Looks good....is good? Scratch building freeform

[metalhead100]

Anyone freeform a scratch build and before final paint ect....just give it the old swing test?....

As you can guess ....I am! Im making a sudo "Promethius Gunship"....It will be 24 to 36 inches long depending on swing test ect.

Rocket science aside........heheh Is this a bad idea?

Flamesuit on....fire at will.......tell me why i should use all those pdfs on CG/CP....that i have downloaded .

And will the cardboard profile method be a bad idea?

Jim

[CPMcGraw]

...Flamesuit on....fire at will.......tell me why i should use all those pdfs on CG/CP....that i have downloaded...

Well, ya got a 60-40 chance of gittin it right with the CG/CP locations, and if ya get it right, it'll fly purtee.

If'n ya don't git 'em right, the hole it digs might be jest big enuff to bury it in, or your shorts are gonna get in a bunch tryin' ta duck...

[metalhead100]

Good one.........

I was just bored and thought id stir up a little discussion..........

From what i have read the cardboard CP method can be way off from the calculated CP......according to old Century documents.

Anyone have a link to a site that plainly covers CP calculations and CG interactions ect.

How about the trial version of rocketsim.... any help?.....

I need to sit down and beat this stuff into my head........and make it fly on paper.

Jim

[CPMcGraw]

...How about the trial version of rocketsim.... any help?.....
Jim

The trial RockSim is great for this kind of testing. Not perfect, as some of us have found out; but good enough to give us stable birds 98% of the time. RockSim is ideal as a "What If?" tool, like VisiCalc was for balance sheets way back when. It's every bit as accurate as the garbage you put in... :rolleyes:

[Engineer Kelly]

I recently started using RockSIM to calculate CP. It sure beats doing the Barrowman method by hand.

[moonzero2]

I recently started using RockSIM to calculate CP. It sure beats doing the Barrowman method by hand.

Yea, but I thought you like doing the math,... you said it was,... ah,... fun.

[Engineer Kelly]

Aha. Yeah i do enjoy it. RockSIM calculates drag and other variables in for altitude though. So i just use it. Because im not sure how to do that by hand. I just let it calculate CP for me to though.

I have checked it by hand though.

[moonzero2]

Yea,... RockSIM is sure GREAT!

I just love playing with nose cone wieght for maximum flying height.

And then with the different engine combinations.

I need to get me an altimeter to compare RockSIM with reality.

[Engineer Kelly]

I have been playing around with two stage rockets in there. I searched through to help for a minute, but how do i get the second stage to ignite?

[barone]

I have been playing around with two stage rockets in there. I searched through to help for a minute, but how do i get the second stage to ignite?
Usually, the hot propellant from the booster is blown into the nozzle of the sustainer, igniting the propellant. You need the "Handbook of Model Rocketry"? I've got one I'll sell to you (all right guys.....no comments about me selling everything :o )

[Engineer Kelly]

O i know how to actually build one. I dont know how to do it on RockSIM so in the simulation they will split apart and all that.

I have the handbook.

[barone]

O i know how to actually build one. I dont know how to do it on RockSIM so in the simulation they will split apart and all that.

I have the handbook.
Oh...sorry. When you build your rocket in RockSim, you design as a two stage. Then you build your booster and your sustainer. Then you load the motors, one for your booster and one for the sustainer. The simulation will run it for you showing staging. Yeah, I know this explanation is really basic but I have to be running the program to explain it better than that.