Building model aircraft from kits. (Part 2.)

In part 1. We looked at tools and glues. In this part I will describe the different

sections of the plan and how the parts of a kit are numbered usually. Most Kits

these days are either produced from the original drawings from many moons

ago, and have changed little over the years except perhaps the quality of the plan

and advances in cutting the parts, either laser or cnc machined. Originally, parts

would have been either printed on the wood for you to cut around or die cut (die

crushed is more accurate). Much of the wood in the old kits could also have been

of dubious quality. An old friend of mine regularly complained of low grade

fence wood , which seemed a little mean until I got my hands on some of the

good stuff.

I will be using the FunFighter kits in many of the examples for obvious reasons

but there are many different methods of building around. The FunFighter being

designed to create the desired model shapes from all sheet balsa and carved

block. This method simplifies the whole build greatly and makes the range very

accessible to the new builder.

The FunFighter range has improved many fold in the last 12 or so years but the

format of the plans and instructions have changed little for most of the range.

This is a work in progress. The Hein is now complete and the rest are coming on

well. For the purposes of this article I’m using the Me 109. The instructions are

mostly complete with Photographs now but the plan can remain largely the same

as it is very detailed. The one issue that came up over the years being that

engines are now slightly longer than when the models were first designed. To get

over this we have included a block of half inch balsa to go behind F1. The nose

ring, in the kits.

I will put up both the existing instructions and the nearly complete version for

comparison in this section of the page. Anyway enough of the claptrap, let’s get

on with it.

As you can see in the picture above, there are top and side views of the fuselage,

half views of the wing and stabilizer (printing was very expensive way back

when) and an exploded view of the fuselage parts and how they go together. Also

some ideas on a colour scheme and suggested radio layout.

You will see that the centre of gravity is clearly marked, as are all the required

parts and their positions.

The plan itself, is used for various operations, The side view is used for marking

former locations mainly but also gives nose shape, doubler and sheeting

positions, servo location and rudder information (optional) and also wood grain

direction and part numbers.

There are various unusual quirks also. For example in some kits the actual

fuselage sides are slightly longer than on the plan. That is because the plan takes

into account, the bend in the finished side sheeting.

The top view gives possibly the most important information of all and that is the

chamfer angle on the two longerons at the tail. This is crucial for building a

straight model. Once the sides are joined at the front end, this gives detail for

when you join the two sides at the rear, Get this wrong and you have a ballistic

banana on your hands . To be honest though it’s not difficult to do as long as

you make the two sides the same length and the join at the rear meets at the right

point it’ll be fine.

You will notice that a centre line is marked on the plan. This should be

transferred onto the formers, before you start building. They will give you a

useful reference of how straight you are building the kit. On most models, the

front 3 or so formers are glued dead square to the fuselage, normally to where

the sides start to curve in towards the tail. At this point the tail end of the sides

should be pulled together and glued / clamped together.

Once this has been done the remaining formers can be put in place (where you

marked their positions remember) and glued in permanently.

Part of the beauty of building from a kit instead of having an ARTF is that you

can change things to suit your preferences. An example of this is, if you wanted

to upgrade fittings (such as follow our recommendations for racing setup), you

can do so at a convenient point in the build.

Something you should get used to is looking ahead while building and this is why

at the start of the manual, you are encouraged to familiarise yourself with the kit

parts and the build, before you start work on the model. This can take a short

while to get used to doing but pays dividends later.

In the case of the upgraded 3mm pushrods, the best time to do this is as you are

fitting the rear formers. This simplifies the fitting of the pushrod greatly as 3mm

rods aren’t very flexible. On the plan, the pushrod is shown clearly and this can

be used to make up the double one to the same measurements. I don’t fit the

other end of the pushrod at this stage though in case I want to reposition the

servos. As the carbon pushrod is a tube, you can score the servo end’s threaded

rod later and epoxy it into the tube or use a ferrule. You can just only use the top

half of the rearmost former if you like to make a clear run for the pushrod.

The rest of the plan is pretty self explanatory; the tail plan gives locations of the

various hinges, elevator joiner and on some models, the tips. Control horn

locations will normally be shown but as long as the holes for the clevises are in

line with the hinges, these aren’t critical on most kits.

The wing plan below gives you details of servo position and sizes / shapes of the

strip wood leading and trailing edges. It also details the shape to which you can

carve the tips and bend the pushrods etc for the ailerons.

A good tip when joining your wings is to ‘jig’ the tips with blocks at the leading

and trailing edges. The plans or instructions will normally give an angle to set

the wings dihedral. In this case it’s 50mm or 25mm at each tip. To achieve this,

cut four small packing pieces 25mm high and pin to the leading and trailing

edges of each tip. This process achieves two things.

