New title, No Chute, Sherlock! Previously SQUIRT! No recovery system!

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BABAR

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Edit 4/12, beautiful flight, proof of concept. I think the best name is, “No Chute, Sherlock.”

Okay, let's push horizontal spin to the limit.

Parts.

one BT-5: 12" long
six BT-5: 1" long

(All from one 18" BT-5 segment)
one nose cone (I will cut base off)
one launch lug


Notably absent
No chute or streamer
No shock cord
No balsa
 

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BABAR

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Learned from BackSpin. Marking the tubes roughly at the attachment site and sanding off the gloss. Doesn't have to be exact.
16174965833058693868520826065216.jpg
 

BABAR

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Tube fins paired up. Lightly glued with wood glue. Will put fillets on the INSIDE, as the outside will get sanded down.
16174973553521997213248299517912.jpg
 
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BABAR

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Trimmed shoulder off cone, with notch for port/vent hole and hole in forward body tube
16174985585253429627034600040521.jpg
 

BABAR

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Fillets on the INSIDE of the tube pairs

Also laying down glue on body tube for double glue joint.
16174995612092397514281246105468.jpg
 

BABAR

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Dremelling off the ridge.

I tried an Emory board and sandpaper, but because of the combo of wood glue and CA, a small barrel Dremel sander gets most of it quick.

I will repeat CA, the fine tune inside and out with sandpaper
16176457916974917337384523064538.jpg
16176463298926814997380812190079.jpg
 

BABAR

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That's the first time I've seen fins cut with scissors!
You know, aside from using the Dremel to sand down the ridge, this is an amazingly simple build (just hope it works!)
 

BABAR

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It’ll take a bit before I get pics and video transferred, and it’s a small rocket. But in any case, it worked. Only damage was the launch lugs broke off (i went with two small ones on one side, I think next version will go with two medium lugs on opposite sides, to keep balance.). Came down on pavement, not sure how the lugs came off, must have been from the rod.

anyway, it was fun. I didn’t think I could pull off horizontal recovery with such a short rocket WITHOUT blowing the nose off and recovering it separately. This would make a great small grass field rocket.
 

BABAR

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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 :wavingsanta:.) 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?
TurbinatorGround.jpg
TurbinatorPad1.jpg
TurbinatorPad2.jpg



 
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Dotini

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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.

On Magnus X-2, I made the fins from a 3" diameter ultra thin wall shipping tube. This means each fin is about 2.36" x 1.9" in area, and project further from the tube than on your model. I don't know about the difference in area to your model, but I feel very pleased about the high rate of spin I'm achieving, and think definitely is related to any Magnus effect. I believe, perhaps incorrectly, that longer fins provide greater leverage or moment arm for the wind to spin the rocket on its axis.

Without taking into consideration the effect upon CP, another of my nagging questions now is, would an additional set of fins (canards) placed very close to the CG bring additional spin to the rocket?
 

Funkworks

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I like this but I can hardly see it in the video. Maybe it's worth adding electronics in one of these to measure downward speed, and to light up some flasher. Because without a parachute and shock cord, these would always be harder to see.
 

Rktman

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On Magnus X-2, I made the fins from a 3" diameter ultra thin wall shipping tube. This means each fin is about 2.36" x 1.9" in area, and project further from the tube than on your model. I don't know about the difference in area to your model, but I feel very pleased about the high rate of spin I'm achieving, and think definitely is related to any Magnus effect. I believe, perhaps incorrectly, that longer fins provide greater leverage or moment arm for the wind to spin the rocket on its axis.

Without taking into consideration the effect upon CP, another of my nagging questions now is, would an additional set of fins (canards) placed very close to the CG bring additional spin to the rocket?
The canards positioned at the CG are a clever idea to promote a higher spin rate. I think it's very plausible and gets my vote.
 

Rktman

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I agree with @Funkworks that it's difficult to see on video. Suggestion: a yellow base color with a simple black roll pattern would help. Or alternately chrome mylar tape against a black background. A basic pattern akin to what @Dotini used would make it "strobe" and be more visible on the video and when tracking by eye.

That said, I DO think your current paint job is a very attractive and eye-catching one, but one better suited to something coming down on a chute or long streamer, where the recovery device would provide the major point of visibility.
 
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Dotini

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The canards positioned at the CG are a clever idea to promote a higher spin rate. I think it's very plausible and gets my vote.
Thanks for that encouragement. I think I will take that direction. Yesterday I received my 2nd Covid shot, and I'm feeling listless and lethargic. About all I'm currently up for is to complete one of my ringtails, one tiny little bead of glue once every 3 hours. :(

A significant choice I must make if I'm to go with canards is, what body tube should I use and what is my weight limit? My current BT50 model is maxed out at 4 oz, the B6-2 just barely works and the C5-3 thrust curve is all wrong for it.

So now, adding canards, my choice is go back down to BT20 and continue working with B motors, or stay with BT50 or BT55, and try the C11-3? My history of working with 24mm motors is shaky, and I've had fins explode off the model at times.
 

mooffle

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Without taking into consideration the effect upon CP, another of my nagging questions now is, would an additional set of fins (canards) placed very close to the CG bring additional spin to the rocket?
With canards what about flat plates in a 'swing wing' config? One on the top, one on the bottom swinging in opposite directions.
 

Dotini

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With canards what about flat plates in a 'swing wing' config? One on the top, one on the bottom swinging in opposite directions.
Good question! I have no idea of all the ways to increase spin. But I am convinced that it is one of the two keys to seeing the Magnus Effect in a model rocket.
 

mooffle

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Good question! I have no idea of all the ways to increase spin. But I am convinced that it is one of the two keys to seeing the Magnus Effect in a model rocket.
I was thinking do this to increase spin towards the front without drastically changing the CP.
 

