The Stabilizers
The horizontal stabilizers begin with the construction of the main spars. The construction of these spars is very similar to the construction of the rudder spar. After marking and cutting the plywood to shape I glued the flanges to the plywood along with the filler blocks. Positioning the blocks took some head scratching to make sure they were all in the appropriate places. The plans measurements have to be changed some to get hinges in the right places. Also, the plans call for these spars to be 46” long but the figures in the plans show 46” inches including the root rib which it shows on the end of the spar. Not a big difference but something to plan for in positioning the blocks as the blocks serve as rib supports in some cases. For the record, I chose to leave the spar 46” and inset the root rib as opposed to shortening the spar and tacking on the root rib. I also lengthened the filler blocks to make sure the hinges could be moved as need be. I used the router to cut the notches in the root end of the spars. The diagonal spars are constructed in like fashion.
After constructing the root rib I began to piece together the “triangle” of the stab. I chose to build the triangle laying flat on the workbench. I measured from the centerline of the spar to the workbench on the root end and shimmed the outboard end to the same height above the bench with the main and diagonal spars. I then clamped the root rib in place and checked that all components were vertically square and that all measurements were correct. I disassembled, glued and rechecked all measurements.
Construction
of the stab ribs is relatively straightforward. It requires quite a bit of
measuring for each rib as no dimensions are given in the plans. I made some
“extras” due to bad measuring. I made the main body of the ribs with the face
grain of the ply vertical and the nose rib grain horizontal just like the wing
ribs. Remember to check nose rib dimensions. The plans are not exactly to
scale. The #4 “sister rib” is slightly smaller than the #4 rib. There is no
pattern for this nose rib. Also, the #4 sister rib will not fit between the
spars if you glue both cap strips to the rib prior to placement between the
spars. (This is because the hinge block inside the spar limits the ability to
work in the rib.) I glued on one side and glued the other side on after the rib
was placed.
The picture at left is the left stab inverted on the workbench. The main spar was leveled on the workbench. The blocks are used to hold the ribs vertical and square to the main spar while the glue dries. The small clamps on the sister rib are holding the cap strip in place.
Next was to position the nose ribs. Temporarily placing the leading edge stringer in the nose ribs as a guide was helpful in making sure everything lined up as it should. I added 1/8” ply gussets to both sides of the nose ribs.
I laminated three pieces of maple for my wire attach blocks. Rather than notch the maple block to fit the recesses of the ribs and spar, I used spruce inserts in those areas to give me a level surface to glue the maple block to. I drilled a ¼” hole in the block as I plan to use a bushing in the hole as I did on the wing wire blocks. I am not building the folding wings so I did not add the block for the holding pin.
I laminated two pieces of spruce to use for the blocks inside the root end box. I made inserts for the spars here also so the blocks are not notched. I marked the edges of the blocks on the outside of the box just so I would know where they are when the box is closed and I need to drill holes for the attach brackets. I also fabricated the top and bottom ply covers for the box. I glued on the bottom cover and the blocks.
I also glued on the nail strips on the forward diagonal spar. I left 3/8” vent slots in the middle of each bay on the bottom side.
I have decided to use plywood leading edges on the stabs. I cut back the nose ribs to allow for a leading edge “block” that will be shaped to match the airfoil. I also notched the spar on the outboard end for the gussets between the spar and the tip bow. After fabricating the tip bow and the gussets a trial run with it all together seemed to work well so I glued the block to the nose ribs. After the epoxy was dry on the nose block I glued in the tip bow and gussets.
I had already cut the notches in the root end nose ribs for the hand- hold area called in the plans. Since I decided to use plywood leading edges, I needed to fill these notches for glue contact area. I mixed some glass beads with T88, filled in the areas using masking tape to hold the mixture until it dried, then sanded the fill flush with the rib.
I then marked a centerline on the leading edge of the leading edge block and marked the leading edge airfoil shape on the root end of the block. I then block planed the leading edge block to the airfoil shape. Afterwards, I marked the radius of the tips and cut off and sanded the tips to shape.
I
covered the leading edges of the stabs with two pieces of 1/16” plywood
per stab. After cutting the plywood to shape, I soaked what will be the most
forward edge of the plywood in the bathtub for about 2 hours. I used a 3” piece
of PVC pipe with 1” holes drilled in it as a bending form for the leading edge
pieces. I clamped about 3” of the forward edge of the plywood around the PVC
pipe and left for a couple of days with a dehumidifier blowing over it. The
plywood was then glued to the stabs with T88 and left clamped for several days
to make sure the epoxy had plenty of time to fully cure. I sanded the leading
edges of the plywood to blend to the leading edge airfoil shape. I then mixed
some glass beads with some Clear Coat sealer and spread it over the leading
edges to fill the small dips between the nose rib high spots. I notched the
rear face of the stab spars for clearance of the elevator horn. The stabs are
ready for covering.
Home The Wings - Page 3 The Elevators The Landing Gear
General The Wings - Page 4 The Fuselage - Page 1
The Wings - Page 1 The Wings - Page 5 The Fuselage - Page 2
The Wings - Page 2 The Rudder The Fuselage - Page 3