Building the Stinson SR-9 (4)

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Last time we were talking about building the forward horizontal tail surface (stabilizer) and how a little extra effort helps all those parts to fit right. The first photo shows the entire tail surface built up and ready to be sanded. This time I’d like to discuss several of the steps involved in building the rear surface (the elevator) and preparing both parts of the horizontal tail to fit together properly later on. Since there are several images to share, I’ll present each of them with its own caption to explain what’s going on.

This is the horizontal tail assembly ready for sanding.

I’m using spacer blocks and weights to align the elevator core parts for glueing(note that they aren’t lined up over the plan right now).

Can you spot the flaw? No matter whether it’s the result of inaccurate parts cutting or my alignment error , the angled tip (balance section) core has to fit against the adjacent ribs.

Here's the fix. I cut an insert from 1/8" sheet balsa to fit between the tip core and the ribs.

The little balsa shim is glued in place. Note that the two ribs at the bottom (nearest the shim) are glued together as well as to the tip core. The top rib is part of the fixed tail, and there is a 1/16″ spacer between, under the tape.

The outer edge of the elevator consists of two laminations of 1/4″ x 1/16″ balsa. These go on one at a time. I have moistened the first strip with water to make it pliable. It’s stuck in place along the trailing edge with medium CYA and here I am bending it around the tip by rolling the elevator assembly over it and applying pressure.

Here is the entire elevator tip assembled, ready for sanding.

I have assembled the elevator against the fixed stabilizer where it will eventually be hinged in position. Notice that there is a 1/16" gap between the elevator balance tab and the angled stabilizer tip...this wil allow free control movement after final assembly. Sanding comes next.

2 Comments

  1. It has been between 50 and 60 years since I last built a balsa kit model. I’m now exposing my grand son to that hobby (12 yrs). I can’t recall how we fastened the paper to the framing. Can you help?
    Thanks

    • David,

      The simple answer is “clear dope”. For more info, go to the Building Model Airplanes page of my site and click on the top tab (not the pulldowns), then go to the PT-19 and click the “read the article HERE” link. There are two magazine texts reprined there; the one you want is the second. Also, READ MY BOOK Hey Mister, Will It Fly?…there’s lots of good stuff on covering in there.

      Bob

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