Preventative Maintenance For RC Planes Beginners Fly
The majority of rc planes beginners select are of the Almost Ready To Fly (ARTF) variety. These are popular because they get the rookie into the air quickly and because the manufacturer has done all of the design and construction work, They are virtually guaranteed to offer the tutor and student the best chance of success from the very start.
In spite of these advantages, it is not unusual for your pride and joy to start looking a little bruised and battered after a few flights and untidy arrivals. After a while it is going to need some TLC to ensure it remains fit to fly.
This post will look at some of the things that can be done right at the beginning and early in the learning programme to ensure it remains airworthy for as long as possible.
Installations and Connectors
It is not unusual for the fittings ,etc. in budget priced ARTF trainer kits to be of an economy quality in order to keep the price down to an affordable level. As you gain experience you will begin to appreciate that it is often advisable to examine these items at the outset. If you are uncertain as to their unsuitability, ask for advice from a more experienced modeller.
What are known as ‘fast fit’ items are used to speed up the assembly (we all appreciate how impatient you may be to get first flight logged). I have seen some very dubious bits of plastic included to perform quite serious load bearing duties.
As you will have come to realise, I always advocate a ‘Safety First’ approach to model flying and do not believe it is worth compromising this philosophy. Because of this I do not automatically assume that the accessories included in a model kit are of a suitable standard in every case.
Such things as horns, hinges, servo linkages, screws, bolts, captive nuts and engine mounts, amongst others, have all proved unsuitable for purpose at one time or another. I have gathered together a range of preferred products from reputable manufacturers that I keep to hand ready for circumstances where replacement is necessary.
This ‘standardisation’ has proved to be a shrewd move as it has meant that my models are all of a standard and I only need to keep a few of the items I need to maintain my planes.
European modellers need to understand that many of the Far Eastern manufacturers cater strongly to the American market and as a consequence, the fittings supplied in many kits use US standard thread sizes for such things as pushrods and connectors.
This is fine if the quality is good but if you are unhappy with the quality of fittings supplied, you will need to replace both pushrods and connectors with European M2 standard versions. This same applies to engine mounting bolts and wing fixing bolts which are often US stock sizes.
Pushrod To Servo Fittings
Although in some kits the servos are already installed, it is often necessary to connect the pushrods to these servos. To this end a version of what is called a ‘fast fit’ connector is provided. personally I am not a fan of this type of fitting, much preferring the use of the right angle bend and keeper as shown below.
It is not unusual for this type of ‘fast fit’ linkage to be supplied for attachment to the control surface horn as well. A linkage with this type of fixing at both ends is prone to flexing and also vibration causing the fixing screws to become loose over time.
The only advantage to be had from the use of this type of fixing is that quick and easy adjustment can be made to the length of the linkage. I prefer to measure the distance from the servo horn to the control surface horn and tailor the pushrod to suit. Make a 90 degree bend at the servo end and use a ‘pushrod keeper’, as shown here, along with a metal or good quality nylon clevis and retainer to connect to the control horn (see picture above).
There is nothing worse than suddenly seeing your pride and joy plunge to earth despite the correct control being made at the transmitter. This can so easily happen if the grub screw in a fast fit quick link works loose.
It may not even be the grub screw at fault. There is the bottom retaining e-circlip or tiny hex nut that can come unfastened. If you do insist on using this type of connector I suggest you apply a little cyano to the grub screws and bottom retaining fittings.
Having taken these precautions be sure to examine these fixings on a regular basis to ensure nothing has worked loose. Better safe than sorry!
Control Surface Horns
It is not unusual to discover that control surface horns supplied in ARTF kits are designed to be glued directly into the Balsa Wood adjacent to the hinge line ( see examples here on the right). This is not really good practice as, over time, the wood can start to break down with the applied loads and eventually the horn and wood could part company. There is really nothing to secure the horn other than the bond between the wood and glue.
