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GrossApproximator

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Hello, I'm new to this site, but it looks like you guys can answer my question: I have some LOC 38mm tubing lying around, and I want to finally make use of it. I've always launched small rockets, I want to start launching larger ones, and, true to my nature, I want to scratch build just about everything. However, I've never used LOC tubing before, and I'm not sure how much kick this stuff will take. I want to use 52 inches of the 38mm tubing for my rocket and launch it on 29 mm motors. The design has small fins. What is the largest motor an un-glassed rocket like this one could take (I'd probably never launch it on the LARGEST motor . . . I just want to know where the limits of my design might sorta-kinda be)?

Regards, Sean
 

JDcluster

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The big thing here is you coupling joints; make sure that you have at least 1 caliber or 1 body tube of engagement to connect the tubes together. Estes puts people in a bad habit of using allot less than that. Use Loc's 38mm to 29mm HD cardboard CR's & not the Estes thin poster board ones. Loc tubing will pretty much take any 29mm motor on the market today. I launched a long thin rocket on a G 200 back in 1996 with no glass at all. I do miss all of the old SU G & H motors they once had on the market


JD
 

TheAviator

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I agree with JD. The LOC 38mm tubing will take any 29mm motor on the market today and just scoff at it. You could most definitely get away with some thinner walled tubing if you wanted to.
 

dave carver

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I'll bet it can take any 29 mm motor out there including the I-class ones. We're talking tubing ment for HP flights.
 

ScrapDaddy

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The big thing here is you coupling joints; make sure that you have at least 1 caliber or 1 body tube of engagement to connect the tubes together. Estes puts people in a bad habit of using allot less than that. Use Loc's 38mm to 29mm HD cardboard CR's & not the Estes thin poster board ones. Loc tubing will pretty much take any 29mm motor on the market today. I launched a long thin rocket on a G 200 back in 1996 with no glass at all. I do miss all of the old SU G & H motors they once had on the market


JD
Proformance rocketry still has a few of those old Ellis mountain motors, though I'm not sure if you can still use them
 

cjl

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To join the chorus of replies above, the tubing won't give you any issue. Make sure your coupler is snug and long enough (the overall coupler should be around twice as long as the rockets diameter - one diameter of coupler inserted into each tube being joined). Also, make sure your fins won't flutter. Both the fins and the coupler are at a higher risk for shredding than the tubing itself is.
 

GrossApproximator

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I have another question. My rocket has 3 small forward fins (don't worry, it's still very stable according to RockSim 9) but, since they're in front of the motor mount, I don't really want to use through the wall fin mounts as the fin tabs might interfere with the parachute or shock cord as it deploys. The same problem applies to my rail buttons. Does anyone have any suggestions?
 

TheAviator

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If the fins are small and decorative, they should be fine as surface mount. Alternatively, if you are using the LOC tubing, you can cut a slot part way through the tube and mount them that way. The rail buttons should probably be mounted on your MMT centering rings. Barring that, you can glue wooden stand-offs to the outside of the airframe and screw the rail buttons to those.
 

GrossApproximator

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If the fins are small and decorative, they should be fine as surface mount. Alternatively, if you are using the LOC tubing, you can cut a slot part way through the tube and mount them that way. The rail buttons should probably be mounted on your MMT centering rings. Barring that, you can glue wooden stand-offs to the outside of the airframe and screw the rail buttons to those.
I've always been under the impression that at least one launch lug or rail button should be in front of the center of gravity: If I do this, I'll have to mount my rail buttons to stand-offs, since all of my centering rings are well aft of the center of gravity. Do I need to mount at least one rail button in front of the center of gravity?

Here's the tentative design I've been talking about (I hope this thing works :bangpan:)
 

TheAviator

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Looks good to me. Two rail buttons are generally a lot easier to keep aligned than three, so I would go with two, and no rail buttons need to be ahead of the CG. One on/near the CG and one aft is sufficient.

All you need to do now is build and fly it. Have fun! Oh, and remember, pictures are required here on TRF. (Well, ok, they aren't required, but you will get grief if you don't post them... ;))
 

MarkII

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You won't get grief - you'll just have to put up with a bit of whining from some quarters. :roll:

Mark K.
 

terryg

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The problem is not having the tubing survive a big engine, it is finding the sucker after the launch! A 38mm rocket on an I200 is going to be ways up there.
 
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