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Old Nov 22, 2012, 05:47 AM
If it has wings it will fly...
ckleanth's Avatar
United Kingdom, England, Birmingham
Joined Mar 2011
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just to elaborate on a few things
I've bought this model purely because I wanted a model aircraft around 1000mm wingspan so I can keep in my car and go flying after work when time and weather permits. I've got a few planes most of which are aerobatic models. I've hot an mx2, an edge, a cap, a UMX beast all of which I love but apart of the beast they are too big to keep in the car boot (and be out of sight from thieving twats etc). I wanted a small sbach really and I was initially thinking about the HK 1000mm sbach but after reading the issues with being scaled down and redesigned by a monkey having as result being too tail heavy, I gave it a miss. the HK performance sbach description made fence at the time as they were on about a "performance" model. with advertised flying weight 690g it made sense... but after buying I got this... not really what I was expecting but if it was lighter it could have been ok.

about the LG comment I wasn't going to buy one if I had one that would work. fitting plastic screws you don't brake either the LG or the aircraft on a hard landing. the 3mm wire pretend to be LG did not work for me.

about the prop hang comment.... the calcs was to see the thrust to weight ratio. the control surface areas looked ok and the movement sufficient. I have programmed different rates on my transmitter and its easy to swap as required. the problem was the aircraft weight as you need to spin the prop more to balance the weight with thrust. the issue with that is that kinetic energy is mass moment of inertia * omega ^2. meaning both mass of prop and how fast you spin it will generate the rotational motion one needs to compensate with control surface movement. but because we use a small prop spinning fast this will generate a bigger gyroscopic effect.

never used gyro although bought one some time ago but still intend to try it out.

the prop with the sbach us s 7x5. the comment that this prop is built for speed is rubbish. one can generate the same ammount of thrust depending on prop size and rotational speed. what you choose nerds to be thought through. the prop will generate thrust if you spin it but if you spin it too fast the flow separation will be more, less advance, prop is less efficient.
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Last edited by ckleanth; Nov 22, 2012 at 12:10 PM. Reason: spelling
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Old Nov 22, 2012, 07:16 AM
222 km/hr Parkjet flyer
solentlife's Avatar
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Quote:
Originally Posted by chessgame View Post
I am using a JR TX hence i tone down the throws via flight mode.
ie 50% of original full throws with 50% expo. The figures i quoted earlier is the 50%

The max throw i tried was 75% of original... and it was really bad even at slower speed . My experience with fast planes is that when ur plane speed is really fast, u need to tone it down the throws even further when u full throttle..otherwise even the simple banking or turning is ridiculous to control.
Sorry but still not any wiser .... 50% of original ?? What original ? Full throw can be anything based on where you place the control connection on the servo arm and surface horn. It's why I quote FULL throw and DR throw .. and also it's much better to quote the actual mm up / down as then it makes no odds what radio / connections etc. you use.

My Full throws are cut back using the Dual Rate % on both full and reduced ... and not via the EPA. This then allows me later to increase either if I want independent of the other.

Nigel
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Old Nov 22, 2012, 07:28 AM
222 km/hr Parkjet flyer
solentlife's Avatar
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Quote:
Originally Posted by ckleanth View Post
..............the prop with the sbach us s 7x5. the comment that this prop is built for speed is rubbish. one can generate the same ammount of thrust depending on prop size and rotational speed. what you choose nerds to be thought through. the prop will generate thrust if you spin it but if you spin it too fast the flow separation will be more, less advance, prop is less efficient.
Actually not strictly correct ... you only have to compare a harbour Tug with big prop ... and a powerboat with small prop etc.

One will tow a ship - other will just sit and move water.

The difference is diameter and thrust. Thrust can be huge as in the tug boat or a large airplane prop ... but reach it's pitch speed and it doesn't accelerate anymore ... but load it up so vehicle is moving slower and that thrust bites back in again and she MOVES ! Now take the powerboat or pylon race plane and you see a smaller prop as it's now working on pitch speed and does not want to waste energy in torque ....
The smaller higher revving prop will also stall much easier than a slow revving large diameter prop. We only need to check out the comparison of 3D and Pylon machines and the difference in props is immediately seen.

Comparing the control surface sizes of the EDGE and my 3D waiting for motor combo - totally different ball-game !

igel
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Old Nov 23, 2012, 01:48 AM
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Quote:
Originally Posted by solentlife View Post
Sorry but still not any wiser .... 50% of original ?? What original ? Full throw can be anything based on where you place the control connection on the servo arm and surface horn. It's why I quote FULL throw and DR throw .. and also it's much better to quote the actual mm up / down as then it makes no odds what radio / connections etc. you use.

