How do you go about designing an aircraft?

Aerofoil sections follow trends too. Prior to computers, people sketched out a shape using the TLAR principle. But nowadays it is possible to design foils to meet certain design criteria. You'll need to understand how to interpret 'polars' in order to understand how different aerofoils will behave in terms of lift and drag at different angles of attack. When you understand the polar you will begin to see why one aerofoil might be better than another in some conditions but the opposite might be true when the conditions change.

You might want to google the following...depending how deep you want to delve!

Dr Mark Drela
UIUC Airfoil data site
Airfoil tools
xfoil
Selig/Donovan
Dr Helmut Quabeck

And to answer a couple of your original questions...
Yes, NACA aerofoils are referring to the NACA that became NASA.
HQW 1/8 Mod is a Helmut Quabeck section that has 1% camber and is 8% thick. His earlier sections were named HQ 1/8, for example, and their coordinates are freely available to download. With the advent of PC's and aerofoil plotting software, he realised that there was money to be made and tweaked these sections and added the W to their description. The coordinates of the W series of aerofoils can only be had it you pay for them.
The Mod is a phrase just means it's been modified. The designer will rarely say how it is modified and sometimes it just means "by the time you've finished building and sanding, it will be modified".

Chris001 wrote: none of that fuel mellarky

Now either you meant to write "malarky" (noun: = meaningless talk; nonsense) or intended to write smellarky. As your a sworn and dedicated electron burner I would suggest the latter.

Either way you are digging into a minefield of printed data and in the end you get "brain overload" and it will just give up. How do I know? Been there when getting into( or trying to) understand Linux code for Apache servers. many years ago

Chris - Going back to our earlier discussions:
The models I designed were control line combat models in the late 50s
and early 60s & were my variations of existing designs.
I have dug out 4 model books published between 1960 & 1980 which you will enjoy
browsing through. Articles on basic design, how to get started and model aerodynamics are among
the many subjects covered.
I will box them up & leave them in the hut for you next time I go to Cashmoor.

Colin.

Hi Colin, that's really kind of you, thank you so much. I'm sure there will be loads in them to help me understand some of the principles of aerodynamics and aircraft design.

Chris

Martin Simons book arrived today, a light read it is not But that was what I'd hoped for, and I am expecting to have to put some work in to understand it. I just wish I'd paid attention in my physics and maths classes :pinch: