Success! Not the best video, but nice altitude, quick conversion to horizontal to slightly tailfirst.
The length to diameter ratio is about 24, so this is not really a "SuperRoc" (compare to Estes Fletcher, per HobbyLinc
- Length: 39.25 (99.7cm):
- Diameter: .74 (19mm):
so length to diameter of the Fletcher, a "standard" rocket is 53.04.
This landed on pavement, no damage at all. No bent fins or crimped tube.
So in regard to a comment by
@neil_w a few weeks ago, why use cardboard cutout when simulator programs such as OpenRocket or RockSim are so much better?
In regard to rocket stability in upward phase of flight, the Sims clearly beat the cardboard cutout. But the sims have a relative disregard for the body tube, since at near zero angles of attack, the body tube doesn't present any direct surface area to the airstream. But Horizontal Spin (and BackSlide) rockets use the ejection charge to "kick" the nose sideways. At this point it starts to tumble, and initially ALL rocket surfaces including the body tube are in play.
For a SuperRoc with a long body, the effect of the body tube will potentially be enough to cause the rocket to BackSlide, because the cardboard cut out CP will be IN FRONT of the CG. The rocket tries to fail TAIL first, but the fins hold it up (at least that's my story, I'm sticking to it until
@Rktman corrects me
.) For shorter rockets, NORMALLY the greater surface areas of the fins will tip the rocket more and more nose down until it goes ballistic and lawn darts. With however the fin arrangement here (and on
@Dotini 's wonderful Magnus Rockets), the rocket while falling starts to spin around the long axis of the tube. Conservation of angular momentum as the rocket falls turns the rocket horizontal to the direction of fall.
Previously I have done this with ejecting the noseweight, but
@Dotini has proven it can be done WITH the nose in place.
Differences THIS rocket has from the Magnus series.
This is has much smaller length to diameter ratio, so it proves you CAN keep the nose cone (nose weight) on AND still achieve horizontal recovery with a relatively short rocket.
Advantages here are that with a shorter rocket you are less likely to crimp or bend the body tube at two critical phases of flight, first at the ejection puff when there is a relatively violent lateral rotation of the rocket from the gases vented through the unilateral forward port. Second, when the rocket lands, since the fin unit is wider than the body tube, it the rocket comes down perfectly horizontal the fins hit before the tube, which could cause bending stress.
Another difference is the use of cardboard tubes instead of balsa or plastic fins. I think
@Dotini 's solution with plastic is excellent (versus balsa), as these rockets come down with considerable ROTATIONAL velocity. Balsa would almost certainly break unless heavily braced or otherwise reinforced. Plastic is stronger, may bounce, and his direction of curvature also makes the rotational impact on the curved BACK of the blade, rather than the forward EDGE of the blade.
A third difference which I don't quite understand is that the Magnus effect, if any, from this rocket is FAR less impressive than
@Dotini 's models. Mine seem to spiral, I am wondering if there is MORE Magnus effect from the fin can and LESS from the shorter body tube, so the asymmetry in Magnus force makes it "turn sideways" more at the back than the front, so it spirals rather than moves straight laterally. His Magnus effect is CLEARLY evident and definitely cooler to watch.
Plastic is definitely stronger than my body tube segments, BUT, the body tube fin cutout does have a few advantages. The MASS of the fins is much less, so the rotational kinetic energy (particularly at the edges of the fins) is much lower. I think this helps two ways. First, it takes less energy for the cardboard tube fin "turbine" to "spin up" in the first place, so perhaps the rocket may not fall so far before it achieves enough spin to GET to horizontal attitude. Second, there is less energy to dissipate when the rocket lands, so less energy to CAUSE breakage.
Anyway, aside from featherweight rockets, saucers and backsliders, there are very few rocket designs (to my acknowledged far from exhaustive experience!) that can go from vertical flight to a safe descent mode WITHOUT some mechanical change to the rocket physical structure (typically ejecting a chute or streamer, for tumble shifting the motor, for helicopter or glider deploying blades or for
@burkefj kicking in the elevons or some other glider change.)
I think this would make a nice rocket for small grassy fields.
Anybody want to try it?