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Old Aug 05, 2012, 11:58 PM
AP-stick
ggtronic's Avatar
Montreal
Joined Nov 2005
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Quote:
Originally Posted by boredom.is.me View Post
Hey guys, a little help here...
nice motor ...efficient setup but not 1:1 power ratio if AUW reach 3.5 kg...

5.8g for long range video is not the best choice should need the best
antenna !

2x 4s6000 will endup much more than 3kg thus hard to launch

no need for such HIGH C rating ! 4s5000 will provide 100amp at 20c
2x 4s6000 will provide 360 amp at 20c LOL

telemetry+video link onboard will get a noisy environement and
may lead to GPS fade
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Old Aug 06, 2012, 01:15 AM
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Joined Jun 2012
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Quote:
Originally Posted by ggtronic View Post
nice motor ...efficient setup but not 1:1 power ratio if AUW reach 3.5 kg...

5.8g for long range video is not the best choice should need the best
antenna !

2x 4s6000 will endup much more than 3kg thus hard to launch

no need for such HIGH C rating ! 4s5000 will provide 100amp at 20c
2x 4s6000 will provide 360 amp at 20c LOL

telemetry+video link onboard will get a noisy environement and
may lead to GPS fade
Thanks for the reply ggtronic! I've tweaked the stats a little bit and moved down to 3s. How's this look? New eCalc

So you're saying I should either go with OSD, or Telem, but not both? If I had to choose I would definitely go with OSD. So you think I should go with 900mhz Vtx, with a booster maybe? I am wanting to get some serious range out of this bad boy, thanks for the heads up there! I'm also still confused on what battery I should use to get the needed 12v for the Vtx and camera? Also I know this is off-topic but since I stayed up to watch it I thought I mind as well say something here. MSL (Curiosity) has landed on Mars! We're on Mars again guys! I couldn't believe we had pictures within minutes after touchdown! Absolutely amazing!
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Old Aug 06, 2012, 01:24 AM
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I have been following this thread from the start and have had about 10 flights with the X8. (I have Learned a lot thanks to all the contributors) First full FPV last week all trimming flights till now. I agree with Daemon re the launch but it is the one we get wrong that has me concerned. Ian Davidson gave me the idea so went out and bought cut resistant gloves from the clothes safety shop here in OZ Protector Safety. The gloves are cut resistant and when put on backwards (because the cut protection is on the palm section) gives the back of the hand some protection. The gloves are soft enough to give plenty of feel to hold the TX, after launch pull it off with your teeth or continue to wear it as you can operate all the switches with ease. You can hold the X8 with a firm grip with sand paper or the hook side of velcro as I have installed and does not slide around. Quite a good feel and balances well. I still will be building a launch ramp as well. The is no way I would get anyone to launch the X8 for me as the risk of a prop strike is too high.
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Old Aug 06, 2012, 01:29 AM
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United States, GA, Buford
Joined Nov 2007
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That is one scary looking plane! Nice work.
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Old Aug 06, 2012, 01:30 AM
Look out! The lever!
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United States, AZ, Peoria
Joined Feb 2005
2,601 Posts
Some general comments about the X-8

Hi, All

I have to start this with the caveat that I purchased my X-8 already started so I can't say what it should really be like. I had to tear apart much of it (thankfully the original builder used the crap glue it came with and did a pretty poor job at that) to re-align parts. So - (please excuse the lack of names where appropriate...)

1) The launch issue is a major concern, and for good reason. While some of you choose to hand launch it yourself, it's a pretty dicey job to get it off and flying without taking flesh with it. Personally, my forearms look like corned beef hash and I'm missing a major part of one finger on my right hand (I'm right handed) due to props...mostly from being careless while I was convinced that I wasn't being careless. This finally stopped with the X-8 after reading the discussion and looking at the pictures of the poor guy's hand.

I'll bet that you can get 50 out of 50 launches perfect but it's that #51 that can get you. I used to be a keyboard player and this took a lot from me when I looked directly into a blood soaked mess that was the stub of my index finger after tangling with a 17/15 RFM carbon prop at the end of an F47 Aviox setup and around 1400 Watts. If I wasn't wearing my readers I would've lost my right eye to boot from flying debris.

I'm at a point now that if I can get high enough to throw the X-8 into a nice breeze and then start the prop after it's past my hand, I'll go for it. Other than that, the only options to me that remain are a launcher of some sort or landing gear.

I've launched my ZII by myself without issue, but if I can get someone else to do a side-arm throw for me (as I was doing this past weekend) I go for that.

