Why do spools fly?

[THier]

OK,,

What is the theory behind spools?

They will fly as spools,, if you remove the top plate they won't fly,,, if you remove the base plate they will fly. Can't be base drag,

Tom

[rokitflite]

No matter how many times I see one fly, I still hide behind something when the countdown starts.

[rstaff3]

I thought a spool without the top plate would fly. Why should this be much different that an Art Applewhite Delta saucer with really long motor installed (hanging out the front)?

Spools rocket be the safest rocket of this type I've seen. The only unstable ones I've witnesses spun end over end and still went it an upwards direction. By 'this type' I mean saucers, pyramids, cones, etc.

[les]

Why do spools fly?

Because someone stuck an engine and igniter in them...:p

[The EGE]

Circular plates, IIRC will put the CP 2.2 plate diameters behind the plate. So short spools *may* fly with only the front plate.

They'll almost definitely fly with only the aft plate; as Dick Stafford pointed out, it's just like a saucer with an extended forward tube.

It is base drag.

I still do a double-take when I see one fly. But they fly incredibly stable. Just watch out for wind gusts, they can push the flight over. They don't weathercock.

[rstaff3]

I've seen the front plate only work but have never witnessed the bottom only. I thought Lance Alligood had successfully flown both. But the base drag business makes sense for either. A few years ago someone was selling a wind tunnel report on spools. I think the link is on by blog (the big stability post).

[THier]

Why do spools fly?

Because someone stuck an engine and igniter in them...:p

Good point,,, smarty pants,,, (keeping it "G" rated)

Tom

[rstaff3]

Good point,,, smarty pants,,, (keeping it "G" rated)

Tom

That answer didn't even make sense. I've put motors in plenty of stuff that didn't fly. Well, at least as expected. :y:

[THier]

That answer didn't even make sense. I've put motors in plenty of stuff that didn't fly. Well, at least as expected. :y:


Good point Dick,,, How true,, I remember someone burning up a good portion of the field,, and launch equipment,, and an engine is a mechanical thing,, we use motors,,, but that is being too picky.

Tom

[Scotty Dog]

I saw a cow jump over the moon .A chicken cross the road. And a spool fly. My life is complete. :D Scotty Dog

[shrox]

Why do spools fall in love?

[MarkII]

The spool on the hill sees the sun going down...

Mark K.

[Scotty Dog]

Why do spools fall in love? Because they spool around .

[powderburner]

Why do spools fly?

Because someone stuck an engine and igniter in them...:p

(I am only angry because you beat me to this obvious answer)

From what I have seen of the spools I have launched, they are stable (sorta....they still wobble around a bit) when the motor is firing but immediately go unstable at burnout.

It is my theory that what we are seeing (under powered flight) is a strong jet-pumped ring vortex that attaches to the aft face of the lower plate. (Think of it as a donut-shaped swirl of air with the motor exhausting through the donut hole.) Airflow passing the edge/perimeter of the aft plate tries to turn the corner toward the center, and is also pulled inward as the motor exhaust tries to entrain ambient air. The resulting ring vortex is stuck to the bottom of the plate by local air pressure, and the outer "face" of that same vortex effectively forms a cylindrical surface that acts as an aft stabilizing fin. When the propellant burns out and the high-velocity exhaust is no longer there to pump and maintain the vortex, the vortex dissipates and the spool is no longer stable. (Someone else may have already thought of this reasoning.)

[Micromeister]

They fly because they have burning BP or AP thrusting behind them LOL!!

and Yes they'll fly without a forward plate also. Like the thumb-tack. but note the distance the motor hangs from the rear. more like a forward plate to me...

[H_Rocket]

Well, you can do HPR on a spool

Here is the Armageddojn Industries Spool o'Doom on a Loki I110 Moon Burner at Red Glare.

[Ironnerd88]

Why do spools fly?

Start here...

http://www.apogeerockets.com/education/downloads/Newsletter154.pdf


It's mostly about using RockSim, but it does have useful information.

[powderburner]

Start here...

http://www.apogeerockets.com/education/downloads/Newsletter154.pdf


Apogee shares lots of useful info, but in this case Apogee/Levison may have missed the mark a bit.

