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Old Aug 10, 2015, 04:09 PM
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parajared's 1500 watt FPV Skyfun (140.4 mph)

I got my Skyfun in the air today. At first I tried
Mad Thrust 2200kv
5s 3700mah lipo
5.25 x 6.25 APC prop
100amp Turnigy Plush
HK pilot mega micro

putting me at 1300 grams all-up weight (no FPV gear)

This ended up not being a good propeller for the Skyfun due to the weight. That small of a prop could not generate enough force to be launched and sunk out well below ground level on the cliff I maidened it off before finally taking flight.

The 5.25 x 6.25 prop setup hit a top speed of 132.6 mph
6x4 apc had enough thrust to launch on level ground and topped out at 134.0 mph (according to RcSpeedo). I am a little bummed about this because my hotliner also uses Mad Thrust 2200 and 5s lipo and I dopplared it yesterday at 168 mph.

On the bench my 6x4 prop was pulling 72 amps, a 6.5x6 APC I tried threatened to pull over 100 amps (according to Turnigy power meter) and my 5s 3700mah lipo gave me just under seven minutes of flight time when I was doing speed runs.

Despite having a 175 gram motor and a 80 gram esc strapped to the tail, the plane still wanted to be nose heavy. I accomplished CG, but only with the battery in the middle of the plane which was weird for having so much weight on the tail. It would seem this is a poor choice for an airframe if you want to put a small motor/esc on it.

I used velco to hold the hatch on, and laminate to hold the fairly brittle foam together.

I will post some actual FPV videos on this thread once I have my FPV gear all set up.

testing the Skyfun (134 mph) (0 min 36 sec)
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Last edited by parajared; Aug 18, 2015 at 01:38 PM.
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Old Aug 10, 2015, 07:00 PM
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Old Aug 13, 2015, 07:12 PM
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Nice!!!
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Old Aug 13, 2015, 07:43 PM
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None of what you discovered, surprises me in the slightest.

For context for other people, see the thread that started this
http://www.rcgroups.com/forums/showthread.php?t=2475076

As expected the hotliner is much faster with the same or less power. (Will take 57%
more power to get the Skyfun up to 168mph because it's so much more draggy)
As expected, the Skyfun came out nose heavy.
I am surprised it went that fast with stock foam control surfaces.

I'll bet it was quite loud.
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Old Aug 14, 2015, 09:08 AM
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Quote:
I am surprised it went that fast... I'll bet it was quite loud
Quite loud yes, but it's all by design, the extra loud noise creates a scary environment for the airplane and frightens it into achieving higher performance. This is all highly scientific information and you can trust me, I work in the medical field.

The plane is small, white, loud and difficult to see. I imagine if I flew by a hiker or someone it may go unseen for an interesting case of WT F was that!?
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Old Aug 14, 2015, 09:21 AM
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Quote:
Originally Posted by parajared View Post
quite loud yes, but it's all by design, the extra loud noise creates a scary environment for the airplane and frightens it into achieving higher performance. This is all highly scientific information and you can trust me, i work in the medical field.

The plane is small, white, loud and difficult to see. I imagine if i flew by a hiker or someone it may go unseen for an interesting case of wt f was that!?
lol....
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Old Aug 14, 2015, 09:56 AM
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I've flown a Stryker with an eflite six series 2700kv motor on 4s and that thing was insanely, sarcastically loud! I loved it! I lived up in a big valley and even when I was around a mile away, I could blip the throttle and actually hear the demonic prop scream echo off the walls of the valley!

Such a cool sound.

The shriek of plastic shredding the air with unbridled fury, raw rotational force torturing the air.
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Old Aug 14, 2015, 11:27 AM
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That's the most fun part is the fantastic noise it makes!
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Old Aug 14, 2015, 11:43 AM
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Only if you're the pilot. A lot of other folks don't care for loud RC planes out in the wild.
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Old Aug 15, 2015, 01:43 PM
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I took the Skyfun out today and broke my personal best three times: 136.2mph, 138.8 and 140.4mph.

I really like how my jet is flying and I feel like I am really getting a locked in feel for it. My goal is to break 150mph,
1) because it's a nice round number
2) to harass Daemon
" I doubt one of those has ever gone 150mph" -Daemon
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Old Aug 15, 2015, 01:56 PM
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We will need to see it verified with a certified radar gun....

How do you plan to get it that little bit extra to 150??
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Old Aug 15, 2015, 02:12 PM
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Quote:
We will need to see it verified with a certified radar gun....
Yeah, I'm not sure how accurate the rcspeedo phone app is but I am buying a receiver with a video recorder so I can show the GPS OSD speed too. I will have double proof then (sorta).

Of course I'm not quite in a lie about your top speed situation just yet. Going 140 on a skyfun is like telling your buddies that you went 100mph in the family car: yeah it's faster than normal, but anyone can do it.

Quote:
How do you plan to get it that little bit extra to 150??
1) cleaner runs: the thing just disappears into the distance so quickly it's hard to get lined up for a good hard fly-by. Maybe focus on getting a bit of a dive before passing overhead. Once I get the FPV gear going I think it will be easier to line up for a good solid pass while flying FPV than line-of-site.
2) play with the prop: I could shave down my 6x4 to a 5.75 or 5.5x4 or maybe I could put a 6x5 prop on it and see what it does
3) weight reduction: I chose 3700 mah 5s so I could get some endurance. I have an 1800mah 5s just sitting there that could be used on my jet. This would lighten the load considerably and perhaps get the 150 I'm after.
4) go up a cell: My motor is rated for 80 amps and is meant to be used with 6s. I have some 3s 1800s I could serialize into a 6s 1800. Perhaps the extra rpm and power will give me that extra 10mph I need.
5) tape down the hatch: there is a fairly large gap where air can enter the hatch and potentially slow the ship down.
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Old Aug 15, 2015, 07:15 PM
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Just one caveat to my " I doubt one of those has ever gone 150mph" statement that I
should have mentioned earlier. I am talking about FPV piloted. It's not a very slippery airframe,
and it's going to be less so with the rest of the FPV gear installed. I don't really care
what it's pushed to LoS piloted other than as it pertains to the strength of the airframe itself
(which is why I was specifically surprised that the foam elevons would take the speed you've gone so far.
Mine eventually gave up).

BTW, I've got an FPV plane that's done 138mph (GPS ground speed), with the motor off, coming out of a dive.
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Last edited by Daemon; Aug 15, 2015 at 07:30 PM.
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Old Aug 29, 2015, 02:16 PM
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Hey Daemon,
a few posts back you mentioned control surfaces being bad on your skyfun. Now that I have the FPV working I am experiencing an issue where after I pass a certain speed (maybe around 130 mph or so) the plane just locks in position and inputs on the controls don't seem to have much effect. The plane only gets steerable again when I back off the throttle.

Do you think it's the control surfaces or something else? I am using Hextronik Mg-14s on this build which allegedly give 2.2kg/cm of torque.
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Old Aug 30, 2015, 01:33 AM
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The foam surfaces flex with less than 2.2Kg worth of force. Could certainly be that much
aerodynamic load.
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