My Full throws are cut back using the Dual Rate % on both full and reduced ... and not via the EPA. This then allows me later to increase either if I want independent of the other.

Nigel
I understand the need for mm measurement as opposed to the above.
Cos like you said, even if you have the same computer settings, the mechnical settings (which hole for your clevis and length) also may different.

For mm range, i have posted that earlier.


For computer settings on what i am using.
My TX settings
JR tx has DR , EPA and Expo.
When i say full throw of original, i mean keep End Point Adjustment (EPA) at 100% , Dual Rate (DR) at 50% and Expo at 50%

This will give you the desired effect of the throw range which i am using if you are adjusting it via JR TX.
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Old Nov 23, 2012, 03:20 AM
222 km/hr Parkjet flyer
solentlife's Avatar
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Quote:
Originally Posted by chessgame View Post
I understand the need for mm measurement as opposed to the above.
Cos like you said, even if you have the same computer settings, the mechnical settings (which hole for your clevis and length) also may different.

For mm range, i have posted that earlier.


For computer settings on what i am using.
My TX settings
JR tx has DR , EPA and Expo.
When i say full throw of original, i mean keep End Point Adjustment (EPA) at 100% , Dual Rate (DR) at 50% and Expo at 50%

This will give you the desired effect of the throw range which i am using if you are adjusting it via JR TX.
OK ... mmmmmm

Me - I too keep EPA at 100% both ways as then I can adjust the DR individually instead of DR then acting on a reduced EPA setting.
But to be honest Tx EPA is not much use to others as the real deal is the actual mm movement at the surfaces and is why I quote the full rate and reduced rate mm's.

Nigel
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Old Nov 23, 2012, 04:36 AM
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Quote:
Originally Posted by solentlife View Post
OK ... mmmmmm

Me - I too keep EPA at 100% both ways as then I can adjust the DR individually instead of DR then acting on a reduced EPA setting.
But to be honest Tx EPA is not much use to others as the real deal is the actual mm movement at the surfaces and is why I quote the full rate and reduced rate mm's.

Nigel
No worries mate ! have fun this weekend ! i am looking forward to you posting about your maiden flight !

Need some competition in getting this plane as fast as possible ... evil smile
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Old Nov 23, 2012, 06:33 AM
If it has wings it will fly...
ckleanth's Avatar
United Kingdom, England, Birmingham
Joined Mar 2011
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re Nigel
were more or less saying the same thing but I was mainly expanding on the gyroscopic effect a prop has. its all relative (size,mass,mass moment of inertia and then speed. a smaller rc prop will have to spin faster to produce the same amount of thrust but then weight/size decreases. the decrease in weight is liniarly proportional but the increase in speed is ^2. one needs to put some numbers to see the actual increase/decrease in rotational energy but I rekon a smaller prop will increase the tendency for the aircraft to twist.
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Old Nov 24, 2012, 09:35 AM
222 km/hr Parkjet flyer
solentlife's Avatar
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People aint kidding when they say this is a handful ! I rolled her out with a 3S 2200 in her as a maiden job - that weighs similar to an 1800 4S.

She took of like a scalded cat ... but as soon as I eased the stick - she stuck her nose down hard ... So there's me fighting to keep the nose up and click that trim ... she's out on aileron as well - so it's a right hand doing as much as possible to keep her under control and left hand trying to get those trims set ... I'd closed her to about 2/3rds throttle but she was still going like a bat out'a hell ...

Well I couldn't hold her she got quite a distance away while I was trying to get the trims done ... she rolled over and in she went.

Damage :

Compression to general front area - hot water straightened that out but still crease lines showing.

Motor mount shed two legs - replaced with lite-ply ring and motor bolted to that ... with spacers to give right and down correction due to the compression I can't remove.

Landing gear ripped out of bottom and small part of fuselage next to it - glued back with 5 min erpoxy.

Fuselage seam split along bottom - opened up and 5 min epoxy applied ... taped closed.

Prop broke - bought spares anyway.

Amazingly the cowl and spinner survived relatively unscathed ...

Conclusion :

Mine was seriously out of trim to make her dive for the deck and also roll right. It was a fight to keep her under control ...

Control throws - ONLY after trimming her out and getting her as you want her should any throw be more than 5mm up / down ...

This machine takes no prisoners ..... even on the 3S I had in her ... she was quick ...

..........................

