Please see my thread "Twist Lock Nosecone" in the Building Techniques section (found near bottom of page 2) for a more detailed write up of how to fabricate the system.

Many of you will remember my Maxi Alpha 3 explosion from the June 14, 2020 launch report. An E12 let go on the launch pad and ruined the motor mount. The body tube burst apart between the fin roots and twisted the engine hook, and a large fireball shot out the top and roasted the shock cord. This is the second big Alpha of mine to suffer the same fate and it's been sitting on the work bench ever since waiting for repair. The winter build season has arrived, so I picked it up last week and got to work.

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I started with the motor mount removal. A few evenings of whittling with a fresh #11 X-Acto got rid of the damaged tubing. It was built with through the wall fin attachment so I was very careful to only remove the mount and leave the fins intact. I didn't want to cut away too much because I needed the fins to locate the new mount exactly, without it ending up slightly canted or off center.

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A new mount was made from scrap tubing. I cut up a spent D12 to make an engine block and straightened the motor hook. I needed a connector to join the new mount to the existing stuffer tube. As a rule my stuffer tubes are heavy duty to mitigate burn through and this one is no exception. The problem is that the I.D. doesn't match the new mount. I made a connector with dissimilar ends from another spent casing. I peeled away the layers to attain a good fit and honed out the inside to reduce bulk. A hook retaining ring was made from a 1/4" wide strip of paperboard.

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Satisfied with the dry fit of the components, I glued the coupler into the stuffer tube. The hook ring had to be held between the fins while the new mount was installed. Of course this worked fine when I tested it, but not so much after I applied glue to everything. It took several tries to get that mount to pass through the hook ring and onto the connector. Once in place I added glue to the ring edges and the fin tabs along the mount. That's all for now. Next installment will address the body tube repair.

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Nice work on the internals Erik. Looks like the thru the wall mounted fins probably contained what could have been even more damage between the other fins. Weather here it’s supposed to rain tomorrow I am hoping to get a little rocket work done in the garage myself too.

__________________
Steve Naquin
TRA# 677 L2
NAR# 85518 L2
SAM# 0052

🚀 In Construction: Der Blue Maxx/Minie-Magg 5.5” & Vander-Burn MDRM Clone w/Stickershock23 Custom Decals
🚀 In Paint & Detail: USR Banshee
🚀 In Build Queue: Estes Doorknob w/Vander-Burn Rocketry Upgrade Kit [Sport Decor], Semroc Centurion-F, Semroc Egg Crate
🚀 In Repair: SLS Lil’ Hustler, SLS Aero-Dart 1969 Trim
🚀 Stay Tuned For Fall 2021 Launch Dates

Thanks. Luckily the damage didn't extend past the blue/white paint break.

I was lucky. The big blowout my Wizard had on Sunday was mostly contained to the extreme rear. Nice work.

__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Mini Dactyl Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II, Xarconian Cruiser Semroc Cyber III

Ready to fly: Estes - Solar Sailer II Semroc - Earmark, Groonie Der V 1/2

I made some progress on the Max construction this week.

Drei Maxxx : Engine retention in place, stuffers double walled, three hole centering ring at top, and all fins attached. Plenty of fillets will be needed on this one.

Der Bigger Red Max: Engine hook fabricated, rings on, fins cut out and attached, and tube slotted.
Those plywood fins are heavy. Instead of adding nose weight I may cut them up into a lattice and skin them like the MDRM, just haven't decided yet. I originally went with plywood because I didn't have bass wood stock wide enough and I was concerned about warpage.
I ordered some wood sealer from erockets but it hasn't arrived yet.

It was a crisp 12F degrees this morning so I don't see any primer/paint opportunities this weekend.
Guess I'll finish up the Maxi Alpha repairs today.

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I worked out the tube repair panels for the MA3 last night. Considerable time and effort was spent trying to remove all the thick glue fillets from the fins without damaging the wood surface. A segment of BT-80 was cut lengthwise into three equal parts to make patches. Each was then trimmed to fit between the fins. Another ring of tubing 5/8" wide was also cut and divided equally to produce forward tabs that fit under the undamaged rocket body. These tabs will allow a glue joint to secure the the small amount of patch that extends just beyond the mid centering ring. The remaining three sides of the panel will glue to the fin roots and rear centering ring. A little more finish work after the glue dries and I'll be ready for paint.

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