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  1. #1
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    7th October 2013
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    Cardboard tube DOES have its limits...

    Sigh...

    At OROC's Summer Skies launch last weekend, I shredded my old Excel Plus. I flew it on a K375NW, the Aerotech boost-sustain motor that goes in the 54/2560 case. (It boosts on a grain of Warp-9 propellant, then sustains on White Lightning.) Here is a link to my full launch report.

    Per the photos below, the cardboard tube just folded under the high thrust, right below the ebay (not pictured). After 11 flights, the old airframe just gave up. The main chute also was reduced to shreds.

    Click image for larger version. 

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    Video of shred with some amusing commentary...
    https://picasaweb.google.com/1048031...31378055414834

    You'll notice that the sharp Warp-9 boost was what did the rocket in.
    I emailed Mike Fisher and he pointed out that the last time he saw my rocket, it had dents in the airframe, and that those are what usually lead to shreds. Makes sense...

    So you might say that "after over a year of searching, I finally found the limits of cardboard." I like to push my rockets pretty hard, so the eventual shred of this rocket did not come as a huge surprise to me.

    Wilson Alness
    www.wilsonalness.com
    TRA #13848, L3
    NAR #83247, L3
    L1 - PML Small Endeavour, H128W
    L2 - Binder Excel Plus, J350W
    L3 - Performance Rocketry/Wildman Competitor 4, M1297W

    "Never flying a commercial motor again..."

  2. #2
    Join Date
    20th February 2009
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    Quote Originally Posted by AlnessW View Post
    Sigh...

    At OROC's Summer Skies launch last weekend, I shredded my old Excel Plus. I flew it on a K375NW, the Aerotech boost-sustain motor that goes in the 54/2560 case. (It boosts on a grain of Warp-9 propellant, then sustains on White Lightning.) Here is a link to my full launch report.

    Per the photos below, the cardboard tube just folded under the high thrust, right below the ebay (not pictured). After 11 flights, the old airframe just gave up. The main chute also was reduced to shreds.

    Click image for larger version. 

Name:	IMG_2440.jpg 
Views:	173 
Size:	105.5 KB 
ID:	179807
    Click image for larger version. 

Name:	shred.jpg 
Views:	183 
Size:	183.9 KB 
ID:	179808

    Video of shred with some amusing commentary...
    https://picasaweb.google.com/1048031...31378055414834

    You'll notice that the sharp Warp-9 boost was what did the rocket in.
    I emailed Mike Fisher and he pointed out that the last time he saw my rocket, it had dents in the airframe, and that those are what usually lead to shreds. Makes sense...

    So you might say that "after over a year of searching, I finally found the limits of cardboard." I like to push my rockets pretty hard, so the eventual shred of this rocket did not come as a huge surprise to me.
    Any flight data you could post?

    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  3. #3
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    Quote Originally Posted by dixontj93060 View Post
    Any flight data you could post?
    Yes - I have data from one altimeter, but the other had its battery knocked loose so it didn't detect launch or fire any charges. I'll get that posted soon.
    Wilson Alness
    www.wilsonalness.com
    TRA #13848, L3
    NAR #83247, L3
    L1 - PML Small Endeavour, H128W
    L2 - Binder Excel Plus, J350W
    L3 - Performance Rocketry/Wildman Competitor 4, M1297W

    "Never flying a commercial motor again..."

  4. #4
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    I would call that a fitting end to a great career.
    Jarrett Dorough

    Most people are average

  5. #5
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    Quote Originally Posted by grouch View Post
    I would call that a fitting end to a great career.
    I agree! As per my signature this was my L2 bird, no less...
    Wilson Alness
    www.wilsonalness.com
    TRA #13848, L3
    NAR #83247, L3
    L1 - PML Small Endeavour, H128W
    L2 - Binder Excel Plus, J350W
    L3 - Performance Rocketry/Wildman Competitor 4, M1297W

    "Never flying a commercial motor again..."

  6. #6
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    18th January 2009
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    Quote Originally Posted by AlnessW View Post
    So you might say that "after over a year of searching, I finally found the limits of cardboard."
    You found the limits of mushy cardboard. All it takes is one crease in the airframe to weaken it. That K375 is no big deal in one of our kits that does not have damage. One reason for a pre-flight inspection with a critical eye for such things.

    For creases like you had, there is a fairly simple fix. You soak the area in thin CA which will bring the integrity back. I probably should have mentioned that the last time I saw your rocket, but I didn't know you had big future plans for it.

  7. #7
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    Quote Originally Posted by Binder Design View Post
    You found the limits of mushy cardboard. All it takes is one crease in the airframe to weaken it. That K375 is no big deal in one of our kits that does not have damage. One reason for a pre-flight inspection with a critical eye for such things.

