#5 ½ jack plane. This is a really nice size that can do all the jack plane jobs and also function as a small panel plane for flattening panels.
When set up with a more cambered blade, it excels at initial roughing work. Your arms wont feel like limp spaghetti from throwing a cast iron plane around all day. Light weight=good.
See our ‘plane adjustments’ page for all the details and video.
#5 ½ : 15″ long with a 2 1/4″ wide blade.