How to repair squishy loc body tube?

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BradMilkomeda

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Hey folk!

The quick: How would you suggest repairing a "crack" or "squishy-ness" in a cardboard body tube?

I was able to successfully get my L1 last month at LDRS 36 on a Loc IV with a H123W motor using a Chute Release on a 30" elliptical Fruity Chute.. Here is a wonderful shot of the flight that Todd Harrison posted on the Tripoli Facebook group:
17855166_10103460927215926_3394788330973761770_o.jpg


That was a great flight, which was followed by another on a H148R. But the last flight of the day ( as always ), had some problems. I used a H242T last, and I think the delay was a little short, the the parachute came loose from the chute release and was deployed at apogee. Being ~2000ft high, and no altimeter information, I'm not sure if it was the early deployment at speed or a poorly packed chute release that cause the problem. The rocket did come down looking OK. But upon closer inspection I see some body tube damage in the middle:

DSC_6578.jpg

Judging by the white paint on the rail button, I presume the nose code hit the body tube there. The apparent crack is more that just cosmetic, as with a strong force of a thumb it feels a little squish.

I would like to continue to push this rocket with some I motors, so I think a repair is needed to maintain integrity. This entire rocket was make with just wood glue, as that seem sufficient and is my preference. However, is seem like fiber glass and epoxy may be needed here. My thoughts on repairing are:

  1. Sand of paint, down to body tube
  2. paint on laminating epoxy ( Cheap small quantity, like Bob Smith 20min?)
  3. Apply 2 oz fiber glass
  4. Smooth and spread out
  5. wrap tube with wax paper
  6. Sand, patch, sand, paint....

Does that sound like a reasonable procedure? Any alternatives?

Thanks!
 

75Grandville

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Depending on where your centering rings are placed, you might be able to cut out the damaged section, then use a coupler (or two) and some new body tube. I've used that approach myself, on more than one rocket. Including my L1 bird. I actually had to splice the MMT and the body tube. https://www.rocketryforum.com/showt...d-planned-L1-cert-attempt&p=719377#post719377


Depending on how things are attached, you might also be able to slide a coupler down inside the body tube for strengh, although given the length of the rocket it might be tricky.
 

ThirstyBarbarian

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I agree with 75Grand above. If you can slide a coupler down to the squishy part, that should stiffen it up. Then maybe wick some thin CA in from the outside to harden the damaged tube. Sand and paint.
 

terryg

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The damage does not look severe enough to spend a whole lot of effort to repair it. What does the rail button screw into? If it is not screwed into a centering ring, it could be removed and a small amount of epoxy injected to reinforce the airframe (cover hole with masking tape and place face down to cure). Other wise as Thirsty says wick some thin CA from the outside and sand and paint. With typical engines you would fly with this kit, I doubt you will have any problems.
 

BradMilkomeda

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Depending on where your centering rings are placed, you might be able to cut out the damaged section, then use a coupler (or two) and some new body tube. I've used that approach myself, on more than one rocket. Including my L1 bird. I actually had to splice the MMT and the body tube. https://www.rocketryforum.com/showt...d-planned-L1-cert-attempt&p=719377#post719377


Depending on how things are attached, you might also be able to slide a coupler down inside the body tube for strengh, although given the length of the rocket it might be tricky.
The damage is no where near what happened to you. The motor tube is 20" long. The damage is between the centering ring, so I can't easily slice a couple down. It would have too be a butcher job to get a coupler there.

The damage does not look severe enough to spend a whole lot of effort to repair it. What does the rail button screw into? If it is not screwed into a centering ring, it could be removed and a small amount of epoxy injected to reinforce the airframe (cover hole with masking tape and place face down to cure). Other wise as Thirsty says wick some thin CA from the outside and sand and paint. With typical engines you would fly with this kit, I doubt you will have any problems.
The rail button has a low profile weld nut secured with a little epoxy on the other side. I think getting little epoxy on the other side is a good is a good first step and see how if firms up. Maybe drill another small whole to help with getting the epoxy in.

Any recommendation for this epoxy; some kind of thin, slow (60min) should work?
 

DaveHein

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I've used a strip of fiberglass wrapped around my LOC-IV to repair a hole caused by landing in a tree. The repair worked great, and I flew it several times after that on H and I motors.
 

terryg

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"Any recommendation for this epoxy; some kind of thin, slow (60min) should work?"

Any 30 min epoxy should work. DevCon 2 ton 30 min epoxy can be found at Ace Hardware for a small purchase. West Systems, U.S. Composites, Aeropoxy etc. if you are going to buy a larger amount for future use.
 
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DinoAP

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Minwax wood hardener. Few drips on the inside.....hard as a rock.
 

terryg

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Another approach is to use Elmer's Glue-All max. Drill a hole, add a little moisture to activate the glue and squirt it in. It foams up as it cures and sticks to almost anything.
 

3stoogesrocketry

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I would disagree with this particular application, not enough epoxy in the WH.
If the damage is between the centering rings , you could use a small blade to cut a 1/2 inch square hole in the damaged region . then just pour in some expanding foam. Clean up the hole , then glue your window back in. Sand it and paint it.

Eric
 

BradMilkomeda

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I ended up drilling a couple holes, injecting about 2cc of the G-Flex epoxy I had with a little bit of the 407 filler. The rail button has a weld nut on the other side. So I threaded a screw with some vaseline to keep it functioning. While it was drying I keep the rocket very level to help the epoxy flow evenly. At first a little bit to the one side then with the main crack a the bottom. The tube feels pretty good now, perhaps a little weaker, but I'm still going to try a low powered `I` motor when I get a change. With the 3 centering rings, with one being above this point, I think the motor tube would do bit distribute the flight stresses around this potentially weaker point.

Here are some pics of the progress. The last one is really brutal on the finish, it actually still looks pretty good.

Loc IV repair - 1.jpg
Loc IV repair - 2.jpg
Loc IV repair - 3.jpg
Thanks for all the helpful suggestions!
 
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