Ultra Stupid Funjet!!!

[Gabe]

Yeah Kent - we'll move the post when you start the thread. If you got any photos of the new bird, go ahead and throw them up.

[akent]

I'll do that soon! The Sniper is an awesome machine. I should not have mentioned it here though! Oh well, you know how I get excited about things!

I finally put a speedo on the U.S. Funjet. My radar gun is useless with these.

I was a little disappointed when it hit 138 on the first run and 142 on another. I don't really know what I was expecting, but when you can fly a 110mph version in all manner of ways and then you have this seemingly stupid one that you can't stay into the throttle for more than maybe 2 seconds, it just is odd that it's only what, 30mph faster than the other one?

Seems odd. Very odd.

I WILL get some video soon.
Man, if I were you all, I would question me! I just can't bring myself to think about videos when I fly these things. I did buy a single pitot tube speedo and that's what the speed reading came from. It is this one that I have in the U.S. Funjet:
www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=7838

There is an all electric fun fly at the Austin field this weekend! If anyone wants to play, come on down!
www.hcamonline.org/2010eflyin.htm

Free for all combat?!?!?!? I'm all over that!!
Kent

[19000rpm]

Nice speedo. I don't think I'd be able to think about making a vid of a plane doing 142 mph without a lot of practice.

A thought or two: If you think about what it takes to get another 30mph out of an model aircraft in that speed range; there may be some aerodynamic and structural factors that are exponential, rather than linear, all of which would effect the control you have. In addition: A piece of foam, or a control surface, or a piece of hardware, that was fine at one speed will start to be less effective at another, higher speed, because you aren't just adding 30mph, you're approaching either the materials or construction methods limit. Maybe both. New territory new challenges.

[Gabe]

Yup - right on 19k. Speed is a cubic relationship to the power output. I don't remember the specifics, but there are speed ranges in which the aerodynamics play more important roles. For Strykers, it was 100-120mph, 120-150, 150-165, 165+ Or something like that.

Kent, I've read reviews about the pitot tubes and they don't seem to be accurate at higher speeds. In order for speeds to be considered for records (or at all for that matter), they must be measured by a doppler radar gun or by a doppler analysis of a video sound file. Data logging from an ICE or Eagletree must be included.

For speed runs, you need to be as close to grass skimming as possible - but 20-30' off the deck is acceptable. You cannot come out of a dive and you must be at WOT 3 seconds before and 3 seconds after the camera. That's the darksiders' requirements.

All that aside, I know that the pitot tube isn't THAT far off and you have definitely achieve a serious darkside status. What a rush!!!! I love these speed demons!!

[akent]

You are right about the rush, Gabe! Last Sunday, after my first flight, I was a little disappointed in the speed, one guy said, "Well, why are you shaking, then?"! True! It gets the adrenaline really going!

Even though it's only 30 mph faster than the other Funjet, the thing looks and sounds WAY WAY WAY Faster! It is far LOUDER!

I'll try to get a video this weekend. Maybe I can set the camera out on the runway when I fly the U.S.F. to get a doppler. It would be interesting to see how far off the speedo is. I have read some reports that say the speedos are very accurate. I don't know though.

I understand what you all are saying about speed increases needing huge amounts of power increases, and that it is certainly non-linear. I certainly didn't realize it was a cubic relationship at some point. I thought maybe some exponential was at play though.

I suppose a good analogy is my boat. I have a Donzi 22ZX that ran 62mph stock with 330hp. It now goes 80mph with 550hp. That's only 18mph faster with 220 more HP!!! It feels REALLY REALLY fast at 80.

Take care,
Kent

[akent]

Oh, I don't remember mentioning before, but the torque of the motor in flight moves the rear end of the Funjet to where the motor is rubbing on the foam! It has rubbed about a 3/16" groove in the foam!
I can't move the fuselage like that by hand, well without thinking I'm going to break it! That's a HUGE amount of torque!
Kent

[Gabe]

Jeeze that's some torque! I would say that you may want to lay some glass around the motor mount to prevent that from happening. That could be part of the reason for your torque roll.

I was reading over on RC Groups and Mopar posted about torque roll. He said at high speeds, its typically due to foam twist. You may want to consider throwing in some additional CF tubing in the wings and some lightweight glass or just painting it with epoxy like Mopar does. That may just solve your issue.

[akent]

Alas, this U.S. Funjet consists now of many more pieces of foam that are flatter or at some angle other than what the designers intended.

Ugh.
====
I flew this earlier yesterday at the Hill Country Aeromodeler's all electric fun fly.
After they saw this thing fly last weekend, they asked me to fly it solo as a demo of how fast you can make an electric plane go. My speedo last weekend showed 142mph. I didn't check it at the fun fly.