1). Sets the correct dihedral angle.

2). any inaccuracies in the wing are lost at the join where they will do least harm.

Many wings are joined using white glue on the foam parts, Once this has dried

then a 2” fibreglass bandage is epoxied around the join, This needs to be done

neatly or it will show through the covering. I find that if you tack it on the

bottom trailing edge of the wing with a tiny spot of cyano it will stop the cloth

from dragging while you spread on the epoxy. Also if you apply masking tape ½”

either side of the cloth before you thinly spread the epoxy, it leaves a much nicer

edge. Peel off the tape before the epoxy goes off though eh? You only have 5

minutes. After 24 hrs or so you can sand this back to a smooth finish but beware,

DO NOT sand into the wing skin here it is the most highly stressed part of the

wing.

The design is far more than adequate to deal with racing loads even, but it is the

skin that gives it the strength.

Well I hope that all of the above has left you with a little more idea of what a

plan looks like and what kind of information it will offer you. As technology

advances and kits become more complete then detail on the plans becomes less

necessary and if you see the Hein plan which is our latest, you will see what I

mean. Carry on reading for some details below on how parts are normally

numbered and identified.

It is worth some time and effort to keep your plan safe. Your kit comes with most

of the hard work done for you in terms of cutting out the parts but if you break

parts of the model later on, with the plan handy you can trace the part and easily

make a new one. I would run off a couple of copies at the local copy shop. It costs

about £3 a copy. They can even put it on a memory stick for you.

Identifying Kit Parts.

It is good to know that when kits and plans were produced years ago, terms,

prefixes and part numbers were normally done to some kind of standard, albeit

an obvious one. Leading and trailing edges always referred to wings, tails, fins

and fairing for example.

Wings of course weren’t always made of skinned foam. The more traditional

method was to have wing ribs and spars, many of the free plans in the magazines

will give this type of build. The wing ribs were normally numbered R1. To

whatever number of ribs were required number 1 being at the wings centre.

Other wing parts were stamped with a W for obvious reasons.

Wings using ribs and spars also required sheer webs that form a box structure

and the whole is made up like a sandwich. Spar is laid down on the plan first

followed by the ribs all fitted vertically. Next the top spar goes on top and the

sheer web (either ply or vertical grain balsa) goes against the spar, between the

ribs forming a box. In the picture below you can see the three stacks of sheer

webs, next to the ribs.

Tail parts were ‘You guessed it’ given a T.

Fuselage components are slightly different. The sides will be just a part number

as it’s fairly obvious what they are. You will hear talk of longerons. These are

usually the long straight lengths of strip wood that make up the structural

framework of the fuselage.

Stringers are usually to give aerodynamic shape and are normally long and thin.

Formers are generally the flat parts that hold the fuselage sides apart and make

the aircraft rigid through its cross section. These normally start at the nose as

F1. And continue up to F8-10. At the tail. Just to confuse you it’s not unusual to

find half formers for making say, the cockpit area. Often this will be F5a. For

example.

In the picture below you can see the numbered formers on the plan of a Fairey

Phantom, notice the slots cut around the outside of the formers. These are to take

stringers that will give the fuselage its sleek rounded shape. This method is used

mainly where ultra light weight is required or for scale appearance.

Generally this type of build is done by laying down a frame or crutch to which

half formers are fixed. The stringers are then added for strength and shape

before the whole is removed from the plan. Once this is done the other half of the

formers are fixed off the plan and the stringers added to finish. This can work

very well; it was common in free flight models.

F2. Is more often than not, the former that takes the engine mount. This is also

known as the firewall and fronts the tank bay. It usually has a hole in for the fuel

pipes to run through.

When you look at the building manual, very often there will be a parts list and a

drawing of any items that are part of a cnc cut sheet, so that you can check off all

the required parts. It is at this stage you must notify of any missing bits as many

suppliers cannot replace parts once the build has started.

So, now you are all much wiser than me and are more than ready to embark

on your first or second more successful kit build. I am sure that you’ll love the

experience if you take your time and make sure you prepare well.

There may well be one or two points that I’ve missed but don’t hesitate to ask. I

sincerely would love to encourage more people to get involved in building. If

you’re lucky enough to have a workshop to use then I promise you that with the

heater on, on a cold winters day and a big mug of tea, There’s nothing like the

smell of freshly bashed Balsa wood in an aeromodellers workshop.

Have Fun.

Daren.