Ultra Stupid Funjet!!!

[akent]

I was flying into about a 20mph headwind too!

I was just happy to be flying that crazy thing!
Kent

[akent]

Here's a castle ESC plot of that flight.
I am becoming a fan of Castle now!

Attachments:

[Gabe]

If you look at the amp curve, you'll notice how the amps unload at WOT. It will spike and then drop off right away. All your measurements should be taken at 1 second after the peak amp spike on your WOT runs. Just eyeballing, but I looks about 2200 watts! Wow!

It would be cool if you could hold WOT for a few more seconds on your passes. According to the data you're only getting 2 seconds or so of WOT. Take her way out till you can barely see comfortably, open her up and count to 2 after she passes. Release the throttle and gently pull up and and start a slow, sweeping turn coming back. Make sure you have fluorescent colors on top and dark on bottom or you'll lose her in the distance.

[akent]

Well, no more joy.
I got in some of those ultra super duper 2200ma 6s 'Nano Tech' batteries.

The first one I flew went too fast again. Like my first fast Funjet, it would go too fast to where full right aileron would not counteract the torque. This thing was really fast. Too fast.

I tried another pass and I even gave it some right aileron before I nailed it. Same thing. After it went super fast, I had no control and it was veering left.

Ok, one more try. I stayed in the throttle maybe another second and it was almost the end of it as it went left and inverted and started to head down. I let off, but it was at least three seconds before I could gain control again.

Dayum. I can't believe that this thing went from Ok to control to completely out of control. Who knows how fast it was going. It was stupid. That's all I know.

I am officially now retiring this airframe from dark status. The hot stuff is going into a new Ultra build! I'm putting my crashed Funjet stuff into this airframe. Oh yeah, I had a Spektrum brownout today that crashed my 'normal' Funjet. That sucks!

I have a new rule in my hangar. No Spektrum 'parkflier' receivers in something that can go more than say 100 yards away.

Oh well. That crash was actually kind of cool. It went straight in and was caught in a tree! Pieces of everything went everywhere!
Kent

[akent]

Oh yeah, I need to pull the data from the ESC! I love that part! It will be interesting to see what it reads this time.
Those last readings were with a much smaller battery.

[akent]

Hey Gabe:
You can only nail this stupid Funjet for a max of about 2 seconds before it goes out of control. It was that way with my first one too, but you could let off and have it become mild again quicker.

With the new battery, it's less than 2 seconds max at WOT. It teleports forward, rolls left (counteracting full right elevons).

There is some MAJOR frame flex going on here. And there is some MAJOR motor torque going on here. I did add several pieces of CF to the frame!

I hope the Ultra airframe can cope with this! It is way more rigid.
I'll find out!!!!
Kent

[Gabe]

Ah bummer Kent!

Sounds like you've reached the limits of the foam ailerons and airframe. Even with CF tubing and strips, it can only be so strong. I can't remember which servos you had in there, but you may have reached their limits as well. If you don't already have them, try the HiTec MS65 or 85's with 2-56 push rods. You can buy heavy duty control horns from Du-Bro as well. There's a little foam cutting involved to make them fit, but it will be worth it. Hi-Tec may even make micro sized servos that drop right it, but I haven't looked yet.

Here's what I recommend. In order to protect your investment and the people within the vicinity that you're flying in, I would give the balsa elevons a whirl. Find some balsa stock that has a lot of grains in it so it doesn't flex. Now follow the build log of my darkside Stryker since its the same for the elevons.

Next, I'd install that additional .210" DIA CF tubing like we usually do, and then its time to glass that bad boy. That will eliminate almost all of your flex. I ordered some 1/2 oz (lightweight) mesh from Horizon Hobby. I think it was about $7. Use the Z-Poxy 30-min epoxy and get a 2" brush to paint it over the glass. Make sure it soaks through. You can even paint a light coat on first, lay the mesh over it, and then paint the thick coat on top.

If you want an easy glass job, use the Min-Wax polycrylic. Its not as strong as the Z-poxy, but it has the consistency of water and goes on soooooo easy.

When all is said and done, I would simply paint the top of the FJ now with epoxy to strengthen it. This minimizes the glass work to the bottom and keeps the bird looking sweet and clean. You'll need a new brush for this though. Once that Z-Poxy dries, kiss your brush good bye.

Its really only another few hours of work, but you will be much happier with how your FJ handles, especially at those crazy speeds!

[akent]

Thanks Gabe. I'm studying my Ultra as we speak!
====
Phase 1 complete!

All old 'normal' Funjet parts are now in the new stupid Funjet frame after the crash. I can't wait to fly this. It should be really like it's on rails, since I've added all that rigidity.

The Ultra frame is on the bench with all of the old stupid internals sitting by it! I am studying this. The carbon rod they include with this is REALLY RIGID! It's like no other carbon rod I've ever seen.

I don't know if I can fit the speedo in these, as I'm now running receivers with the remote. These take up a lot of room.

I'll try to figure something out. One of these days I want to do a doppler vs. pitot speedo comparison.
Kent

[Gabe]

That would be a cool experiment. I'd be interested in seeing the results for sure!

[akent]

Well, I found an app for my Droid that is a doppler speedometer in realtime. It even speaks the speed!
I had a friend hold it while I did some passes with the Ultra. It was hitting 148-150 in a straight line, running an APC 6.5x5 pylon racer prop. I still don't have the pitot speedo installed.
I am super happy with how the Ultra handles. I can do WOT loops with this thing! And at WOT, full roll rates looks like a drill bit!!! You can't even see the wings! The last time I did that, it tore the vertical stabs loose...
Oh, and the elevon hinges tore loose, too. Welders glue works great on this foam.

This thing is wicked!!
Kent

[Gabe]

Holy moly! That's insane!!

What's the name of the app? I wanna see if the iPhone has it.

[Gabe]

Found it! Can't wait to try it!

[akent]

Well, a couple of weeks ago I crashed stupid Funjet #2. Both crashed on hand launching. These things are heavy and hard to launch. Once you throw it, these torque over inverted at any throttle able to keep it flying.
Bummer deal.
I do have a Jetapult, a bungee launcher, that works great. I had been using that with the second Ultra, but I didn't have room for it a couple of weeks ago, and the results were bad.

I have Funjet Ultra #3 on order, along with yet another receiver. Two AR6200's were destroyed with these crashes, along with 2x6s nano-tech batteries.

I plan on experimenting with different power on this one. I have a HET 2w25 that I plan on running on 5s with an ICE 100 ESC.. There is a fellow in north Austin running this setup who is hitting the mid 160's.

Should be fun at least until I bury the thing again!
Kent

[Moparmyway]

akent,
You should try launching the next speedy FJ totally vertical. Give enough throttle so it feels like she wants to lift off out of your hand, throw vertical and as soon as she clears your hand, nail the throttle. She will torque roll on you, but she will be heading straight up. Do NOT try to correct anything, or give any stick inputs untill she stops rolling, then you will have total controll of it.

Also, the stock elevons should be re-enforced at minimum, best is to install ROBART hinges and stiffen up the stock elevons with some epoxy, CF, or some glass.

Check out here for more info
www.rcgroups.com/forums/showpost.php?p=16752909&postcount=405



**EDIT**
Just read that you and Gabe have the bungees working well, happy to hear that, but in a pinch, you can still launch vertically without plunking it if you dont have the bungee, or if something breaks on the bungee.

[Gabe]

Great post Mopar!

BTW guys, I owe all my knowledge of Darkside Strykers and FJ's to Mopar. He is a moderator on the original Darkside threads.

Thanks for sharing your wisdom with us buddy! Keep posting!