2012, 07:59 PM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
1,372 Posts
Quote:
Originally Posted by giuseppi View Post
I saw somewhere, probably earlier in this thread, Nitrocharged modded his by moving the complete fan assembly back in the airframe a bit to help achieve correct CG to accomodate the battery.
Hate to quote my own post but here's a video relative to it. Hope you don't mind, Dave.

g

http://www.google.com/url?sa=t&rct=j...sw19-HIFRUBOig
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Old Feb 09, 2012, 05:09 AM
Epoxy Flyer
Australia, NSW, Sydney
Joined Dec 2011
14 Posts
Mig 29

Brian,

Good to see another video of the Mig. I have my CG about 1/2 cm in front of the recommended position and for me it seems pretty good there. I am using the Rhino 600 mAh batteries, so probably like your 600 mAh battery it helps with the balance. Although I don't have the battery all the way forward.

One change I made to mine was to align the control rods, so they now go from the inside of the servo arm to the inside of the control horn. Pushing more directly along the control wire seems to result in less flex. The only issue I had was some control horns came loose, but a bit of epoxy and they seem solid now.

The nose of my Mig is probably a bit shorter than yours - as I don't have soft snow for a nose in.

Nev
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Old Feb 09, 2012, 06:43 AM
Registered User
Joined Sep 2010
285 Posts
Just got a kit of parts and I plan to fit the elevator servo in the rear and make an all flying elevator like the real thing . That will move 2g to the rear and allow the lipo to go further back and help with this nose heavy cg problem .
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Old Feb 09, 2012, 02:20 PM
Registered User
Joined Feb 2012
2 Posts
2.2 gram servo voltage question

Hi all.

After spending most of the day reading the whole thread (its really a book actually) , I need to ask a potentially already answered question:

I have a kit version of the F86 on the way with a TURNIGY Plush 6A /.8bec/6g Speed Controller and two HK-282A Single-Screw, Ultra-Micro Servo 2g.

I dont think they will last on the voltage supplied from the speedy, so here is my question: how do I limit the voltage to less than 4.8v for the servos?

I would hate to wreck the plane due to something so silly. I live at over 3000m ASL and I think every gram saved will help, hence the tiny servos bought...

Regards
Stevo
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Old Feb 09, 2012, 03:01 PM
Team30 Micro EDF
NitroCharged's Avatar
Adelaide, Australia
Joined Apr 2004
11,199 Posts
Some say use a diode as it's the easiest way (in line with the red wire going to the servo).

I use a 1117 3V regulator to do the same thing but this way the voltage stays constant throughout the discharge of the lipo.
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Old Feb 09, 2012, 03:17 PM
Fear me, I'm a space-duck.
hanzie's Avatar
Nederland, GE, Wageningen
Joined Nov 2011
288 Posts
Yes, in this setup a diode would probably be the easyest solution. Each diode in series decreases the total voltage by about 0.7 volts. Since this particular esc supplies 5.0 volts, the voltage with the diode will be about 4.3 volts, which is low enough for the servo's to stay alive.
A voltage regulator works too ofcourse (I used one to power the receiver in a small glider) but it might be bit harder if your not familiar with electronics and soldering.
Hanzie.
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