February 26

Applying RC Model Aircraft Decals

No matter what type of model we fly, scale warbird, aerobatic or a simpleCitabria Pro Scratch Build sports model, the final detailing or trim  applied to the model is what really adds the finishing touch. There are several ‘commercially’ available types of decal around, some are better suited to a particular ‘type’ of model but not so suitable for others.

As a newcomer to model flying it is unlikely that you will be considering building a scale masterpiece. The normal progression from a basic trainer will be a sport aerobatic type designed to help you hone your flying skills. Hopefully you will be nurturing a desire to build your own plane either from a kit or from a plan. There is nothing quite like the sense of achievement to be gained from building your own model.

Should you decide to take this route, you will eventually reach a point where you will need to apply covering. To make the plane more easily visible in flight you will need to consider applying suitable rc model aircraft decals.

Although there a number of decal types available, the most suitable for this sort of model are those manufactured from Vinyl. This is the same material used for automobile decals. They are relatively easy to apply and are great for standing up to glow fuel, petrol (gas), and exposure to the sun.

Vinyl model aircraft decals are available as printed or solid colour. They are simply cut out of a carrier sheet and applied to the airframe after covering/painting. It is important to take care not to get dust, hairs etc…under the decal. The smallest imperfections will be magnified into BIG ones!

Applying Your Decals

The best tip I can give when applying these decals is to remove about ½ of the paper backing, and position the decal where it needs to be and burnish the exposed edge down. Gradually pull the backing away whilst slowly burnishing the decal down in smooth strokes using a soft cloth to avoid scratching the surface of the decal. Work from one end of the decal to the other, pushing out any air bubbles as you go.

Don’t be tempted to remove all of the backing in one go, placing into position and starting to burnish from the centre  outward as you will end up with a horrible bubbly mess.Vinyl Grafics

Here is a video that shows how to get the best results.  You will notice that the decal being applied advertises one of the many custom decal manufacturers.

At the end of this post I have gathered together a selection of trusted manufacturers both in the USA and the UK who can make decals specific to your needs.

Patience, good preparation, a steady hand, and warm room will produce the best results. Apply the graphics when the temperature is above 55 degrees F (15 C).

Most vinyl decals comes in one piece, sandwiched between a clear application layer and a waxy backing paper. Both of these are removed during the installation process. The adhesive side of the decal is protected by the backing paper which peels off easily.

On the other hand, the adhesive on the vinyl decal is EXTREMELY sticky, so be very careful when you come to peel it away. The vinyl will stretch if you are too rough with it and that is NOT a good thing.

There are two ways to apply your decals: DRY or WET.

Dry Method

This is fine for smaller decals and takes the following procedure:

Ensuring your hands are spotlessly clean, start by peeling off the backing layer taking great care not to bring it into contact with any unclean surfaces and hold the exposed surface very carefully in your fingertips. Decide which edge is  the first to be positioned (top, bottom, left, right) then place the chosen edge of the decal where you want it.

Slowly lay the rest of decal down on the surface whilst pressing down gently behind the raised portion making sure good contact is being made with the surface. This should eliminate the chance of air bubbles being trapped. Once the decal is completely flat and smoothed down thoroughly, gently peel off clear application tape from decal.

If you have taken good care your decal should be lying totally flat to the surface with no air bubbles in view. If, however, you have a few such bubbles take a new scalpel blade, and with the tip, puncture the centre of the bubbles whilst rubbing them down.

Wet Method

This method is useful for applying medium to large one piece decals. Large decals will need to be flattened out in a warm room before applying. Roll the decal out flat on a large surface and weight it down so that the application tape and backing paper can relax in the heat of the room.

You will need a piece of hard plastic (an old credit card is ideal) or “squeegee”. Mix a weak solution of soapy water in a spray bottle or mister (1 or 2 drops of dish washing liquid per cupful of water is required). Don’t use an excess of soapy water, if you saturate the surface or the sticky vinyl adhesive too much – it won’t stick.

In this instance spray the surface LIGHTLY with the soapy water, remove the backing paper entirely from the decal and spray the adhesive side lightly also.

Lay the decal adhesive side down on the damp surface. The soapy water enables the positioning your decal perfectly on the surface after you have removed the backing paper entirely and helps in the removal of any bubbles.

Starting at any side (top, bottom, left, right) and place the edge of decal where you want it. Slowly lay rest of decal down on the surface. If needed, gently slide the decal to the exactly where you want it. Using your “squeegee”, or plastic, gently smooth out any air or water bubbles on decal, working from the center to outside edges. Do this to avoid trapping air or water bubbles.

