Video & Flight report - Shoestring Stunter (Maiden V.2.0)

Vibing Good Mojo your way Mr. Rusty !!!!!! I think I may have the Gods of Crash cornered up here in Missouri, so have at it !!!!

Kim wrote:... I think I may have the Gods of Crash cornered up here in Missouri, so have at it !!!!

Haha, I'd hate to wish than on you, but I'll take it this time.

Good luck, sounds like you will have great weather. Looking forward to your recap tonight.

Finally! I made a stooge from three 12" stainless steel skewers. Now I need do clean them and sneak them back into the kitchen drawer. But it worked fine and I didn't even get the cord tangled around my ankles.

Clear oil

I followed Brodak's diagram and opened the uniflow vent and plugged the overflow. I put a full 3 ounces in the tank, cranked it and set it to a stumbling wet 2-stroke, as recommended by CEF members. I made a remarkably pretty takeoff that would have earned max points on the score sheet. After she was airborne the engine unloaded into a steady 2-stroke and reminded me how hard it pulls. Being used to finger-tipping the babies, I immediately had to wrap my fist around it. Steady as she goes and at the end of the first lap I pulled off a loop, which caused the engine to shut down. I then made a beautiful landing worth max points on the imaginary score sheet, but of course it was off camera. So I backed up the camera about 20' for the next run.

So I reset everything and cranked it, but still clueless about the engine shutoff. That didn't last long, as soon as I cranked it I saw a steady stream of large bubbles parading through the line. Well there ya go. I switched the feed line and the uniflow vent to see if maybe that was the problem, but same thing. So I said screw it, let's go normally vented, plugged the uniflow vent and opened the overflow. Voila, no bubbles. Again I needled it for a very rich 2-stroke and launched.

Now we're cooking. I flew a couple of laps and flipped it and flew some inverted, and it responds to control input just the same as normal flight. Check that off the list. I pulled my first loop and it sputtered but kept running. I did some more, forgetting I should have counted the loops with steel cables. I never did get around to an outside loop, but I did do one of my "infinity symbol" figure 8s. All was well, just that sputtering in the loops. But I did 5 or 6(I'll count them when I make the movie) wingovers, and not bad ones if I do say so myself. I've watched two other guys at the club and they ease out of them, but I love screaming straight towards the ground and pulling out in a snap. I didn't disappoint, and I realized I had an audience I heard an exclamatory shriek right after I pulled out of one of them. I scattered the wingovers throughout the flight until I started wondering when it was going to run dry.

As I flew laps draining the fuel I took a look at the plane and it seemed to have some excessive yaw to the outside. I hope I can pick it up in the video. I could not tell if the wings were level but I'll check for that in the video too. Anyhoo, the fastest lap times(not counting the end-run leanout) were exactly 4 seconds. And the engine run on 3 ounces from crank to dry was exactly 5 minutes. I was glad when it finally quit, and I coasted in for a bouncy bumpy landing worth crap for points on the score sheet, and of course that one was on the video.

So, what did I learn from this version of maiden flight?

• Four second laps are probably too fast. All of the pros I watch on the Tube fly about 4-1/2 seconds. For this I'll try my 10x4 prop next time.
  
  
• It still sputters in the loops. Maybe there's not enough prop load on the engine? For this too, I'll try my 10x4 prop next time. I'm currently running a 9x5. It would be nice to kill two birds with one stone.
  
  
• If none of the above works, I'll try a 9x4 prop, which is the minimum recommended for the Thunder Tiger. That should slow it, and possibly help the engine performance by lightening the load rather than increasing it. I have lots of props, APC, MA, and Top Flite wood.
  
  
• It yaws out too much(possibly, but it's hard to tell without a spotter). So maybe I'll remove some engine offset. It doesn't have a lot now, but I don't really want to cut the rudder off and reposition it yet. I'll save that until I get the engine/fuel straightened out.
  
  
• As hard as it pulls, it makes me think I should replace the leadouts with beefier wire than the current 45# test wires.
  
  
• It used every last drop of fuel in the tank before it finally cut out and landed.
  
