My 10" Goblin weighed 42 lb on the pad with a 75/6000 M745 for my L3 cert. Don't forget about the recovery gear, electronics, and the motor casing & propellant weight. Without motor I believe mine weighs around 29 lb.
Keep in mind an I-600 weighs 21.5 oz. not 14 pounds.
The way to save te remaining weight is to step up what you need. You don't need all the increased weight of an AV bay, etc. at the L1 level. As long has you have good internal fillets and the fins glued to the airframe, you don't really need the externals if you fly with an I. We're talking about a top speed of 90-120 MPH, depending on motors. My Subaru can go faster. Whether you mount your electronics in the fincan or the nosecone, all you really need at the L1 level is to place the altimeter in a place where the bay does not also have to bear the load of the rocket. That way you keep your overall altimeter bay weight in the 6-8 ounce-range instead of the 3-4 pound range. Build the rocket in such a way that the additional components can be added later when they are needed. Add the additional fillets after the L1 flight, go to a more robist recovery system, etc.
Base drag aside. I am attaching the very quick, based on memory design of the goblin, just adding in a mass component to factor in additional weight. Weight is close to 26 lbs. with an I-600. If the fins are square the stability is .56 ca. If the fins are airfoiled, stability is .605 ca...so yes, there is a difference, but it's the other way that what I had though earlier. Mea culpa. With fins square, altitude is simmed to 371'. Airfoiled..411'. Not much but on a low altitude flight ever foot is precious. All the way around, airfoiling the fins will help. Plus when you put a REAL motor behind it, they will contribute a lot more.
Motors included in the sim are the I-600, the L2200, and an M1830, a good fun motor that will give it a kick, is relatively inexpensive, and will not take it into transonic speeds.
I say do it. The math works out, and it would be fun to see this thing sputter into the sky on an I. What you should do is film it at 60 FPS so you can watch it in slo-mo.
Oh, and Dave...you're a photographer. Think of how spectacular the shot would be if this launched with an L820. Yes there are motors that will take it higher and faster, but there aren't many other L's that can do it with more style and louder. A deafening slow launch on a skid with this thing would look ands sound awesome.
Good luck.
View attachment I-Goblin.ork
