Repairs, repairs, repairs...

 Let's face it - if your model airplane lives long enough, repairs will be necessary.  Hard landings are a fact of life.  So is "hangar rash", pet damage, or the ceiling hook that comes out at an inconvenient time.

This can be a problem - or an opportunity.

This Sopwith Pup tail doesn't look bad, but it's actually badly broken under the covering.  That's because the plane nosed up and then over after too fast of a landing.  The fin and rudder outlines are soft 3/16" balsa.  Kit makers love this stuff, because it's easy for their dies to punch through.  Structurally it's a poor choice for the job.

The plane needs a new fin and rudder.  Since they're off, might as well put some positive incidence in the stabilizer to get rid of the down elevator deflection we've been flying around with.  A razor saw and permagrit sanding tools (not shown) make short work of this.

Here's the new fin and rudder outline being tried on for size.  A solid 1/16" sheet balsa web will be much more resistant to crushing, and only adds a little weight.

The web pieces with hinge pockets cut out, and frame member locations marked.

Outline pieces (1/16" balsa cut out with scroll saw) added to one side.  Ribs are 1/16" square basswood.  Only a little heavier than balsa, much more dent proof.

Upright piece on fin and rudder tip are plywood for extra strength.

One advantage is you automatically end up with hinge pockets in the right places.  No slitting or hogging out required.

The finished repair.  Also replaced elastic thread rigging with steel fishing line used for wing bracing wires.

With the incidence angle correction, plane flies better inverted and will also do outside spins.  Better than new!