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SS1 Vertical Stabilizer Assemblies
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The vertical stabilizer assemblies are extremely complex. In addition to the structures themselves, they will contain the control surfaces (elevators and rudders), wiring, and servos. They need to be lightweight, yet strong enough that they won't fly apart during the rocket boost or crumple upon landing. And they need to be perfectly aligned with the airframe and the airfoils.
Our cousin John made the first pass at making a set of booms.These had a plywood core and foam sides. The foam was to be be shaped and covered with fiberglass.
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Unfortunately, there was miscommunication between John and me, and the beautiful work he did was the wrong size. (This is one of the risks of a project that is constructed is multiple locations with lots of contributors. I'm surprised it hasn't happened before.)
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After living with the plywood core booms for a while, I started noodling on a few different ideas. The thin luan plywood was a lot heavier than it should have been, given the amount of reinforcing that would be required to keep if from flapping in the breeze as it flew. So I decided that a foam core would be preferable.
I cut the outline of the vertical stablizer booms with the hot wire cutter. (Not shown -- click [HERE!] for details.)
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I cut the outline of the vertical stablizer booms with the hot wire cutter. Next I used a 3/8" radius router bit to round the edges. It takes a gentle hand and to keep the router from shredding your styrofoam.
My router table has an attachment on the guide that accepts a vacuum cleaner hose. That saves a lot of clean up, because the foam bits get everywhere.
But cutting and shaping the booms is the easy part.
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The real strngth and rigidity of the booms will come from the fiberglas skin; but when it came to mounting the the booms onto the airfoil, and also monting the horizontal stabilizers onto the booms, I needed a sturdier base than foam with a fiberglas skin.
I made plywood plugs for each mounting location. I also used angled aluminum to run as a strut between the two mounting locations to help bare any stresses and and provide some lateral strength. The aluminum is very lightweight - the plywood not so much, but there isn't a lot of it.
This photo is of the front mount. The holes align with the ends of the tubular aluminum struts that run from wingtip to wingtip through the airfoils.
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The mounting point for the horizontal stabilizer. Notice the channel cut into the styrofoam. The angled aluminum strut sits flush with the surface of the foam.
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Here is the inner and outer view of the mounting locations installed into the foam core.
The mounting pieces are flush with both sides of the booms; this way they will become integrated into the entire fiberglass skin once it is applied, as will the angled alumninum strut.
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I glued the assembly in place so that they wouldn't shift around on me when I started fiberglassing. It doesn't add any strength to glue it to the foam, but it will make things easier later on. There is nothing like being up to your elbows in epoxy and realixzing that your work is coming apart.
The cores are sandwiched between sheets of polypropylene on the floor of my garage in order to keep things flat and flush. The 45-pound weights have been used countless times for tasks just like this. I have no idea where they came from.
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The next step is to apply fiberglass to the foam. Here I am using a pattern to cut the fiberglass cloth before applying it to the foam core assembly.
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I always feel quite good about getting that first layer of glass on a foam core assembly. First off, if is less likely to get damaged from my infamous clumsiness as I ricochet around my workshop. Second, the added strength on the part suddenly makes it feel like a real piece of a rocket
The booms will be covered in three layers of fiberglass - two layers of 6oz glass and one layer of 3oz glass. If you don't know a lot about fiberglassing but are composite-curious, there is a lot of documentation about it elsewhere on our web site. Click [HERE!] to learn more.
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To see how these parts get assembled with all the others, click [HERE!].
INDEX
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