Their description of the phenomenon ("...dynamic center of pressure (cp) of flat plate lying perpendicular to a flow lies behind the plate along its central axis due to a base vortex that forms when the air begins flowing over its surface") reflects a mistake that is easy to make. Think of it this way: if the stability was due to the described airflow, the spool would be stable all the way up....and all the way back down.

If you watch a spool configuration in flight you will see it begin to tumble when the thrust quits. This occurs whether you use a booster motor or a motor with a delay charge and ejection charge. This clearly indicates that spool stability is due to an aerodynamic effect caused by the thrust. I can't see any way around that.

Stability can only be imparted to a spool configuration (which has no "normal" or conventional fin area on the aft end) if there is something else attached to the spool body which acts the same as side-facing fin area. It is my guess that there is a ring vortex behind the aft spool plate, strengthened by the motor thrust which jets through the center of the vortex. I would expect (intuitively) that the vortex would extend 0.5 to 1.0 diameters behind the aft plate, not 2.2 diameters. The vortex remains "attached" to the plate due to a low-pressure zone on the aft face; the low pressure is created by the circulation of the vortex itself. I am not sure that the imparted stability has anything at all to do with airflow ahead of the aft plate, or moving around the outside edge of the aft plate (traditional subsonic aerodynamics would suggest that airflow attempting to turn the sharp corner of the outer edge of the plate would stall and separate)

When the motor quits, the vortex weakens and quickly dissipates, and the spool becomes unstable again.

[MarkII]

The POF article doesn't actually deal with spools. In addition to their wide base, the types of rockets described in the article have other design features that keep them in stable trajectories after the motor stops thrusting. The process that makes spools stable is somewhat comparable to the base drag vortex phenomenon, but is more complex due to the spool's shape (an extreme hourglass).

I suspect that rockets using base vortex-induced stability need to have a velocity about some critical threshold for the vortex to form, but unlike spools, they don't need the additional contribution of the motor's exhaust jet to maintain the vacuum behind the base. They maintain stability as long as their forward velocity is above that critical limit. I see something that appears to be this process quite often when I launch my Art Applewhite saucers and cubes. During the thrust and the brief coast time they move fast enough to be stabilized by base drag. At apogee, when the their air speed suddenly drops to zero, they tumble or "flip over." (Unlike traditional rocket designs, these polygon shapes don't slow down in a gradual coast, but instead slam to a stop in mid-air as soon as the forward momentum drops below a critical speed.) As the larger, heavier polygons descend, they quickly regain the needed velocity for the base vortex to form again, and they "aerobrake" or drop in a stable manner with the air flowing over the top surface. Although fast enough to impart stability, the descent is still slow enough to constitute a safe recovery due to the high drag of the design. The smaller, lighter versions of his rockets often do not drop at a high enough speed to regain this stability; instead, they tumble as they descend, continuously flipping end over end in much the same manner as a tree leaf falling from a branch. In the process, they maintain a very low descent rate that is equal to or often even slower than that of rockets returning on parachutes.

MK

[ScrapDaddy]

I just built a rocket out off an unused toilet paper roll 2 centering rings and a MMT, will it fly since it is basically a spool? :confused:

[shrox]

Who made the first spool rocket and why?

[cjl]

I just built a rocket out off an unused toilet paper roll 2 centering rings and a MMT, will it fly since it is basically a spool? :confused:

With no endplates you mean? No, it won't. You need at least one of the endplates for a spool to work.

[ScrapDaddy]

With no endplates you mean? No, it won't. You need at least one of the endplates for a spool to work.

_lW8p8-y1K0 I beg to differ, and i just entered it in the SNF competition :D

[Scotty Dog]

Who made the first spool rocket and why? How about; 1379-Peter The Great-Warfare-Siege of Chioggia,Italy
:confused2: Scotty Dog

[MattieShoes]

_lW8p8-y1K0 I beg to differ, and i just entered it in the SNF competition :D

You do realize toilet paper is flammable, right?

[troj]

Someone actually wrote an article, with lots of math and other items guaranteed to give you a headache...

Going from memory, it has to do with the pressure differences on the face of the plate due to changed angle of attack. As the "rocket" (very loose use of the term, just like saucers) tilts, pressure increases on the upper side and decreases on the lower side, causing it to tilt back into alignment. This is what causes the wobble you often seen in spool and saucer flights.

