Hi everybody,
I currently live in Germany, and with rather strict explosives laws, I am in fact limited to C engines and one stage designs only.
Still, I am always looking for a small engineering challenge. With the C-engine limit, lots of rocketry challenges are excluded from the start (high power, payloads, clustering, staging - you name it!).
What keeps intriguing me, however, are boosted gliders, so I have put some thought into building one (for irrational reasons I prefer rear engined gliders). At first I thought about a glider with rigid balsa wood wings in delta form with a pop pod design, not unlike this Concord semi-scale design.[1] Once Id have some experience, I might have thought about adding RC capabilities.
The huge problem is the weight: If you want to have anything that looks like a decent glider even from the ground, the balsa wood wings (not to speak of the RC components) would make any design too heavy to be launched on a C engine. Furthermore all rigid wing gliders have to overcome their typical stability problems, but that I estimated surmountable. Still, huge rigid wing areas result in high drag, which doesnt necessarily help to achieve impressive performances with C engines
Then I found an old Gemini design, which was to be recovered using a Rogallo Wing.[2] Given the fact that it might be designed to use some fabric that might be used for parachutes as well, this idea seems to have a rather promising wing area o weight ratio.
I thought of a design that does not use a paraglider design (in which case it was just a parachute in the form of a Rogallo wing), but directly attach the wings to the outside of the body tube. The fabric would allow them to be folded together during the launch phase, held back by the very short booster stage (to which also the fins are fitted). The boost stage would only be about 10 cm long to fit the engine and fins. After engine burnout the booster stage would separate with the engine and be recovered with a small streamer. The separation also sets free a spring or elastic band mechanism that unfolds the wings.
I figure that this type of wing would make it harder to trim the glider for the glide phase, but it would most certainly be the lightest type of wing, and thus allow a bigger model under the given limitations.
My problem is concerned with the unfolding of the wings: The overall approach I have in mind is to have the wings under tension when folded. The booster separation would release this tension and the wings would fold up. The main problem is to create the tension. I thought about spanning an elastic band from one wing through the body tube and to the opposite wing. But I am not sure whether this is the technically most elegant solution, and whether this rubber band wouldnt require too much maintenance or changing.
Another way could be to join both wings with a hinge that has some spring mechanism, although I am not sure yet about its design and where to get the spring.
Do you know of any such design? Do you have any advice concerning the method and design of the various fold/unfold mechanisms?
Any help is very much appreciated!
Andre
[1] https://homepage.mac.com/georgegassaway/GRP/Plans/Sport/Concorde.htm
[2] https://en.wikipedia.org/wiki/Rogallo_wing
I currently live in Germany, and with rather strict explosives laws, I am in fact limited to C engines and one stage designs only.
Still, I am always looking for a small engineering challenge. With the C-engine limit, lots of rocketry challenges are excluded from the start (high power, payloads, clustering, staging - you name it!).
What keeps intriguing me, however, are boosted gliders, so I have put some thought into building one (for irrational reasons I prefer rear engined gliders). At first I thought about a glider with rigid balsa wood wings in delta form with a pop pod design, not unlike this Concord semi-scale design.[1] Once Id have some experience, I might have thought about adding RC capabilities.
The huge problem is the weight: If you want to have anything that looks like a decent glider even from the ground, the balsa wood wings (not to speak of the RC components) would make any design too heavy to be launched on a C engine. Furthermore all rigid wing gliders have to overcome their typical stability problems, but that I estimated surmountable. Still, huge rigid wing areas result in high drag, which doesnt necessarily help to achieve impressive performances with C engines
Then I found an old Gemini design, which was to be recovered using a Rogallo Wing.[2] Given the fact that it might be designed to use some fabric that might be used for parachutes as well, this idea seems to have a rather promising wing area o weight ratio.
I thought of a design that does not use a paraglider design (in which case it was just a parachute in the form of a Rogallo wing), but directly attach the wings to the outside of the body tube. The fabric would allow them to be folded together during the launch phase, held back by the very short booster stage (to which also the fins are fitted). The boost stage would only be about 10 cm long to fit the engine and fins. After engine burnout the booster stage would separate with the engine and be recovered with a small streamer. The separation also sets free a spring or elastic band mechanism that unfolds the wings.
I figure that this type of wing would make it harder to trim the glider for the glide phase, but it would most certainly be the lightest type of wing, and thus allow a bigger model under the given limitations.
My problem is concerned with the unfolding of the wings: The overall approach I have in mind is to have the wings under tension when folded. The booster separation would release this tension and the wings would fold up. The main problem is to create the tension. I thought about spanning an elastic band from one wing through the body tube and to the opposite wing. But I am not sure whether this is the technically most elegant solution, and whether this rubber band wouldnt require too much maintenance or changing.
Another way could be to join both wings with a hinge that has some spring mechanism, although I am not sure yet about its design and where to get the spring.
Do you know of any such design? Do you have any advice concerning the method and design of the various fold/unfold mechanisms?
Any help is very much appreciated!
Andre
[1] https://homepage.mac.com/georgegassaway/GRP/Plans/Sport/Concorde.htm
[2] https://en.wikipedia.org/wiki/Rogallo_wing