My wife was there, too. I asked her to take some videos. Where are they? If you ask her, she will say that she took some. If you look at the camera, there are lots of videos of the ground. I think there was a polarity issue...She's done that before with my daughter's cheerleading.....
===
So, they stopped the flight line just for me earlier in the day, for me to fly the U.S. Funjet! I was shaking in my boots. There were hundreds of folks watching.

I did many circuits including some that went out of sight! My favorite pass is to go WOT for about 2 seconds (about the most time there is before you lose it), then head straight up. The momentum makes it really small. Then fly that high around to the other end of the field. Then still without power, come down and nail it once you get down to 10-20 feet up!
There were gasps when I did that!

It was amazing. The announcer was fun.

After I landed, there was a lot of applause! I didn't expect that.

Later on, when I crashed, there were lots of OHs. Yeah, I did that in front of everyone. Ugh.

I launched at about half throttle as normal, it torqued left as normal, but I could not control it at all. The thing went in at full throttle, as I tried to bring it up. Poof. It was very windy, as we had storms coming in...

Anyway, it is a remnant, but the electronics survived, the best I can tell.

I already have my spare airframe on the bench!! I will make this version stronger and faster!!
Kent

[19000rpm]

Awesome Kent. And to think back, not so long ago, you were aprehensive about getting back into planks.

It sounded like the foam was softening up when you posted about the torque groove last week. You can only compress foam so many times before it loses it's structure and fails.

Like a wise man once said, "Every plane has it's first and last flights." Some end up hanging from the ceiling or on the garage wall and some end up in the dumpster.

[Gabe]

Hard times Kent. Bummer man.

But alas we learn from our predecessors. I'd say replace the stock tube with our standard cf tubes used in the Stryker, maybe even one more. I'd definitely go with balsa elevons using the Stryker build as a guide. FinLly get some 1/2 is fiberglass from horizon and use the zpoxy to strengthen that thing. Shouldn't be any issues after that!

That's the same build I'm gonna use. Also there's a thread on rc groups called ultra fun jet - or something like that. Mopar, Gryphon and I have been posting. Check it out, it's new and an easy read.

[akent]

You're right 19k about my being a little worried getting back into planks! I'm really loving it now.
I need to make some time to do a few more threads on some of these things....
I also MUST get some videos!

I read through that thread, Gabe. It is interesting talking about the new Funjet Ultra. Shhh, I have one on order from the UK! I couldn't wait!

So far, I have used the stock fiberglass rod as it was pretty much the same stiffness as a carbon rod I had here. I then put a 5mm flat carbon strip in the top of the wing vertically. WOW did that make a HUGE difference! It's easy to do if you just cut a slot slightly deeper than the carbon strip and then fit it in there. Thin CA and it ain't going anywhere!
I don't think the wing will give if you stand on it now!

I also put a carbon flat again at the trailing edge of the elevons. I plan on fiberglassing the inside of the fuselage rear and the elevons. I may add a carbon rod to the fuselage bottom as well. I don't know about that yet.

I can't work on it now until next week. My daughter is going in for shoulder surgery on Friday. Bummer.

Kent

[19000rpm]

Good luck with the daughter's surgery. Is she the one that was in the championships last year?

It's probably difficult too put too much CF in a plane like that. Sounds like you got it all in the right places.

[akent]

Yes, Kendra won two individual national championships last year. She was second at the Worlds in power jumps and she actually won tumble pass!!

Her summer job at a gym saw her able to save a girl while she pummelled to the earth head first. Kendra caught that girl, saving her life maybe, and hence she tore up her own shoulder.
It is very sad.

Kendra's shoulder Labrum was torn 300 degrees around. She is still in a lot of pain. The poor thing. It hurts me.

Kent

[19000rpm]

Wow! What a great girl. A champion in every way.

I tore my shoulder up weight lifting when I was in the service and can relate to the pain. They didn't do much in the way of shoulder surgeries then. At least they didn't to military guys. It took over a year before I could lift my hand over my head and another 10 years of my own therapy to get it back to normal.

[akent]

I'm glad you got your shoulder working! They say Kendra will not be able to work her shoulder for 6 months.

Well, I have been working on U.S. Funjet #2. I tried to use Rustoleum paint on it. Well, it does't stick very well. It is flaking off. I don't know what I'll do yet. It's Fugly right now!
Oh well. I think I'll throw some colored packing tape on it. That stuff sure is light and I think it should add some strength.

I hope to fire it up tonight for prop testing...
Kent