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Nov 15, 2012, 04:41 AM
Registered User
Maybe my idea is rubish but here it goes:
I know that a heavy x8 is difficult to keep above your head and be stable enough so maybe if we fit two small plywood fins where the wings start and at CG will make it easier to hold for hand launching
(WITH TWO HANDS of course so someone else will have to control it)....
Chris
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Nov 15, 2012, 06:06 AM
Registered User
Imagecatcher's Avatar
Quote:
Originally Posted by crazy1pilot
Someone who has a made a launcher, what angle do you set it at and tension of bungee do you use? I would like to build one shortly and have an idea.

Crazy1
I read somewhere 15 degrees so thats what I did. I have 6x 8mm x 800mm bungees that offer 40+kgs at 1.5m stretch. Some have said I will need more for my 4.9kg bird ( I have the motors running at release). You can see my launcher in the attachments and videos.
Nov 15, 2012, 06:12 AM
Registered User

X8 Maiden


Maidened my X8! What a blast to fly!!!! It flies SO steady & super slow for such a big wing. OK, I only had 1 x 4s 4000mHh for the motor & 1 x 2350 3s for VTx in it to test LOS. The through was hair raising both times - a buddy through it for me & both times the nose went straight up but I managed to fly it. But in flight it was rock stable & needed only a little bit of throttle. In the video you can see the Amps & Watts... It has a Eflight Power 32 in it with a 12x8 Carbon prop & it has loads of power - to go vertical is no problem. Tested RTH a few times but it didn't work like it should. It went into a spiral dive each time I have tested it. (came out of it quickly) CG was 1cm behind recommended CG. Will test it again this weekend. :-) Sorry for the bad video, I use 5740Mhz for the signal to the plane & 5860Mhz for the signal to my fatsharks from the GS. Seems they interfere with eachother... :-) Will use the FS with a wire to the GS next time. :-)

X8 wing Maiden FPV (LOS) (7 min 31 sec)
Nov 15, 2012, 09:41 AM
Registered User
Quote:
Originally Posted by hendrix
Maybe my idea is rubish but here it goes:
I know that a heavy x8 is difficult to keep above your head and be stable enough so maybe if we fit two small plywood fins where the wings start and at CG will make it easier to hold for hand launching
(WITH TWO HANDS of course so someone else will have to control it)....
Chris
I have visions of some poor volunteer holding this thing up with 2 hands over his head and tossing it. Goodbye scalp!
Nov 15, 2012, 10:25 AM
Registered User

Is this reasonable


I have a lot of experience with glow engines but practically nothing with electric motors. I tested the motor, esc and battery combination for my X-8 yesterday. Please advise if this is acceptable performance for the plane (my intended use is slow, long, FPV cruising).

All testing done with a 4S 5000 Mah battery, and folding CF 13X6.5 prop:
Amp draw at full throttle 44
Watts at full throttle 602
RPM 8,800

According to Thrust HP I can expect about 6 lbs of thrust and a max speed of 54mph.

This seems to be plenty enough power and low enough current draw to be practical on the X-8. Your thoughts please?

The motor is a Turnigy Aerodrive SK3, 4240, 740KV. After 5 minutes of half throttle running the rear end of the motor against the firewall is slightly warm. The 70 Turnigy amp esc is getting hot, but it is not in moving airflow during testing.

Should I try to provide more cooling air to the motor and esc than what will naturally occur through the air openings in the front of the fuselage which allow air flow through the fuselage then out the rear motor mount holes? Should I try to mount the ESC so that its heat sink is on the surface of the model to get more cooling?
Nov 15, 2012, 11:18 AM
Registered User
You should not bench test this kind setup for longer than absolutely necessary to determine what your current draw is (i try for less than 5 seconds).
You are lucky you didn't burn up the motor or ESC, or both. There is not enough cooling flow for either device on the bench.
That setup has plenty of power for normal cruising and basic loops and rolls.
SK3s are known for quick melting (magnets detach).
I know, I've made magic smoke with one myself Seems all of us glow guys want to "run it up" to check them out, but its not a good idea without some big fans on the bench

