My LT-40 kit comes with flex push rods. Since they are flexible, it seems to me they need some additional support than what is built-in to the model. There are some pretty long spans between supports. Do I need to worry about it? It seems to me that they are SO flexible, that they may bend instead of moving a control surface if under almost any load. I know that some flexing is good (like for nose wheel), but too much would be bad. Suggestions?

I believe that there should be some tubes that look like small straws in your kit. They will be mounted in the fuselage and the rods will go inside them. I haven't built one, so maybe you have to go buy them. Read your instructions about building the fuselage and see if it talks about them. There is a sig lt40 build thread in here too. The fuselage build starts on page 12[sm=thumbs_up.gif]


http://www.rcuniverse.com/forum/m_34...tm.htm#3439708

They also came with my 4*. I used them for about a month or so, and ditched them. I did not like them AT ALL. they started to bend from where they exit the fuse and attach with the control surface. I had mine connected to the bottom of my elevator, Pulling it was ok (down elevator) and when it pushed (for up elevator), it didn't give me the maximum throw because it would bend and if I pushed down slightly on the elevator, I could move it down because the rod would bend ( again it's bending where it exits the fuse and attaches to the surface).
I switched them with metal rods now, no bending and binding. plane seems to fly so much better now.

In San Diego, we have cold nights and warm/hot days.... this sucked because my trimmings would need to be adjusted as the nylon rods would expand and contract.

Sullivan makes a few different types of flexrods. Goldenrods and carbon fiber are but two types. I've used them and, if used right, they are just fine.

At the rear end of the rod, where it would attach to the elevator and/or the rudder, there is a trick I used to make sure they didn't flex at the point outside their tubes. But first, you have to really secure the tubes. I roughed up the tubes with sand paper so that epoxy cured and stayed attached to the tubes, then drilled a hole in the fuselage formers so that the tubes will pass through, or you can put a ply support between the right and left side of EACH of the formers, held in by epoxy, then drill holes on the left and right side to accommodate the tubes, then pass the tubes through. Apply a dab of epoxy at each former (remember, you should have roughed up the outside tubes at the former locations). When you are done, they will not flex.

Now for the rods themselves.

I used 2-56 rods on my Tiger 60, Four Star 40, Goldberg Wildstick 40, Goldberg Progege.. and others. Test fit the rods through the tubes and measure so that you know how much will stick out the rear before the 2-56 steel rod is placed inside the rod. Simply lay the steel rod along side the goldenrod or carbon rod and measure the steel rod to the elevator or rudder at their center point. Now, flex the control surface to make sure that you have enough of the tube cut back so that the rod does not interfere with movement. When satisfied that at the position of the steel rod, mark rod at the end of the goldenrod with a Sharpie or a permanant marker. Make sure you have enough of the smooth end of the steel rod to pass well inside of the goldenrod. Three inches should suffice. It should be very tight if trying to push the rods in by hand.. don't do that, just try it to make sure it's good and tight... meaning if you can pass it in but it with some difficulty, then it is good to go.

Ok.. here is the interesting part. Have a variable speed drill handy. Use a rod that has threads on one end and is smooth on the other end. Make sure that there are no burrs on the smooth end.

Put the rod in the drill chuck threaded side in leaving the smooth side sticking out. Tighten the chuck to the point where the rod is very secure. Don't worry, it won't damage the threads. Don't put the rod to far in the drill.

The next step has to be done fast.

Grab the goldenrod or carbon rod with a good pair of pliers.

Coat the steel rod with CA and put several drops inside the goldenrod (or carbon rod).

Just as soon as you coat the steel rod with CA, put it in the hole and start the drill about medium speed and push it in. The CA will act as a lubricant for about 10 seconds so work fast and push it in as far as the line you drew when making your measurement. The CA will cure almost as quickly as you stop turning the rod. Make sure you hold the goldenrod with the pliers well enough to keep it from turing with the drill.

If you do this right, this will NOT flex and will work great.

http://www3.towerhobbies.com/cgi-bin...?&I=LXFU92&P=7


CGr

I used the tubes provided in the kit and put solid wire 2-56 pushrods through the tubes. The outer tube is glued to the plane and the inner tube is threaded a few turns onto the wire. The inner tube acts like a bearing and takes up all the slop between the wire and the outer tube. The wire holds trim very well.

Stan

the way that CGRetired explained how to do it is the best way.i have been doing my golden rods like this for years.it is very important to rough the outer tube up where they pass through the formers and out the back of the fuse to get them secured.i use the fiberglass outer tubes and ca on them.i use a 256 die and thread about half inch of the end of the rod that i thread into the flex rod then add a drop of ca.you can put some pretty serious curves to the ny rod and it doesn't bind.and the metal rod on each end is the same as having a solid rod all the way.