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doubling body tubes

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wwattles

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I'm looking to beef up some Estes kits to mid- and high-power engines, and my concern is the strength of those flimsy Estes tubes. Anyone have any experience with inserting a second tube, LOC material, inside the Estes tube for strength? I'll be using the "make your own tube coupler" method from info-central (http://www.info-central.org/construction_couplers.shtml).

Thanks for the help!

WW
 

Johnnie

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Depending on the size tubes, I would replace it all with Loc tubes period...Estes does use off size tubing though, and some of their cones will not fit standard mid-power tubing...try doubling up with Estes tubing, and keep it light. There is also laminating with glass lay-ups...very messy though.

good luck
 

wwattles

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Alas, I live an an apartment and glassing isn't really an option (I *gotta* get a place with a garage!). I've already got some tubing that is the same size, but the rocket is already built and I'm just trying to strengthen it.

WW
 

powderburner

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if you are ‘stuck’ with trying to mod an existing model rocket, your choices become a bit limited:

option 1
slit same-size BT and glue to inside of main body
pros: preserve appearance (paint job? decals?) of existing design; preserve smoothness of external surfaces
cons: difficulty of applying internal glue evenly; difficulty of applying pressure (from inside out) to inner shell to ensure good bond to outer shell (inflate a kid’s balloon through the middle?); interference with existing internal motor mounts

option 2
slit same-size (or slightly larger) BT and glue to outside of main body
pros: easy to work with, apply glue, position outer shell, press into place with rubber-band wraps
cons: aerodynamically dirty (exposed edges); interference with existing external fins and launch lugs; will require stripping external finish down to bare airframe tube if added to existing model

option 3
add longitudinal stiffening rods (spruce strips 1/8x1/8? carbon fiber rods?) to inside of main body
pros: preserve appearance (paint job, decals, yada yada) of existing design, preserve smoothness etc
cons: difficulty of positioning stiffeners inside BT to attain optimum spacing around perimeter and straightness of installed stiffeners; difficulty of applying pressure (from inside out) to stiffeners to ensure good bond to outer shell (inflate a kid’s balloon through the middle?); interference with existing internal motor mounts; potential for surface roughness of reinforcing members to cause snags on deployment of recovery systems.

option 4
add longitudinal stiffening rods (spruce strips, carbon fiber rods?) to outside of main body
pros: easy to to work with, apply glue, position stiffeners outside shell, press into place with rubber-band wraps
cons: non-scale (if applied to scale model); aesthetically unappealing (unless you LIKE the tech look); aerodynamically dirty (increased wetted area); possible interference with existing external fins and launch lugs; will require stripping external finish down to bare airframe tube if added to existing model

option 5
soak BT with CA, or wood hardener, or thin epoxy
pros: preserve smoothness of external surfaces; fairly easy to swab into inner surfaces with stick and sponge-head; can enhance the strength of the installed motor mount
cons: may soak completely through BT and show incompatibility with previously applied exterior primers, paints, and glues; almost certainly requires good ventilation, or work to be performed outside the house; may require some light sanding to internal BT walls (can you say ‘awkward’?) to ensure smooth deployment of existing recovery system (after curing)

option 6
use what ya got as is, don’t worry about airframe problems (we tend to over-build things here on TRF, and those cardboard tubes are stronger than we give 'em credit for), and if it does have a problem, build the next one a little stronger
pros: you can play with the toys you already have
cons: you need a safe launch field for the first few flights with big motors

Whatever you do, you are now obligated to report back to us on the results of your structural testing program.

And welcome to TRF! We're glad you chose to join us, and we hope to hear lots more from you.
 

havoc821

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Powderburner is right. The Estes tubes are a little stronger than we give them credit for. My Eye in the Sky 1 which was also my first mid power rocket flew on a G38 to ~1500 and came in without parachute (parachute detached from rocket) and slammed into the ground. The only damage was that the payload tube came a little unwound at the seams and the camera mount was destroyed. I'm sure the tubes could handle up to a G80 but I wouldn't put a H or anything in it. Just my 2 cents. :)
 
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