Happy new year! Best wishes for 2019!
I start a more detailed technical report. Not only because I want to advertise my design but additionally because (I think) some people want to design and built their own planes. So this technical report (maybe) will be useful.
I like planes since I was a child and I want to build my own plane. My studies at university (i am a civil engineer) was useful throughout the design. It required to study structural analysis and it is highly recommended study finite element analysis for someone who wants to design a plane. You can design a plane with classic structural analysis and hand calculations but you need a finite element analysis software if you want to solve a sandwich structure and/or to run a flutter analysis. Theoretically, you can solve anything by hand calculations but you will spend a lot of time. It is not possible in the real world.
Also before you choose the software you have to choose structure materials. Because some software isn't solving laminate materials (if you want to build a composite aircraft).
There are a lot of software out there which you can use. From free open source to very expensive commercial like ansys.
I go with open source and low-cost commercial software because I don’t have enough money to buy expensive commercial software and I believe that open source is the best choice (personal opinion)
So I choose Lisa fea software for structural analysis, code aster for non-linear structural analysis, xfoil for airfoil analysis, VLM software for 3d simple analysis (avl or xflr5 aero vsp, or a cheap commercial like Hanley innovations) and OpenFOAM for computational fluid dynamics.
After that, I start to study regulations to make sure that I will design a good plane for me.
At the start, I dream to build a four-seater plane but I think that it is really uncommon to fly with 3 other people, also a four-seater is experimental and it is more expensive to own it, for these reasons I go with the ultralight. But because maybe in future I will need a four-seater, I design it as a four-seater. 2 seats for adults in the front area and 2 seats for children or light adults. Additionally, I plan to build a kit and USA is a very interesting country because it has a lot of excellent homebuilders. For this reason, I designed it as lsa, but strong enough to carry 2 extra children and light enough to fly in Europe as an ultralight. Also, I have to make a low time and easy to build kit, so a well and simple designed composite laminate structure, will be a good choice (maybe the best one).