As mentioned in previous posts, adding some coarse sandpaper in the finger/launch depressions is a must-have. I've been using this for years in anything that I have to hand launch, prop or not.

2) I like the idea of landing gear, either fixed or retractable, but have found in the past that a foam mounted gear doesn't last, at least the foam doesn't, no matter what. If I had another X-8 kit I'd probably construct an inner structure that while snug to the foam, would "float" and support all three gear independently of the foam. The landing gear system would essentially be "wearing" the airframe. Sounds complicated but I'm certain that with a bit of thought an elegant and lightweight frame could be designed and installed. For this one, I suspect that I'll bite the bullet and just cob in a set of gear to some internal lightweight ply to disperse the load. I've already tried the route of a bungee launcher and dragging that equipment around and setting it up is a pain, especially when it's in the hundreds out here.

3) Reading that someone lost their motor while flying (separated from the airframe) I'm not a bit surprised. As I mentioned, my X-8 was partially assembled and the motor mounted when I received it. If what I found is the correct way (according to the manufacturer) to mount the motor, they should hang their heads in shame. I found (after my motor started to wiggle after only a very short time) that what was holding it in were four long "hardware grade" screws, a couple of fender washers, and a nut on each screw. The washers compress the foam a bit, but is this what was intended? I have nothing to compare it to, but when I saw what was going on I couldn't believe it. I assumed that at the very least, wooden dowels extended through the foam to support the screws and washers; not so. Unbelievable!

I corrected this by hacking out the inside foam (about the only glue job I found that was probably done well) as close to the plywood firewall as possible. After then observing that the quality of the wood was about as poor as it could get (soft) I then proceeded to laminate it with two layers of heavy carbon cloth and 4 hour epoxy. The motor (yet another story) was then mounted with the proper hardware that it came with and the tail end of the airframe is now the strongest part of the X-8.

3) I'm far from being an expert but when it comes to wing flex, I don't try to shy away from it unless it becomes excessive or starts to distort or tear apart the wings/airframe. I'm sure it can't hurt to increase the size of the spars a small amount, but I have to ask myself if it's really warranted. I've built and flown a fair number of planes that have both stiff and flex wings and my experience has been that if the plane is flown within it's design envelope, and even beyond to a certain extent, the original design is probably just fine. I have to say, though, that after examining the designers method of motor mounting, those of you who have gone above and beyond to strengthen the wings probably did the plane a favor.

I added the "missing" plywood rectangles with the thought that it couldn't hurt. The little extra weight gained (using decent ply) at least gives me the impression that I've mitigated the overall stress put on the spars. I'm also considering filling the spars with a smaller diameter carbon tube - any thoughts on this? As I said, I don't know that it's really necessary for added strength and (another thought) actually may cause more damage in the case of a pile-up instead of just letting the original spar break.

4) I'm not one for totally overpowering a plane (although I've certainly done it in the past) but don't know what this wing particularly calls for to satisfy the requirements of launching and flying. It came with what appears to be a fairly nice motor from HK (42-38) that would probably keep it flying just fine after it gets going, but my experience with it was that it was marginal at best for launching, either by hand or by bungee, this on a 4S 4500 LiP0. I've since replaced it with an Eflight Power 60 I had in the box 'o' motors, and with a decent prop (I now have a 14-7 on it) or something of a larger diameter up to 16" it should get up to cruising speed right away. My X-8 weighs 7 pound 5 oz balanced, so I believe this setup (with 5-6S) should be fine. Any comments on this are very welcome. I'm an old glow guy and sometimes it's difficult to make the power transition to electric in my worn out brain. My main concern is initial thrust for the takeoff so I'm pretty sure this will do the trick.

5) Going back to the blood, guts, and gore issue, if there was only one thing I took with me from my last job it's the consideration of when you're performing almost any task, to ask yourself "What's the worst thing that can happen"? If I had used this simple tool I'd still have my finger, and I know that it's probably saved me from other forms of harm since then.

Sorry for the diatribe...it's late and I can't sleep but I'll get out of your hair for now. I've read many of the previous posts and learned a lot and appreciate the ideas that are thrown around. This is definitely one of the better threads on RCG.