  
• I need to find out what the air problem is with the uniflow vent. When I tested the tank when new, I could put a measured amount of fuel in it and retrieve exactly the same amounts from either vent. This makes me wonder if the uniflow tube ends too close to the pickup. That could explain the air too, flowing out of the uni tube and being sucked right into the pickup. I'll have to open it up for this.

I was tired when I got there, and really felt off of my game today. And my shoulder hurt after the first flight. So that's all the flying I did. Better to play it safe. I was very happy to get this flight out of the way. I'll have more flying time now that Spring seems to really be here. I didn't even fly the babies today, though they were in the car.

I'm off to crunch the movie now. I'll probably cut out so many of the flat laps, but i'll leave the good stuff.
Stand by for the movie.

Coolo ! Congrats on a Great Day !

Good stuff!!!

Thanks for the writeup. Sorry to hear about the tank. I was lucky in that Ken sent me one that he had gone through and it performs flawlessly. I am sure you will get it sorted. My Ring is tip high level and inverted so I'll be adding some weight. It really helps to have a spotter when doing a shakedown. Glad to hear all went well and really looking forward to the video!

Ron

yahoo! you're gettin there!

thoughts from the peanut gallery...the motor leans out nice after it unloads on take off, but doesn't seem too lean? Yet it sputters on loops? I gotta think thats a fuel draw issue? You might try muffler pressure next time?

With engine cruising along, not rich, but not lean and you're dong 4 sec. laps, i gotta think you need to go 10x4 prop...lol, welcome to the trials and tribulations of control line aerobatics!

The first video upload failed due to a YouTube error. I am resending it.
It should be at the following address in about an hour from the time of this post.
https://www.youtube.com/watch?v=QvSdPcZtn1s&feature=youtu.be

Mark Boesen wrote:yahoo! you're gettin there!

thoughts from the peanut gallery...the motor leans out nice after it unloads on take off, but doesn't seem too lean? Yet it sputters on loops? I gotta think thats a fuel draw issue? You might try muffler pressure next time?

With engine cruising along, not rich, but not lean and you're dong 4 sec. laps, i gotta think you need to go 10x4 prop...lol, welcome to the trials and tribulations of control line aerobatics!

I agree, the 10x4 will be on it next time it flies. Thinking about my flying, it occurs to me, that the loops I am doing are not big round tame precision aerobatic style loops. Rather they are full up 1/2A style high gee panic loops. Next time I will try flying through some Biiiig ol round loops. It might work better.

But I gotta say, the plane will go wherever I point it, I'm impressed. My CG is already 3/4" forward of the plan's CG. I put the muffler on it and checked and the balance point moves all the way up to the lead edge. That's why I'm not using the muffler. No reason I can't try though. Next time out I'll take the time to experiment with it. I just wasn't up to it today. The Thunder Tiger is a really nice, easy to use engine. I like it a lot.

I'm glad it found a good home, if not it would still be sitting off to the side of workbench.

Is it possible to move the engine back 1/2"-3/4"?

Mark Boesen wrote:...Is it possible to move the engine back 1/2"-3/4"?

Nah, it's jammed all the way back already. I could try some foam wheels but I doubt if it would help much. My spinner it light plastic too.

Do lightweight tongue mufflers have pressure taps?
I could add tail weight, but I'm already just over 31 ounces.

Foam wheels would help some and 1/4 oz. of lead in the tail would not be a hardship, but again it turns fine and CG is really not an issue at this point, i just looked at the photo and it seemed like the engine was way forward. Yep, a tongue muffler could be tapped for pressure and might be the ticket.

Full screen is enabled:

Mark Boesen wrote:Foam wheels would help some and 1/4 oz. of lead in the tail would not be a hardship, but again it turns fine and CG is really not an issue at this point, i just looked at the photo and it seemed like the engine was way forward....

That's as far as the notch is cut. Maybe the original builder didn't make it as deep as the plans.

Hi Rusty,

Nice video, i'm impressed.

So, what did you do to engine between first and second flight other then open needle?

I still think its a just little lean, as its sagging pretty good on loops later into flight, also those really tight loops will lean a engine.

