ORIGINAL: Gary Jefferson
I just wanted to update anyone that is thinking about building a Lightning with a P-180 concerning the balance. The final balance required with the smoke system and all of the batteries mounted on the plates in the nose (as can be seen in my previous post) required exactly 18 oz of lead in the nose to balance.
Gary, my numbers were very close to yours. I had 20 oz in the nose with no pilot or cockpit, so I would suspect with the BB pilot, I would be at 18 oz as well.
The center of the engine sits approximately 16 inches behind the CG while the front of the nose cone is approximately 48 inches in front of the CG. Back of the envelope math would say for each pound of engine, you would need about 5.3 ounces of noze weight. It might even be a bit less, given that the extra fuel you would need to carry sits in front of the CG by just a bit. All in all, this might not be too great a penalty for the thrust gain if the 180 performs to spec. With the added weight of fuel, I don't think the thrust to weight ratio with a P180 will be all that much different at takeoff than the Rhino. That would obviously change as the extra 4 pounds of fuel burns off.