Johnny Star Commander (Shrox design)

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Bill S

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Just finished up an Johnny Star Commander rocket by Shrox (sold by Apogee). This was a difficult build, made worse by my having great difficulty in getting the balsa as defect free as possible. This resulted in a lot more Bondo putty on the balsa, with multiple coats of primer, etc. The finished rocket is about a half oz heavier than "nominal", which surprised me - I expected much worse.

I didn't want to attempt the masking for the red areas on the wings, etc, so I broke out some automotive pinstriping. I think it turned out fairly well, all things considered.

Because the rocket is overweight and tends to weathercock, Rocksim says that I should use C5-3, D16-4/6 (calm conditions only) or D10-5 motors.
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Thanks guys. If the scheduled launch happens this weekend, its going to get a flight or two.
 
Finally got to fly the Johnny Star Commander yesterday, on an C5-3. Wind was 5mph-ish, rocket had a little weathercocking but not much. Didn't go as high as I would have liked to see , maybe 300' at best. Safe recovery though, so there's that.

The recommended on the package C6-5 needs 123" of rod to get up to a safe speed, altitude no better than a C5-3 really...

I also Rocksimm'd some other engine choices, such as Quest D16s, but they require a 4' 1/8" rod - the rocket needs 45" to get up to "safe" speed. The club I fly with doesn't have a 4' rod and they didn't seem enthusiastic about my buying a 4' rod and donating it to the club so I could fly the JSC more safely. :( Otherwise, its down to an older Aerotech D10-5, which I have a few of, but they are hard to find these days.

So I don't know how much this rocket will actually fly at this point. Nice display piece, hard to find good engine choices for (C5-3, D10-5, D24)
 
Edit... it was suggested to me that I should add a set of 3/16" launch lugs so I could use the longer 3/16" launch rod, but that would be tricky now since the rocket is painted, etc. I would suggest it as an optional add-on to someone who is building one though so you can use the D16s, etc.
 
I also Rocksimm'd some other engine choices, such as Quest D16s, but they require a 4' 1/8" rod - the rocket needs 45" to get up to "safe" speed.
Try simming with the forthcoming Quest D20s and/or C18s. Motor files are on Thrustcurve.org. It looks to me like (just from the curves) like they have significantly more kick off the rod, although I haven't tried simming anything with them yet.
 
I did some simulated launches with the D20 in the Johnny Star Commander. Lovely. 661 feet vs 594 for the D16-6. Needs 33" of rod, vs 45 for the D16. .6 second past apogee for parachute ejection, very nice. :)

I couldn't find any way to download the data for the C18 yet. Figures... I just picked up a bunch of C12 and D16 motors (Bellevue is having a really good retirement sale), but those D20s deserve a try. :) But they don't seem to be available yet.
 
Beautiful rocket! Would love to see any flight pics or vids!

If you were to build this again, would you upsize the engine mount? I too, will probably get one.
 
Beautiful rocket! Would love to see any flight pics or vids!

If you were to build this again, would you upsize the engine mount? I too, will probably get one.

If I were stuck using C5-3 motors, then yes, I'd upgrade to a 24mm mount and add noseweight (it already has a fair bit). Since I discovered the D20-6 works well in this one (about 600'), probably not needed. If I need more oomph, I can put an old D10-5 in it and see how it goes. Given that this is such a beautiful and hard to build rocket, I don't plan to fly it very often, hence flying to "only" 600' is just fine for me.
 
Thread resurrection! I'm finally building a Johnny Star Commander and was wondering if @Bill S used all of the big square blue weight in the nose cone? It's over 36 grams! 😲

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I did use all the weight.

I hardly fly this rocket; my rocket ended up a bit overweight, and after Rocksimming the design, really the only viable choices for this one are C5-3 (low flight), and a Quest D20-6. Its heavy and draggy.
 
Ah - but the Johnny Star Commander, IBIS, and Sea Sting were all based on stealing parts from Estes Bull Pup bulk kit packages, and the Bull Pup kits had an 18mm mount....
 
Ah - but the Johnny Star Commander, IBIS, and Sea Sting were all based on stealing parts from Estes Bull Pup bulk kit packages, and the Bull Pup kits had an 18mm mount....
Interesting about the Bullpups, didn’t know that. Presumably that doesn’t apply to the current renditions from Apogee.

LPR kits are often underpowered, particularly those that land in the gray zone between two motor mount sizes. I can possibly guess why, but it’s a bit annoying nonetheless.
 
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