Your lap times don't seem that much off, you want to time them 6-8' off deck. A cheep Walmart stop watch is handy, 4.5-4.75

I'm almost thinking open needle just a tad and your there, or switch props to 10x4 with needle as is, fly, then open if needed.

Remember, a engine will really speed up as it runs out of fuel.

As far as CG goes, it seems to turn pretty nice, i don't think i'd even worry about it at this point.

When I cranked it for the second run I saw a parade of large bubbles, one right after the other, parading through the fuel tube. So first, I swapped the pickup and uniflow vent with the same results. Then I plugged the uniflow vent and opened the overflow. When I did that, there was no more air in the tube, so I ran it that way, normally vented. I expect that's why it leaned out more as it used up the fuel. It was pretty rich when I launched.

I'm thinking I need to take a look inside the tank. The uniflow vent might be opening too close to the pickup so it's just sucking up the uniflow air.

I was flying the timed laps a little high. The camera was only a foot off the ground, looking up at the circle, so it may have made some of the laps look higher than they were. That damned sloped field makes me play it safe. I'm flying on the side of a hill with about a 4 foot rise.

You'll see bubbles, thats what its suppose to do, its kinda like a mini water cooler, fuel out, bubbles in! looks weird, but works great!

(also, see my post on stuka stunt : ^)...

http://flyinglines.org/cognitive.uniflow.html

http://www.fraserker.com/heli/uniflow/how_uniflow_works.htm

I read all of that while I drank my coffee. I also replied to the Stuka post. Thanks for the information. I guess I'll try it again with the uniflow setup. If the two vents are side by side, I can certainly see why incoming air from the uniflow vent gets sucked into the pickup, resulting in what I saw and described as a parade of big bubbles. I just never guessed those bubbles in the fuel line would be a good thing. Live and learn.

Kind of a bit off topic of the current discussion, but these are the wheels I use and they are very light and look good IMO.

http://www.hangar-9.com/Products/Default.aspx?ProdID=HAN302

Funny you should mention wheels. Just minutes ago I swapped out the wheels on the SS for a new pair of super light Dubro 2 inchers. I don't know what they weigh but you can hardly tell anything is in your hand. Ain't modern materials tech great! I weighed the plane with every thing on it as it flies with my new electronic scale I got for my BD. The official AUW is exactly 31.1 ounces. Not bad for an epoxy bomb. The plans say 28-30oz. I was hoping to hit that, but... I've got horsepower!

Also, I set the tank back to uniflow and tested for air bubbles in the line. Posted in Marks thread at Stuka moments ago. There are some intermittent bubbles, but I ran an ounce through it and the engine doesn't seem to even notice. So Now it has a 10x4 prop to tame it, and I look very forward to flying it the right way next time, and I bet it works just fine.

From stills of the video, it looks like the wings are level, but I wonder if it isn't yawing out too much. I'll get a spotter next time to help with that. Maybe I'm just being a wuss, but I worry that the yawing is making it pull harder than it should. Definitely going to add beefier leadouts. Oh boy, minor thoractic surgery. Oh well.

So, Ron, how hard would you estimate your ringmaster pulls? 5 pounds or more maybe? Just as a reference that's close to what a half gallon of water weighs.

If it's yawing you can tell by looking at the wheels. If you see only the inboard in flight it's flying straight if you see the outboard then it's yawing.

I bet it pulls more than 5lbs. I suppose you could do the math weight of plane,speed,length of lines etc.

Aren't you an engineer?

Totally kidding.

cribbs74 wrote:If it's yawing you can tell by looking at the wheels. If you see only the inboard in flight it's flying straight if you see the outboard then it's yawing.

Good idea, I didn't think of it even though it's a no-brainer. Not used to having much in the way of wheels on a plane.

cribbs74 wrote:I bet it pulls more than 5lbs. I suppose you could do the math weight of plane,speed,length of lines etc.

Aren't you an engineer?

Totally kidding.

Touche'
A lazy one I guess. If it was electronics I would maybe have thought harder before asking. My son is fresh out of college, I'll get him to think about the math. You'd have to toss in the offset thrust vector and rudder deflection too.