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Gillard

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I'm sure i can't be the first to think this, but why are most of our rockets tubes.
i'm thinking of building a large(ish) rocket.
what would be wrong in building it square based, instead of circular based?
if i used fibreglass sheets, that where joined using triangluar angle, would there be any problems in flight, stresses at the edges etc
The rest of the rocket would be built as usual, with the exception of the nose cone which would be pyramid shaped and made of fibreglass.

It seems that construction of centering squares (rings) would be easier to make. sizes of body squares (tubes) would be easy to make. etc

With smaller model rockets, using carboard for the square sides would make the body far to weak, but on larger builds were glassing can be used, strength is lesson an issue, esp. on larger diameter tubes where internal bracing can easily applied.

So is there an obvious reason why squares don't work?
 

SteveF

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I think tubes are used because round shapes (spheres) are such a good trade off of size, strength, ease of construction, and drag. there are square rocket bodies and other number of sides too - no real reason not to make one if you want. There is a guy/small company that just started up mainly selling on e-bay that is making lpr square rockets but cant remember name. and i believe fliskits or applewhite has paper rockets that are 3 sided and probably others, of course in the odd-roc world are the pyramids and such so go for it
 

stantonjtroy

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Mostly because a box frame (square, triangular, trapazoidal or whatever) has corners. Corners are a potential point of structural failure. Tubes have no corners ergo less potential for failure. Think force vector physics.
 

dlb

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simple physics:
A circle or sphere or tube has more strength than a square or box.
in fact, (this was pointed out by my teacher )some designs, like a dome home can withstand alot more force in all direction than a box type homes.

and round tubes can even gain strength at some points of force.

that being said: I got a square tube rocket and I love it, go figure!:bangpan:
 

MarkII

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If you live in a dome house, you can't tell misbehaving children to go sit in a corner.






In addition to those already mentioned, there is the AAW Six.



MarkII
 

luke strawwalker

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I'm sure i can't be the first to think this, but why are most of our rockets tubes.
i'm thinking of building a large(ish) rocket.
what would be wrong in building it square based, instead of circular based?
if i used fibreglass sheets, that where joined using triangluar angle, would there be any problems in flight, stresses at the edges etc
The rest of the rocket would be built as usual, with the exception of the nose cone which would be pyramid shaped and made of fibreglass.

It seems that construction of centering squares (rings) would be easier to make. sizes of body squares (tubes) would be easy to make. etc

With smaller model rockets, using carboard for the square sides would make the body far to weak, but on larger builds were glassing can be used, strength is lesson an issue, esp. on larger diameter tubes where internal bracing can easily applied.

So is there an obvious reason why squares don't work?

Most rockets are round because 'real' rockets are pressurized fuel tanks, and building a pressure vessel round is 1) the easiest way to distribute the pressure forces equally-- ever see an overpressurized cube?? What's it try to turn into?? A ball-- the flat sides bulge. Where does it split when it ruptures?? Along a seam or in a corner, because the pressure forces are concentrated there. 2) A round container is also the most volumetrically efficient-- a perfect sphere encloses the greatest volume in the least space of any shape. 3)aerodynamic lift and drag forces around a sphere or tubular shape are the same regardless of the angle of attack-- whereas square tubes or triangular tubes would have different induced lift/drag forces depending on the angles of the faces of the flats or the corners to the airflow, thereby complicating the aerodynamics.

This last reason is the biggest one when it comes to model rockets...

That said, there have been any number of square and triangular cross-sectioned rockets over the years-- there used to be company that sold only these types of rockets, from laser-cut balsa IIRC... And they have flown successfully. Look at the 'outhouse' rockets, porta-john rockets, phone booth rockets, pyramids, etc. I've even seen cubic payload bays with pyramidal nose cones and adapters flown on top of regular cylindrical rockets, including one flown with a disc-camera aboard.

They'll fly, just make sure they're stable! Good luck! OL JR :)
 

MarkII

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Have you seen the FlisKits Nebula? I have built a few of these. Easy to assemble. (No curves to cut!) Flies like a champ.

  • Triangular airframe.
  • Triangle pyramid nose cone.
  • Triangular profile tubular fins.
  • Triangle tube launch lug (with angle cut ends).
MarkII

P. S. I wanted to call the n.c. a tetrahedron, but it isn't.

 
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artapplewhite

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Here is a better link to the Art Applewhite Rockets Six: http://www.artapplewhite.com/free.html Go there, then click on the picture of the rocket.

The direct URL is changed from time to time so I can be sure the hobbyist has seen, and hopefully read, the limits of liability statement.

I found that a six sided tube was not that much heavier that a true cylinder and had less drag by virtue of less frontal area than 3 or 4 sided tube designs. It is relatively easy to accurately fold a 6-side cardstock tube once some creases are made in it with a straight edge and a ball point pen. Integrated internal cross bracing makes it much more rigid and the built-in launch lug eliminates alignment and placement problems.

Performance is surprisingly good. This rocket has been timed at 195 seconds in a NAR A parachute duration competition with an Estes A3-4T motor and a 8" mylar parachute. Not bad when you consider the NAR A PD "A" division (7-13) record is 180 seconds and "B" division (14-18) is 177 seconds. :wave:
The "C" division record is 510 seconds so I don't see much chance of beating that with the Six but you never know.



In addition to those already mentioned, there is the AAW Six.



MarkII
 

powderburner

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.....but you never know.
What is interesting to me is that this six-sided thing has a nose cone shape that is just about one of the "worst" aerodynamic shapes for low drag in subsonic flight, and here is this same rocket producing championship times. Go figure.

While I'm at it, I would like to extend a big public THANK YOU to Mr. Applewhite for all the stuff he has developed and posted to give away free on the internet. Your efforts, skills, and generosity are very much appreciated.
 

MarkII

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Art, you are wrong about the Six's performance. It isn't amazingly good - it's awesome!

I keep losing them because they go so darned high. But that's OK; I just build more.

I like the MMX superroc version, too. That's fun to fold... ;) :D

MarkII
 

MarkII

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Art, I also know what you mean about the performance of the Six vs. other non-round tube shapes. I have built several 3-sided FlisKits Nebulas and Caution! rockets, and although they both are really fun to build and a blast to fly, the Six beats them handily in performance.

Folks, I can't get over how ingenious this design is. The airframe, shock cord anchor and conventional launch lug are all in one cut-out piece that is very cleverly folded. The fin can and motor mount (with block) are folded from two other single pieces cut out of the same sheet. Only the nose cone requires assembly of more than one piece. And the result doesn't look at all cheap - it is a strikingly handsome rocket. All built from one sheet of printed cardstock, a paper clip and some clay for nose weight.

Even though it isn't "mini" in size, you can easily lose sight of it on an A, as I often do. Put some talcum powder or powdered paint in with the streamer, and use a shiny metallic streamer so that you can more easily track it. Bring binoculars, too.

Tip: I often print out the pattern twice, on two different colors of cardstock. That way, I can make two rockets, each of which has a nose cone and a fin can in a different color than the airframe. I often use fluorescent-colored cardstock or lightweight poster board, which helps with the visibility.

MarkII
 
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spacecadet

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I can confirm that a Toblerone box makes a perfectly acceptable rocket if you get the noseweight right. (See IRW 2003).
Or an Oxo (see IRW 2007).
Tubes are a deal easier to build, though. Slotting in a cylindrical coupler beats having to build another, ever so slightly smaller, box.
However, if an interesting potential airframe comes my way, I'll look into it, tubular or no.
But there's not much point putting two days' work into making a flying brick.
Unless it looks like a brick. Hmm, there's a challenge.

25toblerone.jpg


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