Have I given up ? No way ... I will have this baby in the air and she'll do what I tell her ... I don't give up that easy .............



Nigel
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Old Nov 24, 2012, 10:30 AM
222 km/hr Parkjet flyer
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OK ... repair notes :

The motor is unsual in that the X mount is part of the motor and not bolted on as most. This caused a bit of trouble to replace the broken plastic mount. When you replace the mounting system - make sure you keep the old and know which way it came off ... it's offcentred if you look closely at the screw holes. So matching up your replacement needs to know which way round etc.

The spinner is ;particular to the prop that comes with the model .... the screw tubes in the cone are too close together for a standard APC style prop and need filing back to clear.

The fuselage seams are poorly glued ... remedied by 5 min epoxy.

I'm near finished after approx 2 hrs work on it ... just waiting for epoxy to set on the Landing gear plate.

Nigel
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Old Nov 24, 2012, 11:29 PM
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wow... that is a wild maiden nigel.

i am not sure if the key reason i didnt get the problems is due to my motor esc combo. i am using the ntm 600 plus watts with 40 amp esc.

i tend to do use my own motor/esc comb cos i always want more power... and 600watts is a lot of power for such a small plane ...

i also didnt use the landing gear cos i fly off grass... and the grass field i fly at is vicious.. it has ripped and still ripping beautiful planes with landing gears on the most perfect of landing..
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Old Nov 25, 2012, 01:54 AM
222 km/hr Parkjet flyer
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Heres the vid ....

HK Edge 540 racer maiden crash 24 11 12 (1 min 36 sec)


Now I've been thinking this through and I cannot help but think keeping the CoG forward like some posts on here has helped the crash. This model had a death wish - it just wanted to head for the deck ... I put in full UP trim ... still not enough.

I've rechecked the CoG and I cannot get mine back more than 30mm .. so somethings not right. I even tried a smaller battery ... I cannot get it back more than 35mm ....
I note that many reckon to have CoG at around 35 'ish ... but the root chord is 155mm, with tip chord 80mm ... with a usual safe CoG of 1/3rd ... we are at around 45mm ... which is what manual says ...

I am now going to strip the front of my Edge and lighten her as much as possible to see if I cabn get the CoG back more ... I reckon to bolt the motor direct with spacers to get rid of mounts ...

Nigel
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Old Nov 25, 2012, 02:31 AM
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Quote:
Originally Posted by solentlife View Post
Heres the vid ....

http://www.youtube.com/watch?v=P-8ul...1&feature=plcp

Now I've been thinking this through and I cannot help but think keeping the CoG forward like some posts on here has helped the crash. This model had a death wish - it just wanted to head for the deck ... I put in full UP trim ... still not enough.

I've rechecked the CoG and I cannot get mine back more than 30mm .. so somethings not right. I even tried a smaller battery ... I cannot get it back more than 35mm ....
I note that many reckon to have CoG at around 35 'ish ... but the root chord is 155mm, with tip chord 80mm ... with a usual safe CoG of 1/3rd ... we are at around 45mm ... which is what manual says ...

I am now going to strip the front of my Edge and lighten her as much as possible to see if I cabn get the CoG back more ... I reckon to bolt the motor direct with spacers to get rid of mounts ...

Nigel
saw your video. my cg is at 32mm. i can confirm it works at that cg.

from your vid
a. when u hit full throttle at take off u can see the plane shot up.
b. u cut throttle to trim your plane and were using 3s.
c. unfortunately at lower airspeed,the out of trim plus heavy weight lead to plane stalling... at this point u r fighting for control..

if u recall we said this was a racer, so slow speed means your elevator did not have much authority yet but in built down thrust of the motor had...

d. the only way out is the unconventional which is to add more power...3s at half throttle just didnt give you enough of that to get out of the stall....

i will try to do a vid as it seem so many r having problems with this bird.
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Old Nov 25, 2012, 03:07 AM
222 km/hr Parkjet flyer
solentlife's Avatar
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Quote:
Originally Posted by chessgame View Post
saw your video. my cg is at 32mm. i can confirm it works at that cg.
That eases my pain !! Just looked at changing the mount but the cut-away firewall makes it difficult.

Quote:
from your vid
a. when u hit full throttle at take off u can see the plane shot up.
That was me on up elevator to stop her hitting the dirt bank. If you note as soon as she was up - I let of the UP and she dived for the deck ...

Quote:
b. u cut throttle to trim your plane and were using 3s.
Correct - but speed was still way above what should be a stall speed ... I fly fast EDF's and Parkjets .. so I have a feel for speed and she was motoring ... even at 2/3rds throttle and 3S.

