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 Sailplane Construction Project Session #94

Comet Sailplane Project
Today I started working on interfacing the wing saddle's 3/16" balsa platform with the top of the pylon structure. The pylon's 1/16" side planking first had to be trimmed to match the pylon's center frame contour as shown below. Two 1/16" holes were drilled in the top of center frame for alignment purposes as shown below.
After the three pieces of wing platform were glued together and sanded, a  line was drawn down the center. Two fore and aft 1/16" holes were drilled to match the those in the top of center frame and 1/16" dowels were then inserted to align the wing platform with the pylon structure as shown below.
Since the wing platform has to make good contact with the 1/4" center frame as well as the 1/16" planking on either side of the pylon, a second alignment check must be made to insure that the wing platform on top of the pylon structure will be parallel to the stab platform before gluing the two together.
To accomplish this, two holes were drilled in a length of 1/2" aluminum angle, which was bolted to the forward stab platform's plywood plate with 4-40 nylon bolts and steel nuts as shown below. Using two construction steel square blocks, the aluminum angle was strapped to the steel blocks with rubber bands as also shown below.
Then an inclinometer was used to check the level of the stab platform as shown below.
In this close up, the inclinometer reads essentially zero degrees as shown below.
The inclinometer was then placed on the wing platform to check its reading and after several iterations of set up, trimming and sanding, and set up, etc., the inclinometer read essentially zero degrees with the wing platform sitting on top of the pylon structure as shown below.
At this point it was time to glue the wing platform to the pylon structure. Aliphatic glue was spread liberally down the center of pylon's 1/4" frame. The wing platform was place on top of the pylon structure and the two alignment dowels were inserted. Here is where the procedure gets kind of tricky. CA was used to spot tack the wing platform to the side planking in the center. A very quick check was made to be sure the platform was not tilted. CA was then used to spot tack the wing platform to the side planking at the front and in the back. Again check was made to be sure the platform had not tilted (this looked like a Chinese fire drill). Once the wing platform was tacked to the side planking in a number of places, I checked the alignment one last time. Now I like inclinometers as well as the next guy, but there is nothing like a good old fashioned visual check as shown below.
Finally measurements were made at the outside edges of the work table surface up to aluminum angle on the wing platform. These measurements were essentially equal within the limits that I could measure.  Once I was satisfied with the wing platform's alignment, CA was applied to the entire length of the side planking on both sides. Well guys, that is it for today.....................Tandy

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