Mop up any excess moisture with paper kitchen towel. Finish by peeling the clear application tape very slowly back on itself. Don’t attempt to pull it straight away from the surface. The slow motion and flat angle will allow the vinyl to stay on the surface while removing the tape. The last thing you want to do is pull the vinyl off the surface. Pierce any bubbles with a pin or your sharp scalpel blade and press out the air or water.

If the vinyl decal moves whilst you are attempting to remove the application tape, smooth it back down. You may need to “squeegee” again and mop up any moisture that oozes out from under the decal with kitchen towel and you may need to just give it a few more minutes to dry out then try again. When you are able to remove the clear tape easily with no movement of the vinyl decal you the job is done. .

I advise that you seal decal down. Although fuel proof, normal handling easily damages them due to the ‘soft’ nature of the ink. I always apply a polyurethane clear coat over all vinyl decals to seal them down and protect them from the elements.

Resources

Although there are plenty of standardised sheets of rc model aircraft decals available from model suppliers, particularly for warbird types, there are often times when a set of custom decals will help create a unique colour scheme for a scratch built model.

Below I have brought together a list of custom decal manufacturers that some of you may find a useful resource:

Pyramid models – www.pyramidmodels.com/ (UK)

Model Markings – www.modelmarkings.com/ (UK) – Suppliers of the decals for my Citabria Pro (Photo above)

MT Custom Graphics – www.mt-graphics.co.uk/rcgraphics.php (UK)

Decal Designs Aeroworks – www.decaldesigns.co.uk/aeroworks.php (UK)

Flightline Graphics – www.flightlinegraphics.com/

B & E Graphics – www.bandegraphix.com/

Callie Graphics – www.callie-graphics.com/

Pro Mark Graphics – www.pro-mark.com/

Aero Graphix LLC – www.aerographix.biz/

Cal-Grafx Hobby Art – www.cal-grafx.com/

Aeroloft Designs – www.aeroloft.com/

Bad Brad Graphics – www.badbradgraphics.com/

Although not vinyl decals, the following company offers software for your PC that, along with some other hardware you will require, enables you to print your own decals using either a Laser Printer, Photocopier or Ink Jet printer:

Pulsar Professional fx (Make Your Own Dry Rub-Down Transfers) – http://www.pulsarprofx.com/decalpro/

Parting Thoughts

Vinyl Decals are just one of several types of rc model aircraft decals available to us. Others are more suited to use with scale models where markings need to be finer so that surface features can be revealed under them. I will be introducing some of these in a future post so watch out for it.

I hope that you are continuing to find my posts useful. Please feel free to share them with anyone you think could benefit from their content. Also, if you are new to rc model flying, be sure to visit my website www.rookiercflyer.com for everything you need to get started as cheaply and as safely as possible.

 

 

 

 

 

 

February 19

Flying RC Model Planes – Taking Off

There is a saying in the world of model airplane flying that goes something like this:

LANDINGS ARE COMPULSORY, TAKE OFFS ARE OPTIONAL!”Ready to Take Off

Whenever you decide to commit your model to a take off, the onus is on YOU to ensure everything is as it should be for a safe and enjoyable flight.

What this means is that flying rc model planes is not just about opening the throttle and getting the plane airborne. There are a whole sequence of procedures that need to be checked before you get to this point.

Before I get to talking you through the process of how to take off your model airplane, I need to discuss the checks you must to carry out before flying. Failing to make these checks will inevitably result in either a malfunction or the chance that your plane will be so uncontrollable as to be unsafe to fly to say nothing of your frustrations.

Pre-Flight Check List for RC Airplanes

It is as important for RC Airplanes  to undergo Pre-Flight Checks as it is for full size airplanes. You need to check everything you possibly can to reduce the risk of crashing your model.

Frequency Check

Although most people are using 2.4GHz radio control systems today, there are still a good number that still rely on the 35MHz frequency in the UK and Europe whilst in the USA, 72MHz is still used by some. If you are using any of these (or other) frequencies it is essential that you check the compatibility of both Transmitter and Receiver crystals in your gear before you go flying.

Once at the flying field you should check with all other flyers that they are either on 2.4GHz or that their chosen frequency does not clash with yours.

Radio Range Check

It is so important that you getRange Check into the habit of carrying out a range check prior to every flying session. It should be done before the first flight of each day at the flying field. Follow the procedure as explained in your radio manual for doing a range check.

Those of you who are still using 35MHz or 72MHz or other MHz frequency radio gear should collapse the transmitter fully to carry out this check. 2.4GHz transmitters have a dedicated switch position (usually the buddy box training switch) and a programme setting for this purpose.

