Building Materials, Structures & Processes.

Where to start!!??

building practices are many and varied.
First off, there is the 'old fashioned' open structure of wood, covered with thin sheet in strategic locations, for stiffness and strength.
The wood type varies with the load it has to bear, ie spruce for the spars in the wings, and main longerons in the fuselage, or balsa, for shaping and skinning.
This is then covered over with one or other of various materials, the end product being a waterproof and fuelproof skin that can be coloured to suit.

A more recent version of this is to use spruce for the main structure, but expanded polystyrene covered with a very thin skin of (usually) obechi veneer, for stiffness.
This is then covered with a skin, as above.

Glassfibre is another commonly used material, often used for forming complex fuselage shapes that would be very difficult to carve from wood.

More recently - a substance variously known as foamy sheet - bouncy foam - EPA, and various other trade names, has come into use for non-scale 'fun' models, as it deforms and springs back when it strikes a solid object, so is difficult to break, unlike a wooden structure. Due to it's flexible nature, it tends to be used on smaller models of around 36" wingspan, but with strategically placed carbon-fibre rods, this can be expanded to larger models.

All kinds of common domestic materials can be pressed into use, with a bit of lateral thinking.

Improvements in construction technique

Ask ten people how they build their models, and you will get fifteen different answers!
It's a bit of a - how long is a piece of string - question.

Commercial builders have their own favourite methods, about which i know little.
The home-builder each has his own way of doing things, and his preferred materials.
The best thing for you do do here is to browse the 'construction' threads, and you can see how things go together.

Improving a design -
The whole secret with flying models is that the weight has to be kept to a minimum, whilst structural strength has to be kept to maximum.

You could build something with more cross-members and diagonals than the Forth Bridge, but don't expect it to leave the ground.
At the other end of the scale, you could build something so delicate that if a fly landed on it, something would snap!

I cannot give you any links that will point to them, as it is not my 'field', but have a research into indoor free-flight. Some of the models used there are so delicate that they are virtually transparent. The slightest air turbulence, ie somebody sneezes nearby, and the structure can break!

Why didn't we think of this...
I suppose it is one of those things that 99% of beginners never consider.
Assuming they aren't a 'throw a tube of glue in the box, shake it, and go fly' builders, (artf)
then they will have built a kit or three, and never gave a thought to why a certain part had doublers, triplers, a D box, and a diagonal brace! The plan says stick A to B, so they do, and it usually works.
When they reach the point where the plan is in their head, and the kit is a pile of planks and sticks, they have already learned HOW, if not WHY, a part needs added support.
As a result, providing it doesn't break in normal usage, they don't worry about it. There are just the odd (?) 1% that want to know WHY, and take the study that bit further.