So to resurrect this thread for a minute. I just cloned my goblin (got a semroc nose cone, had the original fin pattern and the original decals because I used to fly em unfinished!). My original goblin was indeed a freebie kit. It says in the plans that the balance point should be 3.625" (10.375 from the nose) from the rear of the rocket. Fine. Alot of estes plans (eg. the A-20 demon) state a figure for the balance point with a motor installed... but not the goblin plans. I guess it's implied, right? But it doesn't *say* in full flight configuration on the instructions, does it now?
My original had a balsa nose cone and I sure as heck never ever added nose weight (I did finish the nose cone but that was it!). I flew it several times until my brother jammed an aerotech e-15 into it and DIDNT put in the streamer! Never saw it again because I couldn't see it come down. Sigh. Now I have a clone all painted up but openrocket says the Cg (w/o motor) is 9 inches from the nose. With a motor it's 10.8" from the nose (D12-7). This seems to be about right with the actual model. With no added weight (the Cg is ahead of the Cp in this config by .781 diameters of the tube) the string test simply fails totally. As I recall, it failed miserably when I was 15 years old too!! The reality is that I'm seeing a Cg about 11 inches from the nose (giving me 3 from the back end.
I'm wondering what the aero/astronautical engineers opinions on this matter are. I sure cannot start the swing test at the speed Openrocket is suggesting off the rod, so without nose weight it starts looking dicey. But I *know* my original flew fine without it... but the swing test on this indicates it really enjoys flying backwards! I know that nose weight is not a terrible option evidently 9-10 grams of weight (.31-.32 oz) is enough for my new goblin to easily pass the swing test.
I guess what I'm really asking here is: did any of "youse guys" fly the goblin back in the day w/o any nose weight added?