A far better type is that shown below with back plates and screws that pass right through the wood and engage in the back plate by creating a thread in the holes provided. Some of these types come with self tapping screws instead of the type of screw shown here. Either are satisfactory and a far better option than the ones above. Some even come with washers and nuts to secure the screws.
When you fit these horns be sure to tighten the screws right up to the nylon back plate so that there is absolutely no movement between the horn and wood. Having said this, do not ‘over-tighten’ them so that the wood becomes crushed.
My technique for mounting this type of horn is to hold the horn in the correct position with the pushrod or clevis holes vertical to the hinge line (see picture below) and mark the screw holes on the covering using a fine tipped CD marker pen. I then drill a fine pilot hole small enough for the screw to bite into the wood as it passes through.
Place the horn back in position and start to turn a screw into the wood. When the screw is starting to show through the wood, place the back plate over the end of the screw and continue to turn the screw so that it threads itself into the nylon of the plate. Start the second screw into its hole and, ensuring the hole in the back plate is properly aligned, tighten both screws through the nylon until the horn and back plate are tight up against the control surface without crushing it.
Pushrod to Horn Clevises
My personal preference is for the use of Euro size M2 spring steel types. Obviously in the USA the preferred types will probably be US 2-56 thread. I am not a great fan of the nylon ones frequently supplied in commercial kits. This does not mean that some may be of a suitable quality but be sure to satisfy yourself that this is the case. If in doubt, get help and advice.
One thing you must ensure is that the fit of the pin through the nylon horn is a smooth bearing fit with little friction but no slop. The best way to ensure this is to select a small drill the exact size of the clevis pin and run it through the hole in the horn. Excessive friction can cause binding which adds extra load on the servo causing it to draw excessive current. This can lead to your receiver battery to run down quickly or your BEC circuit to overheat or worse still, to fail completely.
Also ensure that the clevis clicks together over the horn with the pin fitting correctly in the other side of the clevis jaw. If it remains partly open then there is a good chance that it could slip out of the horn under load.
Although metal clevises are not so prone to coming open as nylon ones are, I still take the precaution of sliding a short length of silicone fuel tubing over the pushrod before fitting the clevis. Once the clevis is located in the horn, I slide this tubing over the clevis jaws to help prevent them parting inadvertently during flight. Safety First Eh?!
Secure Control Surface Hinges
We will finish off this post by looking at the integrity of your hinges. Many ARTFs arrive with the hinges already fitted and in some cases they are not well glued. I am not suggesting that this is the case with all kits but it does happen more often than it should.
It is easy to check this by giving each control surface a firm pull. Even if this indicates that everything is as it should be, take the precaution of wicking some thin Cyano into each hinge line.
Once this is done I obtain some cocktail sticks that I cut down into lengths that are very slightly shorter than the thickness of the control surfaces. Using a drill bit equal to the thickness of the sticks, I drill through the underside of the control surface and through the hinge, stopping short of breaking through the top covering. I then insert one of the short lengths of stick and secure it with a drop of Cyano.
Continue this process until all hinges have been secured. I promise you that this will guarantee the hinges will outlive the model.
On occasion the hinges are set out of alignment during manufacture. In these situations the best thing to do to avoid binding is to cut through the existing hinges leaving them in situ. Cut a new set of hinge slots alongside the severed ones and glue and peg in place a new set of Mylar ones designed for use with Cyano glue (see picture right).
Some models feature torque tubes from a central servo to drive both ailerons. The torque rods can bind in these tubes if they slightly out of alignment. The way to relieve this is to squirt a small amount of WD40 or similar lubricant into the tubes using the narrow tube supplied with the can.
We’ll leave it there for this post. Next time I will cover some more activities you will need to carry out with any of the rc planes beginners purchase to guarantee their longevity.
If you have enjoyed the content of this post, take a look at my website www.rookiercflyer.com to learn everything you need to know to get started in flying model planes.
Catch you soon.