Well the monthy club launch was called off so I needed something to do on a windy Saturday besides the usual weekend chores. I didn't want to do another Estes downscale and I didn't want to start anything that would take too long. I am a big fan of the Pemtech designs and I thought that a shrunken 3FNC might fit the bill for a quick project and a fun build.
I didn't have any dimensions to go by so this is really a 3FNC inspired build rather than a true downscale. Call it a homage.
I started with a quick cad drawing to come up the dimensions that I would use for the build.
After looking at the dimensions on the cadd drawing I realized that this build might present a challenge or two. For one thing the airframe length only came to .825 inches and I needed to fit a motor mount, the nose cone shoulder and shock cord. There was not going to be any room for a recovery device so this would be a nose blow recovery design.
I found a little more room by extending the length of the motor shroud slightly. I also decide on a 3/16 shoulder for the nose cone. Even with these considerations I would only have about a 1/4 inch of clearance between the top of the motor tube and the bottom of the shoulder.
With the dimensions finalized I went back to cadd to lay out the shoud pattern, some centering rings and the fin patterns. I printed the shrouds and centering rings on heavy card stock.
Next I cut out the shroud, formed it and glued it. I also cut out my centering rings. I then got out my tube cutter and cut a piece of BT-5 for the airframe, a one inch length of T2+ for the motor tube and a 1/8 inch length of T2 for a motor block.
On to the fins. The fin patterns were printed on plain paper and cut out. I then selected a piece of 1/32 basswood from my pile and used some 3M GP45 spray adhesive to glue on the patterns following the grain. The fins were cut using a sharp #11 blade and the patterns were peeled from the wood.
I was getting close to having all of the parts together for the build I just needed a nose cone. I went back to the wood pile to find a piece of 3/4 X3/4 balsa. Dang it! I was out! So I settled on the next bigger size I had on hand, 1X1. I took my balsa block back to the workshop and cut off a 2 1/2 inch piece and marked the centers to prepare it for the lathe.
The block was placed in the lathe, rounded off, rough shaped and final shaped to nice gentle ogive form. While still on the lathe I sanded it smooth with 400 and then 600 grit. The final exposed length came out at 2.25 inches which is just a tad more than 4 to 1 or just a tad short of a scaled PML 3 inch cone which was my model. I looked at it and decided it was close enough.
I needed just one more part, a launch lug. I took a 1.5mm drill bit and put three wraps of plain paper around the shaft. I backed it off two wraps applied a tiny amount of Elmers and rewrapped it. I carefully removed the drill bit and set the lug aside to dry.
I now had all of the components needed to complete the build.
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