Dotini

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I was thinking do this to increase spin towards the front without drastically changing the CP.
I had a vaguely similar idea of deploying a set of compressed plastic fins at the front of the rocket, shielded inside a shroud jettisoned together with the cone at apogee. I haven't rejected the idea, but complicated solutions must be a last resort after the direct approach is exhausted.
 

BABAR

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On Magnus X-2, I made the fins from a 3" diameter ultra thin wall shipping tube. This means each fin is about 2.36" x 1.9" in area, and project further from the tube than on your model. I don't know about the difference in area to your model, but I feel very pleased about the high rate of spin I'm achieving, and think definitely is related to any Magnus effect. I believe, perhaps incorrectly, that longer fins provide greater leverage or moment arm for the wind to spin the rocket on its axis.

Without taking into consideration the effect upon CP, another of my nagging questions now is, would an additional set of fins (canards) placed very close to the CG bring additional spin to the rocket?
My bad, they looked so smooth I thought they were plastic!

I am rethinking the differences between your longer curved fins and my shorter ones.

The longer fins are definitely going to generate more torque, which is a plus.

the longer fins will have more inertia, meaning they will take more energy to START turning AND at impact they will have more kinetic energy to dissipate per RPM on landing, both of those are minuses.

Regarding Magnus Force, which I think we all agree is LATERAL to the gravity vector, I think the key factor is which results in the greatest RPM. And I know personally that I do not have the physics knowledge or aerodynamic knowledge to figure that one out. There are competing forces, basically the “cupped” or concave edge always on one side of the rocket generating spin due to higher drag while the only slightly more aerodynamic “curved” or convex edge on the opposite side producing lesser drag.

I think the initial tests could be as simple as a flywheel stuck in front of a household fan. But I am not sure that the results would be the Same for different wind speeds. And those will vary depending on how fast the rocket falls.

you and I kind of went in different directions with length, your rocket has a big advantage in Magnus being longer. I was looking at how SHORT I can get and still have it go horizontal.
 

Dotini

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My bad, they looked so smooth I thought they were plastic!

I am rethinking the differences between your longer curved fins and my shorter ones.

The longer fins are definitely going to generate more torque, which is a plus.

the longer fins will have more inertia, meaning they will take more energy to START turning AND at impact they will have more kinetic energy to dissipate per RPM on landing, both of those are minuses.

Regarding Magnus Force, which I think we all agree is LATERAL to the gravity vector, I think the key factor is which results in the greatest RPM. And I know personally that I do not have the physics knowledge or aerodynamic knowledge to figure that one out. There are competing forces, basically the “cupped” or concave edge always on one side of the rocket generating spin due to higher drag while the only slightly more aerodynamic “curved” or convex edge on the opposite side producing lesser drag.

I think the initial tests could be as simple as a flywheel stuck in front of a household fan. But I am not sure that the results would be the Same for different wind speeds. And those will vary depending on how fast the rocket falls.

you and I kind of went in different directions with length, your rocket has a big advantage in Magnus being longer. I was looking at how SHORT I can get and still have it go horizontal.
My X-2 fins are indeed PETG plastic. Your investigations of shorter length are valuable, as that's also on my list of facts to establish. As length decreases, the odds of a successful backslide/horizontal spin recovery lessen - I think. But in creating Magnus Effect, I think tube diameter plays a major role in the equation.
 

BABAR

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But in creating Magnus Effect, I think tube diameter plays a major role in the equation.
ya know, that maybe the ticket.

how about this.

BT-60 or 80 rocket body, at least 18” long. The bigger tube with shorter length should be less likely to bend or crimp at ejection and landing. The larger tube ALSO should provide more surface area for drag. Most importantly, I agree it should provide far more Magnus effect (this may also be why I saw very little Magnus of my BT-5 bird.)

tube fins, but smaller diameter, maybe BT20 or 50. Unfortunately the natural identical diameter 6 around 1 won’t work, so may need 10-12 and will need some shims to get them even. The shorter hemi-span fins are less likely to break, and the leave less of a “step-off” when landing (I am really curious what caused your original crimp, the ejection of the landing? If the former, your more widely spaced vents may be the answer. Problem is, a shorter length to diameter ratio may NEED more force to pitch out of OpenRocket/Barrowman stability angle of attack, so we go from OpenRocket Stability on boost to CardBoard CutOut Instability for recovery.

Bertha type nose cone. One reason is safety, if things go South, I’d rather have something blunt rather than pointy coming down at me. Cut off the base and most of the shoulder to reduce weight, leave just enough to get a firm sealed glue joint. You could use a hole punch to make your double ports over the nose end of the tube, cross them with the nose cone shoulder, and redrill the holes through the shoulder (base is cut off and open). This strengthens the structure at the ports.

I think Eric @Rktman was talking about the DOWNside Of streamer or chuteless rockets as visibility....well, bigger rocket would definitely be easier to see!

some silver or gold Mylar tape strips extending from nose to tail over fluorescent orange or pink might show some “flash” during rotating descent for visibility as well.

possible functional issue, the huge internal volume may reduce the “puffer pressure” to the vent. May need a chimney or stuffer tube, basically a long motor mount with a forward centering ring just tailward to the port level, and maaaaaybe a bulkhead INSIDE the nose cone to seal off that volume.

imagine! A Big Bertha with small tube fins coming down no chute, not streamer, horizontal, spinning like mad, flashing in the sun, and translating sideways with Magnus Force!
 

BABAR

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I already have a more socially acceptable name for it.

the TURBINATOR!

I’ll be Back!
 

Dotini

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I strongly applaud this approach. By all means go for it!

edit: However, I would caution that you may still need to exceed 25:1 length/diameter ratio in order get your backslide going.
 
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