Posted:December 28th, 2008
Regarding tail-less delta wing models:
I've seen recommendations for C of G ranging from 10% to 20% of MAC for such models. I've built two of Laddie Mikulasko's "Arrows", which are deltas, one which is 50% reduced from the plans, and 5% of MAC ready to fly has worked real well on both these aircraft. The aircraft are very stable, and yet have plenty of elevator authority. I say this is under "ready to fly" conditions because my big Arrow has the fuel tank mounted in the fin, and the CG shifts from 0% MAC to 5% MAC when fueled. The little one is electric powered, and the CG stays at 5%.
I'm not sure, but I think CG on a tail-less delta is greatly affected by the sweep on the leading edge of the wing. I suspect that a very long root chord and a sharp sweep, resulting in more wing area aft, would work with the CG located further aft than 5%, as the wing area aft of the CG is what determines the pitch stability. Just some educated guessing. Hope this helps.