I started with an Autocad file and tweaked the splines until I got something that I thought looked enough like an engine nacelle. I then cut out pieces of cardboard and cut slots in them, creating halved joints, so they could just slip together without any glue. The picture on the right shows what it looks like. The solid top represents where the glass will go, and I used a scrap turbine section to add some visual effect at the bottom.
The table will actually have a 120 degree cutout in the front where that lower rib is. If you look closely, you can see that the 2nd rib from the top is actually 2 ribs thick. I was trying to make some sort of door, but that isn’t feasible.
After I was satisfied with the mockup, I used my table saw to rip strips from a sheet of styrofoam insulation with a 10 degree bevel along the edges. I then cut those pieces into segments that were 4″ high and glued them to form a rough hoop. I fashioned a band clamp from a ratcheting tie-down and then stacked all the hoops once they were cured.
Here they are in my office. I thought that the cardboard one might actually make a neat trash can base if the top piece were taken off. Of course,the top piece would also have served as a nice lid. So maybe I’ll do that some day.
The next challenge was how to contour the foam into a smooth nacelle shape. After some thought, I made a faceplate and glued it to my lathe.(purchased with this project in mind) I then carefully turned the outside smooth to match the cardboard template I made from Autocad.
Once the outside was smooth, I had to do the inside. For this, I clamped a 2×4 to my table saw and ran it inside the nacelle to act as a tool rest. I then one-handed a metal file vertically inside to smooth it down. This worked out really well for a while. Unfortunately, my file was just shorter than the inside diameter of my nacelle. At one point, I let it slip a bit, and BANG! The file got caught between the nacelle wall and the tool rest and shot through the side of the nacelle and broke into pieces against the garage wall. (Several Expletives Followed, as well as a quick “Are you ok?” from my wife. Luckily the sound did not wake the baby)
Here is a picture of my mistake. Now all I learned from this was not to use a tool that is nearly the size of the piece you’re working on. This was really not a catastrophic end to my project because I was going to cut out a section anyway. It just made everything slightly out of balance. At 600 rpm, however, this was not too much of a problem. What I did to mitigate the vibrations was stand the table on the floor and put weights on the inside wall opposite the hole until the nacelle balanced vertically on the small faceplate threads.
After the contours were smooth, I had to coat the foam in wood glue, because you can’t apply Bondo directly to EPS (foam). The Bondo will dissolve the foam and ruin the contours.
I went through probably a quart or so of Titebond 2. Then about half a gallon of Bondo to get it all covered. The picture on the right shows the uncoated, white foam. The yellow part on the left is the wood glue, and you can see the wood glue on the inner wall through the hole.
The beige stuff is regular Bondo, and I chose not to coat the whole thing because that’s where the cutout will be. That stuff is fairly expensive, so less waste this way. I did have to re-balance the table at this point, because the glue and Bondo really is quite heavy, and throws everything way out of whack.
Oh, the disk on the far right is just Lauan plywood that I cut circular on my table saw. The late faceplate is screwed into the back of this. My lathe doesn’t quite have enough swing over the bed to turn this unfortunately.
Oh, and here is a picture of how I turned the outside. I cut a groove into a 2×4 and sat it on my tool rest and clamped it down. The motor is set to the 90 degree position because that was most convenient. By the way, DO NOT turn foam without a vacuum running and a fan to blow the chips away. The foam goes everywhere and static clings to absolutely everything.
I had to pause this project because it was time to build a cardboard boat for 2014.