The Elevators

The elevator spars build like the spars for the ailerons and the rudder. Basically, two pieces of 1/8” ply sandwiching spruce edges and doublers. I matched the doubler locations with the ones on the horizontal stabs so that the elevator ribs align with the stab ribs once everything is put together. I sealed inside the spars and drilled vent holes in the plywood that will become the aft side of the spar. I also marked the location of all doublers on the outside of the spar for later drilling peace of mind.

I decided to drill the spar holes for the hinges prior to any elevator assembly. Using the method described in the plans and the EAA magazine articles written by Mr. Bowers worked pretty well here. See the horizontal stabilizer page for more info on hole locations.

The elevator bows build like the rudder bow. Lay the shape out on the workbench, cover it with waxed paper, drive nails around inside of arc and glue them up. It was hard to get a good scale from the plans. I suspect that photocopying the plans many times has distorted what scale may have been used. I found that the plans gave a good general idea of the shape and from there it was a “bend to suit” proposition. I think the key is the 18” distance at the inboard end. I also found that with help and some fast gluing, you can glue all laminates at one time for one side.

After cleaning the excess glue from the bows and positioning the bow in the correct relation to the spar, I cut the outboard end of the bow to mate to the spar. I notched the outboard 4” of the spar ¼” top and bottom for ¼” plywood gussets. I will notch the bow 1/16” top and bottom for a good fit as the bows are 5/8” thick and the spar end is 1”. I also fabricated the bow to spar gussets.

A friend suggested a neat jig to center the bow over the spar. This jig helps hold the bow at the right height above the spar, which is necessary to measure exact lengths of the ribs. It will also be helpful when the time comes to glue the assembly together. The jig has a cutout that fits over the root end of the spar and a cutout at the top in which the bow rests. With the spar and bow in the jig, I marked the locations of the ribs and measured for their correct length. By the way, when I started this project I had hair on top of my head. (Gussets are not yet glued in place in these pictures.)

Fabrication of the ribs is just like the fabrication of the rudder ribs. With the bow and the spar in the jig, the ribs are glued in place. I used ½” corner blocks on the inboard side of the ribs. I chose not to glue the bow to spar gussets in place yet as I think it will be easier to sand the bow and spar for the gussets with the bow glued on first. After the glue dried the outboard end notches and bow were sanded to fit the gussets permanently.

The elevator horn needs to be permanently attached to the spar at this point. This part becomes pretty involved as several things need to happen at once to glue on the horn. First, the holes have to line up. I did not want to permanently attach the bolts at this point to make it easier and neater to cover the elevator. I put a light coat of petroleum jelly on the bolts to keep them from sticking with glue. Also, the end ply plate was glued on at the same time. (A couple of plans notes: fig. 3-7 shows the end ply cover dimensions as 3”. This cannot be correct as the dimension of the horn is 2 ½” in fig. 3-8 and the spar is ¾”. I made mine 3 ½” – look at it before you build this plate. Also, the cap strips that go top and bottom of the horn are called as ¼” square in fig. 3-7. These need to be 1/8x1/4 to allow for the 1/8 ply that will go top and bottom of this plate. There is no room against the horn to make the ¼” stuff work here. The ¼” square is fine for the strips that run along the rib itself. I failed to realize this prior to gluing this together and as the pictures show, I get to trim this piece in place when I notch the inboard end of the spar for the top and bottom plates.) With the horn in place, I cut the bow on an angle so that the end rib will lay flat against the bow.

Next, I notched the end of the bow and the spar to accept the top and bottom covers of the end rib and glued them in place. I also added balsa filler to the bow to help the transition of the outboard gusset to the bow and sanded it all to shape. I also sanded the bow to the same bull nose shape as the rudder. Two coats of Clear Coat sealer and they are ready for covering and hardware.

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