Check the Balance

You should always check that the model balances at the correct CofG point prior to every flying session. There is always a possibility that something may have shifted within the fuselage to effect the balance point. Don’t assume this has not happened.

If this is to be the first flight with a new model, be sure to check that it balances laterally and that one wing is not considerably heavier than the other.

If yours is a Glow/Nitro powered model, carry out these checks with the tank empty. It is better that the model is slightly nose heavy with its fuel load than to go tail heavy as the fuel is used up.

Check Engine and Wing Bolts for Tightness

It is not impossible that engine vibration during previous flights may have caused the engine bolts to work loose.

Although you may have fitted the wings just prior to this flying session or at home before travelling to the field, it is wise to double check that the wing bolts (if used) are fully tensioned.

The other item that you should check for tightness is the propeller nut or bolts. This is especially important on Glow/Nitro powered planes where vibration may have resulted in a loosening. Not to say you shouldn’t also check the propeller fixing on Electric models also.

Control Surface Movement

Once you have switched on your radio transmitter and receiver, check that ALL control surfaces are operating correctly and freely.

Go through a sequence of stick movements and watch carefully that the control surfaces move in the correct sense. This is especially important for the Ailerons. You wouldn’t be the first pilot to waggle the aileron stick and observe the movement without recognising that they are reversed.Clevis security

Don’t forget to check the integrity of the throttle linkage connections. Give each control surface a gentle pull to ensure hinges have not come loose. Make sure you have brought with you the necessary glues and fixings to rectify any problems in these areas.

Check that the ‘snap links’ are properly closed on the control horn clevises and that the small fuel tubing keepers are slide home to prevent them opening in flight (see right).

Check that the servo output horn linkages are properly attached and that the horn retaining Servo extension saversscrew is properly screwed home so that the horn cannot turn on the spline.

In modern ARTF and other models it is quite common for servos to be located close to the control surfaces requiring extension leads to be fitted between the receiver and the servos. If you have this situation be sure to fit servo lead extension savers to prevent the leads parting company under tension (see right).

Battery Voltage & Capacity Checks

First of all you need to ensure that you have fully charged your transmitter battery, preferably overnight, to ensure it has full capacity ready for a busy flying session.

A word of caution here; many people replace the radio manufacturers supplied batteries with the new generation ‘slow discharge’ NiMH batteries or even LiPo or LiFe batteries that offer greater capacity than the generic types. It is very important to appreciate that these higher capacity batteries require either a higher current output charger or a dedicated Lipo/LiFe charger.

Understand that although your battery checker may indicate aBattery Capacity Tester full voltage reading, this does not necessarily mean that the battery is fully charged. You need to use a ‘Capacity Checker’. This will tell you just how much energy remains in the battery as a percentage of its full capacity rating.

The charger supplied by the manufacturer will normally be a slow charge variety for NiMHs. If you decide to use this charger for the new generation ‘slow discharge’ NiMHs you need to divide the maximum output current capability of the charger into the maximum capacity of the battery to determine the number of hours of charge required.

For example, if your charger is rated at 60mA output and your battery is rated at 2500mAH then the theoretical number of hours required to charge this battery from flat state will be 2500/60 = 41.7 hours.

Should you have a very new set of gear supplied with a LiPo/LiFe battery then the manufacturer should have supplied a dedicated charger for the purpose.

Glow/Nitro planes and Electric planes using an ESC (Electronic Speed Controller) without a BEC (Battery Eliminator Circuit) will require a dedicated receiver battery that, again, you should have checked and, if necessary, recharged overnight. Once again be sure to check the capacity of your battery and make sure you give it enough hours of charge if using a slow charger.

Electric planes often rely entirely on the power battery to supply the voltage to the receiver via a BEC. In this instance you only have to ensure you have fully charged your power battery.

Check Engine Reliability and Tuning

This only applies to those of you using Glow/Nitro engines or Petrol/Gas engines. There is nothing more frustrating than arriving for a day’s flying to find your power unit is refusing to start or run reliably. It is always best to set up your engine before a flying session confident that it will start and run reliably for you the very first flick of the propeller.

I see so many flyers spending an hour or two trying to set up a troublesome engine at the field when they could have eliminated the problems at home. Such problems are often attributable to faulty plumbing, failed glow plug, discharged glow ignition battery, poor engine seals and incorrect needle settings.

Prepare To Fly

Having covered all of the above checks you should have an aeroplane that is fit for purpose. Now you need to carry out a sequence of events that will eventually find you with model on the runway and you ready for Take Off.

