Motor Tube Repair

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Knundrm

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Had a CATO on my King Kraken. The result was that the forward 1/3 of the motor tube burned out but, surprisingly the exterior of the rocket is in great shape.

Link to the CATO attached. It was impressive and I probably wouldn't have minded the cato had the rocket pled off an Immelmann!
https://www.facebook.com/groups/397517811029682/permalink/679846226130171/
My question: has anyone found a creative way to repair this type of damage that does not require removing the fins, cutting the body tube in half, repairing and rejoining the body tube with a coupler?
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I have repaired and extended MMT with glass cloth. Yours looks like cardboard tube. But this works for either. Get another chunk of MMT, cut to length, insert motor wrapped with a couple of layers of saran wrap. I have also used mold release compound, but you may not have that on hand. Anyway, after the motor is inserted into new chunk of MMT and the old portion, that you have already cut off the bad, wrap several layers of cloth around it and glass it in place. the motor keeps everything aligned, and the saran wrap will allow you to pull it out when cured.
 
Why bother. Its still flight worthy. I'd leave it alone
Had a CATO on my King Kraken. The result was that the forward 1/3 of the motor tube burned out but, surprisingly the exterior of the rocket is in great shape.

Link to the CATO attached. It was impressive and I probably wouldn't have minded the cato had the rocket pled off an Immelmann!
https://www.facebook.com/groups/397517811029682/permalink/679846226130171/
My question: has anyone found a creative way to repair this type of damage that does not require removing the fins, cutting the body tube in half, repairing and rejoining the body tube with a coupler?
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Get a flapper wheel and sand it right out . the charing is superficial in most places

That's what I did when I had a similar repair. Dremel, flap wheel, sand out the burned parts carefully. Then I coated the sanded parts with epoxy mixed with chopped fiberglass, put a sleeve of wax paper in the whole tube, and slid an empty motor case up in it while it cured. Once cured, removed motor case, removed wax paper, done. It's flown that way ever since with zero issues.
 
Great suggestions, gents! I really appreciate the recommendations. I was pretty nonplused at the prospect of having to "File 13" my Kraken.
 
Had a CATO on my King Kraken. The result was that the forward 1/3 of the motor tube burned out but, surprisingly the exterior of the rocket is in great shape.
[...]
My question: has anyone found a creative way to repair this type of damage that does not require removing the fins, cutting the body tube in half, repairing and rejoining the body tube with a coupler?

Key question - is the MMT still securely retained and aligned? If yes, your damage is cosmetic, and no structural repairs are required.

To be more verbose - how many centering rings did you use to glue the MMT, and how many of them are still holding the surviving MMT section in place?
If the answer is at least 2, then the fact that the front end of the MMT is singed is immaterial, and you are still good to fly. The actual length of the MMT tube is not important!

If you are down to only 1 centering ring holding the MMT in place, then you need to do something to remedy that.
Your proposal is one way to do it.
Another approach would be to cut out the remnants of the motor mount tube out of the aft centering ring, slide a new MMT tube in its place, and glue it to the two existing centering rings.

HTH,
a
 
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Key question - is the MMT still securely retained and aligned? If yes, your damage is cosmetic, and no structural repairs are required.

To be more verbose - how many centering rings did you use to glue the MMT, and how many of them are still holding the surviving MMT section in place?
If the answer is at least 2, then the fact that the front end of the MMT is singed is immaterial, and you are still good to fly. The actual length of the MMT tube is not important!

If you are down to only 1 centering ring holding the MMT in place, then you need to do something to remedy that.
Your proposal is one way to do it.
Another approach would be to cut out the remnants of the motor mount tube out of the aft centering ring, slide a new MMT tube in its place, and glue it to the two existing centering rings.

HTH,
a
As I recall, there are 2 centering rings on the 38mm motor tube for the King Kraken. The top centering ring is still in place and securely epoxyed to the body tube, though the top 1/3 of the motor mount is mostly burned out and not connected to it.

Based on the feedback received from the Forum members, I'm going to attempt to "debris" the damaged area and build it back up as best I can with epoxy and glass.

Thanks!
 
Update: i attempted to follow the suggestions put forward by those who responded to the question/problem I posed.

I couldn't get a dremel and flap wheel to the burned out portion of the 38 mm motor tube.

So I wrapped some purple 180 grit sandpaper on a 3/8" dowel and commenced with the sanding and debridement of the mortally wounded motor.

I had forgotten (disregarded more likely given how much I disdain sanding) everyone's exhortations to sand the afflicted area lightly and went at the task like one attempting to churn butter in under 5 minutes.

The net result was, upon inspecting my sanding handiwork, I noticed that, what remained out my motor tube was off center. And that, when I attempted to re-align the motor tube, it moved rather freely.

One good tug later and the remains of the burned out tube came free.

Apparently I did a shoddy job in getting the JB Weld on the aft centering ring and motor Tube and better joint on the fwd centering ring was burned out.

So I guess slide in a new motor tube and hopefully due a much better job epoxying it in place!
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