Quote:
c. unfortunately at lower airspeed,the out of trim plus heavy weight lead to plane stalling... at this point u r fighting for control..
I was fighting from moment she took off .. way out of trim ... the lot ... so I go for height .. cut back throttle ... try to get some control sense ... but I lost it. I don't think she stalled ... she just got better of me .. too far away, hard to tell which way she's going, death dive wish .......... all added up.

Quote:
if u recall we said this was a racer, so slow speed means your elevator did not have much authority yet but in built down thrust of the motor had...
Agreed but she was still doing good speed ... I really think that a combo of my loss of orientation at that distance and her nose down death wish added up to my crash.

Quote:
d. the only way out is the unconventional which is to add more power...3s at half throttle just didnt give you enough of that to get out of the stall....
I'm out on the stall ... she was a bucking bronco all across that field ... I think I'd got into that see-saw effect of too much control movement, out of trim model ... I couldn't hit reduced rates as I was fighting the roller coaster ride. I made mistake of taking of at full rate with idea to reduce rates once up ... and trimmed. I was maidening with 8mm aileron and 10mm elevator ... I'm not afraid to admit that most of the crash is my own fault.

Quote:
i will try to do a vid as it seem so many r having problems with this bird.
I think the problem is that this bird is so sensitive with high power whether 3S or 4S. I also note that elevator / stab are aerofoiled such that when aligning neutral - great care needs to be taken .... I think I made error when first setting up by eyeball ... Later when I put a straight edge through the tip chord - I found the eyeball alignment had led to 2mm down elevator.

I should be trying again later today ... and this time she will have DR on take-off ... 5mm up / down on ail / elev ..... Plus I've wound in a few turns of up elevator to cure the death dive !

So lets see what today brings ....

Nigel
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Old Nov 25, 2012, 09:05 AM
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I think we have a pattern coming into focus here, regarding CG and trim. If you look back to my maiden report at post #87 in this thread, you will see that I reported having to put in three or four clicks of "up" trim to neutralize stick pressure. And I was using a CG of 34mm -- about the same CG that you had, right? So what I think is happening here is that the plane designers designed the horizontal stab incidence based on the 40-45mm CG given in the manual. But then when the the folks at HobbyKing tested the plane, they realized that at that CG, the plane was an accident waiting to happen...so they finally settled on putting an 1800 4S battery full-forward in the nose to get that 28-30mm CG that tames the plane down. But the problem is, with the CG much farther forward than designed, the incidence of the horizontal stab is now insufficient. So you need to add "up" elevator trim to restore neutral pitch. And after you do that, the elevator is no longer faired with the stab at neutral trim. And of course, for a maiden flight you set the elevator to be faired with the stab, unless you know it should be different. Which we didn't know, since HK didn't tell us.
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Old Nov 25, 2012, 09:38 AM
222 km/hr Parkjet flyer
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Originally Posted by herk1 View Post
I think we have a pattern coming into focus here, regarding CG and trim. If you look back to my maiden report at post #87 in this thread, you will see that I reported having to put in three or four clicks of "up" trim to neutralize stick pressure. And I was using a CG of 34mm -- about the same CG that you had, right? So what I think is happening here is that the plane designers designed the horizontal stab incidence based on the 40-45mm CG given in the manual. But then when the the folks at HobbyKing tested the plane, they realized that at that CG, the plane was an accident waiting to happen...so they finally settled on putting an 1800 4S battery full-forward in the nose to get that 28-30mm CG that tames the plane down. But the problem is, with the CG much farther forward than designed, the incidence of the horizontal stab is now insufficient. So you need to add "up" elevator trim to restore neutral pitch. And after you do that, the elevator is no longer faired with the stab at neutral trim. And of course, for a maiden flight you set the elevator to be faired with the stab, unless you know it should be different. Which we didn't know, since HK didn't tell us.
Today bears that out ..... still with the 3S in her .. but now with elevator up a touch ... she took off and flew absolutely perfect. Movements I cut back to 5mm each way on both elevators and ailerons ... but into the flight I clicked back to 8mm full rate on ailerons ... I'd also reduced my expo from 60% to 40% on all ....

She was an absolute pussy-cat today .... only trouble is the landing .. she glided on so fast ! Ripped out the LG like everyone else - but that would have happened anyway on the rough ground we use.

So there you are ........... elevators are now absolutely straight after having to give a couple of clicks down.

Next will be 4S in her and let her rip ....

Nigel
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