With you plane suitably restrained and incapable of causing injury to any of your fellow flyers, fuel tank filled or power battery installed you are ready to start up the power plant.  Turn on your transmitter and, if using MHz frequencies, ensure your aerial is fully extended.  Then move the receiver switch to ON and start your engine (Fuel energised engines only of course!). Once running, check for reliable idling and smooth full throttle response.

Check that all of the controls are functioning properly under full power. If anything at all does not react as it should, DO NOT ATTEMPT TO FLY! Your plane is an accident waiting to happen.

With the transmitter switched on, Electric models should be energised by connecting the power battery to the ESC. Wait until you hear the correct recognition tone from the ESC/Motor combo. This will tell you that the ESC is correctly energised and that the supply to the receiver is working correctly.

Smoothly open the throttle and ensure that the motor speed increases to maximum and reduces to a stop in sympathy with the throttle stick movement.

Again, be sure to check all control functions are operating in the correct orientation. I repeat, if anything at all fails to react as it should, DO NOT ATTEMPT TO FLY!

Prepare To launch Skyward

Before taxiing or carrying your plane to the take off point, check the direction of the wind if any. Check the club windsock or tie a piece of ribbon or thread to your transmitter aerial as a wind indicator. This is important as you need to take off into wind so that your plane achieves flying speed more quickly, responds correctly to airflow over the flying surfaces and gets airborne safely.

As the thrust of this website and associated posts are aimed at getting newcomers flying safely I propose to concentrate on trainer type planes. These generally take off from the ground so I will discuss this method of taking off here.

Hand launching is usually applicable to park flyers, smaller planes and those without an undercarriage. I will look at this method of getting airborne in a later post.

Position your plane on the runway nose into wind and prepare for take off. Take a good look all around you and assess the field status. Make sure that there is no-one or nothing that your plane could possible collide with during the take off phase of you flight.

Slowly advance the throttle and, especially if you are flying a Glow/Nitro powered model, be prepared to feed in a little left rudder to counteract the tendency for engine torque to cause a swing to the right.

Continue to increase the throttle to increase the speed of your model. Trainers are designed to have natural lift at high throttle settings so the nose should start to rise as the speed increases. as the nose starts to rise apply the smallest amount of up elevator to encourage the plane to lift off.

Hold the elevator steady and watch the plane climb. If it starts to drop a wing either right or left, use the ailerons to bring them back to the horizontal. If the nose starts to wander off the straight path, use a tiny bit of rudder in the opposite sense to swing the nose back on track.

At no time during this phase should you take your eyes off the plane. Once the model has attained a reasonable altitude of around 40 to 50ft (10 – 15M) commence a turn AWAY FROM THE FLIGHTLINE. This is most important as turning the other way will cause you to overfly the pits area where vulnerable people will be present.

Commence by moving the aileron stick gently in the direction of the turn you want to make. When you see the wings start to respond to this control input, pull back very slightly on the elevator stick to make the plane turn round the corner.

When the model is flying in the direction you want it to, release the aileron input and the elevator input. Because most trainers have self neutralising attributes due to the the wing dihedral, it should settle back into straight and level flight. If it doesn’t do this naturally just apply a little opposite aileron to level the wings horizontally.

Staying Aloft

Having successfully reached a safe flying altitude your previous flight training should be adequate for you to complete several circuits. If this is not the case then I would suggest you shouldn’t be considering a take off on your own.

You need to have practiced maintaining circuits at constant altitude before you even consider either taking off or landing your model. Take offs and landings are much more difficult than flying simple circuits so perfect them before attempting these more difficult tasks.

Flying rc planes safely and competently involves a sequence of events that need to be learned over a period of time if you are to keep your plane in one piece. The old adage “Learn to walk before you learn to run” is very relevant here.

Moving On

I hope the last two posts have helped some of you progress with your flight training. If so, you may find my book “Flying Radio Controlled Model Aircraft “ useful. It will take you through a full programme of instruction on how to fly an rc model plane.

Read the feedback on my website page covering “Research” from those who have used this book to help them in flying rc planes successfully.

If I can help anyone personally please feel free to ask your questions through the ‘comment’ facility at the bottom of this post or on any of my previous posts or web pages at www.rookiercflyer.com.

Colin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

February 12

Landing RC Model Airplanes

Those of you who have followed my website programme at www.rookiercflyer.com model landing approachwill have learned that an aeroplane has four forces acting on it: Lift, Drag, Gravity and Weight.

A model plane, just as a full size aircraft, in straight and level flight has all of these forces in balance. Thrust is equal to drag and lift is equal to weight. Opening and closing the throttle upsets this balance and causes the model to either climb due to increased speed or to descend when the speed is reduced.