I might remember who wrote it; I'll check with him, and if so, try to get it posted.

-Kevin

[rocketman]

Someone actually wrote an article, with lots of math and other items guaranteed to give you a headache...


Remember we're on a rocketry forum here, and thus are rocket scientists, so maths shouldn't be a problem :p

Tom

[ScrapDaddy]

You do realize toilet paper is flammable, right?

Yeah, my neighbor told me that, I ducked and hit the launch button anyway.

[MarkII]

Remember we're on a rocketry forum here, and thus are rocket scientists, so maths shouldn't be a problem :p

TomRiiiiiiiiggggghhhhtttt. I keep forgetting that whenever I resort to pulling out my abacus.

[rcktnut]

_lW8p8-y1K0 I beg to differ, and i just entered it in the SNF competition :D




This isn't model rocketry, it is just another example of model rocket motor abuse. :bangpan:

[GRIFFIN]

_lW8p8-y1K0 I beg to differ, and i just entered it in the SNF competition :D

At the end you scream "YES!!"..........That was the result you were looking for......that was a success??? Next time aim it at a tree. Now that would be a success- T-P'n someones tree at the push of a button.

[Micromeister]

Sorry SD:
NOT yes! that was not a successful flight. it wasn't even a model rocket flight it was just a useless burning of a motor. Your TP roll was not stable, nor did it accomplish anything other then show that a C6 motor can in fact tumble a TP roll into the air, which could have been done any number of other ways with the same tumbling trajectory. Ya need to add at least one disc to the configuration for it to really work.

[ScrapDaddy]

At the end you scream "YES!!"..........That was the result you were looking for......that was a success??? Next time aim it at a tree. Now that would be a success- T-P'n someones tree at the push of a button.

I wanted it to go up, I set the bar pretty low, I was thinking 100 feet tops, I was right.

Micro, it flew up without burning or doing a crazy helix in the air, it was successful in my book.

"Any experiment that yeilds data was a successful one" - Adam Savage.

I was trying to see if a cylinder had the properties of a spool in flight.

[Micromeister]

I wanted it to go up, I set the bar pretty low, I was thinking 100 feet tops, I was right.

Micro, it flew up without burning or doing a crazy helix in the air, it was successful in my book.

"Any experiment that yeilds data was a successful one" - Adam Savage.

I was trying to see if a cylinder had the properties of a spool in flight.

To that end you may be able to claim some limited success as the answer was the same one EVERYONE on this list gave you. NO a cylinder does not have the properties of a spool.
You'll get the exact same results by Throwing the roll of TP in the air, using an inner tube, water balloon launcher or any number of other methods. the "cylinder" as you call it was completely unstable having no redeeming flight worthy characterists what so ever. 100 feet my rosy rear end, that didn't go more than 30 feet tops flip flopping all the way. Unstable is unstable, Add a disc either top or bottom you at least get the thing to fly straight for prehap 35feet LOL!!!

SD you do realize when we come down on you a bit harder then usual it's because we are REALLY trying to help you. Frankly if you were mine you'd have never had the chance to push that particular button, it could have ended very badly for YOU.....You could have been TP'ed.

[Rex R]

why? maybe the same answer as the bumble bee...brute force and ignorance. they don't know they are not supposed to fly :).
rex

[Micromeister]

why? maybe the same answer as the bumble bee...brute force and ignorance. they don't know they are not supposed to fly :).
rex

Exactly!
That's way I have a flying M85 Tank. With enough Thurst Anything will Fly LOL!!!!

[ScrapDaddy]

Exactly!
That's way I have a flying M85 Tank. With enough Thurst Anything will Fly LOL!!!!

I think this is going in my signature! :roll:

I just wanna know why a spool and a cylinder both produce base drag, but only the spool is stable.

[kramer714]

Scrap,

Back to basics, look at a cylinder and calculate the center of gravity vs the center of pressure. Now look at a spool with the same diameter as the cylinder, VERY different Cp.

next understand the difference between dynamic center of pressure and static. Don't worry about the details in the math, just understand the principal. Once you do that it isn't to hard to to figure out if something CAN be stable (WILL be stable takes a little math).

