I think you'll find that most scratch builders are experinced flyers, and rarely (if ever) see a need to scratch their own trainer. Reason being is that there is a large choice of kits and ARFs now-a-days. Also, most beginners; ones who require a trainer, rarely have any 'expereinced skills' required to build an airplane. Kits and ARFs are the way to go. There are a few 60 sized trainer kits, such as the Great Planes PT 60, and there are even a few 1.20 sized trainers.

Unless you require a specific size, and for a specific purpose (other than to learn to fly) you'll be looking at kits. Forst first timers, kits are the way to go. You have everythign you need; parts, plans, and instructions. Some instrucitons / manuals even go as far as to teach some building techniques.