Both of these changes are brought about by use of the throttle alone. This is the way climb and descent is achieved in a full size plane. The application of up elevator has the effect of increasing both lift and drag which overall slows the plane down.

Using both throttle and elevator together is an important aspect of the practical application required when landing rc model airplanes.

Dead Stick Landing

 Imagine the scenario where your model is on final approach and short of the landing strip the engine dies. Many pilots will immediately apply Up Elevator to try and stretch the glide. Unfortunately the opposite will happen and the model will fall short of the landing strip.

From my previous post outlining the use of Throttle and the following post about use of Elevator, you will know that by increasing the Angle of Attack (AoA), not only will you increase lift but you will also increase drag. This causes the model to slow down‎, sink faster and as a result arrive short of the intended landing point.

The other scenario is that the engine dies just over the landing threshold when the plane is too high to land but does not have enough height to go round again. The pilot’s instinct may be to apply Down Elevator to effect a quick landing. The outcome of this is for the model to speed up and as elevator is released, the model zooms upward and carries on off the end of the runway! (Verification that Speed is controlled with Elevator).

Correct Action

In situation one above the best option is to let the model settle into its own preferred glide path. It may land a bit short but it will be considerably closer to the threshold than if up elevator had been applied. It may even by helpful, if you have enough height, to apply the slightest amount of Down Elevator to increase the speed. The height lost will be regained when the elevator is released.

In the second case it may pay to apply a little up elevator to increase AoA and slow the model down with the extra drag this creates. This should result in the model sinking to earth quicker. Unfortunately too much elevator could cause the model to stall which at low altitude could result in partial or complete re-kitting of the model so care needs to be taken with this elevator input.

The safest way to reduce the landing distance would be to make a series of ‘S’ turns. each turn will increase drag and, at the same time, make the approach path longer.

Landing RC Model Airplanes Under Power

Landing Circuit

The diagram above shows a typical landing approach circuit. Prior to commencing this circuit most experienced pilots will overfly the runway before making a turn into the crosswind leg downwind of the landing area.

Unfortunately, when the wind is blowing in the opposite direction many flyers who have not been taught correctly will find it difficult to make the final approach to the landing area from a right hand turn. Their recourse is to fly an approach that takes them to the right behind the strip and turn left handed into the landing phase.

If you are learning to fly for goodness sake don’t get into this bad habit. A good pilot should be capable of approaching the landing from either the left or right. A right handed approach is just the opposite of that shown in the diagram and carries no greater risk so there is no reason to fear it.

Let us take the circuit above one stage at a time.

Having decided to make a landing approach the first action is to bring the model into position at the start of the crosswind leg, downwind of the landing strip. A suitable altitude for this would be around 100 to 150ft ( 30 to 45M).

A learner will usually have his model trimmed so that straight and level flight is maintained at around 60-65% throttle. this should be maintained until the plane has negotiated the next turn into the final downwind leg and is approximately level with the pilot.

At this point reduce the throttle to about 45 – 50% so that speed will start to bleed off and the plane will commence a descent towards the final crosswind leg. As the model negotiates the penultimate turn and settles into the crosswind leg it should have descended to around 45ft (15M) heading towards the final turn to the landing approach.

Once this final turn has been made, reduce the throttle to about 20% setting and line your model up with the landing strip centre line. If you find the model is sinking too quickly, increase the throttle slightly to create more lift and extend the approach.

Just before you cross the runway threshold reduce the throttle to idle. As the model drops toward the landing strip very gentle elevator is required to raise the nose a little and commence a ‘flare out’ at about 3 to 4ft (1M) above the strip. The model should settle gently on the ground without bouncing back into the air.

If there is any evidence of a crosswind you will need to apply a little rudder in the direction of this wind to keep the model’s nose pointing down the centre line of the runway.

Any tendency for the wings to drop one way or another should be controlled using ailerons. Don’t forget that as the model is approaching you, your aileron transmitter stick will need to be moved toward the dropped wing to correct the horizontal alignment.

I have found that most learners benefit from making numerous approaches without actually landing to perfect their approach pattern. The old adage ‘practice makes perfect’ comes into its own in this instance. Commence these sessions by practicing everything above without closing the throttle completely to idle. . Open the throttle again and gain height, overshooting the strip, until you can make another turn into a crosswind leg.

Repeat the routine until the control inputs become second nature to you. This is the time to practice descending to the idle position at which point, open up the throttle again and complete the overshoots from a lower altitude.

