oblong tube

[watermelonman]

I want a section of body tube, probably 2-3 feet long, that is wide in one dimension than the other. I think my best bet is to start with a weak paper tube, crush a little for shape, then apply fiberglass for the real structure. Has anyone else tried similar? Does my thinking seem sound?

 

[TopRamen]

I've done a Transition by slotting a BT then FG.

https://www.rocketryforum.com/showthread.php?69241-Best-Way-To-Reduce-A-Tube-Diameter-Gradually

 

[Marc_G]

Internal oblong supports, perhaps?

If you don't mind sharp creases at each side, then cutting, creasing, then gluing makes sense.

 

[dr wogz]

I have a plan for this (and I too have a rocet idea that's not a round cylinder!)

Let's see how well I can explain in words..

1) you need a central tube. I see mine being the MMT tube. Make it the length you need, or ideally, the length of the rocket itself..
2) you need 'formers' for the intended shape. Basically, centering rings, but cut to the profile of the shape you want. In your case, cut round CRs to your desired oval / obround shape. Ensure the central hole remains concentric to the long & short axis. make a few of these!
3) notch these rings at the 4 quadrant points. the notch should be 1/8" x 1/8" (or larger, I'll explain later) So, each modified CR has 4 notches, each at 90° to each other. (depending on the size, you might want 6 or 8 notches per former.. again, I'll explain later)
4) slip the modified CRs onto the tube. Ensure they are perpendicular & square, and most importantly, that they line up with each other. Now, depending on the length, size, etc.. you want, you might need 2, 3, 4, 16 CRs... (Ok, 16 might be excessive!)
5) Insert a 'stringer' in each of the notches. Insert a 1/8" x 1/8" square balsa stick in each of the notches, so you have 4 stringers running the length of the tube / CR assembly. This is were, depending on the size, you might want to use a larger notch (or just more stringers). Say, to fit a 3/16 x 1/2" balsa stingers.. the top of the stringer should be flush with the edge of the CR.
6) starting on one of the stingers, at the middle of the stringer, wrap a piece of stiff card / paper around the CR / stringer frame assembly and cut / trim when you go once around (meet the starting edge). Glue this to the stringers & CRs..
7) you should have your desired shaped 'body' Framed & papered over..

Now, depending on how strong you want it, you can add more CRs & Stingers to the assembly. You're essentially creating a framed up structure and sheeting it. All the strength is really in the original tube you started with.

You can even use sheet balsa or thin ply wood for added strength instead of paper. you can get 3-ply 1/64" ply, but 1/32" is probably better!

You can alter the CRs to be hexagon, or triangular or some other weird shape...

hope that helps..

 

[hornet driver]

-----Pretty easy to do. It can be done with centering rings cut to the size and shape you need. The trick is making sure they have the right measurement around them . some math skills needed and a compass would help. Or you could just squash the tube to the desired shape and trace out what you need. Be careful, you can split a tube easily. If you hold the tube over steam for a bit it makes the job easier.. I did it on my Wraith build. It was tapered from round at the nosecone end to near flat at the back----

 

[Marc_G]

Hornet- this is super cool. It gives me some very good ideas for my upcoming rebuild of my scratcher "Project Red Queen" that I've been mulling over. Thanks for posting these pics, even if the uploader function is messed up at the moment!

 

[watermelonman]

I tried out my plan of crushing down a cardboard tube and fiberglassing it. It seems to have worked extremely well, though I am at a bit of a loss for a coupler and nose cone!

 

[jqavins]

You wouldn't be thinking of a cluster something like this, would you?

 

[BABAR]

Cut a very short section of your tube (can use scrap) (perhaps a cm long) and shape it to desired conformation. Trace the inside to make a template. Center the hole for your motor mount in the template.
Foam board makes excellent centering rings for LPR and probably if you add an extra ring or two would be adequate for mid power as well. It is very easy to cut, and since it is cheap you don't feel too bad if you screw up a couple of rings in practice.
An interesting thought, you could actually align one set of oval rings in one direction and another, say 90 degrees off, and have a very unique and solid body tube.

 

[BABAR]

regarding your nose cone, it may be possible using the above to leave a section (say 3-6 inches) of tube ABOVE the highest oval centering ring, allowing the tube at this end to remain at its native circular configuration. Thus the "transition" would actually be the end of the body tube, and you could still fit the standard diameter circular nose cone on top.