-bob

PS Just gotta love the graphics on Ducati749r's X-8!
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Old Aug 06, 2012, 02:02 AM
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Canada
Joined Jul 2009
6,225 Posts
I fly my X-8 naked (no camera or GPS gear), but I think a power 60 motor with a 14" or 16" prop (on 5s or 6s no less) is going to be way overpowered, even with a 7+ lb plane. My 1000 kv motor on 3s and 11" inch prop is still trying to pull out of my finger tips when powered up just before release. With your set-up, you may not even be able to hold it with the finger holes. It would also be very dangerous to hand launch with that much power and such large diameter props. A bungee launcher would be an absolute must if you want to preserve what flesh you still have. That powertrain scares the heck out of me.
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Old Aug 06, 2012, 02:39 AM
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Lakewood, Colorado
Joined Aug 2002
28,251 Posts
Quote:
Originally Posted by Opt View Post
How is progress on making it quieter? What about spacing the motor further from the back of the plane ~2" or something like that?
I cut away a bunch more foam (and thinned) on X8 #1 and it's getting quieter,
but still not even close to the Foamaroo which is quite stealthy. Don't think my thinning
extensions on X8 #2 is going to work at all. Separation is a bigger factor
than just eliminating square trailing edges. Moving the motor back has to help,
but then you're messing with your CG, increasing yaw inertia
which may increase yaw waggle, and so forth. My motor mount has
rubber anti-vibe bushings, and I think I'd have do redesign them
to extend the motor back much further. There are some commercial
rubber mounts which already act as longer spacers so maybe I'll investigate
that option.

ian
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Last edited by Daemon; Aug 06, 2012 at 02:57 AM.
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Old Aug 06, 2012, 02:52 AM
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Lakewood, Colorado
Joined Aug 2002
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Quote:
Originally Posted by wep View Post
I don't want to continue nagging about the danger of throwing and make it an endless discussion
Then don't. NOTHING in life is 100% safe, including doing nothing.
Everything is a calculated risk, and we humans often ignore the biggest
risks (driving, crossing the street, eating bad food and sitting on our
asses) and make a huge deal out of risks with smaller odds, but potentially
spectacular consequences. My advice was for those who choose, for
their own reasons to continue to hand launch. If you want to to quibble
over "safe" versus "safer" then assume I meant the latter, and leave it at
that. I am not going to tell everyone (newbies or otherwise) that nobody
should ever hand launch an X8 or any other pusher wing just to be
"safe". They're capable of forming their own opinions based on the
available evidence.

ian
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Old Aug 06, 2012, 03:15 AM
Addicted to Foamies
GasmanR's Avatar
Sydney, Australia
Joined Aug 2006
58 Posts
Quote:
Originally Posted by Daemon View Post
Then don't. NOTHING in life is 100% safe, including doing nothing.
Everything is a calculated risk, and we humans often ignore the biggest
risks (driving, crossing the street, eating bad food and sitting on our
asses) and make a huge deal out of risks with smaller odds, but potentially
spectacular consequences. My advice was for those who choose, for
their own reasons to continue to hand launch. If you want to to quibble
over "safe" versus "safer" then assume I meant the latter, and leave it at
that. I am not going to tell everyone (newbies or otherwise) that nobody
should ever hand launch an X8 or any other pusher wing just to be
"safe". They're capable of forming their own opinions based on the
available evidence.

ian
Here here. As Ian says make your own risk assessment of launching techniques and work within your comfort zone. This thread is a great information resource. By all means feel free to explain the rationale for your decision but respect others who may differ. In my case my comfort zone is to use a bungee cord and PVC catapult ramp as provided by my local flying club.

Chris
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Old Aug 06, 2012, 04:03 AM
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Austria, Wien, Vienna
Joined Feb 2012
304 Posts
agree with ian, nothing is 100% safe - but hand launching an x8 under windy conditions and 30-50% throttle is really easy and 99% safe as my video shows

launching an x8 @ zero wind is more difficult because you need a harder throw and about 60-80% throttle!

http://youtu.be/o07WkzMwWdc?hd=1
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Old Aug 06, 2012, 04:28 AM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
Joined Nov 2006
4,457 Posts
One word keep interesting me " retracts "
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Old Aug 06, 2012, 05:49 AM
never mind the boll⁣⁣⁣ocks
brosius85's Avatar
Australia, NSW
Joined Dec 2010
1,256 Posts
that would limit your landing spots quite considerably. and if you want to use them to take off they will need to allow for a LOT of prop clearance to the ground....
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Old Aug 06, 2012, 09:17 AM
AP-stick
ggtronic's Avatar
Montreal
Joined Nov 2005
1,623 Posts
Quote:
Originally Posted by MysticFlight View Post
Thanks for the reply ggtronic!!
thanks for the MARS hint !

also...

--i prefer all 5V gears so i chose 5v camera & Vtx... keep it simple
this setup will work with all battery 3s 4s 6s...

--5volt 500mW lawmate is a proven setup !