I fly with almost the same setup now without issue. My ESC never goes over 113F even when the outside air temps were 85F+. It is mounted inside in the rear compartment. (Temp sensor monitored).
Last edited by Jeff Watt; Nov 15, 2012 at 02:25 PM.
Nov 15, 2012, 11:35 AM
Registered User
Quote:
I have visions of some poor volunteer holding this thing up with 2 hands over his head and tossing it. Goodbye scalp!
I thought so my self but a helmet could solve this.
When i hand launch mine i always wear a glove.
Chris
Nov 15, 2012, 12:44 PM
Registered User
BldrFlyr's Avatar
Quote:
Originally Posted by Dr.Tom
http://www.youtube.com/watch?v=RModL...=ULRModLGbkQ24

7:11 my X8 launching, hands off,
no need for catapult
(2 cameras, FPV, 2x 5000 4S batt)
Beautiful country. My wife is from Croatia and we spend the summers in Brac and Zagreb.
Nov 15, 2012, 01:56 PM
Registered User
Quote:
Originally Posted by octane81
According to BEVRC price is not set.

When it stalls it will just go into a death spiral , which you really DONT WANT with a FPV plane... not safe.

Take a look here , 2:25
Thins death spiral happend more than once , and it was no mechanical or servo failure. Just stalling..

http://youtu.be/2clR-cSNc1c?t=2m27s
Man really maybe you should a pilot or someone who knows about this.
I did and he told that you should some really simple things.

1st turn off the motor.
2nd remove your fingers from the sticks (set control surfaces to neutral)
3rd turn off auto stabilization or AP or any electronic.

The first thing you expect to see is that the wing will slow with the spiral as it gains speed and finally stop. Then gradually you must increase the throttle ( SLOWLY) get enough airspeed and then continue with your flight. If you fly high you have more than enough time to get out of this situation.

Things you MUST NOT do.
1st allow the AP or auto stab. system to do its job. It only keeps the stall.
2nd increase the throttle to gain more speed. Major mistake. It will increase the spiral diving due to NO support of the wing. This means that the motor will rotate the plane and NOT the prop.

Delta wings have very low stall speed relatively of course but they can easily go to flat spin or spiral dive. Dont give them that chance its bad.

For my X-8 i keep the CoG front kinda 5mm from the manual's CG. This makes the plane to gain speed. Try it !!!!
Nov 15, 2012, 02:12 PM
Registered User

Disregard - Replying to a post that someone revived after almost a year
Last edited by Jeff Watt; Nov 15, 2012 at 02:39 PM.
Nov 16, 2012, 01:59 AM
Person of interest
KiwiKid's Avatar
Quote:
Originally Posted by xviper
I have visions of some poor volunteer holding this thing up with 2 hands over his head and tossing it. Goodbye scalp!
It might be easier just to turn the sucker upside down and give it the full welly


http://www.youtube.com/watch?feature...v=p54WaGqhLPY#!
Nov 16, 2012, 02:02 AM
Registered User
Daemon's Avatar
Quote:
Originally Posted by henlo
It went into a spiral dive each time I have tested it. (came out of it quickly) CG was 1cm behind recommended CG.
A small shift of CG is ok. 15mm behind recommended, is too much. It's flyable, but
not particularly stable there, as you've discovered.

ian
Nov 16, 2012, 02:06 AM
Registered User
Daemon's Avatar
Quote:
Originally Posted by ponoc
Man really maybe you should a pilot or someone who knows about this.
You replied to a post from 2011, before the X8 was even released.
Good luck with that "sticks at neutral position" recovery, if/when your X8 does
someday spin.

ian
Nov 16, 2012, 02:18 AM
Registered User
Quote:
Originally Posted by Daemon
You replied to a post from 2011, before the X8 was even released.
Good luck with that "sticks at neutral position" recovery, if/when your X8 does
someday spin.

ian
Hi - I had the spins, and as an example, added a 2200mah 3s about 150mm from the nose, and it is sorted. Will now do CG and add less right in the nose to keep it like it is.
Nov 16, 2012, 07:42 AM
Registered User
This may not be a workable idea, but what if we simply design a short throwing "stick" for use with the X8? I am sure one of us could cook up an interface between "stick" and fuselage that would keep it flight ready level as you throw it. This idea worked for our ancestors when they were launching spears at game/enemies, and maybe it would work here as well.

And of course this "stick' could be any shape or configuration we want, a modern "atlatl" if you will. It could be as short as practicable, and the extra energy delivered to the plane would make it launch even easier. Best part is no human parts near rotating blades.
Last edited by UncleMatt; Nov 16, 2012 at 10:50 AM.


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