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Rocket repair
#1
OK, so I think I'm going to attempt to repair my MEGA Mosquito with the impacted body tube that crumpled a little. Several have suggested either shoring up the body tube with a coupler inserted inside, or else sanding around inside and soaking it with CA for strength.

My question is what's the smallest (shortest) length connector for the body tube used in the MEGA Mosquito (is it a BT-50?) and what should I expect to pay for such a connector?   

Second, since the connector will slide down inside and reinforce the body tube, doesn't this mean I'll have to take off the tri-fold shock cord glued inside the lip of the body tube?  Also, I need to allow for enough room for the nosecone to fit down into the body tube, but that's the portion that is crumpled.

Any advice?

Thought of something else.
Will the addition of a coupler throw off the CG and CP ratio for this rocket?
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#2
You sure do have a problem there.
Mega M. is a BT-80, that's the coupler you'll need.
I would cut off as much of the top of the crimpled tube as you can,
put in a coupler (cutting it shorter if needed) and adding a bit of new BT-80 body tube for the nose cone to fit in.
Of coarse, you'll need to repaint.
This is all going on what you discribed without seeing pics.

I would look at http://www.unclemikesrocketshack.com or
http://www.sunward1.com for the parts.

Kirk, I looked down the pipe of my Mega M. in primer.
You would be safe to cut off 3 to 4 inches off the top.
This will allow you to put a new shock cord mount in.
You can use any card stock you have laying around.
Manilla folder from the file cabinet, even a cheap business card for the mount.
I hit the sewing center at your local Wally World and pick up 5/16" elastic, and make it at least 36".
Hit the fishing department and pick up a pack of locking snap swivels.
Put one on the chute to the nose cone, and one on the end of the shock cord to the nose cone.
I hope this helps. Hate to see any rocket go in "The for Parts Only" box.
Rather put them in the "Retired" box Smile
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#3
Good advice.
I have found that I can use paper (only slightly heavier than standard printing paper) for my trifold, without the necessity of using cardstock.
The surface is coated with glue, which gives it the strength it needs, without having to employ more rigid card stock.
Never had a failure (other than when the elastic itself breaks... Wink )
Greg Young - L3
TRA 00234
NAR 42065
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#4
BTW, you can easily make a coupler using a chunk of BT-80 or any similarly sized junk tube.
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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#5
Video 
(08-24-2015, 11:36 AM)rstaff3 Wrote: BTW, you can easily make a coupler using a chunk of BT-80 or any similarly sized junk tube.



.
NAR #100544

"The Guide says there is an art to flying", said Ford, "or rather a knack." 
"The knack lies in learning how to throw yourself at the ground and miss."

Launching is Optional... Landing? That Depends on Trees.

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#6
(08-24-2015, 11:36 AM)rstaff3 Wrote: BTW, you can easily make a coupler using a chunk of BT-80 or any similarly sized junk tube.

How does one do that? If it's the same size as the existing BT-80 tube, I can't see how it would fit inside...
unless you were to whack off a short length, and then slice it lengthwise through only one wall... creating either an expandable "wrap around" collar.... or else a slightly compressible internal "inside wrap".

Is that the idea?
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#7
I didn't look at the video but here's how I do it.

1. mark a line on the short piece of tube like you would to mark a fin
2. cut it
3. roll it and put it in the target tube, aligning the end
4, mark an inside line
5. cut off the strip
6. run a piece of tape along the outside, the length of the coupler and overhanging bit
7. slide this into the target tube, making sure the ends are aligned
8. apply glue to the stip you cut off and place it along the cut, inside the tube (the masking tape applied earlier keeps you from gluing the coupler in by accident)
9. I clamp a stray strip of something (plywood, plastic ruler or whatever fits) down on top and let it dry
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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#8
(08-24-2015, 12:15 PM)Kirk G Wrote:
(08-24-2015, 11:36 AM)rstaff3 Wrote: BTW, you can easily make a coupler using a chunk of BT-80 or any similarly sized junk tube.

How does one do that?  If it's the same size as the existing BT-80 tube, I can't see how it would fit inside...
unless you were to whack off a short length, and then slice it lengthwise through only one wall... creating <SNIP> a slightly compressible internal "inside wrap".

Is that the idea?

That is the idea
.
NAR #100544

"The Guide says there is an art to flying", said Ford, "or rather a knack." 
"The knack lies in learning how to throw yourself at the ground and miss."

Launching is Optional... Landing? That Depends on Trees.

Reply
#9
(08-24-2015, 12:27 PM)rstaff3 Wrote: ...

1. mark a line on the short piece of tube like you would to mark a fin
2. cut it
3. roll it and put it in the target tube, aligning the end
4, mark an inside line
5. cut off the strip
6. run a piece of tape along the outside, the length of the coupler and overhanging bit
7. slide this into the target tube, making sure the ends are aligned
8. apply glue to the stip you cut off and place it along the cut, inside the tube (the masking tape applied earlier keeps you from gluing the coupler in by accident)
9. I clamp a stray strip of something (plywood, plastic ruler or whatever fits) down on top and let it dry

When I'm doing big tubes, my process is similar:
1. Cut tube to 0.5"-0.75" over desired lenghth
2. Mark a line with a length of angle
3. Do the math to determine my new Circumference, subtract it from the old and mark the 2nd line that far from the 1st
4. Cut to the 1st line
5. Accounting for blade thickness, cut to the 2nd line
6. Wrap the 'slit' in wax paper
7. Slide this into the target tube
8. Apply epoxy to the 'slit' (the wax paper keeps you from gluing the coupler in by accident)
9. I fold the ends of the wax paper so that the epoxy is contained and then pool plenty of epoxy in there.
10. Once cured, sand the ends square.
Phill Ash
Secretary - SouthEastern Virginia Rocketry Association (SEVRA)
2015 Tot Impulse: 1398.8 Ns (L2, 45 Flights, 57 Motors)
2016 Tot Impulse: 190.3 Ns (L2, 14 Flights, 16 Motors)




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#10
There are often different ways to skin the cat and yours sounds good for bigger AND for thick tubes. HPR requires a better couplers for strength purposes.

Yes, for bigger tubes, I often..gasp...measure and do the math. For MPR and LPR using the method that reuses the removed strip you can even have a small gap. Unless I can see the ends, I never trim them flush. Getting them flush during the build, however, helps ensure a uniform fit all the way. Early on I was careless and found that you can get a good fit at one end and have the coupler a tad loose on the end that's furthest into the tube as it is bonded together.

The wax paper and tape I mentioned serve the same purpose. The wax paper allows for even a better fit, although I seldom do that anymore.
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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