Model airplane kits
- building your own vs. modern pre-builts
Traditional balsa model airplane kits are still favoured by those aeromodellers who enjoy the building side of the hobby as much, or even more so, than the flying side but such kits have taken a beating in recent years, with the advent of foam RTFs.
But with that said, there is growing evidence now that traditional kits are making a comeback, as modellers who bought foam Ready To Fly rc airplanes as an easy introduction to radio control flying are seeking more satisfaction by getting in to the building side of the hobby.
A traditional model plane kit typically comprises the plan and building instructions, all the balsa and ply wood needed to construct the airplane and most, if not all, of the hardware needed such as servo linkages, control horns, undercarriage parts, motor mount, fuel tank etc.etc.
The components of the plane such as wing ribs and fuselage formers may already be cut out either by CNC machine or, more commonly these days, laser. If the parts are not pre-cut then the outline of each one will be printed on to sheet wood and it's your task to accurately cut them out with a sharp modelling knife. Certainly CNC/laser-cut kits are the nicer option!
Strip balsa will also be included in the kit for use as wing spars, leading and trailing edges, fuselage longerons etc.
Incidentally, despite its often soft feel, balsa is actually a hardwood and is ideally suited to model airplane kit construction because of its excellent strength to weight ratio. Thin model-grade plywood is also used in certain areas of a model airplane construction, where more strength is required such as engine bulkheads (firewalls) and landing gear plates.
Above: a traditional balsa and ply kit, my Jamara Pitts S2B.
Model airplane kit construction takes place over the plan which must be laid out on a flat modelling board. Typically the balsa components are held in place, until the glue sets, with pins so the board needs to be soft enough that a pin can be pushed in to it. An alternative is to have a flat steel sheet and use powerful Rare Earth magnets to hold the parts in place.
Different glues are used when building model airplane kits and the type of glue depends on the joint and the wood type/hardness, as well as the builder's personal preference. White wood glue (PVA), aliphatic resins and cyanoacrylate (CA) glues are commonly used on balsa to balsa joints, but where stronger joints are needed such as landing gear plates and engine bulkheads then two-part epoxy resin is common.
Once all parts of the plane (wing, fuselage, tail etc...) have been built then the wood needs to be carefully sanded to a smooth finish, particularly the joints. Any unwanted holes and other imperfections can be filled with lightweight filler and then sanded to shape.
For many, including myself, sanding is the worst job of all but it's worth taking the time because any lumps and bumps in the airframe will show through the covering and potentially spoil the look of the finished model.
When the construction and final sanding of the airplane parts is complete, the parts are then covered in some kind of covering film, a common choice being a heat sensitive film which is put on using an iron. The heat melts the adhesive backing which sticks the film to the balsa, then the iron or a heat gun is used to shrink the film over the model. There's a definite skill to using such coverings and the manufacturer instructions regarding iron temperature settings should be followed carefully; if in doubt, practice on some spare balsa first!
Heat-shrink covering is a relatively modern invention and traditionally balsa model airplanes were (and still are in some cases) covered in lightweight tissue paper (or even silk) with a liquid such as 'dope' applied to the airframe to stick the tissue. Dope is then applied to the entire covered surface and as the dope dries it shrinks, tightening the tissue as it does so.
Many builders of small scale model airplanes still use this method but these days ultra lightweight iron-on coverings are available to replace the tissue and dope method.
Balsa/ply ARF RC airplane kits
If you want a gentle introduction to traditional model airplane building techniques then an ARF (or ARTF) - Almost Ready To Fly - kit might be the answer.
ARFs are 90% finished, including the covering, and they are mostly of balsa and ply construction. All you need to do is some final assembly (hardware) work and install the engine and radio gear yourself. The photo below shows how a typical ARF kit is, fresh out the box:
ARF kits have become very popular in recent years and there are some excellent quality kits out there - and some very bad ones too!
The majority of such kits (good and bad) come from the Far East; if you're going to buy an ARF then do some thorough research before you buy - internet forums are invaluable places for finding out about a certain kit. Read more about ARF kits.
Foam Ready To Fly RC planes
Although there is a very wide selection of traditional balsa model airplane kits available, and an even wider selection of ARF ones, nowadays however it's quite normal for model planes to be constructed from foam; typically most electric powered RTF (Ready to Fly) rc airplanes are made this way and in the last few years there has been a huge surge in the number and variety of these models available.
Foam airplanes are very convenient and are cheaper to buy, simply because manufacturing costs are lower. The type of foam used in model airplane construction is very durable and so the plane can withstand bumps and knocks greater than a balsa/ply airplane can. For these reasons foam rc airplanes are very popular with newcomers to the radio control flying hobby.
But not all RTFs are foam or electric; there are traditionally constructed glow plug powered ones out there too, for example the Alpha Trainer DSM2 and NexStar Select 46 both shown below:
Model airplanes like these let the beginner own and fly a brand new, traditionally constructed model without having to build it! Read more about RTF kits.
If you are thinking about getting in to the building side of the rc flying hobby then your decision is a good one. No aeromodeller will argue the fact that building your own plane from a kit and seeing it take to the skies is far more satisfying than just buying an RTF.
But if you don't yet have the courage or confidence to build from a kit, then consider getting an ARF and give yourself that gentle introduction to model airplane kit construction.
Balsa vs. Depron
Although balsa wood has long been the main material used in model plane kit construction (i.e. anything other than RTF based planes), there is a growing number of aeromodellers who are using Depron foam.
Originally manufactured for floor insulation for the building industry, the qualities of Depron were soon noticed by modellers who quickly discovered its suitability for modelling! The rigidity and ultra light weight of this foam sheet make it an ideal substitute for balsa and as one of my forum members has repeatedly shown, it really is good to work with!
The Depron weight to strength ratio is good but it's not as good as balsa, and so Depron is limited to the smaller/medium scale models rather than large scale ones, and is only suitable for electric powered (EP) aircraft.
RC airplane construction accessories
Various tools and accessories are needed to construct a model airplane from a kit, such as modelling knives, pins and small clamps, modeller's vice and covering accessories as well as various adhesives.
As mentioned earlier a modelling board is also essential, this needs to be something rigid and completely flat. This latter point is so important because any warps or bends in the board will get transferred to the model during construction, and that's really not good!
Browse a selection of tools and accessories.
Discuss model airplane kits in the forum.
Related pages
Vintage rc airplanes - modern-day traditionally built kits.
ARF rc airplanes - more info on Almost Ready To Fly airplanes.
RTF rc airplanes - what to expect from a Ready To Fly airplane.
