Tag Archives: Scarf Joint

Building Aero 3D Day 21: Ribs Glued & Scarf Joints

Today started by reinforcing the scarf joints, seen in the featured image above, using gussets which in this case is made out of wood (filler I believe). The pieces are cut to the width of the sides they are going on (1/4” in this case) and a length that goes a bit past the scarf joint on each end. You can see the glued pieces, using medium CA in the featured image above. In the image at the bottom you can see where weights were left on the spars to keep them flat.

Once that was done we moved on to the wing. Using the big ruler to help keep a straight edge we propped up the trailing edge along it… we started with the ruler at the end closest to us in the picture below (right) and pinned some blocks to support it from the other side.

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Building Aero 3D Day 20: Scarf Joints

Scarf Joint Marked

Yesterday I learned how to make a scarf joint and then proceeded to make four of them. For this model the wing is one piece; however, the spars are not long enough in a single piece so need to make them out of two pieces. Since need one for top and bottom need two of each. The main spars are made out of 1/2” x 1/4” balsa and the other two out of 1/4” x 1/4” balsa.

The rule of thumb (apparently with full scall aircraft too) is a ratio of 12:1. That is for every 1 unit of thickness you need 12 units of overlapping length. I may not have explained that well so here are the numbers for my pieces.

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