An auspicious occasion, ladies and gentlemen. I have this evening opened up the last of the kits from 2013 still in the build pile: The Estes Xarconian Cruiser #3223.
(And if you want one yourself, go buy it now! Estes is having another of its sales — no, this isn’t a holiday weekend, but apparently their Black Friday began a week or so early. For $8.99, vs. the $29.99 list price, plus shipping, you can get one — and free shipping kicks in at $29.99, so buy three and some wadding or something.)
I was a little startled when I pulled out the motor mount tube. Not that I didn’t know this was an 18 mm kit, I just wasn’t thinking about it and have been working (or neglecting to work) on the DRT so long, its small size sort of surprised me.
It’s a BT-55 kit, nearly two feet long. Estes says 3.7 ounces and recommends only one motor: C6-3. Should this be converted to 24 mm? The C6-3’s maximum recommended liftoff weight is 4.0 oz — and it adds 0.83 oz to the rocket, bringing the total to 4.53 oz. This wouldn’t be the only Estes model whose Estes-estimated weight exceeds the Estes-recommended motor’s Estes-recommended maximum, and former Estes designer Matt Steele recently wrote on YORF:
Don’t read too much into the max liftoff weight recommendations. There are a lot of factors that go into a safe flight (diameter, drag coefficient, wind, launch rod length) that make using just the max liftoff weight not much more then a suggestion. The max weights are set very conservatively, due to the very fact that there are other parameters that can influence a safe flight.
Chris Michielssen, who designed the Xarconian Cruiser in 1972 (okay, not really… interesting resemblance though), covered his build of the XC in an epic 33 part blog series starting here, to which I will, you can be assured, be referring frequently in the near future. He built the 18 mm motor mount — then put it aside and installed a 24 mm instead. His final build weight was 4.85 oz! Over 5.5 oz with a motor installed.
And he didn’t even use all the decals.
I’ll follow his example and upgrade the motor mount. Only question is, do I have the parts? Hang on, let me check.