If you’ve ever wondered how to build a straight fuselage from scratch with only a few basic tools, I can assure you that it’s easier than it sounds.

One of my favorite planes is the RCM Basic Trainer. Don’t let the name fool you. Just because it’s called the Basic Trainer doesn’t mean that you have to be a beginner to enjoy it. This is a four-function airplane with ailerons, and it’s pretty good looking, too. Everybody really ought to build one of these. The flat fuselage top and bottom make it even easier to build it straight without a jig.

After you get the fuselage sides and bulkheads cut out, glue these four pieces together to make a basic box. Measure the diagonal distance from corner to corner in the cabin/radio compartment. First measure one way….

If your two measurements are the same, then your fuselage is square. If not, squash the fuselage diagonally until the two dimensions match. You may have to put a squeeze on it hard enough to crack the glue, then reglue it in the right position.

After you have the radio compartment square, put the planking on the bottom of the fuselage, only in the radio compartment area. Then draw a centerline on the bottom of the plane using a straight edge.

At this point you pull the tail together.  I've found that if you do the nose first it's easier to get it crooked, and it will have a severe effect on the tail.  But if you do the tail first, it's easy to get it straight.  Just use the line on the bottom of the fuselage to line up the tail joint.  When you pull the tail together and the line points right at the joint, it’s straight. I like to use a long straight edge instead of my eyeball for greater accuracy

When you’re gluing the tailpost, in addition to being centered the joint also has to be vertical. Glue just the tip of one corner and hold the fuselage in front of you with the tail pointing at your eye. You should be able to tell if the tailpost is parallel to the vertical sides of the fuselage. Shift it until everything is straight, and then glue the whole joint.

After you get the tailpost joint worked out, go ahead and plank the bottom of the tail section. Whenever I buy balsa wood, I always get some flat sheets and some warped ones. Save the flat ones for wing sheeting and fuselage sides, and use the warped stuff for cutting up into little pieces for fuselage planking. Here’s a warped sheet of 1/16″ balsa, in case you wanted to see one.