So, 1/2 ounce is 14.235 grams... I use computer screws for nose weight, and have previously determined that they weigh 0.77 grams each on the average, so that's about 18.5 screws.

I still don't know what epoxy weighs. In the past, I have used a "rule of thumb" that a screw and the epoxy to hold it weighs about a gram. That is nothing more than a guess though.

In effect, I need at least 15 screws, but almost certainly no more than 18, with epoxy to hold them in. I'm thinking 16 screws is a workable guess.

Thanks for the information, pantherjon. Most likely you'll get yours launched long before me, as I'm in NE Missouri... cold and wet here today. I considered a launch on Sunday when temperatures were around 65 F here, but the ground was too wet for reliable recovery.

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

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?

Hi guys-

Actually, I do poke my head in here from time to time... Just not very often! Too many rockets to build so I have to pick and choose which forums I frequent...

I didn't actually weigh the amount of nose weight that I added, I just did swing tests and kept adding small bits until the rocket swung stabily. Sorry I couldn't give you a more clear cut answer!

__________________
Todd Mullin
NAR 80422, L2

Never mind the physics....it's punk rocket science!