January 11, 2013 - Making Triplane Swallowtail Blocks

I started working on the wing spars.  The Triplane wing spars run the length of the entire wing -- 21 1/2 feet for the top wing -- and carry the weight of the entire plane.  So they have to be very strong.  The Triplane has "box" spars which are basically four inch tall by eight inch wide rectangular boxes that run the length of the wing.  To construct the long box spars, I had to construct the spar table first. 

My first task was to make "swallowtail" spacer blocks.   To do that, I had to glue two 1" by 2 1/2" spruce boards together.  I used the same T-88 epoxy glue I used with the ribs. 

Here I have coated each side of the Spruce pieces. 

 
I used my old Oracle computer books to keeps the boards pressed together while they dried for 24 hours.  Might as well get some used out of them. 
 
The two pieces glued together.  I guarantee they aren't coming apart.  Now I have 2" x 2 1/2" stock. 
 
I needed two 41" blocks.  The new miter-saw is perfect for the job. 
 
Two nice 41" long blocks. 
 

Next step is to turn the ends into swallowtails.  I can't describe it.  You will see. 

To make swallowtails, I used my brand-new 3/4" spade bit in the drill press.  First time I've ever used one.  Works great.

 
Now I use the band saw to cut the ends out.  I just put a new blade in the band saw, one designed to cut wood.  It went through the spruce block like butter.
 
This is what a swallowtail looks like.
 
A little sanding and two swallowtail spar spacer blocks are done.  These are for the center wing. 
 
 
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