Carlson Skunk Works

September 14th, 2009

AMF-14H Maranda SN:1026 Construction Log September 14, 2009

Posted by Roger in AMF 14H Maranda SN1026, news

Well, the past couple of weeks has seen the assembly of the wing rear spar frames and the webs for the rear spars. Therefore, progress continues to be made.

The webs for the rear spars were scarfed last week and the assembled spar frames were sanded. This was a bit of a project since my wife has banned any further sanding in my basement work room. Therefore, I had to bring the spars up to the garage for sanding, then clean them off and bring them back to the basement.

Here are some pictures of the wing rear spars during construction:

This is the long view showing everything ready to be glued. I built two of the spar frames like this and will apply the webs to opposite sides so that I end up with right and left spars.

This shows the filler block for the jury strut attachment.

This is the root end of the assembly. I put a stop block at this end to provide a good reference point for other measurements.

Here is the center of the spar where the strut will attach. I cut the filler block a bit long and ended up having to fit the compression strut fillers at rib position 8.

Of course, the tip end of the spar. I ended up using a piece of left over 9mmX18mm material from the front struts to make the end of the spar. Once the glue had cured I sanded it down so that it is now level with the rest of the spar.

Once both of the rear spar frames had been glued and the glue allowed to cure, I cleaned off all of the wood blocks from the spar table. I then took the web material and laid it out for gluing. I left the parchment paper and one layer of wax paper on the table. I ran one web down the left side of the table and the other down the right side of the table.

Before I scarfed the web pieces I marked them so that I would know which pieces went together and in what orientation. That way I made sure the grain was running in the right direction.

I went over to Menard’s and picked up a bunch of clamps. Then I started at the root end and clamped the first piece of plywood to the table, scarf side up to accommodate applying glue. I worked on both webs at the same time, so the joints lined up as I went along.

Then I fitted the next piece of plywood so that the scarf joint was nice and level and smooth. At this point I clamped the second piece of plywood to the table. Next I lifted the end of the second piece of plywood and applied the glue to the joint. When I had glued the first joint of both webs, I laid a piece of wax paper across them, put a short board across the table and clamped the board over the joints. This should apply an even pressure across both scarf joints.

Then I moved on the next joint and continued working my way toward the tip end of the webs. As I moved down the web I moved any extra clamps along with me. I tended to use lots of small clamps to keep the web pieces from moving while I glued the joints. I ended up with four scarf joints in each web.

Unfortunately, I forgot to take any pictures of the process. I will try to get a picture of the fully clamped webs for the next post.

September 2nd, 2009

AMF-14H Maranda SN:1026 Construction Log September 2, 2009

Posted by Roger in AMF 14H Maranda SN1026, news

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.