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Nov 10, 2008, 09:34 PM
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SkyFly Pushrod Modification

Skyfly Pushrod Modification

Here is another version of the Skyfly pushrod modification. I will call it “my” version, because I did it with several goals in mind:

1) Do not remove the electronics
2) Make the modification visually unnoticeable
3) Use as many of the SkyFly2 parts as possible
4) Run the pushrods through the boom
5) Do not cut into the fuselage of the SkyFly
6) Do not alter the center of gravity (CoG)
7) Do not destroy the SkyFly in the process

Anticipated Parts List:

1) 1 SkyFly
2) SkyFly2 pushrods – Part # HCAA3878
3) Du-Bro Mini E/Z Connectors – Part # 845
4) Du-Bro E-Z Connectors – Part # 121
5) Control Horns SkyFly2 – Part # HCAA3886
6) Screw-Lock Connectors SkyFly2 – Part # HCAA3887
7) Screws SkyFly2 – Part # HCAA3881
8) 1/6” shrink tubing

Tools List:

1) Needle-nose pliers
2) Long, curved-nose tweezers
3) Scotch tape
4) White craft paint
5) Dremmel tool and bits
6) Chili Cheese Fritos
7) Parts tray
8) Scissors
9) Various micro screwdrivers

First let me say that I really did not have any major problems with the original pull-pull fishing line and rubber band control system on the SkyFly. It did need continual adjustment…and the rubber bands did start to stretch out, but I did not experience any crashes or failures of the stock system. It actually had a few good points. It was extremely lightweight and it was easy to fine tune. With that said, fishing line does abrade and rubber bands do stretch and/or decay. Since the mod is fairly inexpensive and supposedly gives the pilot more responsive control surfaces, I decided to give it a shot. Let’s do it.

To start, I removed the adjustment screws from the rudder and elevator control horns. I removed the rudder and elevator so I would have more room to work without damaging them. From the bottom of the fuselage, I also removed the screw that holds the boom in place. Removing this screw provided additional room to work inside the opening of the boom.

I reached inside the fuselage and pulled the elevator fishing line crimp forward and then clipped it off of the fishing line. I worked on the elevator first (instead of both at the same time) so that I would not mix the fishing lines up by crossing them. (At this point, I should have enlarged the holes in the boom. I was under the impression that the holes were large enough for the pushrod to pass through, but they were not). I attached the fishing line to the straight end of the control rod with scotch tape and pulled the rod down thru the fuselage, into the boom, and down towards the tail. Had the holes in the boom been wide and long enough, this would have worked like a charm. Instead, the fishing line broke free from the rod. Ooops. I had to rethink my strategy, so I enlarged and lengthened the exit holes in the boom with a Dremmel tool. While doing this, I had to be very careful not to knick or cut the antenna running through the boom.

This time, with holes enlarged, I painted the end of the control rod white and fed it into the fuselage. When I saw the white tip of the rod at the exit hole, I guided it upwards with a small screwdriver (the smallest one I had). Each time, I held the white antenna out of the way with a toothpick. This was not easy, but I am persistent. I repeated my efforts with the rudder control rod. Ah, success.

At this point, I had both control rods entering thru the boom in the fuselage and exiting near the tail. Next, I tried the various EZ connectors on hand to see which ones would fit on the servo wheels properly. They must turn freely when installed to avoid unnecessary friction and strain on the servo motors. The connector shafts have a “head” on them that offers resistance until snapped thru the servo arm. The shaft on the SF2 connectors would not fit thru the hole in the servo wheel. Both the Dubro 845 and 121 fit, but I wanted to use the smaller ones (845) for the tail to keep the weight down.

As you can see, I fed the rods into the boom so that the Z-bend was inside the fuselage. I tested the amount of friction in the tubes and found that by bending the rods up, they created less friction when moved. The SF2 control rods are thin, so they were a little loose in the 121 connectors. To remedy this, I covered the Z-bend with 1/16” shrink tube. With the shrink tube added, the last leg of the Z-bend fit nicely into the 121 slot. With the connectors attached to the rods, I moved them down into position and snapped them into the servo wheels. Lastly, I used needle nose pliers to squeeze the nylon washer onto the head of the connector shaft. I used the long tweezers to retrieve the washer on each unsuccessful attempt to snap it on. I finished the fuselage end by installing the battery and testing the servos with my transmitter. With the fuselage end complete, I moved to the tail end.

I reattached the elevator and rudder. I used a brand new elevator that I modified by installing Dubro plastic hinges. You can see that mod right here. I noticed that the old elevator that had taped hinges was very stiff (not good). The new one swung freely. With the rudder and new elevator in place, test fitted the remaining EZ connectors #845 to the control horns. I snapped them in, but they did not turn freely. I enlarged the holes with the Dremmel tool. I attached the rods to the control horns by using the EZ connectors #845. They are tiny and worked like a charm. With the mod almost complete, I tested and adjusted the control surfaces to center. Next I tested the model to see if I needed to re-establish the CoG. Nope, with the tiny connectors on the tail, and the larger ones in the fuselage, the model balances right at the original CoG. Viola!

Learnings (my opinions)
- While this mod was a success, unless you have extra patience and the proper tools, I think it would be easier to route the control rods on the outside of the boom. It was difficult to feed everything thru the boom.
- Both sets of the Dubro EZ connectors worked well, but the 845’s seem to be the perfect size.
- The SF2 connectors and screws are not a good match for this mod. They would work at the tail end, but may create a balance issue since they are heavier than the 845’s.
- The plastic hinge mod makes a huge difference in control surface flexibility. It is a must have whenever you replace a rudder or elevator.

So, was this a successful mod?

1) Do not remove the electronics (passed)
2) Make the modification visually unnoticeable (passed)
3) Use as many of the SkyFly2 parts as possible (I only used the SF2 rods)
4) Run the pushrods through the boom (passed)
5) Do not cut into the fuselage of the SkyFly (passed)
6) Do not alter the center of gravity (CoG) (passed)
7) Do not destroy the SkyFly in the process (passed, so far)

I hope this helps someone who is considering one of the pushrod mods. Questions and comments are welcomed.

BTW – Here are some of the other pushrod mods. Choose the one that works best for you.

(the links were broken for a while...please let me know if this happens again)
Last edited by Bombay; Mar 03, 2009 at 10:33 PM.
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