Apologies for the temporary silence...illness kicked me in the head for a few days. Back to it!
Quick Recap: The Loc gang spanked their Goblin on an Aerotech J425 Redline on 3/10; that was fun! I wanted to test the other end of the spectrum; hoping that the completed rocket would be light enough to be a small field Class 1 (NO FAA WAIVER REQUIRED!) flyer, yet strong enough to handle a J
maybeK motor. After covering and doing the internal assemblies on page 1 of this thread, here's the remainder of the quick build.
Glue in motor mount, tuck in the tabs. Not much explanation necessary. Mix up a batch of 5 minute epoxy (I like to live dangerously!
), apply a ring or two to the ID of the airframe, part the slits, install motor tube until the fins run into the forward end of the fin slots, tape up the rear.
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Optional Step: external fillets. Yes, I said optional. All the necessary strength is in the solidified, interlocking motor mount/fin assembly, so external fillets aren't really necessary. I do them here for two reasons:
1. I want to seal the edges of the covering and any gaps that occur at the leading and trailing edges of the fins if you're goofy enough to bevel the fins.
2. In case you're sly enough to *intentionally* slightly misalign the centering rings which *intentionally* imparts a slight fin angle which *intentionally* imparts a nice stability-increasing roll rate for your Goblin. Then you might *intentionally* have to fill any slight gaps that might exist. Yep, I *meant* to do that.
Without further ado, I kinda dig the way 5 minute Bob Smith epoxy dries clear and seals up covered rocket surfaces masterfully. No tape, no pvc pipe pullers or fancy sticks; just approximately the right amount of epoxy, a steady finger and some alcohol
(to wipe up your sticky finger and messy rocket).
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Throw on some included decals (YAY!!!) and take a completed dry weight. Not bad! Note, I build LIGHT and always consider saving mass wherever. That said, I built this STOCK (ok, beveled fins).
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Fully prepped with the ultimate G motor (yes, a
real G motor)...the G69 Skidmark.
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Also a good time to address dhbarr's suggestion:
I like to follow up with a thin slice of coupler, but that's just a preference.
Not a bad idea at all! With the motor mount adapter system, you might run into clearance problems in doing so. Simple solution would be to reduce the OD of the adapter's thrust ring a bit using a dremel. Because the fin's root touched the airframe nearly all the way to the rear of the tube, I didn't find any additional reinforcement necessary. Not sayin' it can't or shouldn't be done...:smile:
Now for the true moment of truth. My name and signature is on the local land use permit as the responsible party...I'm not bending no rules. Class 1 weight limit is 1500g/53oz/3.3lbs. Fully prepped with a G69SK:
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51.7oz: Green Light!