Eventually, you will be ready to go to idle and ‘flare out’ into a neat landing.

Aborted Approaches

An ‘aborted’ or ‘missed approach’ is when, having set yourself up for a landing, everything seems to be progressing well but suddenly, at the last minute, you lose your nerve or something goes wrong, and so you open up the motor to full power to climb out so that you can make a new attempt.

Both veteran and display rc pilots still need to do them now and again so there’s absolutely no shame in performing aborted approaches.  Five aborted approaches are preferable to  rushed panic landings so that you eventually land your airplane safely in one piece. rather than in several pieces! When flying an electric powered rc plane don’t lose track of the time you have been flying and your battery pack voltage! Always plan your flying time to allow a margin for extra go-rounds if required.

Landing your rc airplane is the hardest part of radio control flying, and the part that needs the most practice when you’re learning.  Persevere and learn to land well,. Never accept a bad landing without trying to improve on it the next time. Watch those competent pilots at your field who land rc model airplanes time and time again without so much as a bounce.

You can do it too!

In Conclusion

Once again, I hope you have learned something from this post that will encourage you to continue your progress in rc model airplane flight. Learning to do things right is the most rewarding aspect of our hobby and will help your enjoyment in the long term.

I hope you will aspire to achieve the standards of flying demonstrated by the pilots in this video:-

RC Plane Only Best Landings Compilation 

Don’t forget to follow my website tutorials if you are new to the hobby: www.rookiercflyer.com, and discover everything you need to know about getting started.

Colin

 

 

 

 

 

 

 

February 5

Setting Up And Tuning RC Nitro Engines

For many RC flyers there is a certain magic to the sound andEngine Checks smell of Glow/Nitro Engines powering their models around the skies. If you are one of these then the ease of operation and reliability of your engine is an important aspect of your hobby.

In this post I aim to try and help you make life as easy as possible when it comes to operating your rc nitro engines.

Until fairly recently all of my planes were powered by glow/nitro engines and I managed to get the starting and running down to a fine art. There was rarely a time when I needed to spend ages trying to get my engines to perform correctly at the field. Sad to say , this was not so for many of my fellow modellers who often spent a great deal of time trying to get their engines to start and run reliably.

Preparation and Priming

The key to a safe and reliable start up procedure is just this; preparation and priming. These two aspects ensure  confidence in our installation and the knowledge that our engine will start reliably. Let’s take these two subjects in turn.

Preparation

a) Tank Installation and Plumbing:  Although the fuel tank arrangement is not too critical once the engine is running, there are some basic precautions that need to be considered.

Glow Engine and Tank Installation

The fuel tank needs to be installed as close as possible to the engine. Ideally its centre line on or very slightly below the level of the carburettor spray bar assembly as shown here. This arrangement helps avoid flooding of the carburettor when the tank us full. It also gives the muffler pressure a good chance of maintaining fuel flow to the spray bar throughout the flight from tank full to tank empty.

An additional consideration when installing the engine and tank is to ensure that the fuel line from tank to spray bar does not rise above the full level at the top of the tank. With the fuel line as shown in the diagram positive pressure, due to gravity, will ensure that fuel flows to the spray bar for initial priming and is retained throughout the starting procedure.

The diagram above only shows two lines, one for fuel to3-line-tank plumbing for easy de-fueling spray bar and the other for muffler pressure. I personally prefer a three line system as shown here. This avoids having to remove the line from the spray bar in order to refuel/defuel the tank. Note, however, that you need to cap off the extra fuel/defuel line before starting the engine.

Another aspect of this setup is the use of two clunk lines running to the bottom of the tank. Many installations have the fuel/defuel pipe alongside the vent/pressure pipe inside the tank. The setup shown here enables defueling without having to invert the model. It does ,however, require an extra clunk weight to keep the line at the bottom of the tank.

There is also another slight modification that can be made to this arrangement and that is to put a length of rigid fuel pipe from the engine feed line clunk, approximately half the length of the tank, to prevent the tube doubling back on itself ( a “hang up”) in the event of a heavy landing.

As a precautionary part of the engine and tank installation process be sure to remove any burrs from the ends of rigid tubes and around access holes in bulkheads, etc. Check that there are no pin holes in any of the flexible silicone tubes both inside and outside the tank.

Another good precaution is to fit a fuel filter in the fuel fill line. Some people also fit fuel filters in the tank to spray bar line but I feel that so long as the fuel is filtered on its way into the tank, it shouldn’t be necessary to filter it again.

