Vintage Cox Tee Dee .049 speed plane - nice ebay

I share your curisoity Mauricio.  I would like to know more about these monoline systems but I am still unclear how the attachment is made to this connecton.  It must be secure and allow for a twisting motion but it's more of a ball than a square.



Also this mechanism.  It's built in so I can't investigatge it without damaging the airplane.  It looks like a cam that acts on the bellcrank.  I can't get my fingers or anything in there to twist or pull the ball end.



Seems that no one has a theory about the two fuel line connections to the engine. Mine is, a long or short flight duration, but you would have to block the other open end.

OK, here is a video of a guy flying monoline. https://www.youtube.com/watch?v=WBA9cTS9GmA You will notice that he is holding on to the handle pretty tightly. The other hand is just using two fingers to slide the spool in and out to spin the twisted wire on the handle. As far as the attachment of the line, the end of the solid wire line is just looped around and soldered like a normal control line that is wrapped in thin copper wire. It is fed through the wing and spread out carefully over the little button that shows through the unit. The unit has the wire around the button in a similar way, but will not come off. The made up end on the flying wire must have a loop that is not so short that it will come off, but not so long that it falls off. I had one come off once, and it was exciting but not good. As far as the tank, I think it is uniflow so one tube goes to the back of the tank at the bottom, and the other tube should be slightly in front of it. The idea is kind of that the air entering will make a bubble that will float to the inboard side and not interfere with the feed tube. The tube that is not attached to the motor should be facing forward in clean air to give a slight pressure to the tank as it is moving forward at 85 mph. If the pressure tube does not go near the feed tube, and only goes to the top, then it just goes to the pressure backplate.
No one uses the pressure nipple on the plastic carb housing that I know of. They just fall off. There are two tubes on the side that are only for filling. There is a piece of maybe 1" fuel tubing that is used to fill the tank. It is filled through one tube and when full it escapes through the other. After it is full, you just insert the tubing over the other tube to seal the tank, so it is a U shaped silicone or rubber tube.