RE: first spad build
Forgot to add, if you look at the first picture which is the TopDawg, a delta plane, you'll see it's hung by a couple loops of cord. You'll also see there is a wooden dowel plumb bob sitting just above the wing. The loops of cord and the plumb bob all are hanging from the same nail in my ceiling joint. Essentially they are both plumb bobs with the center of each mass pointing from the nail to the center of the earth SO the plumb bob is pointing to the CG of the airplane. 100%, every time. No need to buy CG machines, turn chairs over or having wings slip off of the balancer and poking holes in the monokote. slip the loops of cord over the wing and nose and get the plane hanging level and the plumb bob does it's trick.