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Estes Bull Pup 12D Build (w/ modifications)

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Luzwingnut

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Thought I'd "test" some new building techniques on an old favorite. Wanted to include a motor hook as the original design utilizes a friction setup for motor retention. Additionally, I wanted to try out some "FIX-IT" modeling epoxy and practice doing some fillets between the fins and body. Ive ordered a 12' nylon printed chute...never did like the plastic offerings. The kit BT measured 9 inches long...increased that to 11 inches just to extend the rocket a small bit for CG. Positioned and glued (w/fillets) the small strakes to the nose cone instead of the upper section of the BT...liked the cosmetics better that way. Chopped off the angled molded cone aft section (immediately AFTER the cone's shoulder) to install an eye-screw... but also to assist in putting weight INSIDE the tip of the nose cone. Papered and sanded the fins... THIS is just a "practice" build BEFORE I start putting together my AEROTECH Strong-Arm...and my NorthCoast Rocketry SA-14 Archer.
 

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Nytrunner

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THIS is just a "practice" build BEFORE I start putting together my AEROTECH Strong-Arm...and my NorthCoast Rocketry SA-14 Archer.
If the strongarm has plastic fins like the other AT offerings, use a better epoxy (30min, heck 5 min) than the clay junk. As far as my observances, the only thing the clay has going for it is it sands easily
If the Archer has wood fins, use the same epoxy or wood glue
 

Luzwingnut

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If the strongarm has plastic fins like the other AT offerings, use a better epoxy (30min, heck 5 min) than the clay junk. As far as my observances, the only thing the clay has going for it is it sands easily
If the Archer has wood fins, use the same epoxy or wood glue
Yep. Plastic fins. Will heed your advice. Thanks!
(The Archer has wood fins as you correctly have guessed)
 

bronicabill

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I built mine stock (just waiting on paint to be applied), but sure wish it had motor hooks instead of a friction-fit motor! Wish I'd seen your post before I got so far along on mine!

Note to self: Please, feel free to modify existing kit designs as they are NOT always perfect!!! :D
 

CKaul04

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I got lucky with my Bullpup. I accidentally yanked the motor tube out and thought it would be a good idea to put in an engine hook. I just need the wind to calm down so I can fly it.
 

afadeev

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If the strongarm has plastic fins like the other AT offerings, use a better epoxy (30min, heck 5 min) than the clay junk. As far as my observances, the only thing the clay has going for it is it sands easily
If the Archer has wood fins, use the same epoxy or wood glue
Congrats on a nice build, and well papered fins!
Are you aligning fins by eyeballing, or have a jig?

+1 on "FIXIT" epoxy clay being absolute crap.
It doesn't penetrate the paper fibers, nor attaches to the rough surface areas like an epoxy would. It is also ridiculously heavy, and brittle. Every time I tried using it (threw it away), fin fillets would crack from moderate drops.
The only good news about epoxy clay is that it is easy to remove, which is all you need to know about how poorly it works as an adhesive.
Apogee paddles it aggressively, for what reason, I can't fathom.

Any proper liquid epoxy would be an improvement!

For larger kits, you will want to upgrade from hook motor retention to one of these:
https://www.siriusrocketry.biz/ishop/parts-tools-and-more-11/motor-retainers-117/
https://www.rocketarium.com/Build/Motor-Retainers
 
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Lugnut56

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I also wanted a motor hook in mine when building, so I used a square jewels file to cut a recess into the tailcone to clear the motor hook.

Bulldog 1.jpg
Bulldog 2.jpg
 

jrap330

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If you adding weight via epoxy and other strong built criteria, please do a simulation on flight. My original Bull Pup was marginally stable. Good on A8-3's and B6-4's but C 6 engine...no ..flew horizontal. Assumed it was the smaller forward fins. Estes should have gave more clay weight.
 

Joshua Smith

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Has anyone upsized the motor mount to 24mm? Anyone simmed that? I imagine the nose weight would have to go up a decent amount.

Josh
 
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