Month: June 2016
Now that the ribs are complete, they are set aside and I have spent my time on the front spar.
As I am doing this for the first time, I had to decide how to bevel the top and bottom of the spars to 10 degrees. Table Saw, Circular Saw or Trimmer?? Answer, Trimmer. Perhaps slower but more accurate.
The first picture is the first round of trimming for the cutout for the steel attach bracket. Top and bottom sides are bevelled to 10 degrees. Second picture shows how I used the untrimmed rear spar to be the guide for the trimmer. Third pic, ply doublers completed and trimmed to 10 degrees top and bottom.
I had plenty of trouble glueing the doublers to the spar. They are big surfaces and the T88 would move between the spar and doublers which meant they kept moving. I tried clamping them in the spar racks, but that didn’t work. Flat on the table was better but still they moved. In the end I clamped each side to hold them with weight applied on top to hold them onto the face of the spar. It was a bit of pain. But they are done now. Well drying anyway. Next task a finish sand and filing of all the faces to make them perfect.
Oh BTW the steel brackets dont have the sway wire and stagger wire attaches welded to them yet. Figured it would be easier to drill the spars without them. They are made and will get welded later.
I have set myself a little mini project. Amongst all of the pieces required for the centre section, the ribs are going to be critical. There is four. Only two attach directly to the front and rear spars, so I am taking extra care with these two big 1 1/4″ wide ribs. They will be what sets the correct sizes and squareness of the whole centre section.
Step 1: After cutting the ply sides and routing the capstrip, I glued the front and rear sections for each rib against a completely square external frame. This makes sure the faces and lengths are exactly correct. I used the edge of the table to make the centreline square. Clamped, glued the spruce blocks, clamped them and removed the frame so it didn’t stick.
When I get started….it gets messy in here. Its going to be tight in the plane factory later on when I get to the wings!!
Step 2: Glue in the capstrip and reinforcing spruce
Step 3: Once dried, I then sealed the inside of each of the ply pieces and capstrip that is exposed. Picture below is the completed glueing, masking and one coat on internal surface
Step 4: I have drilled breathing holes in each of the rib sections. There is only holes on the outboard sides of each rib. You can see them in the picture above
Step 5: Glue the remaining outside piece of ply, sand and seal the outside faces of the ribs,with the exception of the faces contacting the spar and spar attach brackets
Note the cutouts and drill holes to attach to aluminium on the outboard ribs will be drilled when in place.
As I get close to ending the shaping of the plywood pieces the next step has been to begin glueing some of the ply pieces together. The process began with cutting, shaping and trimming the ply pieces, shaping the capstrip and spruce reinforcement parts, then glueing them together to make the pieces that will be used on assembly of the centre section. Pics below show glueing the double thickness trailing ribs of the centre section and the method I have used to ensure the front and rear faces of the 4 ribs of the centre section are square.