Carlson Skunk Works

Progress is continuing to be made. Steady by jerks as my grandfather used to say. However, doing a little bit each day during my lunch break is really helping to keep things moving.

The two front spars for the wings are now complete and the two rear spars are in process.

Sunday afternoon I spent a few hours cutting and planing the Douglas fir parts for the rear spars. All the material is now ready at hand.

However, the spar table still needed to be cleared off from building the front spars and prepared for building the rear spars. Therefore, my Monday lunch time was spent clearing the table. I pulled the blocks that held parts in place, removed the wax paper and the parchment paper. New parchment paper was rolled out and stapled to the table and a reference line was drawn the full 16 feet of the table. Then on Tuesday I drew out the rest of the spar full size on the parchment paper and overlaid it with wax paper.

The table now has most of the part for the first spar on it and I have stapled blocks of wood to keep things in place until I can glue them up. Hopefully I will be able to get some pictures of the spar as I build it, but I haven’t had a chance to do so yet.

Here are some pictures of the front spars as the plywood web was installed. As noted in my last post, there are four pieces of 2mm plywood for each web. The middle joint was lined up with the filler blocks where the struts will attach to the wings, therefore, I used a but joint in this location as there is a lot of solid wood on each side of the joint. The other two joints on each wing were scarf joints. The next few pictures show how I laid out the but joint and the finished joint.

First I marked the center of the filler block:

Then I laid one half of the web in place so that it crossed the center mark and marked the end of the web:

Here you can see how much wood is on each side of the joint:

Then the glue is applied, the web is positioned and I stapled everything LOTS!

Here is the scarfed joint toward the root end of the rib, notice that most of this joint just happens to fall across the filler block for the jury strut.

Here is the scarfed joint toward the wing tip. This joint has less support from filler blocks.

All the stapes were removed and this surface scuff sanded before gluing up the other half spar and clamping it in place. The scarf joints required more sanding than the rest of the web just to get all the excess glue off.

I will try to get some detail pictures as I build the rear spars and put them in the next post.

Here is a special picture to round out this post. Saturday was the Antique Aircraft Association local fly-in at the Minden, NE airport. Our EAA chapter was asked to serve breakfast and lunch, so I spent the day watching airplanes. One of the planes is this PT-19 owned by my flight instructor, Ed Nelson of Nelson Aviation in Sidney, NE.