I'm building the Sunward Star Watcher right now, and in fact I'm pretty much done but for the painting; but I've run into an "issue" with it. I've used the alternate "X-Wing" layout for the fins, and the instructions say that nose weight may be needed... but not how much.

I don't have RockSim, but looking online it appears nobody has yet done a RockSim file for this rocket anyway (not even on EMRR), leading me to wonder if there is some reason for this. Does anyone know how much nose weight this beasty needs?

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NAR # 115523
Once upon a better day... SAM #0076
My site: http://rocketry.gonnerman.org

Hmm... I'll partially answer my own question. One reviewer at EMRR said he used "several ounces" of clay for nose weight, while a guest reported using 10 grams of lead sinkers plus 4 ml of Gorilla Glue. There seems to be no science to this, though.

__________________
NAR # 115523
Once upon a better day... SAM #0076
My site: http://rocketry.gonnerman.org

I haven't built one but I just checked out what it looks like and it appears like it should be fairly simple to swing test.

I built mine in the x-wing configuration as well...I could take some measurements and put together a quick and dirty RS file for it...

__________________
Jon
SAM #0396
BAR 02/07
NAR 86940
KF4GUL
Aim high, fly straight!

Aha! I have questions for you:

Did you add any noseweight? If so, how much?

Have you launched it on a C engine?

Did it fly right?

__________________
NAR # 115523
Once upon a better day... SAM #0076
My site: http://rocketry.gonnerman.org

I have launched it, yet don't remember how it flew Still in one piece so it must have flown fine..Almost done with the Q/D RS file...Will post in a couple here...

Ok, done with the RS..Flies fine in the sim with no nose weight..HOWEVER, I couldn't figure how to put the fins in the x-wing configuration-and the nosecone isn't exactly right in the RS file but close enough, and I did a 'mass override' using the weight of my finished one..I also couldn't figure out how to put the fin tips in the sim as well..

Like I said I have flown it(I can smell the burnt BP), I just don't remember how well it flew or what motor I used- I am sure it was a B as the field locally is fairly small..

RS file attached, so if anyone cares to tinker with it and correct the inaccuracies, feel free to..And post your results

Attached Files

Star Watcher.rkt (69.7 KB, 159 views)

__________________
Jon
SAM #0396
BAR 02/07
NAR 86940
KF4GUL
Aim high, fly straight!

Errm... I was the guest who wrote:

"SPECIFIC ROCKET TIP:
10/06 - "The Star Watcher was my first Sunward kit. I e-mailed Angelo Castellano about extra nose weight needed for the X wing configuration, he suggested about a cubic inch of clay if flying in wind. Interestingly he said that in light to no wind, no extra nose weight should be necessary. A quick swing test had my Star Watcher stable, but flying aft about with a C6-5 in place. The CG was 90mm from the rear of the body tube. Time for a quick burst of nose weight. Twelve size 00 split lead sinkers gave me an even 10 grams of nose weight. These were dropped into the nose cone and secured with 4ml of polyurethane (Gorilla) glue. A quick check showed the CG had moved to 135mm from the rear of the body tube. Stable flyer, and one of my favorite rockets until I parked it high in a tree." (M.M. )"

Sorry, talking to the manufacturer and swing testing seems a pretty logical progression of thought to me. Perhaps I should go back to divining the CG with chicken entrails...

I have built four Star Watcher kits in the 'X-wing' configuration and they all fly well on B and C motors.

YMMV, as may your nose weight.

Attached Thumbnails

   

Sorry... perhaps I should have said that there seemed to be no math to it, rather than no science.

I'm personally surprised that the manufacturer hedged so much on this. I'd think that they, being in the business and all, would have coughed up for RockSim and would have had a solid figure for the suggested noseweight.

__________________
NAR # 115523
Once upon a better day... SAM #0076
My site: http://rocketry.gonnerman.org

Angelo doesn't (or didn't) use Rocksim when I spoke to him about the Star Watcher. He said he used experience to guide him, and to be fair, the instructions do have details of how to perform the recommended swing test.

Do Estes use Rocksim?

As for math, gee I counted to twelve, what more can you ask for?

Just an added note: On my built and painted Star Watcher, the unloaded CG is located 8.5" from the tip of the nosecone..Like I said before I have flown mine in the x-wing config with no nose weight, but am going to add 1/2oz just to be on the safe side when I launch it Saturday on a C6-5..Will let you know how it goes, unless you fly yours before I get back then you can tell us how yours did

__________________
Jon
SAM #0396
BAR 02/07
NAR 86940
KF4GUL
Aim high, fly straight!