RockSim. You can learn about it, try it/buy it from here:

http://www.apogeerockets.com/rocksim.asp

I thought so. The problem with rocsim is that it is just too expensive! I would gladly pay $50 for designer software but $120+ is much too high.

Arrow 300 plan request
 

i have tried to convert a comache 3 over to an arrow 300 but my rocksim skills is low.
has anyone done this rocket in rocksim? or even a parts list from an old rocket?
The stage couplers are for me an issue with not knowing where to get them....
peace minatour87

Greetings, minatour87!

As for parts availability, go with SEMROC . You can match up every part on the Arrow 300 from his catalog. Attached below is a representaion using RockSim 9. I think it is very close to at least one variation that saw production.

The Arrow 300 was similar to the Comanche III, but used a class of engines that just don't exist today. Estes went with a 24mm first booster to compensate for the lack of 18mm engines with enough power to move the rocket off the pad. You will need to do the same when you try to fly this model. There are just no 18mm boosters available with the needed power.

thanks for the reply, i am a born again in to the sport, 8th grade i had this rocket and wish to build it again, i have a just started a comanche 3 which is similar, i first thought it was the same but oh well, things change, I am now 40,
my son is 5 and this is a great sport for the both of us. I am learning allot. peace minatour87

Same here! It is kind of fun to mess with but the price is out of my range. I was hoping someone would put up the old version 8 in the auctions...