Check that there are no kinks or tight corners in any of the feed, pressure and fill lines that might restrict fuel flow.

b) Engine Integrity

Before you actually fit the engine into the plane check it over for any potential air or gas leaks. To do this carefully inspect the fit and tightness of the front  shaft housing to the crankcase, the back plate to the crankcase and the cylinder head to the crankcase. All of the screws, nuts and bolts, etc. should be checked for tightness.

Ensure that the carburettor is correctly seated in its spigot hard against the rubber “O” seal ring. Make sure there is no dust or other debris in the spray bar assembly and jet.

Some fuel adjustment needles can be a fairly slack fit in theirAir Bleed carb 2 threads and can move in or out under engine vibration. To prevent this, a small section of silicone fuel tubing can be slid over the needle thread before refitting it. this will create a resistance to free movement of the needle.

The next thing to do is to check the glow plug fitted to your engine. Do this by removing it using a suitable glow plug spanner, connecting it to your glow plug driver and observing that it glows a bright red colour.

Make sure it is the correct type of glow plug. Consult the engine manufacturers data sheet for guidance here. If you are a newcomer to rc flying I suggest a glow plug with an “idle-bar” would be appropriate. This type helps retain heat in the plug element when running at idle and tick-over speeds.

c) Throttle Servo Linkage SetupThrottle Arm Positions

To ensure full range of control the throttle to servo linkage should be arranged so that there is full movement between “tick-over” and “full throttle” with final cut off being achieved via the throttle trim control or throttle cut switch at the transmitter.

If you look vertically down on the air intake of your engine’s throttle barrel then the three barrel air openings that correspond to the arm positions shown here will be those Throttle Barrel Settingson the right. It is important to ensure that the servo output arm positions the throttle control arm at the correct positions for you engine to run correctly and give you the full range of control required.

The opening at “idle” setting should be between 1 & 2mm and should give  tick-over of between 2,500 & 3,000 rpm. The final adjustment will be dependent on the size of your propeller and the fuel used.

Getting Ready To StartProp 2 o clock

Your propeller should be fitted so that the blades are at a 8 o’clock/2 o’clock position when pushed against compression as shown here on the right. This ensures a smart positive flick can be made.

Close the main needle valve so that flooding of the carburettor does not occur while you fill the fuel tank. Once the tank is full you can open the needle again. It needs to be set 1.5 to 2.5 turns from the fully closed position.

If your tank is installed as suggested above the fuel delivery tube from tank to spray bar should fill under gravitational pressure. It may not have been possible for you to achieve a straight line between the tank and spray bar and any unavoidable hump in the tube may prevent the desired flow of fuel.

This can be rectified by placing your finger over the air intake of the carburettor (finger choking) and turn the propeller over until the fuel is drawn through. If the fuel starts to flood into the carburettor by siphon action, raise the nose of the model a little.

Alternatively, if the fuel refuses to flow into the feed tube, raise the tail of the model and repeat the choking procedure or cover the exhaust outlet with your finger and smartly flick the propeller over a few times. This creates a pumping action via the exhaust pressure system.

Priming The Engine & Testing For Fuel

A properly primed engine will usually start immediately so follow this procedure carefully.

With a full fuel line up to the spray bar and the throttle fully open, choke the carburettor using your finger as explained above. Turn the propeller over four or five times to draw some fuel into the engine crankcase.

Take your finger off the carburettor air intake and flick the propeller over repeatedly until the engine feels loose and free. Do not skimp on the flicks, it may take ten or more to ensure the fuel reaches all parts of the inside of the engine.

You will tell this has happened when the propeller turns freely over compression with a wet ‘plopping’ sound. If this does not happen, choke the engine again another two turns and repeat the priming procedure.

The best way to tell if this priming has worked successfully is to connect the glow plug to a fully charged glow driver. Firmly grasp the propeller and slowly turn it through compression. You should detect a kick as it goes over top dead centre (the compression point).

If this kick does not occur the engine is not ready to start and will require further priming or the glow plug is not functioning correctly or it is flooded. This should not happen under the routine above but excessive priming could cause the problem.

Starting and Setting The Main Needle

You are now ready to start your engine for the first time. This is done with the throttle set to ‘fully open’. The reason for this is that if there is any problem with the slow running jet setting, it will not affect the start-up unless someone has screwed the slow running needle fully in. Note that future starts are made with the throttle set to about 1.3rd.

Assuming you have correctly primed the engine it should start on the first or second flick of the propeller or with a mere touch of a starter. Keep in mind that your throttle is set to fully open so ensure the model is securely tethered or restrained and be prepared for a burst of full power!

If your engine bursts into full song but cuts soon after, it is too lean and you will need to open the main needle another half turn. Re-prime your engine and try again.

