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color, no smell and can be cleaned up after a plumbing mishap easily.
Now take a look at the cylinder side of the hydraulic lines. The cylinders in the wing fold have
3mm Festo Push-in fittings as well. The UP-side exits the cylinder at the back face.
First drill a hole into the root rib behind the top rear claw of the wing fold's center wing mount.
That is the best position to feed the hydraulic lines through. Make sure it is big enough so that
both lines can slide through without resistance. When the wings move, these lines will have to
slide a few cm in and out. Connect the DOWN line straight into the cylinder and strap the UP line
to the cylinder with cable ties, so that they will not bind or interfere with the carbon sockets in the
outer wing panels. Then loop the UP line inside the aluminum frame to enter the cylinder straight
from the rear. Please slide the wings on and off several times and make sure that no tube rubs or is
squeezed or pinched inside the socket. Make sure that this is not the case in both UP and DOWN
position of the wing, as the cylinder moves up and down inside the socket during the folding cycle
quite a bit.
We recommend NOT to fill any hydraulic oil until the plane is painted. An oil spill can really
cause a lot of trouble for the paint job later. After the plane is painted and completed, a spill
mishap will not affect the strength and integrity of the wing structure. Baby Oil does lift off slowly
but surely, and it has no or only very little mechanical impact on the sandwich structure, the glue
and the plywood. It will be an unpleasant experience, but not a disaster for the plane.
Still, we will describe the filling and priming procedure at this point. Come back to this chapter
later, after the plane is painted:
Disconnect the return line from the plastic bladder. Extend this return line with a 50 cm piece of
Tygon tubing into a plastic cup placed beside or behind the center wing. Connect a piece of Tygon
tube to the return connector of the plastic bladder and fill it with baby oil. You should keep the
original container you purchased the baby oil in connected to the bladder. Or use a large syringe to
refill the plastic bladder as the pump operates the cylinders the first time. Make sure that you do
not get too much air into the plastic bladder.
We do the priming with the outer wing panels removed! Connect an air compressor and put 3-4
bar of pressure into the accumulator's back side. This keeps the operating pressure low for the
first tests. Then connect the pump battery and immediately the pump should start running.
Squeeze the bladder to get liquid to the pump right away, so that it doesn't run dry. Depending on
the valve and cylinder positions, the wing fold will travel to one end position and the pump will
stop when the pressure in the system has reached the same pressure as inside the accumulator.
Now turn the servo to move the valve to the other end position, and the wing folds should move
slowly to the opposite position. You will find that oil exits the return line, which hopefully still is
feeding into the plastic cup placed on the table outside the center wing...
The pump will switch on and off during the operating cycle, trying to keep the operating pressure
in the system constant. If movement is too slow, increase the pressure in the accumulator by one
or two bar. You should not need more than 4 bar, though, when the outer wing panels are not
mounted, to move the cylinders between their end positions. Cycle the wing fold several times.
Make sure that you refill the plastic bladder after every cycle. That's why we recommend to keep a
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Instruction Manual F4U-1D Corsair
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