    For creases like you had, there is a fairly simple fix. You soak the area in thin CA which will bring the integrity back. I probably should have mentioned that the last time I saw your rocket, but I didn't know you had big future plans for it.
    Interesting to know! Indeed, my Galaxy and NXRS RTV are in much better shape than the Excel was, so I've pondered putting a K700W or maybe an L (like the L730 or L640) in one of them, but those longburn motors like the K270W and K250W are just as fun...

    The CA trick - do you wick it into the airframe?
    Wilson Alness
    www.wilsonalness.com
    TRA #13848, L3
    NAR #83247, L3
    L1 - PML Small Endeavour, H128W
    L2 - Binder Excel Plus, J350W
    L3 - Performance Rocketry/Wildman Competitor 4, M1297W

    "Never flying a commercial motor again..."

  8. #8
    Join Date
    18th January 2009
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    You can also line the inside of airframe with couplers epoxied in, will stiffen it up quite a bit. Did that to my Galaxy.
    Jim Hendricksen
    L-3 Tripoli 9693
    [ICBM, Orangeburg,SC R.I.P.] - QCRS ,Princeton ILL - MDRA , Price Maryland - Woosh, Bong Wisconsin- ROCC, Charlotte NC , ICBM Camden SC
    "Made" member of Chicago & Carolina Rocket Mafia
    Rocketry...........an exact science.......but not exactly !!!

  9. #9
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    Quote Originally Posted by blackjack2564 View Post
    You can also line the inside of airframe with couplers epoxied in, will stiffen it up quite a bit. Did that to my Galaxy.
    One of our local vendors (who stocks Mike's kits) suggests this, as well. I have also been thinking about building one of his new kits with a 75mm motor mount, and fully glassing the rocket.
    Wilson Alness
    www.wilsonalness.com
    TRA #13848, L3
    NAR #83247, L3
    L1 - PML Small Endeavour, H128W
    L2 - Binder Excel Plus, J350W
    L3 - Performance Rocketry/Wildman Competitor 4, M1297W

    "Never flying a commercial motor again..."

  10. #10
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    Cheap and cheerful. The RalphCo Crayon bodies make a perfect "stiffy coupler" for those 4" airframes. I have one stuffed in my Excel Plus!
    "That Crazy Brit"
    Team SNAFU - Shovel Recovery Specialist
    L3 - TRA 13815 - NAR 87999

  11. #11
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    Quote Originally Posted by AlnessW View Post
    The CA trick - do you wick it into the airframe?
    Yes. You can do it from the inside so you don't mess up your paint, but if you can do both sides, even better. To do the outside, you have to cut away the glassine, wick it in and sand smooth.

  12. #12
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    Quote Originally Posted by Salvage-1 View Post
    Cheap and cheerful. The RalphCo Crayon bodies make a perfect "stiffy coupler" for those 4" airframes. I have one stuffed in my Excel Plus!
    Or just use our new HD couplers. Twice as thick walled as the old ones, as well as longer. And they fit better. The old ones were tight, so people sanded them which made them even thinner. These new couplers are even thicker than the airframe tubing.

    I honestly believe that if one of our airframes was doubled up with these new couplers, it could withstand an M without fiberglass or carbon fiber wrap. I intend to try it at some point.

  13. #13
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    Quote Originally Posted by Salvage-1 View Post
    Cheap and cheerful. The RalphCo Crayon bodies make a perfect "stiffy coupler" for those 4" airframes. I have one stuffed in my Excel Plus!
    I see that "Recycles RalphCo Crayons" is living up to his name...

    Quote Originally Posted by Binder Design View Post
    Yes. You can do it from the inside so you don't mess up your paint, but if you can do both sides, even better. To do the outside, you have to cut away the glassine, wick it in and sand smooth.
    Got it. Knowing me and paint I'd probably just do the inside...

    Quote Originally Posted by Binder Design View Post
    Or just use our new HD couplers. Twice as thick walled as the old ones, as well as longer. And they fit better. The old ones were tight, so people sanded them which made them even thinner. These new couplers are even thicker than the airframe tubing.
    The new couplers ARE really nice! Indeed, they fit perfectly whereas the old ones were shorter in length and very, very tight.

    Quote Originally Posted by Binder Design View Post
    I honestly believe that if one of our airframes was doubled up with these new couplers, it could withstand an M without fiberglass or carbon fiber wrap. I intend to try it at some point.
    Really!
    Or should I say "Challenge accepted"...
    Wilson Alness
    www.wilsonalness.com
    TRA #13848, L3
    NAR #83247, L3
    L1 - PML Small Endeavour, H128W
    L2 - Binder Excel Plus, J350W
    L3 - Performance Rocketry/Wildman Competitor 4, M1297W

    "Never flying a commercial motor again..."

  14. #14
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    Quote Originally Posted by Binder Design View Post
    Or just use our new HD couplers. Twice as thick walled as the old ones, as well as longer. And they fit better. The old ones were tight, so people sanded them which made them even thinner. These new couplers are even thicker than the airframe tubing.

