Richard, I don't know if there's any info applicable to your project, but 1) I recalled the Ariane 4 that a team from Switzerland brought to LDRS XX, and found this: http://www.argoshpr.ch/index.php/en/ariane-4/190-ariane-4-project 2) I also remember a Delta III by some people from the midwest, and found this (of particular note is their Simulations page): http://www.rocketryonline.com/rolpresents/index.php?site=insane Mike --- On Wed, 8/10/11, Richard Dierking <redierking@xxxxxxxxxxx> wrote: From: Richard Dierking <redierking@xxxxxxxxxxx> Subject: [roc-chat] Re: Stability: Time to Use the Mojo To: roc-chat@xxxxxxxxxxxxx Date: Wednesday, August 10, 2011, 8:46 PM Thank you! After reading the first couple of replies I was beating my head against my desk and saying "why did I make the fins pink and blue!" and "why did I ask those guys!" I did appreciate the humor. If I showed the rocket core without the strap-ons (I'll use different colored paper next time), you might say the blue fins are large enough. But, the strap-ons hide the size. For one side, the pink fin is 120 cm^2 and the blue fin is 90 cm^2. So, the pink fin has about 25% more surface area but only sticks-out 3/4" more. 4" Goblin fins have about 85 cm^2 per side There are 4 fins on a Goblin and I usually build with 4 fins. I can't do that with a 9 strap-on configuration. As usual, as the mass of the solid engines is consumed, the CG will move forward. But, the strap-ons will shed during the flight and change the CP and keep in mind that each of the core fins are between strap-ons that will be released during powered flight. This really complicates things. I thought about adding fins to the strap-ons but this creates some additional problems like re-contact after deployment and the possible roll force on the attachment points. (one hour later...) I'm going to use the pink-sized fins. Thank you, and I'm going to blame all of you if the rocket's overstable or I become unstable. :) Richard > Subject: [roc-chat] Re: Stability: Time to Use the Mojo > From: allen.farrington@xxxxxx > Date: Wed, 10 Aug 2011 13:49:29 -0700 > To: roc-chat@xxxxxxxxxxxxx > > Pink, definitely. You know, how big should they be if the pods had no CP > effect, but still have the mass? I think that they look small. > > Allen > -------------------------------------------------------------------- > Allen H. Farrington > 818-653-2284 > web: http://www.allenfarrington.org > > On Aug 10, 2011, at 12:58 PM, Richard Dierking wrote: > > > When you're working on something like this Delta II you start to develop > > mind roll. I realized that I need to make a decision on the fins before I > > become a really old man. > > > > So, please look at the two photos showing a blue and pink fin. There will > > be 3 fins and they will be transparent and the rocket's about 6' tall. As > > Barney would say, "time to use our imagination..." Please provide your > > vote. > > > > Thank you. I'm going off to do something simple like work. > > > > Richard > > <bluefin.jpg><pinkfin.jpg> > > > -- > ROC-Chat mailing list > roc-chat@xxxxxxxxxxxxx > //www.freelists.org/list/roc-chat >