Building a flexwing boost glider (part 1)

Normally in the title of a build thread I’d give the name of the rocket I’m building, but this one doesn’t have a name yet.

I’ve been gathering information on glider recovery rockets recently: boost gliders, rocket gliders, and flexwing gliders. I’ve only built boost gliders in the past, so far no rocket gliders, and I’ve never even seen a flexwing glider. In fact I can’t recall ever having heard of them (in a model rocketry context) until the start of this year, which just goes to show how much attention I pay to competition rocketry given that flexwing duration is a Pink Book contest category.

To get the terminology straight, boost gliders are rigid gliders that are lifted into the air by a rocket motor that comes down separately from the glider — almost always in a pop pod with streamer recovery. Rocket gliders come down in one piece, including the spent motor; there are various types depending on how the center of gravity is moved backwards, or the center of pressure forwards, to go from boost configuration to glide configuration. Flexwing gliders are like boost gliders, but not rigid. Generally they go up compressed inside the booster body tube, and deploy at ejection. They look like small hang gliders.

And I just discovered the opposite of a flexwing glider rocket. Rather than a booster carrying a flexwing up, NASA apparently once tested using flexwings to bring boosters down:

Rogallo_booster_retrieve(Source: Wikimedia Commons.)

Apogee Components has a video with accompanying plans (PDF) for scratch building a ¼A flexie. The design, according to the plans, is called “¼A-Engine Flex-Wing Boost Glider”. So, ah, no, doesn’t have a name. But I’m not holding that against it. I’m building one. I have almost all the parts and materials and will get started probably by the end of this week. I thought about calling it “Flexcelsior” but then I remembered “excelsior” means “ever upward”, which is a bad thing for a glider you want to get back, so maybe not.

Not certain it’ll be legal for the Syracuse Rocket Club’s July ½A glider duration contest. Last summer’s glider contest rules said it was open to boost gliders and rocket gliders; it didn’t say anything one way or the other about flexwings. I’m thinking of building a ½A rocket glider, so I can use either or both in the contest — or I can use the Semroc Swift BG, which was an utter failure on its first three flights, but I think I can fix it; more on that later.

(Of course a ¼A model is legal in a ½A contest. Besides, my guess is the design will fly fine on a ½A motor. Maybe higher than I want it going, though.)

Further reading: Besides the Apogee video and plans, more flexwing information can be found on the NAR site in the competition guide.


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