    I honestly believe that if one of our airframes was doubled up with these new couplers, it could withstand an M without fiberglass or carbon fiber wrap. I intend to try it at some point.
    Mike, are these new couplers used in the av-bay offerings?
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  15. #15
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    Quote Originally Posted by dixontj93060 View Post
    Mike, are these new couplers used in the av-bay offerings?
    Yes.

  16. #16
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    18th January 2009
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    Quote Originally Posted by AlnessW View Post

    Really!
    Or should I say "Challenge accepted"...
    Try at your own risk. I have not confirmed this yet. I was going to try a 75mm baby M in a Tyrannosaur.

  17. #17
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    Interesting. I have a Lightning Bolt kit to build that I was thinking about glassing. Maybe I'll pick up a some of your HD couplers instead and build it that way.
    "Keep your charges reasonable and tie the knot..."

    2016 Stats
    *Number of Flights: 20
    *Total Impulse: 40,457.0 Ns

  18. #18
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    Quote Originally Posted by chuck5395 View Post
    Interesting. I have a Lightning Bolt kit to build that I was thinking about glassing. Maybe I'll pick up a some of your HD couplers instead and build it that way.
    It will make the airframe over twice as strong. The stock airframe can handle K's and certain L's, so I don't see a problem with small M's, but we'll see.

    I also have 75mm motor mount tubes and centering rings that I'll be adding to the web store, for those that want to build it with bigger mounts. For now, I still recommend fiberglass or CF wrap.

  19. #19
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    Quote Originally Posted by Binder Design View Post
    It will make the airframe over twice as strong. The stock airframe can handle K's and certain L's, so I don't see a problem with small M's, but we'll see.

    I also have 75mm motor mount tubes and centering rings that I'll be adding to the web store, for those that want to build it with bigger mounts. For now, I still recommend fiberglass or CF wrap.
    I would certainly want to do mine in 75mm regardless of how I'd reinforce the airframe, for sure. For the couplers - would you glue them in with Titebond?
    Wilson Alness
    www.wilsonalness.com
    TRA #13848, L3
    NAR #83247, L3
    L1 - PML Small Endeavour, H128W
    L2 - Binder Excel Plus, J350W
    L3 - Performance Rocketry/Wildman Competitor 4, M1297W

    "Never flying a commercial motor again..."

  20. #20
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    Sorry about your Loss.
    I've found that Papering a Body Tube with 110# Cardstock using TB II as the glue enhances its Rigidity to an incredible degree, as well as the previously mentioned adding of Couplers.
    Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn

  21. #21
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    Quote Originally Posted by AlnessW View Post
    I would certainly want to do mine in 75mm regardless of how I'd reinforce the airframe, for sure. For the couplers - would you glue them in with Titebond?
    Yes, titebond, but you have to thin it with water first. They'll grab if you don't. And if you go full length with the motor tube with plenty of centering rings, You won't have to worry about the booster section buckling.
    Last edited by Binder Design; 6th August 2014 at 04:40 PM.

  22. #22
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    I assume that one would put these couplers in above the upper motor mount centering ring (assuming that the fin can section really doesn't need this extra support). Could you simply slide them all in and then only glue the upper most coupler? My thought is that that the other couplers would be held in place at the bottom by the centering ring and at the top by the glued in coupler. Thoughts?
    "Keep your charges reasonable and tie the knot..."

    2016 Stats
    *Number of Flights: 20
    *Total Impulse: 40,457.0 Ns

  23. #23
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    Quote Originally Posted by chuck5395 View Post
    Could you simply slide them all in and then only glue the upper most coupler? My thought is that that the other couplers would be held in place at the bottom by the centering ring and at the top by the glued in coupler. Thoughts?
    The glue adds the axial strength. Otherwise, they are just floating and provide wall strength (radial) only.

  24. #24
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    If it were me, I'd line the whole booster section, then use the centering rings cut for the coupler ID X MMT OD. Probably overkill for the booster section, but we are talking M's here. No matter what, it will still come out to about half the weight of fiberglass tubing.

  25. #25
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    Understood. Thanks for your input on this. I'll probably work on this in the off-season.
    "Keep your charges reasonable and tie the knot..."

    2016 Stats
    *Number of Flights: 20
    *Total Impulse: 40,457.0 Ns

  26. #26
    Join Date
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    Great suggestions, thanks! I think I'll probably do something like this for a winter build, as well.

    Wilson Alness
    www.wilsonalness.com
    TRA #13848, L3
    NAR #83247, L3
    L1 - PML Small Endeavour, H128W
    L2 - Binder Excel Plus, J350W
    L3 - Performance Rocketry/Wildman Competitor 4, M1297W

    "Never flying a commercial motor again..."

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