gregoryshock

I have the Hog Bipe by Sig. I've been wondering how hard would it be to change the push rod system from nylon to something like carbon fiber, after the plane is already built and covered?

DavidAgar

My Feedback: (108)

If you have the nylon rods installed in the fuse, you can use metal pushrods as well if there are not to many sharp bends. Good Luck, Dave

jester_s1

Are you talking about the nyrods that have the narrow nylon flexible rod that fits inside the plastic sleeve or are you talking about a standard pushrod that's made from nylon? Why are you thinking of changing them anyway?

jetmech05

To use an old aviation saying " if it a it broke don't fix it"

smithcreek

My Feedback: (25)

To answer the question, it depends on how the original pushrod exits. Carbon fibre rods that start in the forward section of the fuse generally need a fairly long exit hole due to the geometry. On the rudder then need to have clearance to move in and out and on the elevator they need clearance to move up and down without binding. If the original pushrod simply exited through a small plastic tube it might be a fair amount of work to re-do the exits which may require modifying the frame to provide a place to adhere covering.

Now, the IMO part of the answer: Unless there are problems with the pushrod system a Hog Bipe won't see a dramatic improvement even going from a well built nyrod setup to carbon fiber.

JohnBuckner

My Feedback: (1)

OK first may I say that I too am an advocate of the 'don,t fix it if it ain,t broke' theory. But I suspect that you are showing concern about your older ship. In many cases there may be good reason for that concern as far to many ships suffer from the 'Wet Noodle Pushrod Syndrome' that were build with the Ny Rod system.

Now this system can be functional but this is entirely contingent upon the proper installation and in far, far to many cases this did not happen. Fouled up wet noodle pushrods is a very common problem with many of the ships I help people with. This problem is
particular abhorrent is it may not even be obvious at first glance but will affect the flying of the airplane in a very negative way.
This is almost always caused by the failure of the builder to support the outer housing in every bulkhead.

There is a very easy Litmus test for this problem with any airplane you might encounter and only takes seconds. While I also check the rudder pushrod but the most important is the elevator pushrod. You need only to power up the radio or grasp the servo output arm with one hand to hold secure, then simply grasp the control surface close to the control horn and push the rod in compression if there is little resistance and the rod just bows somewhere, You got a problem. You should easily be able to push a surfaces horn in compression and the servo horn is moved. if the servo is not moved with the power off you have a problem.

The obvious solution if you are to keep the nyrod system is surgery (usually done in the bottom of the fuselage to secure the nyrod at each bulkhead. Another spot that often bows excessively is when the fellows cut off outer housing flush with the fuselage far to far ahead of the control horn leaving the inner rod to bow.

Now since you asked about Carbon Fiber rod. Yes it can be made and is far better but the key is it cannot be bent and must run totally straight even the wire rod end should have no bends. This means the rod must exit the fuselage where it needs to and this must be planed for. This system is very easy and inexpensive and it can be done very quicly. Here is a link to the a tutorial on the rods use and these are not fancy with fancy fittings. The CF rods are a perfect slip fit for 2/56 dubro threaded rod end wire. This tutorial will explain how it is done I have gotten most every one using this rod system locally and it very popular. I even was able to convince the LHS who now carrys Derrols carbon rod that is a slip fit for 2.56 rod ends as well as 4/40 rod ends.

http://www.darrolcady.com/Carbon_Fiber/carbon_fiber.htm

John

gregoryshock

Thank you for the advice. I checked my push rods and they are secured to every bulkhead. I checked the servos and they look fine. What appears to be happening is the Nylon Push Rods appears to be growing. Is this a common problem with Nylon Push Rods?

jetmech05

I have found that I have to re trim as the day gets hotter. I don't use ny rods any more

LesUyeda

"is the Nylon Push Rods appears to be growing. Is this a common problem with Nylon Push Rods?"

Yes. They once offered the same thing with a "carbon fibre" center to alleviate this condition.

Les

scale only 4 me

My Feedback: (158)

Another trick I've used is you take a solid full length push rod, Say a 36" 2-56 threaded end for standard size nyrod, you cut short 1/4" pieces of the inner nyrod and slide them over the solid rod say every 2" or so, then the solid rod slides in the outer nyrod housing perfectly and you're left with solid rods on both ends. No more growing/shrinking with heat/cold and it's a much more solid feel to the system..
I've done this with the larger 4-40 nyrod systems too