The other extreme is that the engine starts but runs rough and eventually stops. This means that the needle is set too rich and requires screwing in half a turn at a time until the engine continues to run.

In the happy event that the engine continues to run from the start you are ready to make adjustments to the main needle to obtain maximum revolutions.

You will know when the correct setting is achieved if by raising the nose of the plane upward toward the vertical the engine neither gains or looses revs.

If a drop in revs is detected with nose up, place the model back on the ground and open the main needle slightly and check again.

An alternative approach is to keep the plane on the ground and squeeze the exhaust pressure tube flat. This will eliminate the pressurisation from the tank. If the engine looses revs then a slight opening adjustment of the main needle is required.

Slow running & Throttle Response

All new engines should be set up for reliable slow running before they leave the manufacturer and should rarely need adjustment to the slow running jet. In all of my years of experience with new engines I have only once needed to make an adjustment to a slow running jet.

My advice would be to check the throttle response of your new engine by steadily closing and opening the throttle and unless it does not behave as you would expect, LEAVE WELL ALONE!

If for any reason the pick up from idle is not consistent then a SMALL adjustment may be required. I DO emphasise here the word ‘SMALL’. The difference between reliable and unreliable ‘pick-up’ is usually no more the 1/8th of a turn of the adjustment screw.

Depending on the make of engine you have purchased there will be one of two types of carburettor.

The ‘air-bleed’ type. This has a small screw with a spring on the sideAir bleed Carb of the barrel assembly that partially closes off a small air bleed hole in the front of the body.

If, when the throttle is smoothly opened the motor speeds up but then slows and cuts, then the air bleed screw is set too lean (too open).

The solution here is to turn the set screw IN no more than 1/8th of a turn. Re-start the engine and check the response again. If it still fails to keep running, adjust the screw another 1/8th of a turn although this should rarely be necessary.

The other type of carburettor is the ‘dual or twin needle’ type. As you can Twin needle carbsee, this type has a secondary needle to control the slow running which is situated in the centre of the rotating throttle barrel.

In this instance, rather than screwing the needle in to create a richer mix of air and fuel, the screw is turned OUT. The difference being that you are increasing the amount of fuel in the mix rather than, in the case above, reducing the amount of air in the mix.

An over rich mixture at the idle position will cause the engine to be reluctant to speed up smoothly and you may detect fuel being sprayed out of the carburettor. Stop the engine and make the appropriate adjustment to rectify this.

In the case of the ‘air bleed’ type turn the screw OUT 1/8th of a turn or, in the case of the ‘twin needle’ type, turn the needle IN 1/8th of a turn.

Repeat these adjustments until the engine speeds up to full power without hesitating when the throttle is opened fully in about one second.

I repeat what I said at the beginning of this section: New engines should NOT require adjustment to the slow running jet.

General Problems

If your engine gives you trouble starting then it is likely that one or other of the following possibilities has arisen:

  1. The battery is not properly charged or the glow clip / leads have a bad connection or continuity.
  2. The glow plug has failed, is the wrong type, the filament has become distorted or the engine requires a longer ‘run-in’ period.
  3. The carburettor is worn or is poorly machined.
  4. There is a gas leak: at the plug washer; around the plug’s central electrode seal; on the carburettor or engine.
  5. The fuel filter is blocked or the main carburettor jet is dirty ( often bits of silicone rubber from the feed tubes can cause this).
  6. The tank clunk has become ‘hung-up’ (doubled back on itself) or the muffler pressure nipple is blocked.
  7. The throttle servo linkage is ‘wandering’ in operation due to excessive vibration and wear.

Glow plugs are disposable items and do need to be replaced from time to time. Repeated replacement due to ‘blowing’ them is often a result of running an engine too lean at high load. Excessively high compression ratio can also cause this problem as can the presence of metal swarf and bits of grit either in a new engine or due to slow disintegration of an old engine.

Final Thoughts

There is no valid reason why modern RC Nitro Engines should present their operators with problems providing they understand the workings of said engines and know how to get the best from them. This post is aimed at helping you do exactly that and, providing you follow the guidelines closely, you should gain great enjoyment from their operation.

Don’t forget that these miniature power plants can bite you! Treat them with the greatest of respect and don’t take chances. Whirling propellers and human flesh are not the greatest of friends. They also get very hot so beware!

Please don’t hesitate to contact me via the comments facility here at the end of this post if you need my help. If you have found the post helpful, be sure to visit my website www.rookiercflyer.com especially if you are new to the hobby. Everything you need to know about getting started is there.

Looking forward to hearing from you.

Colin