Been able to fly a
football (real football, Steve Young signature model, 4th and waaay long),
pizza (14 inch)
lots of saucers
beer bottle (rocket shaped like, not glass),
paint roller tube rocket
hamburger bun (yes a real hamburger bun)
mop (the mop was really cool to see go)
broom (mops work better)
pumpkin (plastic pumpkin filled with glow sticks that ejected at altitude)
and last weekend flew an 8" foam mushroom (on a G flew like a banshee)

All were stable. Not boasting just saying it isn't too hard to figure out if something will be stable before launching it. Want to fly a roll of TP you can make it stable, need help, ask,

Steps, a) Think, 2) plan, 3) build), 4)rethink 4a) convince someone else that it will work 5)launch.

Getting something off the ground doesn't make it stable.

I will go back and hide now..

[jim fustini]

I launched a scratch built spool once. on G-80T it was not pretty. I won,t get "Spooled" again. :roll:

[RocketRick]

Steps, a) Think, 2) plan, 3) build), 4)rethink 4a) convince someone else that it will work 5)launch.

Getting something off the ground doesn't make it stable.

I will go back and hide now..

I need to stop helping you with step 4a....

http://farm5.static.flickr.com/4094/4906739574_81e9b18169_z.jpg (http://www.flickr.com/photos/crayonrocketry/4906739574/in/set-72157624757153198/)

- Rick

[cjl]

Awesome picture :D


What kind of tubing was that?

[MarkII]

The recent posters have a point. Jumping on a trampoline does not give you the ability to fly, it just makes you ballistic. (You aren't flying, you are falling.) The same is true when you loft a simple cylinder shape with a model rocket motor. The fact that it isn't tumbling end over end doesn't mean that it is flying, except in the crudest sense. A totally unstable rocket will usually get kicked up into the air for a couple of seconds when the motor thrusts, too, before it flops back to the ground, but that would never be regarded as a flight by anyone's definition. An object that leaves the ground for a brief interval isn't necessarily thought of as flying during its period in the air.

[kramer714]

way to rat me out Rick.....

um, that one was my kids rocket... (points to 10 yr old in the next room) really it was.

Actually the Dancing Noodle of Doom flew better than that picture makes it look, take a look at http://www.flickr.com/photos/crayonrocketry/sets/72157624757153198/ find the series of picts Rick took. Believe it or not it continued going up after that wiggle.

The body tube was pool noodle, a bit bigger than the average ones, the fincan was a tubefin made from, you guessed it pool noodle, the nosecone was 1/2 of a foam football. There is 100g of nose weight to, um, help stability.

Stable, not so much, that is why it didn't make the stability list. The problem wasn't aerodynamics, it was natural frequency. Someone suggested to my kid (really it was his rocket) that he stiffen up the center, his answer was..why?

Cool to see, at ROCtober he plans to launch it at night with a sparky.

The kid is the skinny blond haired kid holding the noodle (without the fin can), My favorite picture is http://www.flickr.com/photos/crayonrocketry/4906206665/in/set-72157624757153198 look at the smoke trail!!

http://www.flickr.com/photos/crayonrocketry/4906218705/in/set-72157624757153198 is the Shroom of Doom before launch, now that on flew stable!

[GRIFFIN]

I have never really understood the fascination of the "spool" untill today.
I finished off a roll of wire at work the other day and figured I would give it a try.
I just took a section of 29mm motor mount tube and "2-part foam'd" it in place, stuffed a motor in it and set up the camera......I must say I was impressed. I used an Aerotech F-26 (removed the ejection charge) I didnt expect it to go as high (hench the street light and yes this was in front of my house- and yes oficer, this is a science project for school)

I just had a full day of high power launching the day before and somehow, a stupid spool still got the "rocket juices" flowin'.

watch the whole video, you will see the spool at the end of the flight at the top right hand side of the screen.

http://www.youtube.com/watch?v=tU9JTi9wu80

[kramer714]

the video is great!!!

Something bout the 'it looks like it shouldn't fly so well' is part of the fun.

Where do you launch HPR? I have a nephew in Palatine who would have fun seeing a HPR launch.

[GRIFFIN]

the video is great!!!

Something bout the 'it looks like it shouldn't fly so well' is part of the fun.

Where do you launch HPR? I have a nephew in Palatine who would have fun seeing a HPR launch.

Yea, we were lucky with the camera placement. We go to Bong in Wisconsin for the high power launch.