Question: Should I expect to add weight to the VMAR Phantom in order to have the CG in the correct location? If I must add weight, where will it normally go and how much do you think I will need?

Answer: This will depend on the weight of your engine, servos, receiver and in particular the weight and location of your airborne battery pack.  

Additional Information: The VMAR Phantom accomodates two stroke engines in the .60-.91 size range. As of 2005, engines in this class are often built from the same casing and although the crankshaft may be a bit heavier in a .91 the case is a bit lighter. Hence, in many brands there is not much of a weight difference between a .60 and a .91 two stroke engine. Many popular engines in this class weigh, with muffler, approximately 24 oz.

Radio receivers generally do not vary in weight much between brands. Servos can vary in weight from servo to servo(ball bearing heavy duty servos weigh more than standard servos) and airborne battery packs can be significantly different depending on their voltage and mAh capacity.

Experience with a variety of standard servos, 4.8V-6.0V nicad packs and .60-.91 size two stroke engines weighing approximately 24 oz with muffler has shown that for first flights 6-8 oz of weight in the tail is needed for a CG location that is somewhat nose heavy. After first flights moving the CG back slightly within the recommended range may be desired and require 10-12 ounces of weight in the tail.

These guidelines are NOT considered to be suitable for all situations. If your engine is heavier than 24 ounces, you may need more weight in the tail. If you are using a 6.0V 2000 mAh airborne battery located in the aft end of the model you may need less additional weight in the tail than if you are using a 4.8V 600mAh battery. Each model should be carefully checked for CG and compared with the recommended CG location. First flights should be slightly nose heavy (forward CG location) and no model should be flown with a CG outside the recommended range.