GP F4 Phantom Retract question
 

Hello, I'm currenlty building a Great Planes F4 Phantom II and I've run into a little problem installing Robart Mechanical Retracts. If you look at the top of the wing, you'll see the retract servo plate at the bottom center of the wing. I need some suggestions on the best way to run a push rod from this location. If you look at the bottom of the wing, you'll notice that the rod must clear the wheel well along the top sheeting, then bend downwards inorder to connect to the retract.

The problem is this must all be done AFTER I sheet the top of the wing, which is next to impossible. I attempted to use Flexible Cable Pushrods instead of wire push rods, but it didnt help the problem... Any advice or pictures would be great thx

RE: GP F4 Phantom Retract question
 

I solved this same problem on a Spitfire by using 'Golden Rod' outers which were fixed in place while building, then pushing a standard 2/56 pushrod through it after sheeting when the mechanicals needed to hooked up.

I eventually gave up on mechanicals and now tend to use air retracts in most planes.

RE: GP F4 Phantom Retract question
 

Hmm, Well I already have something simillar installed now...So i'll try to run a push rod through later... But once I get a push rod through, Im running into another problem.

THe retract servo plate is located flush with the sheeting of the wing. but when I fish the rod through under the sheeting, the rod is under the servo tray which means somehow i need to bend it up at the round hole i made and over to the servo on top of the wing...what a freakin pain...

RE: GP F4 Phantom Retract question
 

The retract servo's I use are the slimline ones so they can be mounted down into the wing.
Can you relocate the mount down in the wing?
How much room have you got above the wing? Can you mount the servo upside down, with the control horn down in the wing?
You could do this by using snap on ball links at the servo end. Just a thought.

RE: GP F4 Phantom Retract question
 

Well, I cant mount the servo upside down, I need clearance for two metal pushrods for the ailerons. But it might be possible to mount the servo below the sheeting with a little modification. I'm waiting to hear back from another member to see how he completed this step before I mod anything...It sounds like he used the same solution I'm trying, with using outer nylon flex push rods...thanks for your replies

RE: GP F4 Phantom Retract question
 

When I built my F4 many moons ago, I just went with Spring Airs. No fuss, no muss.

RE: GP F4 Phantom Retract question
 

Just cut the sheeting out...it's only balsa. A sheet of balsa is only $1.00 or so. you must have some extra balsa .
It'll save you a lot of headaches of trying to work around it. Go throught the trouble of
mounting the servo unside down just for a sheet of balsa ?

Do whatever you need to do with the linkage and makesure everything works before you sheet it again,
becuase your going to have to make adjustments with the rods after you make those 2 90 deg bends.
Makesure you make the bends so it clears the servo when the servo pulls.

RE: GP F4 Phantom Retract question
 

I have plenty of extra balsa sheets, the problem is that the rods have to be installed after the sheeting. I contacted GP and i found the problem.

THey wanted the builder to have the option of using standard or retract servos. So to do this they made the servo tray longer than its supposed to be as shown in the manual. And i guess never got around to changing it. So all I have to do is cut away at the servo tray until its below the surface of the wing and then rig a flex pushrod under the sheeting and I should be good to go.