Build Log: Converting a 31" Super Cub to .049 Power (revisited)

Glad you got the video going on, sorry to see you crash though.

Cribbs may have a point there, and it sounded throttled up,and looked pretty fast, the foamy just couldn`t handle the thrust/speed very well.

Did you have enough control surface and throw to counter the spiral?

Hey guys, that flight was before I started this thread. The problem was that, the wings were much too fragile for the speed it was flying. it shot straight up, and into a sharp turn until the right wing half folded over into a spiraling crash. The engine is a little big. If I built it light enough, it would have flown with an .020. The damage was almost nonexistent, just loosened up the cowl screws.

I have since started this thread, and done the following -

Added an RC throttle/muffler

Upgraded internals to 72mhz, 9g servos, (including throttle) voltage regulator to bring the 7.4v Lipo to 4.8v for the receiver. I will probably switch over to 2.4 so I don't have to use a radio that takes 8 batteries. Added struts to the wings.

It flies OK now, about 3 minutes and glide far enough to land softly. It runs rough in the air, to rich or too lean. I have a flight video but do not know ho to get it from DV to youtube.

Cool with the new/er mods and the minimal dammages thus far.

I don`t know about the video , sadly I havn`t gotten that far myself.
But throttled049, it should be ok now right?

Jaspur_x wrote:
But throttled049, it should be ok now right?

Yeah, it is still a little tedious flying it.. Just takes some getting used too.

I see now, I thought that was after the rebuild. What exactly is your engine doing in the air? Does it run well on the ground? Is it tanked or external? Post some more info if you can, I bet collectively we could figure out the rough running. I replied to your PM btw......

That is a black widow right?

It is a pre-96 Black Widow, with an 8cc internal tank - no room inside the plane. It runs excellent on the ground once it warms up, but in the air throttle response is slow and the engine sounds like it is running too rich. I richened it up and it ran even worse, so I am thinking it is richening itself up in flight. Which is odd, because I though they leaned out.

There is a one problem with all of this, not sure if I mentioned it.

I cannot take the engine off. I ran allan bolts through the back of the firewall and into the ears of the engine's backplate. I coated them in epoxy and it has worked. I do not even know where the pickup tube is, or if it is rotten.

I know, REALLY slack thing to do, I was overexcited and just wanted it finished.

PM replied Ron.

If you want to get epoxied screws out, put your driver in the screw head and heat it with a soldering iron and it will soften the epoxy enough that it lets go of the screws. I broke a screw of in my Li'l Satan firewall and had to extract it with a soldering iron and needlenose. That epoxy is some strong stuff.

So, it is a Black Widow with a 8CC control line backplate tank I take it??.

If so,,

Your probably sloshing fuel away from the fuel pickup during flight.

You could try running pressure and a non tanked backplate an it may improve.

Which throttle are you running? A throttle ring I would assume but I can`t recall the last close-up pic I saw. often times (I`m told) when throttling a cox that was designed to run without throttle, they go rich or lean depending on the type of throttle you use. I would have to look over my old notes to be quoting someone very much in the know, but spitting and sputteeing is common when throttling too.
The very best throttle I ever saw run, countered the mixture variances due to throttling via air/fuel intake adjustment while simultaneously restricting exhaust;this caused no rich or lean tendencies like are caused by throttling exhaust or intake alone does.

I`m not discounting any other answer to your problem, just adding that it may simply be your throttle method that is causing your rich mixture condition.
I am off to find the information and source of this info to back up my statement.

All the info is in this thread, just takes some reading.

Yes, it is the standard 8cc tank the BW shipped with. Dragonfly muffler/throttle combo.

I ran these screws, head on the rear of the firewall, and into the backplate ears on the other side. The only way to remove the motor would be to pull it off, or pull the firewall off and unscrew the bolts.

Maybe this will help ~

I used the combo off the dragonfly -

Incredible amount of vibration with that dragonfly tank setup. I had a perfect balanced prop and it still caused me alarm as it was just a black plastic blur at full sing.

So long as you didnt distort the tank to badly and cause a air leak in any way as you drove your mounting screws thru, it should work fine.

The dragonfly muffler/throttle ring makes the engine go rich when you close it off.

I do not have the tank from the dragonfly. Aluminum 8cc stunt tank. Check back to page two I think, there are some pictures. Maybe page 1 too.

Will leaning it out help? After the flight, I dropped some fuel on the head - it immediately boiled off/vaporized.

microflitedude wrote:I do not have the tank from the dragonfly. Aluminum 8cc stunt tank. Check back to page two I think, there are some pictures. Maybe page 1 too.

Will leaning it out help? After the flight, I dropped some fuel on the head - it immediately boiled off/vaporized.

Ok, gotcha. well, with that tank you are fighting a losing battle. It's a Control line tank,,as such, it is meant to have the pickup tube positioned to the outside,, for fuel pickup by centrifugal force (fuel slung to the outside of the tank as the model swings in its circle). Stuff you probably already know. A clunk style tank is preferred for flying R/C. With your control line style tank, fuel sloshes away from that pickup when you flip upside down, turn to the left, turn to the right, ect. and you get what you are getting now,,erratic running.. I know bucks are tight, but once you can,,purchase a clunk tank, a tank style backplate and start there first before moving on to flight tuning. It will run fine sitting motionless, but once the fuel sloshes during flight, you get a crazy motor.

Lets fix that issue first if you can do so, then move onto flight tuning, which will be the easy part.

PV Pilot wrote:

microflitedude wrote:I do not have the tank from the dragonfly. Aluminum 8cc stunt tank. Check back to page two I think, there are some pictures. Maybe page 1 too.

Will leaning it out help? After the flight, I dropped some fuel on the head - it immediately boiled off/vaporized.

Ok, gotcha. well, with that tank you are fighting a losing battle. It's a Control line tank,,as such, it is meant to have the pickup tube positioned to the outside,, for fuel pickup by centrifugal force (fuel slung to the outside of the tank as the model swings in its circle). Stuff you probably already know. A clunk style tank is preferred for flying R/C. With your control line style tank, fuel sloshes away from that pickup when you flip upside down, turn to the left, turn to the right, ect. and you get what you are getting now,,erratic running.. I know bucks are tight, but once you can,,purchase a clunk tank, a tank style backplate and start there first before moving on to flight tuning. It will run fine sitting motionless, but once the fuel sloshes during flight, you get a crazy motor.

Lets fix that issue first if you can do so, then move onto flight tuning, which will be the easy part.

Thanks for the info, that explains all of it. I wish I knew this before. I seems like with all the FF and RC mods I have seen this would be ab bigger problem. Will I damage the engine the way it runs now?

I have a Sullivan 1oz clunk tank, (NOT a fun tank to build) which I think is the smallest clunk tank out there other than the dragonfly/RC bee. There is no room in the plane, though. Possibly on the wing? This is going to be more trouble than it's worth.

Bring the engine mount forward and position it right behind the mount.
Or make a tank that is a of a suitable shape for this application.

nitroairplane wrote:Bring the engine mount forward and position it right behind the mount.
Or make a tank that is a of a suitable shape for this application.

The nose would be so long you have to add weight in the tail.

I think I will leave it as is, for now anyway. At least it flies!

Yeah I suppose at least you can just go out and fly.

I have decided the death of this plane is clearly seen and unavoidable.

Death by fuel erosion. Slowly eats away at the plane until the mount gives. Is EPP foam alcohol safe? I would make the clean up easier.

Then, maybe then I will try CL. Then I have decent engine.

Yeah that may be your best bet.