--use good quality seperate sbec

--long range flight are hard to achieve... every single RF component onboard can
kill your range or uhf RX ! i dont say you cannot have both telemetry+VTX... but
i think it will be a big challenge

--i also have APM2 onboard and use EZosd to send position data on audio
channel and will try to use both minimOSD + EZosd together ? we are
searching for minim OSD mAh display solution (we are a team to work with
our X8... )

--fpv long range is something you should not promote in north america...
so big achievement usually endup as private & personel... america air space
is important & serious !

for me... 2km radius playing area is enough to have fun
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Last edited by ggtronic; Aug 06, 2012 at 09:28 AM.
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Old Aug 06, 2012, 09:30 AM
Registered User
Joined Feb 2010
13 Posts
X8 Build Info
The build was completed with some info from this forum and from my own experience. Big thanks to the contributors.

Ply plates made to help locate and retain wings.
Carbon tubes inserted into fuse and wings to accommodate the carbon spars
Front insert 10mm OD 7.5mm ID Front Spar 7.5 mm OD 6.5 ID approx 610mm long
Rear insert 12mm OD 10mm ID Front Spar 10mm OD 8mm ID, 885mm long
Wings and hatch retained by 4mm plastic wing bolts. The ply plates were tapped to 4mm for the wing bolts to locate into.
The hatch had two tabs glued on the front to hold and locate the front and the rear ply plates where the magnets went were replaced with thicker ply and drilled and tapped to 4mm to take the nylon bolts.
Aileron servos were inserted into the wing and the control rod exited on the top of the wing to match to the control horns.
The winglets were glued in place and short wooden dowels were inserted to locate them on the wing.
The complete plane was covered with 3/4 oz fibre glass cloth using a Deluxe Materials water based epoxy called Ezecoat. The X8 was lightly sanded all over to give cloth and epoxy something to key to. Then two coats of epoxy were applied over the cloth. (not a hundred percent happy with the water based epoxy adhesion to the foam but has held up well so far)
The X8 was then airbrushed painted all over with automotive water based paint (Auto Air) and clear coat sealed.

Equipment Installed
Futaba 36MHz RX
Immersion RC 5.8GHz Video TX and a Clover leaf antenna
FY31AP Flight Stabilisation and Hornet OSD
My Fly Dream Antenna Tracker
Security2000 Camera PZ0476P Camera mounted on a pan and tilt servos
Turnigy Plush 60Amp Speed Control
5Amp UBEC
Turnigy 3 cell 1500mAh Flight Battery
Motor Battery Turnigy 3 cell 5000mAh battery or a 4 cell 5000mAh battery
Motor Turnigy 3648/6 790kv
Prop folding Aeronaut 12 x 10 c/w prop stop

All up weight ready to fly 2.8kg

I did weigh the wings and fuse before glassing
Wing left 255gm bare foam, glassed complete with spar tubes 342gm (no winglets fitted)
Wing right 271gm bare foam, glassed complete with spar tubes 325gm (no winglets fitted)
Fuse bare foam 427gm, fuse glassed with C/F inserts complete with hatch 632gm
Plain painted ready to fit out 1610gm

I think I got it all. Modifications since test flights.
I cut the hump of the bottom and installed two small fins on he underside below the motor, to get a better sit and reduced angle of attack on touch down. I put a layer of 2oz cloth on the exposed part on the bottom. I found if a wing tip dragged it would slow down and the increased airspeed on the other wing caused a ground loop. As others have said it will go on in ground effect but if you get the speed right it comes in nicely.

I am very pleased with the way it fly's very smooth and it covers the ground very quick. I wanted to get a bit more airspeed than the SkyWalker and that it does. I only intend to fly local short hops about half hour duration. I have about 10 flights with it and one full FPV last week. Test flights took a little longer sorting out the FY and trying different motor prop combinations. A couple of pics of the finished X8.

If I built it again I would install retracts and only use them for take off.
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Old Aug 06, 2012, 09:41 AM
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Canada
Joined Jul 2009
6,225 Posts
Quote:
Originally Posted by G-Forced View Post
One word keep interesting me " retracts "
I would love retracts for my X-8 but they would have to be very long legged. Look up some YouTube videos of the Eflite Scimitar taking off from anything other than smooth, clean pavement. If there is any gravel, your prop won't last long enough for it to get off the ground. The wheels, especially the mains, will throw gravel up like a wide rooster tail and shred the prop. I've stopped taking off from gravel with my Scimitar and only take off from mowed grass and even then, I mow it even shorter. Grass will also damage the prop. Too bad the X-8 couldn't have a high mounted rear motor. EDF powered would be interesting but you'd need a very powerful unit or 2 of them (like and A-10 Warthog) and they would need to be mounted above the wing line.
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